Document QgjbROy8NBdByyXx93o4jGLqo

Guide for the Safe Handling of Fluoropolymer Resins November 2012 Acknowledgement This guide has been developed by the members of the Fluoropolymers Committee of PlasticsEurope (the Association of Plastics Manufacturers in Europe), the professional representative body for the European polymer producers. The association has more than 100 member companies, producing over 90% of all polymers across the EU27 member states plus Norway, Switzerland, Croatia and Turkey. PlasticsEurope wishes to acknowledge the Fluoropolymers Division of the USA Society of the Plastics Industry (SPI) for permission to use extracts from the SPI Guide to the Safe Handling of Fluoropolymer Resins. Disclaimer The information presented in this brochure is provided free of charge and submitted in good faith and is correct to the best of PlasticEurope's present knowledge. Following the Guide does not guarantee compliance with any regulation nor safe operation of any processing facilities. Users are cautioned that the information upon which this guide is based is subject to change that may invalidate any or all of the comments contained herein. PlasticsEurope will be unable to accept responsibility or claims from any party, related to information presented in this brochure. Freedom under patents, copyright and registered designs cannot be assumed. Version 6 Contents Introduction 1 Chapter I: Fluoropolymer Resins Types and Properties 2 1 - Resins types 2 2 - Thermal properties 3 Chapter II: Potential Health Effects 5 1 - Polymer General Toxicology 5 2 - Health hazards during hot processing and toxicity of decomposition products 5 3 - Specific hazards of compounds containing pigments and fillers 6 Chapter III: Processing Hazards and Precautions 7 1 - Sintering 7 2 - Melt processing 7 3 - Paste extrusion 7 4 - Coating/Impregnation 8 5 - Machining 8 6 - Welding 8 7 - Soldering, Welding and Melt Stripping of Metals coated with Fluoropolymers 9 8 - Cleaning and Maintenance of Process Equipment 9 9 - Spillage 9 Chapter IV: Occupational Hygiene 10 1 - Ventilation 10 2 - Personal Protective equipment 10 3 - Personal hygiene 11 Chapter V: Fire and Explosion Hazards 12 1 - Ignition characteristics 12 2 - Extinguishing agents Fire and combustion toxicity 12 3 - Extinguishing agents 13 4 - Fire fighting 13 5 - Explosion protection 13 6 - Specific hazards of Fluoropolymers with powdered materials 13 Chapter VI: Environmental Information, Recycling and Disposal 14 1 - Environmental Information 14 2 - Recycling and Disposal 14 3 - Recycling of Packaging 15 Chapter VII: Food Contact 16 Chapter VIII: Medical Applications 17 Appendix A - Addresses of fluoropolymer producers in PlasticsEurope 18 Appendix B - PlasticsEurope statement on TFE monomer toxicology - Effect on fluoropolymer safety in use 19 Appendix C - Safe handling of fluoropolymer dispersions 20 Appendix D - The inhalation toxicity of combustion products of PTFE and similar fluoropolymers 21 Appendix E - Addresses of recycling companies 23 References 24 Introduction Fluoropolymer resins are produced and sold worldwide by several manufacturers. They have found application in nearly every field of modern industrial, technological, and scientific endeavour. In applications ranging from power generation to emission controls on vehicles to semiconductor manufacture to aerospace, fluoropolymers provide superior performance in products that contribute to increased safety in offices, homes, industries and communities. Of the many properties that characterise fluoropolymer resins, one of the most important is the resistance to heat. While few plastic materials have continuous service temperatures much above the boiling point of water, fluoropolymer resins can withstand the temperatures inside baking ovens and in the engine compartments of jet aircraft. The combination of resistance to a broad range of fuels, solvents and corrosive chemicals, heat resistance and excellent dielectric stability means fluoropolymer resins yield an extremely versatile family of engineering materials. These unique properties may provide certain essential performance characteristics needed in the event of fire, in fluid containment or exclusion, electrical overload and similar emergencies. Due to the general inertness of the fluoropolymer resins, they fall outside all definitions of hazardous materials within European transport regulations and Regulation (EC) No 1272/2008 on classification, labelling and packaging of substances and mixtures. As with any natural or synthetic material, overheating or combustion of these resins can produce toxic effluents. Additives used with fluoropolymers may also present certain hazards. This guide includes information on the safe handling, processing and use of the materials identified in Chapter II. Although compounded fluoropolymers or resins in the form of micro-powders or lubricant powders will not be dealt with in detail, due to the variety and number of formulations, some general comments will be included in this guide. 1 Chapter I Fluoropolymer Resins Types and Properties 1 - Resins types The main resin types covered by this document are shown below. Some companies may offer other specialist fluoropolymers which are not included in this guide. Reference should be made to the supplier for specific information on the handling of these polymers. ETFE ETFE is a copolymer consisting mainly of ethylene and tetrafluoroethylene, having the formula [(CF2-CF2)x(CH2-CH2)y]n often modified with a small percentage of a third monomer. Depending on the molecular structure the melting range is 210C to 270C. It is melt processible and is supplied in the form of pellets, powder and dispersions. PTFE ECTFE PTFE is a polymer consisting of recurring tetrafluo- ECTFE is a copolymer of ethylene and roethylene monomer units whose formula is chlorotrifluoroethylene having the formula [CF2-CF2]n. PTFE does not melt to form a liquid and cannot be melt extruded. On heating, the virgin resin [(CH2-CH2)x(CFCl-CF2)y]n. It is often modified with a small percentage of a third monomer. Depending forms a clear coalescable gel at 330C+/-15C. Once on the molecular structure, the melting range is processed, the gel point (often referred to as the 190-240C. It is available in the form of translucent melting point) is 10C lower than that of the virgin pellets and as a fine powder. resin. PTFE is sold as a granular powder, a coagulated dispersion/fine powder, or an aqueous PVDF dispersion. Each is processed in a different manner. PVDF is a homopolymer of vinylidene fluoride having the formula [CH2-CF2]n or a copolymer of vinylidene FEP fluoride and hexafluoropropylene having the formula FEP fluorocarbon resin is a copolymer of tetrafluoroethylene and hexafluoropropylene with the [CF(CF3)-(CF2)x(CH2-CF2)y]n. PVDF homopolymers melt at 160 - 175C, copolymers from 135 - 170C, are melt formula [(CF(CF3)-CF2)x(CF2-CF2)y]n. It has a melting processible, and are supplied in the form of powder, point range of 260-270C and is melt processible. It pellets, and dispersions. is supplied in the form of translucent pellets, powder or as an aqueous dispersion. THV THV is a terpolymer of tetrafluoroethylene, PFA hexafluoropropylene, and vinylidene fluoride with the PFA fluorocarbon resin is a copolymer of formula: tetrafluoroethylene and a perfluorinated vinyl ether having the formula [(CF(ORf-CF2)x(CF2-CF2)y]n where [CF(CF3)-CF2)x(CF2-CF2)y(CH2-CF2)z]n. THV is melt processible with melting points from 120 to 230 C ORf represents a perfluoralkoxy group. PFA melts at depending on grade. It is available as pellets, 280C minimum and is melt processible. Some agglomerates or aqueous dispersions. grades are chemically stabilised. It is available in the form of translucent pellets, powder, and as an The suppliers of the above materials and their aqueous dispersion. addresses are listed in Appendix A. Many different grades or classes of each type of fluoropolymer resin are available. Individual suppliers should be 2 contacted for specific product information. 2 - Thermal properties Although fluoropolymers are amongst the most thermally stable polymers known, they will start to decompose slowly when heated to elevated temperatures. There is some contradiction in the published literature as to the exact temperature at which decomposition occurs, reflecting the difficulty in analysing trace element emissions. However, significant decomposition occurs only above the recommended continuous service temperature for the polymer in question. The quantity of effluent evolved remains small until temperatures above the normal processing temperature for the polymer are reached. Rates of thermal decomposition for various fluoropolymers have been determined (PlasticsEurope, 2000) using a thermogravimetric analyser. Samples were heated in dry air flowing at a rate of 30 ml/minute. The temperature was increased at 20C/minute from room temperature to the test temperature. The samples were then held at constant temperature for one hour and the weight loss during the hour was measured (isothermal weight loss). The rate of weight loss was determined for each polymer at a series of three constant temperatures (four for PVDF). The test temperatures used were different for each fluoropolymer and were chosen according to the increasing thermal stability of the polymer. The results are shown in figure 1. Figure 1 : Typical weight loss of Fluoropolymers heated in air 1 ETFE FEP ECTFE 0,1 PVDF THV PTFE PFA 0,01 200 250 300 350 400 450 500 Temperature (C) Weight loss (% per h) 3 It should be remembered that within any one polymer type, different grades will have different thermal stabilities according to properties such as molecular weight. The data presented in Figure 1 give a general indication of the relative thermal stabilities of each polymer. Reference should be made to the polymer supplier if precise information is required on an individual polymer grade. Typical melting points, continuous service temperatures and processing temperatures for the different fluoropolymers are given in Table 1. Table 1 : Typical melting points, continuous use and processing temperatures of Fluoropolymers Polymer PTFE PFA FEP ETFE ETFEECTFE PVDF THV Typical melting point (C) 340 265-310 250-270 210-270 230 160 110-230 Typical maximum continuous use service temperature (C) 260 225-260 205 150 150 140 70-130 Typical processing temperature (C)* 380 360-380 360 310 280 230 200-270 * Note that the processing temperatures in this table are actual polymer temperatures, not oven or equipment temperatures which may be significantly higher. 4 Chapter II Potential Health Effects 1 - Polymer General Toxicology Fluoropolymer resins are known for their high chemical stability and low reactivity. These compounds are of low toxicity, demonstrating little if any toxicological activity. Where toxicological studies have been conducted on fluoropolymers, no findings of significance for human health hazard assessment have been reported. None of the fluoropolymers is known to be a skin irritant or sensitiser in humans. Following grossly excessive exposure to fluoropolymer resin dust by inhalation, increases in urinary fluoride were produced. No toxic effects were observed, however. Many resins are formulated with additives such as fillers, pigments or surfactants, to provide favourable processing, or other characteristics. These additives may present other hazards in the use of the resins. Some of the additives may have regulatory occupational exposure standards. The Safety Data Sheet provided by the resin suppliers should be consulted for specific health information on the additives used in their products. 2 - Health hazards during hot processing and toxicity of decomposition products During the hot processing of fluoropolymer resins, some fume will be generated, even at the temperatures reached during normal hot processing, and it is necessary to assume that the resulting fume will present a potential health hazard. It is essential that adequate ventilation is provided to prevent exposure to the fume in the workplace. (See Chapter IV). The potential consequence of overexposure to the fumes from fluoropolymers decomposing under these conditions is "Polymer Fume Fever". This is a temporary, influenza- like illness with fever, chills and sometimes a cough which lasts approximately 24 to 48 hours. Onset of symptoms may not be apparent for up to 24 hours. As a precaution, any person thought to be suffering from polymer fume fever should seek medical attention. The illness is also associated with exposure to the decomposition products produced by smoking tobacco products, such as cigarettes, which have become contaminated by fluoropolymer resins, even by trace quantities. It is essential that smoking and tobacco products be banned in work areas where fluoropolymer resins are handled. The four main types of product formed in the decomposition of fluoropolymers are fluoroalkenes, hydrogen fluoride, oxidation products and low molecular weight fluoropolymer particulates. In the case of PTFE there are many studies in the published literature and these report a wide variety of results for the reasons outlined above. The general pattern, however, is that the monomer, tetrafluorothylene, is the principal gaseous product formed at the gel point of the polymer (330C). As the temperature increases to around 450C in the presence of air, carbonyl fluoride and hydrogen fluoride become the main products. Also some carbon monoxide may be formed. Carbonyl fluoride hydrolyses rapidly in the presence of moist air to hydrogen fluoride and carbon dioxide. Small amounts of hexafluoropropylene may also be found at these temperatures. The highly toxic perfluoroisobutylene has been detected as a minor product at temperatures above 475C. When the temperature reaches about 800C, tetrafluoromethane begins to form. There is a similar decomposition pattern for other fluoropolymers. Decomposition products tend to form at lower temperatures to a degree which depends on the type and amount of comonomer in the fluoropolymer. (Recent studies indicate the formation of PFIB at 5 temperatures from 360 C for some types of FEP). Health hazards of the most significant decomposition products are as follows: Hydrogen fluoride: The odour threshold of hydrogen fluoride is significantly less than the occupational exposure limits (TWA 1.8ppm - 2000/39/EC). Inhalation of hydrogen fluoride at higher concentrations will give rise to symptoms of choking, coughing and severe eye, nose and throat irritation. In severe cases, and possibly following a symptomless period, fever, chills, difficulty in breathing, cyanosis, and pulmonary oedema may develop, which may lead to death. Acute overexposure to hydrogen fluoride can also result in injury to the liver and kidneys. Carbonyl fluoride: Effects following inhalation, or skin or eye contact with carbonyl fluoride may initially include: skin irritation with discomfort or rash; eye corrosion with corneal or conjunctival ulceration; irritation of the upper respiratory passages; or temporary lung irritation effects with cough, discomfort, difficulty in breathing, or shortness of breath. Respiratory symptoms may be delayed for several hours. Some European Countries apply an occupational exposure standard of 2ppm (8-hour TWA). Carbon monoxide: An odourless gas which reduces the oxygen carrying capacity of the blood, resulting in a decreased capacity for exertion, increased load on the heart and with severe exposure, unconsciousness and death. PFIB (perfluoroisobutylene): PFIB is highly toxic by acute inhalation, and exposure to concentrations above 1ppm for any significant period of time can be fatal. The US ACGIH has ascribed a TLV - Ceiling level of 0.01ppm to PFIB. TFE (tetrafluoroethylene): Tetrafluoroethylene is a colourless, odourless and flammable gas that is very poorly soluble in water. Tetrafluoroethylene has a very low toxicity after acute exposure and has no cardiac sensitisation potential and it has no genotoxic potential in vitro and in vivo. TFE has been found to be carcinogenic in animal studies and under the REACH regulation EC/1907/2006, industry has agreed TFE is a category 2 (GHS Cat.1b) carcinogen A multicentre epidemiology study to study the carcinogenic impact of TFE in humans, if any, involving the major producers of TFE, is ongoing. The US ACGIH has established a TLV of 2.0ppm (8-hour TWA) for TFE. The implications on fluoropolymers safety in use is dealt with in Appendix B. HFP (hexafluoropropylene): Hexafluoropropylene is a colourless, odourless gas that is very poorly soluble in water. Hexafluoropropylene has a low toxicity after acute exposure.HFP is generally considered to be non-gentoxic. Repeated or prolonged exposure to HFP may cause toxic effects to the kidney. The US ACGIH has established a TLV of 0.1ppm (8-hour TWA) for HFP. 3 - Specific hazards of compounds containing pigments and fillers Filled and pigmented fluoropolymers are in widespread use. The normal precautions for handling fluoropolymers need to be observed. Users need to note any additional hazards arising from the fillers or pigments themselves. Although many of the commonly used fillers and pigments have low toxicity, some are abrasive, and may cause irritation in contact with the skin. Avoid skin contact with filled or pigmented fluoropolymers, or inhalation or ingestion of filled or pigmented fluoropolymer dust. Refer to the sections of Fire and Explosion Protection and Specific Hazards with Powdered Materials. (Chapter V). Contact your supplier prior to using filled and/or pigmented fluoropolymers for specific safety recommendations. Before a user mixes pigments, fillers or other materials with fluoropolymers, health and safety information must be obtained from the vendors of the added materials and the compatibility with the fluoropolymer must be checked. 6 Chapter III Processing Hazards and Precautions 1 - Sintering Sintering operations require the use of high temperature ovens in which various amounts of decomposition products are formed. Ovens must have forced ventilation with sufficient air flow to prevent formed gases from entering the work space during oven operation and when the door is opened. Ovens must be regularly maintained and, in particular, gases from the oven must be kept from leaking into the work area. Temperatures in excess of the normal sintering range must be avoided. To assist in this, ovens should be equipped with an independent high temperature cutoff, triggered by an increase of approximately 5% of the desired sintering temperature, in addition to the normal control system. Both systems need to be calibrated at regular intervals. It is important that an interlock is provided which cuts off the heating if the forced ventilation is interrupted. If the oven temperature exceeds the high temperature cut-off setting, the heaters must be switched off and the oven must be cooled to ambient temperature and properly vented before the door is opened. Compounds containing fillers may be more sensitive to decomposition than PTFE alone and may require the use of lower temperatures. When opening sintering ovens after overheating, appropriate personal protection is recommended, e.g., protective clothing, a self-contained breathing apparatus, thermally insulating gloves, safety glasses, etc. 2 - Melt processing Melt processing of fluoropolymer resins at excessively high temperatures or exposing them for extended times at processing temperatures can cause decomposition. Such decomposition may produce gases and generate pressures in processing equipment sufficient to "blow back" through the feed port. If no vent is available for these gases, as in some compression moulding equipment, pressures can develop which may rupture metal parts and possibly cause injury to personnel near the processing equipment. It is considered bad practice to stand in front of an extruder for this reason. The exhaust from the vacuum pump used to control the length of the melt cone during extrusion is likely to contain decomposition products from the fluoropolymer and should be discharged outside the workplace. Corrosion-resistant materials must be used for processing equipment because of the corrosive properties of the melt at high temperatures. Contact your material suppliers for specific machine information. If a fluoropolymer resin melt begins to darken, the colour change is an indication that thermal degradation has begun. If an operator believes that thermal degradation is occurring, zone temperatures should be lowered and the fluoropolymer resin purged from the equipment. Fluoropolymer resins should be processed on equipment having accurate, reproducible temperature control. Temperature cycling should be less than +/- 5C. 3 - Paste extrusion Processing PTFE coagulated dispersion/fine powder resins requires extrusion by a special process, commonly known as paste extrusion. This involves mixing the resin with a lubricant, usually volatile petroleum fraction. The use of combustible and flammable liquids of relatively low flashpoint is a significant potential fire and explosion hazard. Electrically conductive containers must be used for 7 the solvents and equipment should be earthed to reduce ignition sources. In addition, solvents often have health hazards due to inhalation and/or skin contact associated with their use. Appropriate precautions must be taken for the safe use, storage and handling of fluoropolymer resins containing solvent-based lubricants. Follow the recommendations of the lubricant supplier. Removal of the lubricant after extrusion may take place in a separate batch drying oven, or in a continuous oven in-line with the extruder. Appropriate precautions need to be taken to minimise the risk of forming explosive mixtures of lubricant and air, and to prevent ignition. With inline operation, the drying oven is immediately followed by a high temperature sintering oven, and there is the possibility that incorrect operation would cause flammable vapour to be carried into the sintering zone, where it would almost certainly ignite. It is essential to have fire extinguishing equipment available. For small fires, portable carbon dioxide extinguishers are usually adequate, but a permanent installation, which can rapidly fill the complete oven with carbon dioxide in the event of a large fire is advisable. Ventilation of the drying and sintering operations requires the same precautions as described earlier in this section for operation of sintering ovens in the work place. 4 - Coating/Impregnation The processing of fluoropolymer aqueous dispersions normally requires a heating process to remove water and surfactant prior to sintering the fluoropolymer. Some surfactants and their degradation products are flammable and may have specific irritant or other adverse affects on health. The oven used to remove these products must be provided with forced ventilation to prevent a hazardous build-up of vapour. Furthermore there may be significant build up of decomposition products in the ovens. Protective equipment should be worn when removing such deposits. Contact your dispersion supplier for specific information. Some coating systems may contain organic solvents in addition to the fluoropolymer resins. These solvents may be combustible and flammable liquids of relatively low flash-point and therefore present a potential fire and explosion hazard. In addition, the solvents often have health hazards due to inhalation and/or skin contact associated with their use. Appropriate precautions must be taken for the safe use, storage and handling of fluoropolymer resins containing dispersion medium or additives, following the recommendations of the supplier. Fluoropolymer dispersions are made using fluoropolymer processing aids (FPA). In most cases the levels of FPA have been reduced to trace amounts. 5 - Machining Grinding, sawing, and machining fabricated shapes of fluoropolymers are performed routinely in fabricators' shops. All normal high-speed machining techniques can be used provided the tools have sharp cutting edges. Coolants are recommended to improve production rates and quality, and they will serve to control any tendency toward overheating, eliminating the need for special ventilation. Dust generated by machining products manufactured from fluoropolymer resins are generally considered a "nuisance dust". It is commonly recommended that occupational exposure limits of 10mg/m3 total dust, 5 mg/m3 respirable dust be used. However, machining products manufactured from resins which contain fillers, pigments, or other additives may produce hazardous dusts due to the presence of fillers and other additives. Consult the additive supplier or Safety Data Sheets (SDS) for further information on additives. 6 - Welding Special precautions are necessary when welding fluoropolymer parts to one another. Hydrogen fluoride is generated in significant quantities by the process. Complete skin and eye protection is necessary as well as the appropriate respiratory protection which may include the use of self-contained breathing apparatus. 8 7 - Soldering, Welding and Melt Stripping of Metals coated with Fluoropolymers 8 - Cleaning and Maintenance of Process Equipment Major uses for fluoropolymers are in electrical insulation. In many cases, soldering or use of a heated element to remove insulation or the coating from a metal substrate are routine operations. The combined effects of temperature, quantity of resin, exposure time, and ventilation conditions are important factors for worker comfort and safety. The use of local fume hoods as described in the ventilation section is strongly recommended. Direct application of welding arcs and torches using temperatures above 400C can quickly destroy the usefulness of parts made from fluoropolymers. During such treatment, toxic fumes are liberated, and it is advised to remove all fluoropolymer parts before such treatment. Where removal is not possible, such as in welding or cutting coated parts, mechanical ventilation should be provided to prevent exposure to fumes and personnel protection should be worn. Cleaning and maintaining process equipment components (dies, screen packs, screws, etc.) may involve pyrolysis of residual polymer. As much polymer as possible should be removed (e.g. with a brass brush) before finally burning off. Appropriate hoods should be designed to completely exhaust the gases and particulates that are formed. Reference should be made to Chapter IV for additional information on ventilation. Processing vessels and ovens can be considered as confined spaces and special procedures may be required before allowing personnel access for cleaning. 9 - Spillage Fluoropolymers spilled during handling should be cleaned up immediately and appropriate measures should be taken to prevent the creation of a slippery surface. It is advisable that some sort of antislip flooring and steps should be provided in areas where fluoropolymer resins are regularly handled. Slippery surfaces in walking and working areas pose an increased accident risk. 9 Chapter IV Occupational Hygiene 1 - Ventilation As with most polymers, minute quantities of residual gases may diffuse from the resins, even at room temperature. Therefore, as a matter of good occupational hygiene practice, resin containers should be opened and used only in well ventilated areas. Personnel should be instructed to minimise exposure whilst opening and closing containers. Ventilation is required in hot processing operations where fumes may be released, such as drying, extrusion or sintering. In addition it may be required in "cold" operations such as spray coating, blending and high speed grinding or machining to remove aerosols, mists or particulates. Appropriate exhaust ventilation should be selected dependent on the nature of the process involved and local conditions. Proprietary systems may be available for specific activities, eg., spray booths or fume cup boards and where possible these should comply with relevant standards. In other cases local extract ventilation may have to be specifically designed for the process concerned. In either case, ventilation systems should always be designed or supplied by competent extract ventilation specialists. The design of the extraction hood, ducting system and fan should be based on a good understanding of the emissions involved. This may include environmental and process conditions which could affect the emission or cause a secondary emission. It will be necessary to specify the required capture velocity at the point of the emission sufficient to ensure adequate control. This is related to the velocity of the emission and any associated air movements or currents. Good design of the hood (e.g., slots, rim ventilation, annular extraction, booths and cabinets) is important for efficient elimination of off-gases. It should be designed taking into account all the emission characteristics. The most effective hoods are those which enclose or contain the emission. More air is required as the level of containment decreases. The required extraction volume to give an adequate velocity at the point of emission should be determined. It is possible to calculate this using published formulae. The ducting, fan and air cleaner can then be correctly designed to match the extraction volume requirements. Further ideas on design and information can be obtained from your resin supplier. As described elsewhere in this guide toxic gasses may be generated during the processing of fluoropolymer resins. Processors are advised to allow sufficient degassing of the product prior to further handling of the finished article. 2 - Personal Protective equipment At processing temperatures fluoropolymer melt can cause severe burns; therefore, appropriate protective measures including safety glasses, gloves, and arm protection (gauntlets) are recommended during processing. Jewellery should not be worn. If dust cannot be avoided when handling fluoropolymer resin powders or during machining operations, respirators or dust masks should be worn. Refer to your supplier's Material Safety Data sheet for specific guidance. While processing and handling filled compounds, in addition to the dust masks, eye protection and protective gloves may be required. Fluoropolymer dispersions contain wetting agents which should not come in contact with the skin. It is necessary to wear protective gloves and other protective clothing to prevent skin contact when handling these products. The spray application of coatings must 10 be performed in suitably equipped spray booths. Depending on the efficiency of this system, operators may also be required to wear goggles, respirators and gloves. It is recommended that the spray booth be equipped with a water bath to precipitate the spray mist. See Chapter VI for disposal guidance. 3 - Personal hygiene In regular training of personnel it is important to emphasise that tobacco products must not be carried or used in work areas. Smoking tobacco contaminated with even very small amounts of fluoropolymer resin can cause "polymer fume fever" by inhalation of the effluents. See "Health hazards during hot processing" in Chapter II. To prevent traces of fluoropolymer resin powders being carried out of the work area on clothing, it is advised that personnel should store their work clothing separately from their normal clothing (double locker or separate changing rooms). Personnel should be provided with adequate washing facilities and required to use these regularly. Further guidance on the handling of dispersion products can be found in Appendix C. 11 Chapter V Fire and Explosion Hazards 1 - Ignition characteristics The self-ignition temperatures (SIT) of solid PTFE products measured in accordance with ASTM D 1929 are in the range of 500C to 560C and hence are far above those of materials capable of sustaining combustion when the ignition source is removed. For comparison the SIT of cellulose containing materials such as wood, paper, board etc. is 240C to 245C. All fire and flammability tests show that fluoropolymers are amongst the most difficult plastics to set on fire. If a flame is applied to the surface of these polymers it will ignite because of the formation of gaseous decomposition products. However if the flame is removed combustion ceases. During the combustion of fluoropolymers little or no smoke is produced. Care should be taken however to avoid the inhalation of smoke generated by all combusting materials, including fluoropolymers. The exceptionally low flammability of the fully fluorinated fluoropolymers is also indicated by their limiting oxygen index (LOI) measured in accordance with ASTM D 2863. The oxygen index is the minimum concentration of oxygen of a mixture of oxygen and nitrogen that will just support flaming combustion of a material The LOI for fully fluorinated polymers such as PTFE, PFA and FEP is greater than 95%. For polymers which are note fully fluorinated, the LOI is between 30 and 60% depending on the molecular structure. This compares with values of around 20% for cellulose products. PTFE does not form flammable dust clouds under normal factory conditions. PTFE and other fluoropolymer powders fall into dust explosion class STO. 2 - Extinguishing agents Fire and combustion toxicity Fluoropolymers are normally a minor component of most structures. They have a very high ignition temperature in comparison with most other organic materials and it is difficult to sustain a flame. This means that it is unlikely that fluoropolymers will be involved in a fire on their own. It is important to take account of the properties of all materials present in fires when assessing the potential health consequences of exposure to the combustion products evolved. If fluoropolymers are involved in a fire, the hazardous gases and vapours produced include hydrogen fluoride, carbonyl fluoride, carbon monoxide, low molecular weight fluoropolymers and particulates. The toxicology of the combustion product has been investigated extensively, and it has been shown that particulates have potential, under certain laboratory conditions, to be extremely toxic. A more detailed assessment of the combustion toxicology of fluoropolymers is given in Appendix D. In a real fire situation it is not likely that any fluoropolymers present will contribute to the overall toxicity of the combustion products by virtue of the normally expected thermal degradation products (e.g. hydrogen fluoride) and will not dominate the overall toxicity due to the production of extremely toxic products. 12 3 - Extinguishing agents 5 - Explosion protection All extinguishing agents such as water, carbon dioxide, dry powder, foam are suitable for fires involving fluoropolymers. Extinguishing agents which are most appropriate to the surrounding materials, location of the fire and the stage of fire development should be used. For established fires water is the preferred extinguishing agent. 4 - Fire fighting In the paste extrusion process flammable lubricants are normally used. The possible risk of fire or explosion through the formation of flammable vapour/air mixtures should also be taken into account. Similarly with PTFE powder compounds containing carbon and metal powders, measures to prevent static charge accumulation should be taken if dust/air mixtures are likely to occur in operations such as mixing. Fluoropolymers are difficult to ignite and will not themselves sustain a flame so will make no contribution to the start or spread of fires. However if they are involved in a fire they can decompose and may contribute to the toxicity of the fire gases formed. Chapter II and Appendix D provide more information. It is therefore important to take normal industrial fire precautions in factories processing fluoropolymers to reduce the risk of a fire. Since the possibility of a fire starting and spreading can never be completely ruled out the relevant local authorities should be advised of the chemical nature of the fire gases. In the event of a fire, the fire service should be warned of the possibility of the presence of toxic and corrosive gases. Self-contained breathing apparatus must always be worn when extinguishing fires or when conducting cleaning up operations in the presence of fire effluent. Suitable measures should be taken to prevent exposure of members of the public. If individuals are exposed, treatment may be required for inhalation of hydrogen fluoride or the other decomposition products or for skin contact with hydrogen fluoride. It is imperative that firefighters and their equipment are thoroughly decontaminated with a water wash down after fire and smoke exposure. 6 - Specific hazards of Fluoropolymers with powdered materials Finely divided fluoropolymer resins can become extremely combustible in the presence of various metal fines. For example, metal fines (e.g., bronze, aluminium) mixed with powdered PTFE when exposed to high temperatures (above about 370C) may react violently producing fire and/or explosion. Exothermic reactions may occur even at sintering temperatures leading to fires. Other fluoropolymer materials may react at higher or lower temperatures. In addition other materials known to catalyse these reactions include silica, silicium carbide, titanium dioxide, metallic compounds and glass fibres or beads. There may be other materials that can cause such reactions. Contact your materials suppliers for specific information. 13 Chapter VI Environmental Information, Recycling and Disposal 1 - Environmental Information Neither fluoropolymers themselves, nor any of their decomposition products pose any threat to the ozone layer and, consequently, they are not subject to any form of restrictive regulation under the terms of the Montreal Protocol, the US Clean Air Act Amendments (1993) and its labelling provisions, nor proposed legislative measures within the European Union. Difluorochloromethane (HCFC22) is used as a feedstock in the production of the principal monomer TFE used in fluoropolymer manufacture. This substance has an ozone depleting potential of less than 1/20th of that of standard trifluorochloromethane (CFC11). The Montreal Protocol and subsequent regulations, which deal with the control of ozone depleting substances, recognises that substances which are used as chemical feedstocks and destroyed in the process are thus removed from the environment. When used in this way the ozone depleting potential is zero. For this reason the Protocol specifically excludes these substances from its regulation. The European Regulation on substances that deplete the ozone layer (Regulation (EC) No 1005/2009 of 16th September 2009) allows the use of HCFC as feedstock agents with no limitations (article 7). The feedstock substance is defined as "any controlled substance or new substance that undergoes chemical transformation in a process in which it is entirely converted from its original composition and whose emissions are insignificant". 2 - Recycling and Disposal Recycling options are available for all fluoropolymers. Where separation from other materials is not practical, landfill options may be considered as fluoropoly- mers are inert. Incineration of fluoropolymers should only be carried out using approved incinerators (see below). Polymer scrap resulting from the processing of fluoropolymer resins should be recycled where possible. This can be done by the processor himself or on a large scale mainly by specialist multinational recycling companies. At present compounds containing fillers such as glass fibre, carbon or bronze are recyclable to a more limited extent than unfilled fluoropolymers but outlets for recycled compounds are being developed. A list of some of the recycling companies is given in Appendix E. As fluoropolymers are used predominantly in small components of larger finished products it is usually impractical to separate, decontaminate and reclaim the small amounts of fluoropolymers used. The presence of fluoropolymers is not a barrier to recycling the main component. For example steel articles containing small amounts of a fluoropolymer article may be re-smelted and the metal recovered. Industrial fluoropolymer waste may be landfilled in accordance with local regulations. Fluoropolymers are environmentally neutral and are particularly suitable for landfill as they are inert, resistant to high thermal load, do not contain harmful elements which can leach out and do not emit gases. The preferred option for disposal of fluoropolymer aqueous dispersions is to separate solids from liquid by precipitation and decanting or filtering. The solids may be landfilled or incinerated according to local regulations. The liquid filtrate may be discharged to a waste water system in accordance with local regulations or permits. Industrial fluoropolymer waste containing additives such as solvents, primers or thinners must be regarded as special waste. Companies should contact 14 their local waste disposal authorities for details of the relevant waste disposal regulations. Fluoropolymers can be incinerated in special waste incinerators, at a minimum temperature of 800C. Control measures, such as wet scrubbing with alkaline solutions, may be necessary to maintain the emission of hydrogen fluoride below that specified by National or local regulation. Typical emission limits of hydrogen fluoride are 1 to 2mg/m3. This method of disposal is most relevant to disposal where the fluoropolymer is a component of a larger article. 3 - Recycling of Packaging Containers and drums used for the supply of solid grades of fluoropolymer resins may be re-used within their safe working limits for other products but it is essential to ensure that there is no trace of fluoropolymer powder left in the container. Otherwise there is the risk that someone re-using the container could transfer powder onto tobacco products and subsequently suffer "polymer fume fever" (see health hazards during hot processing in Chapter II). Containers used for the supply of fluoropolymer aqueous dispersions may also be re-used but must be carefully washed out to remove all traces of fluoropolymer dis persion. The washings from the container may be discharged to a waste water system in accordance with local regulations and permits. Collection and recycling schemes exist for both plastic and fibreboard containers. Contact your fluoropolymer supplier for details. 15 Chapter VII Food Contact The inertness of sintered fluoropolymers and their resistance to high temperatures have made them a good candidate material for articles to be used in contact with foodstuffs. In Europe the framework regulation (EC) No 1935/2004 covers all materials and articles intended to come into contact with food. This regulation requires that Materials and articles shall be manufactured in compliance with good manufacturing practice so that, under normal or foreseeable conditions of use, they do not transfer their constituents to food in quantities which could: Endanger human health, bring about an unacceptable change in the composition of the food, or bring about deterioration in the organoleptic characteristics. Plastic Materials and Articles coming into contact with food are regulated by the Regulation (EC) No 10/2011 and its amendments, known as the Plastics Implementing Measure (PIM). Under this Regulation plastic articles and materials intended to come into contact with food shall have all their monomers or starting substances, as well as their additives listed in the European Union list of authorised substances, given in Annex I of Commission Regulation (EC) No 10/2011 and are required to comply with an overall migration limit and specific migration limits for the authorised substances used in the production of the polymer. It is the responsibility of the supplier of the finished article to ensure compliance with these limits. (Note that from 1 January 2010 the list of additives in Directive 2002/72/EC relating to plastic materials and articles intended to come into contact with foodstuffs became a positive list.) Commission Regulation (EC) No 10/2011 is applicable from the 1st of May 2011 and repeals the Plastic Directive 2002/72/EC and its amendments. The present Regulation is not applicable to coatings on non-plastic substances. There are only a few countries (Germany, The Netherlands and the USA) which have specific regulations or recommendations for coatings with fluoropolymer resins. In both cases the compliance with the regulations depends on the polymer family and on the grade used. Consequently, users should contact their suppliers to obtain information. This is a very complex area of European legislation which is subject to frequent review. It is important that suppliers of articles intended for food contact seek expert advice to obtain an up-to-date position. In the case of export to the USA, it should be noted that many fluoropolymers have been cleared by the US Food and Drug Administration for use in contact with food. The primary regulations governing fluorocarbon resins are 21 CFR 177.1380, 177.1550 and 177.2510. However additives that are not an essential part of the polymerisation process must be cleared under an appropriate food additive regulation such as 21 CFR 175.300 or 21 CFR part 178, or be subject of a prior sanction, food contact notification, be considered GRAS (generally recognised as safe), or not be reasonably expected to become a component of food. For limitations and details it is necessary to refer to your supplier. 16 Chapter VIII Medical Applications Fluoropolymers have historically been developed for industrial applications. Due to their excellent properties they also have been used over a number of years in a wide range of medical applications. A variety of devices containing fluoropolymers have been evaluated. Various small and bigger PTFE tubes, different small articles and films are in use mainly for short term applications. However to our knowledge, no fluoropolymer producer has ever developed a fluoropolymer product for specific medical use. There is no general regulatory approval of a fluoropolymer resin for medical uses. Each specific type of medical product must be submitted to appropriate regulatory authorities for approval. Manufacturers of such articles or devices should carefully research medical literature, test and determine whether the fluoropolymer is suitable for the intended use. They must obtain all necessary regulatory agency approvals for the medical product including any raw material components. Examples of both successful life saving cases and inappropriate devices can be found in the published medical literature. For EU member countries, the European Directive on Medical Devices should be followed as well as any applicable national regulation. The PlasticsEurope fluoropolymer suppliers have policies restricting sales of their materials for medical applications. Before investing resources in testing and seeking regulatory approval for a medical device that incorporates a fluoropolymer, users should consult their supplier to ensure continued access to the material. 17 Appendix A Addresses of fluoropolymer producers in PlasticsEurope AGC CHEMICAL EUROPE, LIMITED Hillhouse Int., P.O. Box 4 Thornton Cleveleys Lancashire FY5 4QD United-Kingdom Tel: Fax: Web: www.agcce.com Email: M@agcce.com ARKEMA Rue d' Estienne d'Orves 92705 Colombes CEDEX France Tel: +33 (i) 49 00 8o 8o Fax: +33 (i) 49 00 83 96 Web: www.arkema.com Guest member: DAIKIN CHEMICAL EUROPE Immermannstrasse 65D 40210 Dusseldorf Germany Tel: +49 211 179 22 50 Fax: Web: www.daikinchem.de www.daikin.com DUPONT DE NEMOURS INTERNATIONAL 2, Chemin du Pavillon P.O. Box 5o CH-1218 Le Grand-Saconnex (Geneve ) Switzerland Tel: +41 (22) 717 51 11 Fax: +41 (22) 717 51 09 Web: www.dupont.com 18 DYNEON GmbH Industrieparkstrasse 1 84508 Burgkirchen Germany Tel: Fax: Web : www.dyneon.com www.dyneon.eu HEROFLON S.R.L. Via A de Gasperi 4 25060 Colleberato (Brescia) Italy Tel: +39 030 25 20 211 Fax: +39 030 25 11 495 SOLVAY SPECIALTY POLYMERS ITALY S.p.A Via Lombardia 20 20021 Bollate (Milano) Italy Tel: +39 (O2) 38 35 1 Fax: +39 (O2) 38 35 z6 14 Web: www.solvaysolexis.com Appendix B PlasticsEurope statement on TFE monomer toxicology - Effect on fluoropolymer safety in use Tetrafluoroethylene (TFE) has been shown to cause cancer in rats and mice exposed to relatively high concentrations of TFE vapour for their lifetime. Various types of tumour in kidney, liver and the haematopoietic system were seen. Studies comparing the metabolism of TFE in humans and animals, suggest that the risk for developing some of these tumours is lower for humans than for rats and mice. A multicentre epidemiology study involving the major producers of TFE is ongoing. TFE is used as a building block in the manufacture of solid plastic materials such as PTFE and other fluoropolymers, which are normally sold as powders, granules or aqueous dispersions to specialist processors who convert these polymers into finished articles. Tests on solid fluoropolymers sold by PTFE manufacturers to processors have failed to detect TFE. Aqueous dispersions may contain traces (less than 1 ppm) of residual TFE. High temperature processing of fluoropolymers may generate low levels of TFE. However effective ventilation, which is currently required to prevent acute health problems such as polymer fume fever or exposure to HF, is sufficient to prevent any potential exposure to TFE. Analysis of fabricated articles shows no detectable TFE: this applies to articles made from both solid fluoropolymers and aqueous dispersions processed under recommended conditions. 19 Appendix C Safe handling of fluoropolymer dispersions The handling hazards for fluoropolymer dispersions are mainly determined by the stabilising surfactant used in the product. Please refer to individual safety data sheets for specific handling information. In general it is advisable to avoid skin and eye contact and ingestion. When processing dispersions refer to the chapters II & III on thermal decomposition of fluoropolymers. Do not discharge dispersions to lakes, streams or waterways. Disposal to water will produce a milky appearance. The fluoropolymer component is not toxic. The stabilising surfactants have varying ecotoxicity profiles and users should contact their supplier for more detailed ecotoxicological information on their particular product. Preferred options for disposal are discussed in Chapter VI. Fluoropolymer polymerisation aids (FPAs) In previous editions of this guide Appendix C covered the safe handling of fluoropolymer dispersions containing FPAs - fluorinated surfactants such as ammonium and sodium perfluorooctanoate. The member companies of PlasticsEurope have implemented technologies to significantly reduce FPAs in their dispersion products. FPA specific safety measures are therefore no longer required for dispersions supplied by PlasticsEurope members. However, dispersions are offered by producers outside PlasticsEurope that have not implemented these technologies. If those products are used, the suppliers should be contacted for the appropriate safe handling instructions. 20 Appendix D The inhalation toxicity of combustion products of PTFE and similar fluoroploymers A considerable number of studies have been conducted to investigate the toxicity of the combustion/thermal degradation products of PTFE. Prior to 1982 it was considered that the major products, including hydrogen fluoride and carbonyl fluoride, were responsible for the toxic effects seen in rats exposed to the evolved combustion products of PTFE, toxicity being approximately ten times greater than for the combustion products of wood. However, in 1982 Levin et al., using the newly developed National Bureau of Standards small-scale test method for assessing the toxicology of combustion products, reported an unexpectedly high toxicity when testing PTFE. They found an LC50 of 0.045mg/l for PTFE products as compared with 20-40 mg/l for a standard sample of wood (Douglas Fir).This unexpected result could not be explained in terms of the expected combustion products and led to an extensive investigation of this phenomenon by a number of laboratories. A number of reviews of these studies were presented at the Interflam '90 conference (Purser, 1990, Fardell, 1990; Clarke van Kuijk, et al., 1990a; Clake, Seidel, et al., 1990b) which, together with several other publications (Warheit et al., 1990; Lee and Seidel, 1991), provide an interesting explanation for the extreme toxicity associated exclusively with thermal degradation products of PTFE or similar perfluoropolymers. In brief, there are a few critical parameters essential for expression of extreme toxicity. Thermal degradation must occur under non-flaming conditions. Experimental design must allow for recirculation of evolved fume through the combustion area, as in the NBS apparatus, or for rapid exposure to freshly generated fumes, as described by Warheit et al., (1990). The particulate phase of the degradation products is clearly responsible, specifically with regard to the size of the particles evolved. When fumes are generated in a temperature range of approximately 450-800C the particles generated are extremely fine, typically less than 0,05 microns and in an apparatus such as the NBS chamber, will be confined to a relatively small volume. They will rapidly undergo thermal coagulation producing fume particles of greater size and lower number concentration and which will spread throughout the 200-litre exposure chamber. As they recirculate through the furnace they may undergo de-aggregation and dispersal, stabilising at the ultrafine particle size and producing extreme toxicity. In a dynamic system such as that described by Warheit et al., (1990), if exposure is effected before coagulation occurs extreme toxicity is also seen but if coagulation is allowed to occur initially the toxicity is reduced considerably. It has been suggested that the specific requirement for fresh or recycled fume to induce extreme toxicity may also relate to free radical production during pyrolysis and indeed relatively stable alkylfluoroperoxy radicals are reported to have been detected (Fardell, 1990). Nonetheless, the most critical factor appears to be the size of the particles when inhaled. This dictates the proportion that will deposit in the alveolar region where damage is seen, but possibly more importantly, the interaction of the particle with the epithelial cells. There is increasing evidence that ultrafine particles of sizes less than approximately 0,05 microns of even highly inert materials such as titanium dioxide are substantially more toxic to the lung compared with larger particles (Oberdorster 1990, Johnston 1996) due to direct penetration into 21 or reaction with the epithelial cells. The extreme toxicity of PTFE pyrolysis products is consistent with this picture. The toxicity of PTFE pyrolysis products is influencing decisions by regulators on many potential uses of PTFE due to direct extrapolation to real, large scale fire scenarios where humans may be exposed to combustion products. However, caution must be exercised in such extrapolations. The only time that extreme toxicity has been demonstrated has been under closely controlled experimental conditions. It is not inconceivable that such conditions could be reproduced in a real fire but other factors must also be taken into consideration. Firstly, experimental studies have shown effects only when using PTFE or fluoropolymers alone. A number of studies have been conducted on "mixed" materials, for example where PTFE was combusted with wood (Purser, 1990), and extreme toxicity was not observed. This is more appropriate to real fires which generally involve mixtures of materials, the smoke particles from which will be larger in size and will tend to scavenge and hence detoxify fine PTFE particles. Secondly, in full scale fire tests using a number of potential ignition sources for perfluoropolymer-insulated cables (Clarke, van Kuijk, et al., 1990b), the toxicity reported in rats exposed to the combustion products was consistent with that expected of the principal toxic agents carbon monoxide, hydrogen fluoride and carbonyl fluoride with no indications of extreme toxicity. Therefore, it is more likely in a real fire situation that any fluoropolymers present will contribute to the toxicity by virtue of normally expected thermal degradation products but will not dominate the toxicity due to production of extremely toxic products. 22 Appendix E Addresses of recycling companies MIKRO-TECHNIK GMBH & CO Betriebe KG 63886 Miltenberg Germany Tel: +49 9371 4005 92 Fax: +49 9371 4005 70 Web: www.mikro-technik.com SHAMROCK TECHNOLOGIES bvba Heersterveldweg 21 B-3700 Tongeren Belgium Tel: +32 12 45 83 30 Fax: +32 12 45 83 40 Web: www.shamrocktechnologies.com UNITED POLYMER MIXERS Ramgatseweg 14 NL-4941 AM RAAMSDONKVEER The Netherlands Tel: Fax: 23 References Levin, B.C., et al "Further Development of a Test Method for the Assessment of Acute Inhalation Toxicity of Combustion Products" National Bureau of Standards (US), NBSIR 82-2532 (1982) Lee, K P and Seidel, W C. (1991). Pulmonary response of rats exposed to polytetrafluoroethylene and tetrafluoroethylene hexafluoropropylene copolymer fume and isolated particles. Inhalation Toxicology, 3, 237-264. Clarke, F B, van Kuijk, H, Valentine, R, Mokovec, G T, Seidel, W C , Baker, B B, Kasprazak, D, Marovec, G J, Bonesteel, J K , Janssens, M and Herpol, C H (1990). The inhalation toxicity of smoke from fires involving perfluoropolymers : full scale fires, proceedings of Interflam '90, 287-295. Clarke, F B , Seidel,W C, SchererV Jnr, Clins D Jnr, Olsen, A and Bonesteel, J. (1990). Formation, identity and coagulation of fluoropolymer-derived smoke aerosols. The relationship between aerosol behaviour and observed toxicity of fluoropolymer smoke. Proceedings of Interflam '90, 297-304. Fardell, P. (1990). UK studies of the toxic potency of PTFE in fire. Proceedings in Interflam '90, 257-271. Oberdorster, G, Ferin, J, Finkelstein, J, Soderholm, S and Gelein R. (1990). Ultrafine TiO22 particles as a model for studying overload related mechanisms. J. Aerosol Med. 3, 79. Purser, D A. (1990). Recent developments in understanding of the toxicity of PTFE thermal degradation products. Proceedings of Interflam '90, 273-286. Warheit, D B, Seidel, W C, Carakostas, M C and Hartsky, M. (1990). Attenuation of perfluoropolymer fume pulmonary toxicity : effects of filters, combustion methods. and aerosol age. Exp. Mol. Path. 52, 309-329. Johnston C J, Finkelstein J N, Gelein R and Oberdorster G (1996). Characterization of early pulmonary inflammatory response associated with PTFE fume exposure. Toxicology and applied pharmacology, article 0208, academic press, May 1996. 24 PlasticsEurope AISBL Avenue E. van Nieuwenhuyse 4/3 ii6o Brussels - Belgium Phone +32 (0)2 675 32 97 Fax +32 (0)2 675 39 35 @plasticseurope.org www.plasticseurope.org Produced by the members of the Fluoropolymers Committee of PlasticsEurope. 2012 PlasticsEurope. All rights reserved. )ir( Plastics The Material for the 21st Century Pilot-Scale Fluoropolymer Incineration Study: Thermal Treatment of a Mixture of Fluoropolymers under Representative European Municipal Waste Combustor Conditions Dr. Gehrmann, Hans-Joachim1; Dr. habil. Bologa, Andrei1; Dr. Aleksandrov, Krasimir1; Bergdolt, Philipp1; Dr. Taylor, Philip2; Dr. Schlipf, Michael3; Dr. Ameduri, Bruno4; Gunasekar, Priyanga5; Kapoor, Deepak5 1 Institute for Technical Chemistry (ITC) at Karlsruhe Institute of Technology (KIT); 2 P Taylor & Associates, LLC, USA; 3 Pro-K, Germany; 4 ICGM, University of Montpellier, France; 5 Gujarat Fluorochemicals Significance and Motivation A recent study by Conversio, a consultancy based in Germany, has shown that at its endoflife approximately 85% of all fluoropolymers end up in wastetoenergy recovery incinerators. A subsequent question of regulators was: Do fluoropolymers get fully incinerated without any formation of short chain or long chain PFAS? A recent project executed by the Karlsruhe Institute of Technology (KIT) in cooperation with Socit Gnrale de Surveillance (SGS) was conducted to assess the same. Experimental Parameters Main applications of the four highest volume fluoropolymers (PTFE, PVDF, PFA and FKM) representing more than 80% of commercial fluoropolymer production based on data from ProK (German association of polymers processors) were considered. Postuse samples from these applications were incinerated as a mixture under standard operating conditions for municipal and industrial waste incineration. Figure 1 presents the experimental conditions. Experiments were conducted under two sets of conditions over a period of 9 days. The first experiments were conducted at a process setting of 860C and 2.0 s residence time. These experiments were conducted in three stages. Initially, background tests were performed using natural gas and 100 kg/h wood chips. This was followed by the same fuel conditions with the addition of 320 g/h of fluoropolymer. The final test involved switching back to background conditions. The duration of each of these tests ranged from 9 - 13 hrs. A second set of experiments was conducted at a process setting of 1100C and 2.0 s residence time. These tests were conducted in the same sequence as the first set of tests. The feed rates for the wood chips and the fluoropolymer mixture were identical to the tests at 860C and 2.0 s residence time. The test duration for this second set of tests also ranged from 9 - 13 hrs. 1|Page Figure 1: Experimental setup The fluoropolymers were fed as a mixture at relative proportions that correspond to the mass fractions sold in the European marketplace. These data are also shown in Figure 1. Suspension and emulsion polymerized PTFE application samples represented about 70 mass percent of the fluoropolymer feed rate. The main operational parameters for the two sets of tests are summarized in Figure 2. The temperature of the flue gas outlet exiting the rotary kiln was in the range of 800900C. The temperature of the flue gas postcombustion chamber outlet was very close to the targets for these tests (860and 1100C in the combustion chamber for setting 1 and 2, respectively). The O2 and CO measurements for setting 1 and 2 varied somewhat. For setting 1, the values were 11.2 vol % dry and 0.2 mg/m3, respectively, while for setting 2 the O2 measurements were somewhat lower (7.0 % with an increase in the CO concentration (1.2 mg/m3). The water vapor concentration as measured in the boiler exit ranged from 6.2% in setting 1 to 8.49% in setting 2. 2|Page Rotary kiln combustion chamber mass flow wood chips main air mass flow heating oil volume flow natural gas volume flow combustion air inclination rotation speed temperature flue gas outlet thermal power volume flow natural gas to burner D4.1 sum of volume flow combustion air to burner D4.1 volume flow natural gas to burner D4.2 sum of volume flow combustion air to burner D4.2 residence time temperature flue gas post-combustion chamber outlet (with control) CO (level E2) O2 (level E2) thermal power total thermal power rotary kiln and post combustion chamber volume flow O2 CO water vapour unit kg/h mN3/h kg/h mN3/h mN3/h rev p.m. C MW setting S1 RUN 1, 2, 3 98 setting S2 RUN 4, 5, 6 98 418 423 61 46 4 4 872 753 2 0.2 0.4 800 - 900 1.1 0.9 mN3/h mN3/h mN3/h mN3/h s C mg/m3 Vol.-% dry MW MW mN3/h Vol.-% dry mg/m3 Vol.-% wet 22 35 671 429 22 35 671 428 2 860 1095 0.2 1.2 11.2 7.0 0.46 0.72 1.59 1.67 3958 11.9 1.35 6.20 3238 9.0 1.64 8.49 boiler / fluegas Figure 2: Main operational parameters at two experiments There were multiple sampling locations for this study. Flue gas was sampled near the exit of the combustion chamber (location 1), at the exit of the boiler (location 2), and at the entrance to the stack (location 3), while liquids and residues were also sampled and analyzed after each RUN (see Figure 3, Test facility sampling locations). The test facility BRENDA comprises a rotary kiln with a postcombustion chamber, a boiler for heat recovery and a flue gas cleaning system, which complies with German emission regulations (17 BImschV). The thermal power of the rotary kiln is of maximum 1.5 MW, while that of the postcombustion chamber is about 1 MW, which results in a total thermal output of BRENDA of maximum 2.5 MW. The fluoropolymers mixture after blending with wood chips and consequent weighing was delivered to the rotary kiln. To secure optimal combustion conditions, natural gas and heating oil were supplied additionally to the rotary kiln, while the post combustion chamber was supplied with natural gas only. The mass flow of the fluoropolymers mixture was set at 320 g/h, which corresponds to a pure Fluorine mass flow of 230 g/h. This level increases the fluoropolymer ratio to fuel, while at the same time keeps the Fluorconcentration below the total halogen limit of 1%, as set by the legislature. The combustion gases of the rotary kiln enter the post combustion chamber (PCC). It contains two natural gas burners staggered in an antiparallel manner, with a slight shift to each other. The temperature and the residence time in PCC were adjusted mainly with the help of the above mentioned burners, supported by a slight shift of about 200 kW into the post combustion chamber. 3|Page Figure 3: Test facilityBRENDA at KIT The minimum residence time is calculated according the methodology of the German Technical Supervision Agency ("TV") from 2007. The data which were published in the report were recalculated and then adapted to the operational conditions in this study (Setting 1 and Setting 2). Figure 4 presents the layout of the post combustion chamber with the geometry relevant for the determination of the residence time. Fig. 4: BRENDA layout with details relevant for the residence time 4|Page Table 1 shows the detailed values for the design of the settings. The volume flow of the required flue gas amount to reach the two seconds was calculated with a target value search. Table 1. Parameters calculated for the residence time in the PCC PFAS Project, Level E1b setting 1 Start post combustion zone [m] 1 meter above 7.65 the burners Temperature in the post combustion chamber 860 (PCC) [C] setting 2 7.65 1100 Volume flow VPCC [mN3/h wet] after boiler 3947 3257 Cross section PCC [m2] Volume flow VPCC [m3/h] Height h [m] level E1b Residence time from start PCC zone to level E1b [s] 2.82 16,382 10.88 2.00 2.82 16,382 10.88 2.00 The two seconds are the residence time of flue gas from start of postcombustion zone until PFAS sampling point E1b, calculated with calibrated temperature measurements on the top of post combustion chamber (PCC). The flue gas was sampled for both shortchain and longchain PFAS in addition to organic and inorganic fluoride. Volatile organic C1C4 fluorocarbons were also sampled using a tedlar bag at all three sampling locations. At location 2, gasphase HF was measured in near realtime using a tunable diode laser (TDL). The purpose of the three gasphase sampling locations was to assess the potential emissions of PFAS at different locations in the system and to use this data to assess potential sources of PFAS in this system. PFAS sampling of residues and liquids is also shown in Figure 3. In addition to these three sampling points, flue gas scrubber water upstream of the SCR catalyst was collected and analyzed for PFAS. Table 2 provides a list of analytes measured in this study and the Limit of Quantification (LOQ). In addition to PFAS and fluoride ion, volatile C1C4 fluorocarbons and trifluoroacetic acid (TFA) were also measured. The C1C4 fluorocarbons were measured by gas chromatography coupled to mass spectrometry (GCMS). Adsorbable organic fluoride (AOF) was measured using Combustion Ion Chromatography (CIC) and inorganic fluorine in impinger samples were measured by Ion Selective Electrode. TFA was measured using Ion chromatography (IC) and long chain PFAS from impinger samples were measured using Ultrahigh Performance Liquid Chromatography coupled to tandem Mass Spectrometry (UPLCMS/MS). HF was also measured at the postcombustion zone location using TDL spectroscopy. Appendix 1 presents a list of longchain PFAS measured in this study. 5|Page Table 2. Analytes and reporting limits Analyte Volatile C1C4 Compounds (CF4, CHF3, C2F6, C2HF5, CF2=CFCF3, cyC4F8) Adsorbable Organic Fluorine Inorganic Fluorine Trifluoroacetic Acid PFAS (see Appendix for list of compounds measured) LOQ 530 ug/m3 2 ug/L 0.1 ug/L 0.02 ug/L 0.02 ug/L Note: LOQ for AOF, Inorganic fluorine, TFA, and PFAS are for aqueous samples. Experimental Results Fluorine Recoveries Fluorine recoveries ranged from 69 to 84% using the TDL (at sample location 2). The variability in these data from run to run was low. In contrast, the impinger data analyzed at the same sample location showed about 10 to 20% lower fluorine recoveries. The data are summarized in Table 3. The TDL data provide strong evidence for complete mineralization of fluoropolymer feed mixture. Run Settings Table 3: Fluorine Recovery (TDL Measurement) HF (TDL) volume flow @standard wet conditions volume flow @270 C mg/mB3 wet Gas [mN3/h] [mB3/h] Fluorine g/h Fluorine Recovery % 860C, > 2s, oil + 2 nat. gas + wood chips + 230 g/h F 1100C, > 2s, oil + 5 nat. gas + wood chips + 230 g/h F 23.50 23.93 25.80 25.44 26.58 26.93 3,956 3,952 3,943 3,299 3,231 3,217 7,866 175.64 76% 7,859 178.62 78% 7,841 192.16 84% 6,560 158.53 69% 6,424 162.23 71% 6,397 163.64 71% Longchain PFAS A large majority of the PFAS measured in impinger samples were near or below reporting limits (>98% of data collected at 860C and >96% of data collected at 1100C). Table 3 presents PFAS data for 4 compounds where measurements exceeded reporting limits in several cases. Of particular note is a HFPODA measurement which exceeded reporting limits by a factor of 47. Maximum PFBA, PFBS, and 6:2 FTS measurements exceeded reporting limits by much lower factors, ranging from 9 - 12. These data was reanalyzed to assess the veracity of data. The results are also presented in Table 4. The results indicate that the high measurement values for HPFODA could not be reproduced. The results for PFBA and PFBS were also lower when reanalyzed. The lack of reproducibility of data and the lower 6|Page measurement values upon reanalysis suggests that crosscontamination is a possible reason for high measurement values for HPDODA, PFBA, and PFBS in the initial analysis. PFAS analyses of wastewater and ash residue samples indicated a large majority of the samples were below reporting limits. One notable exception was a deslagger water bath sample where HFPODA was a factor of 16 above the report limit. Initial Analysis PFAS Compound PFBA PFBS 6:2 FTS HFPODA Table 4. PFAS Analysis of Impinger Samples RL (ng/m3) 2.8 1.4 1.4 1.4 # > RL 5 22 17 31 ng/m3 (max) 35.8 19.5 12.5 66.3 ReAnalysis PFAS Compound PFBA PFBS 6:2 FTS HFPODA RL (ng/m3) 2.8 1.4 1.4 1.4 # > RL 0 7 11 16 ng/m3 (max) 2.8 10.7 16.2 25.2 Note: For each data set, the total number of measurements equal 54: 27 for each combustion condition. Shortchain PFAS TFA was nondetect for all 76 impinger samples analyzed, at a reporting limit of 14 g/m3 (ppb). Volatile Fluorocarbons (FC) Tetrafluoromethane (CF4) was the only volatile FC detected in the GCMS analysis. Values of CF4 at stack were near detection limits (2027 g/m3) and detected in 2 of 14 samples. The results are considered questionable because CF4 was only detected in one postcombustion sample. There is no plausible reason for larger CF4 values downstream of the combustion unit unless a noncombustion source is considered. Discussions There is one prior published pilot-scale study of the combustion of PTFE (Aleksandrov et al. 2019). Combustion tests were performed at two conditions: 870C and 4 s residence time and 1020C and 2.7 s residence time and wood chips were used as the supplemental fuel. The prior study burned 0.3 wt % PTFE. Sampling was performed at a single location, downstream of the waste heat boiler. Thirty-one PFAS compounds were sampled and analyzed (see Table 1 of Aleksandrov et al. for a list of PFAS measured). 7|Page Fluorine recoveries were determined indirectly via IR water vapor measurements. The fluorine recoveries ranged from 56 to 78%, with three of the four tests yielding recoveries less than 70%. Eleven PFAS compounds were detected from the combustion and/or control samples and each at a level above 100 ng/m3 in at least one sample. PFOA was detected in all but one sample and at values as high as 2.7 g/m3 (see Table 3 of Aleksandrov et al.). The current study differs from the prior test in two important ways. The fluorine recoveries in this study were determined from direct spectroscopic measurements and were above 70% in five of the six tests. Secondly, PFAS reporting limits were on the order of 1 ng/m3 or less and a large majority of samples (>98%) were at or below reporting limits. The current study provides strong evidence that incinerating a mixture of fluoropolymers under representative municipal waste combustion conditions leads to complete mineralization of the C-F bonds, no significant emissions of long-chain PFAS, and no significant emissions of TFA or light fluorocarbons such as CF4 or C2F6. The prior study did not provide evidence that the PFAS detected were from sources other than the combustion of PTFE. Conclusions The study clearly demonstrated that fluoropolymers are converted to inorganic fluorides and carbon dioxide. The inorganic fluorides detected were hydrogen fluoride. A large majority of samples indicated that longchain PFAS were below levels of 1 ng/m3 (> 99% of samples associated with 860C condition and > 98% of samples associated with 1100C condition). There were no short chain PFAS detected post incineration. TFA was nondetectable in all samples with a reporting limit of 14 g/m3. The results confirm that fluoropolymers at their end of life when incinerated under representative European municipal incinerators conditions do not generate any measurable levels of PFAS emissions and therefore pose no risk to human health and the environment. The main reason to include fluoropolymers in the EU PFAS restriction proposal was persistence (resistance to degradation in the environment) in the environment. The absence of organic fluorides and more specifically PFAS in tests representative of municipal waste incineration confirms complete mineralization of fluoropolymers and provides critical data in support for exempting Fluoropolymers from the EU REACH PFAS restriction proposal. References TV report from 19th of January 2007: Expert opinion on compliance with and monitoring of the combustion conditions (residence time, temperature) in the afterburning zone of the THERESA test facility at the Forschungszentrum Karlsruhe GmbH Aleksandrow, K, Gehrmann, H-J, Hauser, M., Matzing, H., Pigeon, D., Stapf, D., and Wexler, M., Waste incineration of Polytetrafluoroethylene (PTFE) to evaluate potential formation of per- and Poly-Fluorinated Alkyl Substances (PFAS) in flue gas, Chemosphere, 2019, 226, 898-906. 8|Page Appendices 1. List of long-chain PFAS analytes analyzed in this study 9|Page 10 | P a g e 92 SECTION I.2 Classes of Materials Used in Medicine C. FLUORINATED BIOMATERIALS Fang Liu1 and David W. Grainger1,2 1Departments of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, Salt Lake City, UT, USA 2Bioengineering, University of Utah, Salt Lake City, UT, USA INTRODUCTION Fluorinated biomaterials have a long history of biomedical device and biomaterials applications. These materials are generally carbon-based polymers, liquids, and gas precursors to films that all contain large amounts of chemically bonded fluorine (i.e., perfluorocarbons). Fluorinated materials can be solids, liquids, thin films, coatings or gels, depending on their chemistry, processing,and mode of use. Fluoropolymers in general are thermoplastic polymers analogous to hydrocarbon-based polyethylene (PE), but highly fluorinated; some or all of the hydrogen atoms attached to the PE carbon polymer chain are replaced by fluorine (F) or fluorinated alkyl (perfluorocarbon) side groups. In some cases other halogen atoms (e.g., chlorine, Cl) are also included with F to slightly modify polymer properties (Drobny, 2005). Notably, fluoropolymers show unique propertiesnot achievable by other polymer materials, including chemical inertness, extreme hydrophobicity and solvent resistance, low coefficients of friction, high design tolerances for device fabrication, and temperature resistance (Drobny, 2005). These properties facilitate fluoropolymer use in specific technologies where most hydrocarbon-based materials do not perform well, either in device manufacturing or their applications. Nevertheless,as with all biomaterials, fluoropolymers perform best only in certain biomedical applications, and often carry a considerably greater cost than their hydrocarbon analogs into medical device designs. Just two years after the first commercial launch of completely fluorinated polytetrafluoroethylene (PTFE), as DuPont's now well-known TeflonTM product, after World War II ended, this new polymer was implanted in animals for the first time (Leveen and Barberio, 1949). However, early PTFE materials processing difficulties limited device capabilities. In 1963, Japanese researchers reported a new process for expanding PTFE films to produce highly uniform, continuous fibrous porous structures that, after thermal processing, retained this microstructure with vastly improved mechanical strength (Oshige, 1967). In 1972, this expanded fibrous material was first used experimentally as a venous graft substitute (Soyer et al., 1972), and a year later as an arterial bypass implant (Matsumoto et al., 1973). Several years later (1976), expanded PTFE (ePTFE) was refined to production scales by Gore, allowing increased access and clinical use of this more versatile PTFE form in commercialized biomedical products (Gore, 1976). This enabled fluorinated biomaterials to be employed in biomedical applications both inside and outside the living host, facilitating entry as an important class of polymeric biomaterials that are seen in the field today. Biomedical interest in fluorinated biomaterials focuses on several unique properties: lubricity; high sizing tolerances for device fabrication; and select aspects of reasonable biocompatibility resulting from both unique chemical and morphological properties. Understanding certain aspects of fluorinated chemistry is important to appreciate their material properties and broad utility in biomedical products. INTERESTING FLUOROPOLYMER CHEMICAL AND PHYSICAL PROPERTIES DERIVED FROM THEIR POLYMER CHEMISTRY, MOLECULAR STRUCTURE, AND BONDING Replacing large amounts of hydrogen in C-H and C-C bonds in organic materials with fluorine as C-F chemistry, using several different chemical means, results in dramatic changes to the fluoromaterial's physical and chemical properties. Technologically desirable characteristics of perfluorinated materials are identified from how they interact distinctly with other media (e.g., heated fabrication machines and device extruding dyes, as well as tissue, blood, proteins, and other polymers). Single fluorine bonds with carbon are the strongest carbon bonds, some 25 kcal/mol-1 stronger than C-Cl (Smart, 1994). Fluorination also strengthens adjacent aliphatic bonds: the CF3-CF3 bond is 10 kcal/mol-1 stronger than the CH3-CH3 bond (Smart, 1994). This makes alkyl fluorides 102-106 times more stable than the corresponding alkylchlorides in solvent and thermal reactions (Smart, 1994). Exceptional thermal and chemical stabilities observed for perfluorinated materials then result. Fluorine's high ionization potential energy and low polarizability provide relatively weak intermolecular forces, low interfacial energies, and low refractive indices in fluorinated materials. This is important to interfacial applications, (see section on Surfaces Modified by Fluorination Treatments below). Fluorine's larger atomic radius compared to hydrogen provides a rational basis for the observed structural differences between perfluorocarbons and hydrocarbons; chain movement energies (i.e., C-C chain rotational barriers) for various fluorinesubstituted bonds are significantly higher than barriers in analogous hydrocarbon systems (Smart, 1994). Partially fluorinated commercial polymers, polyvinylidene fluoride (PVDF) and ethylene-trifluoroethylene copolymer (ETFE), have zig-zag polymer chain conformations with different C-F dipole alignments along the chain (Smart, 1994), while perfluorocarbons with only C-F bonds (e.g., PTFE, see below) assume helical chain orientations with C-F dipoles distributed axially around the chain helix (Doeff and Lindner, 1989; Zhang et al., 1989; Sun et al., 1994a,b; Kobayashi and Owen, 1995; Bar et al., 1997; Stone et al., 1998). PTFE, for example, as a model for high molecular weight perfluorocarbon chains, is known to have a rich phase diagram of several distinct helical solid phases (Scheirs, 1997). This polymer helix basically encases the inner carbon-carbon polymer backbone with a tight outer shell of fluorine groups, protecting the carbon bonds from reactants, and also contributing to unique chain-chain interactions in PTFE and helical fluorinated polymers. Although most fluoropolymers share unique properties (e.g., thermal and chemical stability, lubricity), their mechanical properties are slightly different, depending on whether they are fully fluorinated or contain some hydrogen atoms. Generally, partially hydrogenated fluoropolymers exhibit higher stiffness than fully fluorinated polymers (i.e., perfluoropolymers). Perfluoropolymers exhibit greater elongation and higher maximum service temperatures that benefit device engineering and thermal processing. DISTINGUISHING THE DIFFERENT FLUOROPOLYMERS Fluoropolymers can be classified into homopolymers and copolymers by the monomer(s) used in their polymerization. They are divided into either "partially fluorinated" or "perfluorinated" (i.e., 100% C-F bonds) based on the amounts of fluorine in the polymer chain. Figure C.1 lists currently available commercial biomedical fluoropolymers. Polymer chemical composition affects the resulting materials' properties; only certain fluoropolymers exhibit properties attractive for biomedical products. As one selection criteria, Figure C.2 (Scheirs, 1997) compares some selected mechanical properties for different biomedical fluoropolymers (Drobny, 2005). Polytetrafluoroethylene (PTFE) PTFE (DuPont trade-name TeflonTM) is perhaps the most commonly analyzed fluoropolymer. As described above, fluorine's large size and mutual repulsion of adjacent fluorine atoms causes PTFE macromolecule chains to exhibit a twisting helix, comprising 13 CF2 groups per 180 turn, distinct from the classic planar zigzag chain typical C Fluorinated Biomaterials 93 for PE (Bunn and Howells, 1954). Figure C.3 shows this important conformational chain distinction that imparts certain unique physical properties to the fluoropolymer. Helical PTFE chains are often of very high molecular weight (>106) from their polymerization by reactive TFE gas. The helical polymer chains pack into solid crystallites like long, parallel, stiff molecular rods; individual PTFE polymer molecules can slip on each other as quasicylinders sliding under shear stress. Tight helical packing and chain-chain slip make PTFE the most lubricious polymer available, with a low coefficient of friction (0.1). This is a major selection criterion for manufacturing fluoropolymer tubing for catheters. Unfortunately, this also makes PTFE solids very susceptible to cold flow (creep) under stress - a major reason for their contraindication in mechanical applications (i.e., poor bearing and joint surfaces) (see Box 1). Mutual repulsive forces of adjacent fluorine atoms keep the PTFE chain backbone from bending. Low energy barriers to chain-chain slip events result from low chain-chain interaction energies. PTFE's very high bulk solid fractional crystallinity means that it scatters most visible light wavelengths, resulting in its characteristic opaque white color. PTFE's high molecular weight and rigid helical chain conformation also produce high melt viscosities (e.g., 1012 Pa/s), ~6 times higher than most thermoplastic polymers. This viscosity FIGURE C.1 Abbreviated names and molecular structures for some biomedical fluoropolymers. FIGURE C.2 Comparison of mechanical properties of some select biomedical fluoropolymers. (Adapted by permission from Modern Fluoropolymers, Scheirs, J. (Ed.). John Wiley & Sons, Ltd., copyright 1997.) 94 SECTION I.2 Classes of Materials Used in Medicine FIGURE C.3 (A) PTFE twisted zigzag chain compared to polyethylene (PE) molecular zig-zag chain; (B) Side space-filling views; and (C) top views, of PTFE chain versus hydrocarbon chain (PE). Bunn/Howells ref: "Adapted by permission from Macmillan Publishers Ltd:, Bunn, C. W. & Howells, E. R., "Structures of Molecules and Crystals of Fluoro-Carbons," Nature 174, 550, 1954. (http://www.nature.com/npg/index npg.html) BOX 1 Sir John Charnley and the PTFE Replacement Hip Bearing Convinced that hip joint repair could not use metal-on-metal bearings, Professor Sir John Charnley's early work on hip arthroplasty techniques in the early 1950s used a TeflonTM-on-Teflon solid bearing to resurface the arthritic femoral head and acetabulum. These TeflonTM-on-Teflon bearings failed within two years from mechanical creep and particulate issues. His further innovations created a femoral stem and metal head articulating against a Teflon cup-socket inserted into the acetabulum. High Teflon wear occurred with joint articulation, producing severe osteolysis, loosening in the surrounding bone and, as a result, requiring many revision surgeries. Teflon's poor performance in this articulating joint application prompted the adoption of high molecular weight polyethylene as a better bearing surface - an innovation that persists to today. is excessive for conventional melt processing fabrication methods for thermoplastic medical devices (e.g., extrusion and injection molding). This requires a high continuous service temperature (~260C) for processing PTFE into devices. Therefore, as PTFE does not dissolve in any solvents, PTFE processing technologies are similar to those of powder metallurgy. This involves form casting of pre-polymerized PTFE granulated powders or latex formulations, followed by mold compression and thermal sintering. PTFE's high thermal stability is key to success under the extreme processing conditions required for molded device parts (Drobny, 2005). Fluorinated Ethylene Propylene (FEP) FEP is a copolymer of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP), first produced by DuPont in 1956 (TeflonTM FEP) to reduce PTFE's high crystallinity and melt viscosity. This improves FEP processing characteristics while maintaining high perfluorination. Bulky FEP perfluoromethyl groups produce defects in solid fluoropolymer crystallites, reducing polymer melting point, impeding chain slip, and reducing solid cold flow (Drobny, 2001). FEP combines the unique mechanical and chemical properties of PTFE with the melt-processability of more conventional polymers. FEP has a maximum service temperature of 204C, and a slightly higher coefficient of friction than PTFE. It is used in biomedical devices in place of PTFE. Polyvinylidene fluoride (PVDF) PVDF is a homopolymer of the vinylidene monomer (CH2CF2), and is sold as KynarTM. PVDF has the highest flexural modulus of all fluoropolymers, due to the interpenetration of larger CF2 groups crystallizing with adjacent smaller CH2 groups on adjacent chains. Unlike other fluoropolymers, PVDF is soluble in highly polar solvents (dimethylformamide, tetrahydrofuran), acetone, and esters (Drobny, 2005). PVDF's unique high dielectric constant, high dielectric loss factor, and interesting piezoelectric behavior under certain conditions result from this chemistry and result in solid state structures. Fluorine's shielding effects to all neighboring CH2 groups provides PVDF with good chemical resistance and thermal stability (Scheirs, 1997; Drobny, 2001). These are all valuable properties sought in specific medical device applications. Fluoropolymer Melt Processing Because most perfluorinated polymers do not dissolve in many solvents, their bio-medical products are often made by melt extrusion, where polymers develop flow upon melting in normal extrusion equipment. This technique, common to all polymer devices and chemistries, exposes fluoropolymers to very high temperatures in order to reduce their viscosity and improve flow characteristics for extended device production runs and product lengths. Fluoropolymers FEP and PVDF will readily melt flow when heated, typically above 260C. This permits uninterrupted feed of fluoropolymer resin into the parts extruder to produce long continuous lengths of product (i.e., medical tubing). By contrast, PTFE extrusion is limited due to difficulties in its materials handling, size of the stock pre-forms, and tubing. However, PTFE's poor melt processing presents an important opportunity: PTFE tubing can be manufactured to very small dimensions, with wall thicknesses as small as 2.54 10-3 cm and tolerances of 1 10-3 cm. This engineering benefit is largely due to PTFE's inability to melt flow, allowing more precise control over its use in small dimensional, high-tolerance extrusion forms. This unique PTFE property is essential for producing medical products requiring tight size tolerances, such as small diameter and multi-lumen tubing with multiple precision passages for advanced catheters. Original Gore-TexTM and Generic Equivalents (ePTFE) PTFE film extrusion under anisotropic loading conditions produces expanded TeflonTM (ePTFE). Its microarchitecture exhibits pores axially aligned along the stretch direction, resulting in a unique fluoropolymer fabric material with an oriented microporous architecture. This was originally commercialized as the fabriclike Gore-TexTM material (Gore, 1976). ePTFE's porous structure is characterized by regular PTFE nodes interconnected by PTFE fibrils (Figure C.4A), distinct from solid PTFE shown in Figure C.4B. In ePTFE internodal spacing or distance (i.e., PTFE fibril length between solid PTFE nodes) is important to control device implant behavior (McClurken et al., 1986), and this can be controlled from 1 to 100 microns (Santiago et al., 1981) while retaining some properties similar to PTFE, e.g., biological adsorption, low tensile strength, low modulus of elasticity, water penetration control, and easy sterilizability. Porous ePTFE structures also allow important mechanical modulus-matching properties in tissue sites better than other polymers for many soft biological C Fluorinated Biomaterials 95 (A) (B) (C) FIGURE C.4 (A) Scanning electron micrograph of ePTFE showing regular node-fiber open materials structure (scale bar, lower right corner = 10 microns). (We kindly acknowledge B. Wagner, W. L. Gore & Associates, Flagstaff, AZ, USA, for ePTFE micrographs). (B) SEM of solid TeflonTM showing the cross-sectional porous structure resulting from the compressed sintering of PTFE particles (we acknowledge P. Hogrebe for these SEM micrographs). (C) Dense continuous top surface (scale bar = 25 microns). tissue applications (Mole, 1992). Porosity also importantly encourages in-growth of tissue, and hence moderate levels of tissue mechanical fixation. Bulk PTFE does not exhibit this property. The micropores also present active sites for stable blood clotting, an important property for conditioning implanted vascular graft surfaces to limit their chronic blood coagulation. Surfaces Modified by Fluorination Treatments (Grainger and Stewart, 2001) Bulk perfluorinated materials' intrinsically higher costs and often substandard mechanical properties limit their applications. When only fluorinated polymer interfacial properties are desired, then fluorinated surface layers can 96 SECTION I.2 Classes of Materials Used in Medicine be chemically deposited or coated over other mechanically superior substrates to impart fluorinated properties only at the surface. This surface application limits bulk fluorocarbon costs and their performance liabilities. As developed further below, fluorinated surfaces can be produced by plasma deposition of gaseous precursor monomers, direct solid powder or solution overcoating and casting/evaporation, and solution phase fluorinated component blooming. High surface fluorocarbonation produces unique interfacial properties, imparting specific, technologically attractive features including low solid-state surface free energy (or low water wettability and permeability), surface lubricity, and chemical resistance and durability, to device surfaces. Table C.1 shows that perfluorinated polymer surfaces exhibit low interfacial energies (indicated by Zisman c values), correlating directly with their utility as low adhesion, low water-wetting, and low friction surfaces. Substituting either hydrogen or another halogen for fluorine along the polymer backbone results in significant increases in c values (as seen in comparisons of PTFE with highdensity polyethylene (HDPE)), PVDF:poly(CH2CHF) has a c~25 mN/m, approaching that for polyethylene (HDPE, see Table C.1). Another important outcome of this low interfacial fluoromaterial energy is that fluorinated species thermodynamically prefer to coat a material's surface exposed to air. Hence, fluorinated components will migrate from deep inside fluid coating mixtures to "bloom" and enrich as a coated overlayer at the solid-air interface. Surface-enriched films of fluorinated components reside at surfaces even if fluorinated components are doped only at trace or minority components into bulk coating materials. Therefore, fluorinated surfaces can be fabricated using minority fluorinated components added to a bulk material if they are allowed to move to that material's surface (e.g., from coating solutions), off-setting the intrinsically high costs of fluorinated materials. Emphasis on surfacefluorinated coatings and films has therefore increased as technological needs drive new, improved, and less expensive methods to put this chemistry over biomaterial surfaces. Several coating strategies have sought to create, organize, and orient -CF3 and -SF5 terminal groups from films over any surface to provide such properties. High surface density and organization of these groups is necessary to achieve their technological properties. Alignment of perfluorinated chains terminating in this -CF3 or -SF5 chemistry at the surface is required. Orienting the side chains in fluoroalkyl side-chain acrylate and methacrylate films enriches surfaces with side chain-terminating -CF3 groups (Bunn and Howells, 1954; Clark and Muus, 1962; Russell et al., 1986; Naselli et al., 1989), and lowers solid interfacial energies. Perfluoroalkyl-grafted polysiloxanes also exhibit side chain orientation of their perfluorinated chemistry, sometimes with spontaneous perfluorinated group organization as a film or coating (Hare et al., 1954; Pittman, 1972; Schneider et al., 1989; Tsao et al., 1997; Clark, 1999). Gas plasma-deposited thin fluorinated coatings are also well-developed for this purpose (D'Agostino, TaBLE C.1 Surface Energies for Perfluorocarbons versus Analogous Hydrocarbonsa Substance PTFE1 PVDF HDPE2 n-pentane n-hexane n-octane Decalin Benzene Solid Interfacial Energy (c, mN/m) Perfluorocarbon hydrocarbon 18.5 31 25 31 18.5 31 9.4 15.2 11.4 17.9 13.6 21.1 17.6 29.9 22.6 28.5 aSmart, B. E. (1994). In: Organofluorine Chemistry: Principles and Commercial Applications; Banks, R. E., Tatlow, J. C. & Smart, B. E. (Eds.). Plenum Press: New York, NY, Chapter 3. 1c values. 2l/v values. 1990), representing a mature industry and biomedically relevant materials treatment (e.g., for vascular devices and intraocular lenses; Ratner, 1995). BIOMEDICAL APPLICATIONS Biomedical applications of fluoropolymers, fluorocarbon coatings, and perfluorinated fluids and gels all include clinical interventional and luminal access devices (catheters in many forms), and more permanent implants (cardiovascular (Stanley, 1982), dental (Ratner, 1993), ocular (Legeais et al., 1998), craniofacial (Valdevit et al., 2000), urological (Reid et al., 1995), and abdominal (Grannis and Wagman, 1995) applications) as well as substantial non-implanted medical tubing and biotechnology components (protein blotting and filtration membranes). Annually, millions of perfluorinated polymer components are used worldwide in biological milieu both in vitro and in vivo. PTFE (TeflonTM) and ePTFE (Gore-TexTM) are widely used in medical tubing, advanced catheters, vascular grafts, meshes, sutures, and other medical implants. PVDF is used for biotechnology blotting/ separation membranes. Table C.2 provides biomedical applications of more popular fluoropolymers. Clinically, ePTFE vascular grafts, including dialysis-access grafts, and TeflonTM-FEP catheter components are the most widely used fluorinated material medical devices. Other biomedical applications are described below. Fluorinated Material Biological response Fluoropolymers are often regarded as chemically inert under most biological conditions. As noted above, they have some mechanical shortcomings under cyclic or continuous shear (creep). This makes applications in loadbearing situations (i.e., joint replacement, wear surfaces) difficult. Additionally, fluoropolymer surfaces are not inert to host TaBLE C.2 Decade 1970s 1980s 1990s 2000s Fluorinated Biomaterials Biomedical Applications Biomedical applications Implantable vascular grafts, peripheral catheters, and catheter introducers Guiding catheters, protein blotting membranes, tissue meshes, tubing Endoluminal stents, blood substitutes Drug-eluting stents biological reactions, including protein adsorption and blood clotting, either in vitro or in vivo. In fact, extremely tight binding of serum albumin to fluoroplasma-deposited surfaces (Kiaei et al., 1992), high levels of fibronectin and hemoglobin on PVDF (Paynter and Ratner, 1985), and various serum proteins (Dekker et al., 1991) including significant fibrinogen (Chandy et al., 2000), and high levels of both fibronectin and albumin (Grainger et al., 2003) on PTFE are observed in vitro. Importantly, protein adsorption to fluoropolymers is also observed in vivo (van Wachem et al., 1985; Roald et al., 1994), including fibrinogen activation, fibrin deposition, and platelet activation from blood, often deliberately promoted to stabilize blood reactivity on ePTFE vascular graft materials in vivo (Hoffman et al., 1986; Callow, 1988; Roald et al., 1994). Therefore, non-specific protein adsorption is significant, often irreversible, on fluoropolymer surfaces, leading to their desired utility as efficient protein blotting membranes. But different proteins from different media (i.e., serum versus plasma versus blood) produce different interfacial reactions to fluorinated surfaces. From serum in vitro for example, substantial amounts of albumin adsorption hinder serum-mediated cell attachment to fluoropolymers. This albumin passivation against further biological reactivity helps render the surface bio-fouling resistant. Clinical human cell-based vascular graft endothelialization to improve their blood compatibility is also generally poor on non-porous fluoropolymer chemistries (Kempczinski et al., 1985; Callow, 1988; Dekker et al., 1991; Schmidt et al., 1991; van Kooten et al., 1992; Roald et al., 1994; Legeais et al., 1998). This poor cell-fluoropolymer attachment has often been interpreted as "biological inertness," but results instead from substantial plasma protein adsorption on fluoropolymers (Baier et al., 1984) that does not support cell attachment and growth. Serum albumin, the most abundant protein in blood, blocks most cell attachment and other protein binding (Kesler et al., 1986; Zilla et al., 1989). Fibronectin, collagens, and other trace matricellular proteins (e.g., osteopontin, laminin, vitronectin) are cell-adhesive proteins. The observed general inability of non-porous fluoropolymers to support cell attachment has been related to excessive adsorption of albumin over cell-adhesive proteins (e.g., fibronectin) from serum - a media lacking clot-forming fibrinogen (Grainger et al., 2003). Pre-adsorption of specific cell-adhesive proteins (e.g., collagen or fibronectin) to fluoropolymers is used C Fluorinated Biomaterials 97 to promote reliable cell adhesion (McClary et al., 2000; Koenig et al., 2003). Therefore, little evidence suggests that fluoropolymers can be intrinsically "biologically inert." In fact, the opposite is true; solid fluoropolymers are intrinsically reactive and adsorptive to most every protein studied, and the nature of what types of proteins are adsorbed dictates the fluoropolymer's biological reactivity. For example, porous fluoropolymers with 60-80 m voids, including ePTFE, can facilitate rapid blood clotting, cell and bacterial in-growth in blood. These interactions occur by blood-based protein adsorption, clotting, and cell/bacterial adhesion, with additional physical integration and engagement into the ePTFE pores (Clark et al., 1974; Clowes et al., 1986). PTFE (TeflonTM) Mesh and Fabric Vascular Implants The innovation that enabled the spinning of PTFE paste into a fiber that could be woven or knitted into fabric or mesh produced a fabric-like fluorinated material (Berry, 1951). Attracted by solid PTFE's reported "blood compatibility" claimed in early animal acute in vivo studies, PTFE weaves were applied early in vascular grafts (Edwards, 1959). However, these early woven vascular grafts exhibited both high early failure rates and substantial late failure rates. Graft thrombosis was the most frequent early complication, accompanied by a high mortality rate (Boyd and Midell, 1971). Gore-TexTM (ePTFE) vascular grafts supplanted these earlier PTFE weaves in this application and are discussed below. Thrombosis is a general property of fluoropolymer meshes and weaves in blood, passivating surfaces rapidly for acute short-term use, but limiting long-term blood-contacting applications. ePTFE and TeflonTM Soft Tissue repair Meshes TeflonTM fibrous mesh has been used to repair abdominal wall defects (Ludington and Woodward, 1959) and hernias (Gibson and Stafford, 1964; Snijders, 1969; Kalsbeek, 1974). However, it does not reliably integrate into body tissues, is not sufficiently infection-resistant, and exhibits wound complication rates too high for routine hernia or abdominal repair use. ePTFE mesh is clinically used to repair hernias of many types (DeBord, 1998), reducing risks of several complications (DeGuzman et al., 1995; Lo Monte et al., 2009) (see Box 2). Infection and intestinal obstructions remain an issue for ePTFE mesh. However, they are better controlled with antibiotic therapies without mesh removal. ePTFE meshes have also been used as abdominal surgery barriers against surgical adhesions (Tulandi, 1997; MorrisStiff and Hughes, 1998). ePTFE is also FDA-approved for many different plastic surgical facial defect reconstructions and augmentations, but is contraindicated in cosmetic lip augmentation, temporomandibular joint reconstruction, cardiovascular defects, and dermal placement (Levine and 98 SECTION I.2 Classes of Materials Used in Medicine BO X 2 ePTFE hernial Mesh Nearly a million hernial repairs are performed annually in the United States. Clinically, hernial repair meshes are implanted to bulk the abdominal wall at the herniated site. Tissue in-growth and organized fibrogenesis are deliberately promoted in these meshes to stabilize them in the abdominal tissue. ePTFE meshes and their combinations with polypropylene meshes are clinically available as a hernial repair product. However, ePTFE's lack of resistance to infection, and inability to effectively engage tissue, promote on-growth and organized fibrogenesis makes these meshes inferior to more popular polypropylene and polyester synthetic polymer meshes. Berman, 1995). Nonetheless, commercial sources for these plastic surgery materials are discontinued. ePTFE Vascular Implants Because of abundant protein adsorption, ePTFE's porous inner surface is often claimed in vascular implants (blood) to clot blood rapidly to stabilize further surface coagulation and promote formation of a host "pseudointimal lining" that maintains blood compatibility under high flow, high shear applications. Its porous outer surface promotes peri-graft cell and tissue infiltration that mechanically stabilizes the prosthesis in place, preventing kinking (White, 1988). Unlike most animal models, humans do not reliably form stable cellular "neo-intimal"endothelial cell linings in these grafts, limiting their success. ePTFE is currently used most widely to fabricate medium sized (4-10 micron internode) vascular grafts for use in specific clinical blood vessel replacement indications (Kannan et al., 2005), including major vessels affected by disease or trauma, and arteriovenous hemodialysis grafts (Jenkins, 1976; Konner, 2005). ePTFE vascular prostheses are most clinically successful in high blood flow, low resistance conditions (i.e., large peripheral arteries >5-6 mm diameter, such as the descending aorta). They are generally not suitable for smaller arterial reconstructions (e.g., coronary circulation and peripheral vascular placements) under high resistance, low flow conditions that allow continued clotting and loss of patency. Typically, ePTFE suffers from thrombosis, poor healing, lack of compliance, and excessive intimal and anastomotic hyperplasia leading to stenotic complications. Their routine placement in high flow vascular environments allows them to remain patent despite their thrombus generation (see Box 3). arteriovenous ePTFE Grafts for Dialysis access Hemodialysis - essential for patients with end-stage renal disease - often requires regular, repeated (weekly) access to large blood vessels capable of producing high flow rates through an external artificial kidney device. BOX 3 The ePTFE Vascular Graft and a Bizarre and Costly Patent Dispute The 1974 patent filing from W. L. Gore & Associates, Inc. for the invention of the vascular graft resulted in the eruption of one of the most expensive and notorious medical device patent disputes in history. To challenge Gore's patent validity, a competing company started from former Gore employees and consultants - International Medical Prosthetics Research Associates, Inc. (IMPRA) - filed their own competing patent based on work from a pediatric heart surgeon, Dr. Goldfarb, investigating ePTFE at Arizona State University. IMPRA also agreed to fund Goldfarb's research in exchange for exclusive rights to Goldfarb's patent. But, after an extended period without IMPRA support, Goldfarb dissolved his IMPRA ties. Eventually, IMPRA returned patent rights to the doctor, but not without a nasty struggle. Goldfarb then licensed his still-pending patent to the C. R. Bard medical device company, seeking to obtain a piece of the vascular graft market from Gore and IMPRA. In 1995, the US Patent and Trade Office Interference Board declared that the Goldfarb patent (still pending) invalidated the Gore patent on the vascular graft - a decision upheld twice in US appeals court. Goldfarb was finally awarded his patent in 2002, still licensed to C. R. Bard, invalidating the Gore patent. But Gore continued to sell its ePTFE vascular grafts until Bard filed suit in 2003. The trial, first "settled" in 2007, found Goldfarb to be the rightful graft inventor; that his patent was valid, and that Gore had willfully infringed the patent in its vascular products. But it is not over yet: in 2009, Gore's claims of inequitable conduct against Bard were denied, and damages against Gore were increased to a total of $410 million. Gore then appealed this verdict (Frankel, 2009). In 2012, citing "substantial evidence" that Gore infringed a patent for vascular grafts, the U.S Court of Appeals upheld assessed penalties on Gore for past interest, royalties and fees. Resolution of the case is estimated to yield about $1 billion for Bard from Gore, among the largest settlement in patent litigation history. Interestingly, the judgment also allows Gore to keep selling their products on the markets as it is in the public interest to allow competition in the medical device arena. Hemodialysis patients typically undergo cannula puncture of skin, underlying tissue, and vasculature to provide this access to the external artificial kidney. Repeated trauma to patient skin, tissue, and blood vessels from 13- 17 gauge access needles produces notable complications including hyperplasia, thrombosis, hematoma, occlusion, infection, and other morbidities. Vascular access complications remain the main reason for hemodialysis patient hospitalization. Synthetic ePTFE arteriovenous (A-V) grafts are surgically placed across the basilic vein and brachial artery to permit cannula access and reduce tissue trauma complications. A-V prosthetic graft failure rates are substantial (>50%), leading to increasing use of native fistulas and catheters (Li et al., 2008). However, synthetic grafts reliably provide high blood flow rates shortly after placement, as they do not require maturation before use. In A-V ePTFE grafts, stenosis occurs most commonly at the graft-venous anastomosis. Histologically, macrophages are seen in large numbers in the adventitial and medial layers in the anastomotic tissues from A-V ePTFE grafts (Kapadia et al., 2008). Multi-Lumen Catheters Fluoropolymers are important for biomedical tubing, and are central to advanced multi-lumen small gauge medical-grade tubing required in many new minimally invasive catheters. These catheters permit surgeons to perform several invasive procedures through several lumens in a single inserted catheter device without removing one entire catheter to insert another. Catheter in vivo exposures are usually short-term, typically using endoluminal access, and increasingly are minimally invasive. As described above, PTFE's unique properties and stable thermal processing methods allow PTFE multi-lumen tubing precision manufacture unlike any other material, and this is a very important fluoropolymer in this particular use. Guiding Catheters An important clinical device with a long track record, the guiding catheter helps the clinician deliver stents and other devices endo-luminally. Central to the guiding catheter is a PTFE inner liner with its superior lubricity and low friction coefficient that slides within an outer lumen. Lubricity is so critical to this device function that FEP, as the second-most lubricious material available, is insufficient as a catheter liner. During catheter construction, PTFE is chemically bonded onto the tube's outer diameter to enable slip. Bonding is accomplished by using an FEP heat-shrinkable fusing sleeve. After depositing PTFE over the liner the FEP mold is removed from the device, leaving a smooth outer PTFE jacket on the liner within the catheter outer liner. PTFE Catheter Introducers Now over three decades old, the PTFE "introducer" facilitates catheter insertion into a patient's vein, taking full advantage of PTFE's endoluminal lubricity and precision tubing processing. Once the catheter is inserted, the PTFE outer sheath can be removed from the patient, leaving the implanted catheter behind. The introducer exploits PTFE processing that molecularly orients the fluoropolymer material in the tubing-based sleeve over the catheter. This allows PTFE tubing to be readily split and torn longitudinally from the catheter in situ, enabling the surgeon to remove a PTFE introducer from a patient while the primary catheter remains in place. Perfluorocarbon Liquids and Emulsions as Oxygen Carrying Blood Substitutes Low molecular weight perfluoro-fluids can be aspirated into the lungs directly or injected as submicron-sized C Fluorinated Biomaterials 99 emulsion droplets into the blood to facilitate oxygen transport, exploiting their high oxygen carrying capacities (Winslow, 2005). Liquid perfluorocarbons in the lung eliminate the gas-lung interface, acting to reduce tension in the lung alveolus, and reducing mechanical work required to breathe during respiratory distress and lung surfactant deficiency. Emulsions made from dispersing perfluoro fluids into water using interfacial droplet stabilizers (emulsifiers) create sub-micron perfluoro-droplets, much smaller than red blood cells. This provides enormous oxygen carrying capacity in blood to supplement normal oxygenation in microcirculation. Several commercial products have been clinically available, most recently OxygentTM (Alliance Pharmaceutical, USA), consisting of two different perfluorocarbon fluids stabilized as a micro-emulsion using egg phospholipids. The product is eliminated from the blood after injection by macrophage/monocyte clearance, and is exhaled eventually from the lung. Fluorinated Liquids in the Eye as Experimental Vitreous Substitutes Detached retinal repair and other ophthalmic surgeries require oxygen-permeable viscous liquid vitreous substitutes. Perfluorinated oils and polymers have intrinsic high oxygen permeabilities and solubilities with suitable viscosity control. Perfluoropolyethers, perfluorinated alkanes, and perfluorinated silicone oils have all been studied in ocular vitreous applications, but still lack convincing safety, toxicity or efficacy to date to produce an approved product in this context. Fluorinated (Meth)acrylates and (Meth) acrylated Perfluoroalkyl Silicones as Cross-Linked Polymer Cores for Soft Contact Lenses Exploiting the intrinsic high oxygen permeability well known for perfluorinated materials, rigid gas permeable contact lenses (RGPs) have used many variations on cross-linked perfluorinated acrylates and perfluorinated polyether silicone gels as lens cores to improve extendedwear contact lens on-eye performance. Increased ocular acuity under high-throughput inexpensive but precise lens fabrication methods, with high lens oxygen transport, is sought. Many patents describe many fluorinated polymer gels in this regard, with most major lens manufacturers developing these lens core materials. Fluorinated Materials as anti-Fouling Coatings for Intraocular Lenses (IOLs) General cellular reactions to implanted polymer intraocular lenses replacing cataracts can result in cell migration onto, and adhesion to, the lens, with optical interference (clouding) requiring IOL replacement. To prevent cells 100 SECTION I.2 Classes of Materials Used in Medicine from migrating onto and coating the IOL's optical lens surface (typically a thermoplastic), thin optically transparent plasma-deposited fluorocarbon films or layers of other fluorinated polymers are deposited on the IOL rear surface. Several patents describe this approach and application. PTFE Paste Injectable Bulking agent TeflonTM particles formulated as an injectable paste have been reported for the treatment of vesico-ureteric reflux (VUR) (Puri, 1995), corrected by sub-ureteric injection of a PTFE paste (Puri and O'Donnell, 1984). Sub-ureteric paste injection by endoscopy has successfully addressed primary and secondary VUR in children for nearly two decades (Le Guillou et al., 1984; Dodat and Paulhac, 1987; Puri, 2000). Similarly, PTFE paste was introduced nearly 4 decades ago to treat female stress urinary incontinence (Beckingham et al., 1992; Politano, 1992; Meschia et al., 2002). However, this device does not have regulatory approval, due to high risks for PTFE microparticle migration and granuloma induction, especially in lymph nodes, kidneys, lungs, and brain (Aaronson et al., 1993). Applications of TeflonTM paste injection are still reported (Harrison et al., 1993; Lopez et al., 1993; Herschorn and Glazer, 2000), but its side-effect concerns limit clinical use. Ligament replacement The Gore-TexTM ligament prosthesis comprises a single long fiber of ePTFE woven into loops. Mechanical testing shows that the resulting ultimate tensile strength is ~3 times that of the human anterior cruciate ligament (ACL). Creep and bending fatigue testing validate this ePTFE device as a strong synthetic ACL replacement material (Bolton and Bruchman, 1985). The Gore-TexTM ACL prosthesis is currently FDA-approved for use in patients with failed autogenous intra-articular graft procedures (Mascarenhas and Macdonald, 2008). However, while acute performance shows promising stability in the knee, extended use and implant time produce significant ligament loosening, and other knee stability problems. Sutures PTFE also finds limited use as a suture fiber in various forms. Both PTFE monofilament and ePTFE fibers are surgically proven, with clinically accepted surgeon handling and lubricity properties. Additionally, PTFE is blended into other common surgical sutures used for myocardial heart valve prostheses fixation. Poly(ethylene terephthalate) (PET polyester) braided sutures are impregnated with PTFE polymer to limit wrinkling of the braid and consequent swelling. PTFE hydrophobic properties likely help protect the polyester braid from water uptake and hydrolysis (Bhat, 2002). ThE MONEY JOINT Most biomaterials used for jaw joint reconstruction were introduced to markets prior to the 1976 Medical Devices Amendment Act that required device manufacturers to prove that their devices were safe and effective. A legal loophole that required manufacturers only to prove that their devices were "substantially equivalent" to a preAmendment device allowed temporal mandibular joint (TMJ) implants marketed soon after 1976 to enter the market without testing. Two designs widely used as TMJ replacement surfaces were Dow Corning's Silastic and Vitek's Proplast-Teflon product. Vitek developed and sold Proplast sheeting (TeflonTM FEP film laminated with a porous composite material of PTFE and carbon) in the 1970s. Implants modified in the 1980s comprised TeflonTM film laminated to PTFE and aluminum oxide. These implants, ~1 cm2 in size, were cut from sheets in the operating room and sutured into the TMJ joint. In 1983, the FDA allowed Vitek to market a pre-cut disc because, under the law, the company needed only to convince the FDA that its device was "substantially equivalent" to Dow's Silastic disc marketed years earlier. In 1986, several reports of catastrophic biomechanical failure of the PTFE implant were linked to a giant cell reaction leading to bone resorption and pain. Further analysis documented device failure rates of 10-25%. By 1992, implant success rates below 20% were reported. Animal studies performed only after failures in humans began showed complete erosion of the TMJ implant within a "few months." In early 1990, with implant failures increasing, the FDA recalled Vitek's products. Predictably, Vitek declared bankruptcy with its rising product litigation costs, but continued to market their TMJ implants. Surgeons continued to implant them until eventually the FDA seized all products from Vitek, as well as its subsidiaries. SUMMARY Due to their unique chemistry, fluorinated materials, primarily fluoropolymers, have attractive properties of biomaterials interest, including chemical stability, low adhesion/friction, non-wetting, high protein adsorption, high oxygen permeability, and precision tubing manufacturing. Low cell adhesion in serum and high intrinsic blood coagulation in plasma and blood both result from distinct media-dependent protein adsorption treatments and the physical form of the material. Expanded PTFE provides fabric-like properties with controlled pores and high surface area to alter device-related mechanics, processing, and tissue responses, while promoting rapid blood clotting. Solid fluoropolymers also have attractive precision engineering and device processing properties essential to producing several medical device classes where fine dimensional tolerances and biocompatibility are required. This enables fabrication of multi-lumen, high-tolerance, small dimensional tubing for advanced catheters. GLOSSARY Blooming: a term used to describe the spontaneous enrichment of certain chemistries at the surface of a bulk matrix, usually associated with the surface enrichment by low surface energy chemistry-like fluorinated materials. This phenomenon is used to promote a surface enriched in trace components like expensive added fluorinated chemistry by allowing them to spontaneously diffuse from the bulk material to the surface. Blotting membrane: a thin, porous, hydrophobic, high protein-binding capacity polymer membrane (e.g., PVDF) used to transfer proteins from a gel electrophoresis separation process for further probing with antibodies to identify the proteins as a blot or spot. ePTFE: expanded polytetrafluoroethylene, produced from PTFE films under anisotropic stretching to yield a unique node-fibril microporous morphology in a fabriclike sheet form deemed important to biomedical utility in implanted biomaterials. Fluorinated biomaterial: a material intended for a biomedical application made from a base material that contains significant amounts of chemically bonded fluorine. Fluoropolymer: a fluorinated polymer, also perfluoropolymer, usually thermoplastic, with high content of fluorine atoms replacing hydrogen atoms along the carbon-based polymer chain. Perfluorinated material: a material wherein all hydrogen atoms are replaced with fluorine, generally making C-F bonds. 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ACRYLICS Joe Antonucci1 and Sabine Dickens2 1National Institute of Standards and Technology, Gaithersburg, MD, USA 2American Dental Association Foundation Pattenbarger Research Center, Gaithersburg, MD, USA INTRODUCTION The modern development of tooth-colored dental polymeric composites owes much to R. L. Bowen of the American Dental Association for his pioneering studies at the National Bureau of Standards, now the National Institute of Standards and Technology. His recognition of the excellent matrix-forming potential of epoxy resins (oxiranes), as well as their poor ambient polymerization characteristics (slow under anionic catalysis and uncontrollable under the more rapid cationic catalysis then available) led him to the discovery of a unique hybrid monomer which combined the low polymerization contraction of epoxy resins with the excellent setting behavior of acrylic monomers (Bowen, 1956). His classical synthesis of the bulky, thermosetting dimethacrylate, Bis-GMA, 2,2-bis[p(2-hydroxy-3-methacryloxypropoxyphenyl)] propane (Figure D.1), his preparation of silica fillers that combined translucency and radiopacity while matching the refractive indices of the resin matrix, and his utilization of the technology of silane coupling agents, ushered in the modern era of esthetic dental composites (Bowen, 1963). MONO- AND MULTI-METHACRYLATE MONOMERS Acrylics based on the monofunctional monomer methyl methacrylate (MMA) combined with poly(methyl methacrylate) (PMMA) and a low viscosity dimethacrylate for cross-linking are mainly used in orthodontic appliances, e.g., bionator, bite plates, palatal expanders, retainers, and for removable prosthetic devices, such as partial and full dentures, temporary crowns, and bridges. Basic MMA/PMMA mixtures activated with chemical initiators have been widely used as bone cements for orthopedic applications (Shalaby et al., 2007). Further development has led to the incorporation of PMMA fibers, resulting in composites with moderately increased moduli and improved toughness (Gilbert et al., 1995). MMA and other monomethacrylates of moderate size and viscosity are only occasionally incorporated into dental restorative materials due to their relatively high molar double-bond concentration, and thus, increased polymerization shrinkage. However, functional monomethacrylates are widely used in adhesive formulations, and as coupling agents in composites, and are discussed below. Base and Diluent Monomers In preventive and restorative dentistry a variety of di- or multimethacrylates are photo and/or chemically cured into polymers that function as pit and fissure sealants, adhesives, veneer materials, and when combined with fillers, as esthetic or loadbearing composite restoratives. Typically, dental resins are composed of mixtures of two or more monomers that combine a relatively high viscosity dimethacrylate (base) monomer with a low viscosity dimethacrylate comonomer such as triethylene glycol dimethacrylate (TEGDMA) to obtain resins with workable rheologies. The base resins 2,2-bis[p-(2-hydroxy3-methacryloxypropoxy) phenylene]propane (Bis-GMA), ethoxylated bisphenol A dimethacrylate (EBPADMA) or 1,6-bis(methacryloxy-2-ethoxycarbonylamino)-2,4,4trimethylhexane (UDMA) (Figure D.1) are among those CHAPTER 8 Fluorinated Biomaterials for Cardiovascular Surgery Charles Baquey,i* Marie-Christine Durrieu,1 and Robert G. Guidoin2 1INSERM, O577, Bordeaux, F-33076 France; Univ. Victor Sgalen Bordeaux 2, F-33076 France 146, rue Lo Saignat, 33076 Bordeaux Cdex, France 2Department of Surgery (Biomaterials), Facult de Mdecine, Pavillon Ferdinand-Vandry, Universit Laval, Qubec G1K7P4, Canada Contents 1. Introduction 380 2. Blood--vessel wall relationships (interactions of flowing blood with the vessel/vascular prosthesis wall) 381 2.1. Role of the surface free energy or surface tension 381 2.2. Role of electrical parameters 381 2.3. Scenario for blood--material interactions 382 2.4. Role of dynamic factors 384 2.5. Role of the morphology 385 3. Requirements for a cardiovascular biomaterial 386 4. From polytetrafluoroethylene to microporous teflon-based vascular prostheses 388 4.1. State of the art related to vessel repair or replacement: Evolution and role of PTFE 389 4.2. How to improve the functional patency of ePTFE-based prostheses? 392 4.3. Chemical modifications of fluorinated polymers: A way to the improvement of their haemocompatibility 394 4.3.1. PTFE case 394 4.3.2. PVDF case 396 4.3.3. P(VDF-HFP) case 401 5. Conclusions 402 References 404 Note from the Editors 406 Abstract The biomedical area did not miss the tremendous development of macromolecular materials and their applications, which has followed the rapid expansion of petrochemistry during the twentieth century. In fact, these materials are widely used to design a lot of 'Corresponding author.; Email: @baguey.com FLUORINE AND HEALTH A. Tressaud & G. Haufe (Editors) DOI: 10.1016/B978-0-444-53086-8.00008-4 e; 2008 Elsevier B.V. All rights reserved. 380 C. Baquey et al. medical devices that are at physicians' disposal to care patients. Some of these devices, commonly used in medical care units, such as syringes or tubings, are disposable, whereas others, such as joint prostheses, vascular substitutes, artificial lens, suture thread, are implanted in the body for an unlimited time, hopefully. Considering the cardiovascular area only, the introduction of polymeric materials induced outstanding advances, as they allowed, for instance, the design of arterial substitutes from woven, knitted and non-woven synthetic fabrics, thus opening a new therapeutic option for the replacement of diseased arterial segments beside the grafting of an autologous venous segment, the availability of which is necessarily limited. The polyethylene terephthalate (PET) takes a prominent place among the materials which are used for this application, but it meets the strong competition of the expanded polytetrafluoroethylene (ePTFE). Known for its chemical inertia and great thermal stability, this polymer, which is not easily processed, has many assets (biostability, heat sterilisable) in comparison with its main competitor, the PET, even if like the latter, it does not satisfy all the requirements a material used for the making of arterial substitutes has to comply with. However, different approaches are proposed to improve the situation, such as surface processings specifically designed to increase the polytetrafluoroethylene (PTFE) haemocompatibility on the one hand, or the choice of other fluorinated polymers on the other. 1. INTRODUCTION Because of inherited lesions or of an evolutive disease of their wall, arteries may become unable to ensure an adequate transport of the blood to organs and tissues, which may create a risk of myocardium infarctus or aneurysm rupture followed by a fatal haemorrhage for patients concerned by such (or suffering such) vascular diseases. After Gluck's pioneering works [1], which paved the way to the modern vascular surgery concepts, the replacement of a carotid segment by an autologous venous graft was no longer a dream, and these patients could be surged to repair or replace their diseased arteries. In this respect, vascular surgeons have at their disposal, various devices which do not satisfy all the requirements which are listed below, but which may compensate some of the functional deficiencies their patients encounter. Following Gluck's works, various materials including metals and glass have been used for the design and making of vascular substitutes, but the first clinical studies related to the use of flexible prostheses made from a non-biological material were reported only after 1952 by Woorhees et al. [2]. Taking into account what is known about the flowing blood-artery wall relationship, different criteria which have to be satisfied by a blood-contacting material, and more specifically by an arterial substitute, can be identified. This rationally designed strategy, mainly documented by studies carried out during the seventies and later on, was not given the priority as surgeons chose 20 years earlier, pragmatic solutions based on the use of polymeric materials among which polyethylene terephthalate (PET) and polytetrafluoroethylene (PTFE) a little later took leading positions. Fluorinated Biomaterials for Cardiovascular Surgery 381 2. BLOOD-VESSEL WALL RELATIONSHIPS (INTERACTIONS OF FLOWING BLOOD WITH THE VESSEL/VASCULAR PROSTHESIS WALL) Interactions of blood, or more precisely of plasma macromolecules and blood cells with the vessel wall, should the latter be natural or artificial, depend upon several parameters: the mechanical properties of the vascular conduit, on the one hand, the morphology and the physical and chemical characteristics of the blood-contacting surface on the other. 2.1. Role of the surface free energy or surface tension Surface tension, or surface free energy, is a parameter which corresponds to the residual binding capacity of a material surface, that is, the binding capacity of atoms or groups of atoms which constitute the border surface of the material of interest. This binding capacity may be uniform, as is the case for non-oxidised metals, but most of the time it is the resultant of several components that are respectively related to the various types of atoms or atom groups present on this surface including ionic sites, hydrophobic sites, polar sites or hydrogen atom donors or acceptors. Accordingly, most of the material surfaces appear as mosaic-like structures. The nature of the potential sites of interaction and the microtopography determine the interaction phenomena of materials with biological media and especially with blood. 2.2. Role of electrical parameters Blood cells and vessels walls are negatively charged, the corresponding isoelectric point lying at a pH between 4.8 and 5. Sawyer and Srinivasan [3] measured a voltage difference between endothelial layer and blood. Negatively charged surfaces give rise in the presence of an electrolyte solution to a double electric layer responsible for the recorded potential value C0 (Fig. 1a). As the distance from the wall increases, C0 decreases linearly down to a value equal to C0/2.3 according to the Stern theory. The corresponding distance (l) to the wall is known as the Debye length. At distances greater than l, the potential decreases exponentially to zero, the decaying potential being characterised by the so-called zeta (z) potential (Fig. 1b). The distance from the wall, corresponding to z, defines the shear plane and depends upon the flow conditions. For a given electrolyte solution (i.e. the nature and concentrations of ions in blood are known), z increases linearly with the flow rate [4]. Since the vessel wall is negatively charged, it repels the negatively charged platelets, and it helps in preventing thrombogenic phenomena. Experimentally, Sawyer et al. [5] demonstrated that on positively charged surfaces [>200 mV/normal 382 (a) + + + + + + + + + + + - - - - - - - - - - - -- - (b) Y0 Potential Y C. Baquey et al. Y0 /2.3 z 0 l Shear plane Distance from the wall Fig. 1. Variation of the electric potential near a surface in the presence of an electrolyte solution. (a) Electrical double layer at the surface of a solid positively charged, in contact with an electrolyte solution. (b) The variation of the electrical potential when the measurement is made at an increasing distance from the surface, and when the liquid phase is mobile at a given flow rate. The zeta potential (z) can be calculated from the streaming potential, which can be measured according to the method described by Thubikar et al. [4]. hydrogen electrode (NHE)] thrombosis occurred systematically, while thrombosis never occurred on surfaces with a negative potential (<0 mV/NHE). However, surface potential cannot be the unique criterion of non-thrombogenicity. The superficial distribution of the charged site plays an important role as far as plasma protein adsorption is concerned and, upon their adsorption, these biomolecules may trigger the coagulation cascade in spite of exposing a net negative charge to the bloodstream. 2.3. Scenario for blood-material interactions According to the above developed considerations, surfaces can be described as a mosaic-like structure of which individual elements contribute locally and specifically to their residual binding capacity and their electrical potential. The individual characteristics of these elements and their microtopography determine, via a first series of interactions with water molecules and small solutes, which plasma Fluorinated Biomaterials for Cardiovascular Surgery 383 proteins adsorb and how they do it, when blood comes into contact which these surfaces, according to the following scenario. At first, and according to their surface tension, materials show an affinity for water which corresponds to their wettability. Polar materials and materials bearing ionic sites, whether these properties are intrinsic or brought about by the contacting medium through adsorption phenomena of ions, are obviously the most wettable. Hydrophobic materials do not interact with water, but instead promote its intermolecular organisation, as in the case of oil or parafins. The contribution of water to the entropy of the system is thus decreased. This first step may occur simultaneously with (or may be immediately followed by) the interaction of free ions in solution on the one hand, which interact with ionic sites present on the material surface for previously mentioned reasons, and the interaction of small solutes in solution on the other. Obviously, ions and small solutes contribute to a local alteration of the water organisation in the interfacial region. The second step concerns proteins and other biological macromolecules, which will adsorb at the blood-material interface. These adsorption phenomena are controlled by the nature and distribution of available binding sites as determined by the type of material and the state of its surface after the previous step. Biological macromolecules are themselves characterised by a superficial distribution of binding sites when they are free in solution. If there is a good fit between this distribution and the one exposed by the material surface, macromolecules may adsorb without any conformational change; among available macromolecules, those for which this fit is the best have the greatest probability to adsorb. However, adsorption may occur together with a conformational change if such behaviour is thermodynamically favoured [6]. Furthermore, these adsorption phenomena may give macromolecules an opportunity to be activated, that is, zymogens will give active enzymes. In this way, the so-called coagulation contact phase starts. The third and final step involves blood cells, and more particularly platelets and polymorphonuclear neutrophil leukocyte also known as granulocytes. According to the material surface state after the various events which have occurred previously, cells may or may not adhere to the material; for platelets, adhesion may be the initiating step for their activation and aggregation, since activation of platelets involves the release by their cytoplasmic granules of active promoters for thrombogenesis and platelet aggregation. Cell adhesion is not only due to physical and chemical phenomena as for protein adsorption, but also implies biochemical mechanisms involving cell membrane glycoproteins. C5 to C9 complement{ components may bind to platelets and amplify platelet release and aggregation already induced by thrombin. It may be noticed that platelet activation may also result from contact with air, which cannot occur under { The so-called complement system consists in a set of 21 proteins aimed at contributing to the defence of the organism against foreign bodies or microorganisms or even abnormal cells. 384 C. Baquey et al. implantation conditions, but which is possible during a session of extracorporeal circulation. Similarly, neutrophil adhesion arises from an increase of their adhesiveness due to the effect of the anaphylatoxin C5a on the expression of adhesines at the membrane of the neutrophils; C5a is generated by the complement activation processes, which may occur during the plasma protein-material interaction step. 2.4. Role of dynamic factors Surface physics and chemistry play a major role as far as blood-material interactions are concerned. However, the observed processes depend as much on the local flow patterns of the blood near the material surface as on these surface characteristics. It has been shown that plasma protein adsorption, which occurs as soon as blood comes into contact with a given surface, is clearly influenced by the local shear stress [7]. As discussed by Leonard [8], the concentrations of activated coagulation proteins in the interfacial layer (i.e. the layer sitting between the main stream in a vessel and the wall) are strongly influenced by flow factors, and the net concentrations are determined both by biochemical reactions producing activated coagulation factors and by convective-diffusive factors that serve to moderate the concentrations of inactivated and activated coagulation proteins. Furthermore, the presence of high concentrations of activated coagulation proteins may favour the activation of platelets and leukocytes. These two blood cell types are able to undergo activation via collisions, which are favoured by turbulent flow or particular conditions such as those created by vortices. Platelet and fibrin deposition are strongly influenced by plasma and cellular factors, by properties of the vessel wall and by flow, as shown experimentally with the model of the everted deendothelialised rabbit aorta, used by Baumgartner [9]. Platelet attachment to subendothelium{ is determined predominantly by physical factors controlling the rate of platelet transport to the subendothelium at low shear rates (800 s1). In addition, platelet deposition was found to be highly dependent on the concentration of red cells, an effect attributed in part to the fact that red cells, by increasing the radial movement of platelets, enhance their diffusivity by several orders of magnitude compared to that theoretically predicted and experimentally measured in platelet-rich plasma. Weiss et al. [10] have shown that platelet deposition is at a minimum at a shear rate of 50 s1, while fibrin deposition on subendothelium from non-anticoagulated blood is at a maximum at the same shear rate. At low shear rates (250 s1), fibrin { The inner surface of vessel is composed by a monolayer of adjacent endothelial cells. This layer is called endothelium and the underlying tissue is called subendothelium. Fluorinated Biomaterials for Cardiovascular Surgery 385 deposition is independent of platelet density and integrity. At a higher shear rate (650 s1), platelets must possess all their physiological properties to promote fibrin deposition. At much higher shear rates (2600 s1), fibrin deposition decreases despite increasing platelet deposition. It will be later proposed that an ideal blood-contacting surface would be one on which endothelial cells could adhere and grow normally to create a complete endothelium endowed with the physiological functions of such tissue. But the correct expression of such physiological functions requires normal blood flow conditions. And the correlation of thrombosis with regions of disturbed flow suggests that shear stress may alter the production of endothelial cell-derived products and directly affect endothelial cell function. Secretion of tissue plasminogen activator by cultured endothelial cells increases within an hour after exposure to arterial levels of shear stress [11], while secretion of the related inhibitor (plasminogen inhibitor-1) by the same cells is unaffected by shear forces over the physiological range. Endothelial cells produce vasoactive substances, which modulate the permeability of vessel walls; accordingly, shear stresses may indirectly affect this wall parameter by influencing the secretory activity of endothelial cells. Prostacyclin, a potent inhibitor of platelet aggregation, is derived from metabolisation of arachidonic acid by endothelial cells, and shear stress increases its production rate [12]. It is postulated that this effect is due to perturbations of the permeability of the plasma membrane changing the cytosolic Ca2 content and leading to an increase in phospholipase C activity (through the by-passing of the receptor requirement), which contributes to a higher production of arachidonic metabolites. Shear stresses may also affect the construction and secretion by human endothelial cells of von Willebrand Factor polymeric forms that are involved together with fibronectin and fibrinogen during shear-induced platelet aggregation. In addition, shear stresses may play a role in the mechanism of platelet aggregation, probably through an increase in the readily available amounts of ADP, should the latter be due to an increased lysis of platelets, or to a greater release of their granules content. 2.5. Role of the morphology Materials may be compact or porous. In the case of compact materials, smooth surfaces are preferred, as blood cells will encounter fewer opportunities to be injured by asperities or morphological singularities when blood flows in contact with such surfaces. The chance of cell trauma of mechanical origin depends obviously upon the size of these morphological irregularities and upon local flow conditions (shear stress, tubulences, vortices, etc.). Wurzinger and SchmidSchonbein [13] have shown that the number of platelets adhering to PVC 386 C. Baquey et al. surfaces could be multiplied by a factor of 3 with surfaces featuring peaks or valleys with averaged heights or depths around 9 mm compared to polished surfaces, knowing that the diameter of platelets sits around 1.5 mm. Porous materials may have a closed porosity, which lowers their density and can be varied to optimise their mechanical properties, as this is carried out for some kinds of vascular grafts. For such materials, surface morphology must fulfil same requirements as those fulfilled by compact materials. Materials with an open porosity are not generally directly exposed to flowing blood for long. A widespread example of such materials is found with knitted or woven PET-based vascular grafts. These grafts may be immersed into blood to allow the latter to invade the fabric mesh where it coagulates, the resulting matrix acting as a new lining offered to the flowing blood. 3. REQUIREMENTS FOR A CARDIOVASCULAR BIOMATERIAL The above considerations show how it is important for the design of a vascular substitute to pay attention to its mechanical properties, to get similarity of dynamic behaviour between this substitute and the vessel it is to partly replace. The bloodstream that will flow through this artificial conduit must not suffer any alteration able to induce any local turbulences or high wall shear rate. This requirement may be satisfied insofar as the mechanical compliancy of the prosthesis (see Table 1 for definition) is equivalent to that of the natural artery it will replace. In fact, the arterial blood flow is pulsatile and characterised by a pressure wave which should propagate itself across any section of the arterial tree without encountering any sudden change of mechanical impedancy (potentially responsible for energy consuming reflected waves). The viscoelastic properties of their wall, featuring a composite structure, allow natural arteries to increase Table 1. Comparison of the respective evolution of the compliancies of a natural artery on the one hand and of an expanded polytetrafluoroethylene prosthesis on the other hand when the blood pressure increases Blood pressure (mmHg) 60 80 100 120 Femoral artery 6.5 4.7 4.1 3.8 Expanded polytetrafluoroethylene 0.9 0.85 0.78 0.8 Compliancy: Measures the ability of an artery to increase its section (and obviously the volume of blood, which can be contained in a given segment of this artery) upon an increase of TransMural Pressure (PTM) compliancy is expressed as ((DV/V) 100)/DP as % per mmg Hg. Fluorinated Biomaterials for Cardiovascular Surgery 387 their diameter according to a non-linear pattern, as the blood pressure increases; the greater this pressure, the smaller the relative increase of the diameter (see Table 1). It is expected that the laminar blood flow regimen will not turn to a turbulent one, when it crosses over an anastomosis between a natural artery and an arterial prosthesis (or between the latter and again the natural artery), if the prosthesis has a compliancy similar to that of the natural artery. The turbulent regimen is undesirable as it increases the probability of collision between blood cells and causes great variations of the wall shear rate, the consequences of which are detrimental in several respects: intimal lesions, platelet activation, peri-anastomotic hyperplasia and false aneurysms formation. Whichever is the targeted application several fundamental requirements must be satisfied. Devices designed for the replacement of arteries, and then the materials used for the making of these devices, must be mechanically adapted to suffer for many years stresses resulting from the pulsatile blood pressure. They must feature as well, an adequate level of haemocompatibility, this criterion being easier to satisfy as vessels to be replaced have a larger diameter. Lastly, they must be biocompatible, which means that they are able to promote adhesion and healing of surrounding tissues without inducing any heavy inflammatory process or fibrosis or any other undesirable process. As a matter of fact, chemically inert materials, such as polyesters like PET on the one hand, or PTFE on the other, drew the interest of specialists, and were used as woven or knitted fabrics (for PET and PTFE initially), or as non-woven fabrics for PTFE (later on) to make tubular conduits; the porous wall of the latter was supposed to favour the above mentioned healing process. In fact, the wall porosity allows a transmural ingrowth of blood capillaries, the latter providing a potential source of cells for the endoluminal endothelialisation of the artificial substitute on the one hand, and oxygen and nutriments to the neointima on the other as does the vaso vasorum capillary network through the wall of native vessels. In addition, this parietal microvasculature helps to strengthen the host's defences against infectious processes, of which the risk is objectively increased by the implantation of a prosthesis, as bacteria easily adhere onto the surface of the latter. However, a compromise must be established between the above mentioned advantages brought by vessel substitutes with a porous wall and the blood loss suffered by the patient as soon as his blood is allowed to flow through such substitutes. In fact, the blood stops leaking rather rapidly as it clots when it comes into contact with the artificial surface of the vascular prosthesis. Nevertheless, and as a consequence of this blood loss, patients may need a blood transfusion, which may expose them to specific risks. That is the reason why vascular prostheses makers proposed in the early eighties, devices with an impervious wall. Such devices were prepared by soaking classical woven or knitted polyester prostheses into an albumin or collagen solution, and by a further cross-linking of the absorbed protein [14]. In vivo, the resulting proteinaceous reticulum is 388 C. Baquey et al. Fig. 2. A type of surgical vascular suture. progressively resorbed, and a few days after implantation, the primary porosity of the prostheses is again available for an eventual ingrowth of blood capillaries. Last but not least requirement, artificial arterial substitutes must be able to be connected to the host's vessels using sutures, the only reliable mean surgeons trust (Fig. 2). The connections performed must be stable and blood tight for as long as the prosthesis will remain patent. This last condition has supported the interest of surgeons for vascular prostheses made of woven or non-woven and knitted synthetic fabrics. The following sections give an outline of the different steps that line the evolution of materials for the cardiovascular system, and present some prospective solutions that have been proposed and supposed to improve the performances of these materials. 4. FROM POLYTETRAFLUOROETHYLENE TO MICROPOROUS TEFLON-BASED VASCULAR PROSTHESES Among these materials, two polymers the PET and the PTFE, which was discovered in 1938 by Roy J. Plunkett (after Peska et al. [15]), hold a predominant place, and obviously our comments will mainly concern the second one. The perfluorination of ethylene leads to the starting vinyl monomer for the synthesis of the polyethylene perfluorinated homologue; according to the propylene content of the starting hydrocarbon, the resulting fluorinated polymer may include a more or less great proportion of perfluorinated statistic copolymers of ethylene and propylene; the so-called Teflon FEP corresponds to one of such blends. Because of the high energy of the C-F bond, PTFE is extremely stable; its high molecular weight (>106 g/mole) renders it insoluble in all usual organic solvents, and resistant to relatively high temperatures, as it can suffer permanently as high temperatures as 260C. Because of the strong electronegativity of fluorine, PTFE is not Fluorinated Biomaterials for Cardiovascular Surgery 389 flammable, and demonstrates a high chemical inertia. Moreover, its surface free energy (18 ergs/cm2) is the lowest in comparison to that of usual polymeric materials; in fact, PTFE is the hydrophobic reference material, its hydrophobicity being likely responsible for conformational changes (with already mentioned biological consequences) proteins suffer when they adsorb onto its surface. Its high melting temperature (>320C) and the high viscosity of the melted polymer prevent its transformation according to procedures used with classical thermoplastics. Accordingly, a specific transformation protocol, derived from the powder metallurgy technology, has been developed to produce flexible tubings fitting with surgeons' wishes. According to this protocol, PTFE pellets are mixed with naphthalene, which plays a role of lubricant during the high temperature extrusion of this blend into tubes. The latter are modified by a process including several cycles of heating and mechanical stretching. This process, which is carried out at a temperature close to the PTFE melting point and favours the coalescence of PTFE crystallites, as well as induces the elimination of residual naphthalene, strongly alters the structure of the wall and create a macroporous, non-woven fabric with a high percentage of its volume composed of transmural void spaces. The structure that is formed is called expanded polytetrafluoroethylene (ePTFE), consists of layers of short, interlocking, circumferentially oriented, solid bands of the polymers (nodes), which are linked together by numerous, fine, filamentous bands (fibrils) that are longitudinally oriented, respect to the graft, and perpendicular to the nodes (Fig. 3A,B). Grafts have been investigated with internodal distances ranging from 5 to 90 mm in an effort to optimise haemocompatibility and endothelial cell attachment; however, the grafts in current clinical use, all have average internodal spacing of about 30 mm. These grafts are easily handled by surgeons and can be sutured securely; however, they have two drawbacks: they are prone to kink under severe bending and to collapse under the compressive action of surrounding tissues. To prevent these bad phenomena, companies have proposed to stake the graft wall with a propylene rib, but the abrasive effect of the latter on the material wall during the prostheses use induced potentially more severe risks for the patients. 4.1. State of the art related to vessel repair or replacement: Evolution and role of PTFE Like PET, which further became more and more popular under various trade names (Dacron in USA, Rhodergon in France, Dallon in Russia and European Eastern countries), PTFE was initially used as thread, which could be woven or knitted to obtain vascular prostheses. These resulting woven devices, in which two sets of threads, respectively called weft and warp, cross each other perpendicularly, are known to easily fray near anastomoses. For knitted devices, in 390 C. Baquey et al. Fig. 3. Microstructure of expanded polytetrafluoroethylene as shown by scanning electron microscopy with different internodular species (a) 30 mm; (b) 90 mm; (c) 12 mm. (N: Nodules, F: Fibrilles) Fig. 4. Vascular prosthesis made of woven polytetrafluoroethylene. The photograph shows the great ability of the fabric to fray. which these two sets of threads may not only interlace but also lock up with each other, fraying in less important, but still occurs due to the PTFE fibre characteristics. The ends of the primary devices as proposed by Edwards [16] (after Harisson experiments [17]) frayed rather easily (Fig. 4), especially when they were beveledged. However, these devices showed rather good clinical performances in spite of an uncertain healing. Ruptures might occur near the anastomoses when Fluorinated Biomaterials for Cardiovascular Surgery 391 silk was used to realise the sutures, as silk is partly biodegradable, while Teflon fibres kept unaltered for several decades after implantation [18]. Nevertheless, woven PTFE arterial prostheses were no longer used, as surgeons preferred to use prostheses made from woven or knitted PET yarns. Later on, these polyester-based prostheses met the competition with prostheses made from microporous Teflon (Fig. 5) or ePTFE, better known under various trade names such as Gore-Tex, IMPRA, Vitaflon, etc. Microporous Teflon was first used by Ben Eiseman in 1972 [19] for the making of membranes fitting oxygenators used for extracorporeal circulatory assistance. As several benefits seemed to be related to the use of this material (less damaged blood cells, no or little protein depletion, no or few clot deposition, neither embol release), he tried with his team to extend its applications. They carried out a series of experiments with piglets, such as the implantation of microporous Teflon conduits as substitutes for the portal vein, the inferior vena cava, the external iliac vein, and obtained a permeability rate equal to 80%, 2 months after implantation, taking into account the data from 27 experiments. In a pancreatectomised patient (pancreatectomy being a consequence of a cancer), 32 months after the implantation of such an artificial graft as a substitute for the portal vein, these graft was still permeable. Such success encouraged major companies, such as W.L. Gore and IMPRA, and vascular surgeons to develop the use of such grafts as arterial substitutes, and several teams carried out experimental studies which show them performant for various implantation sites. The first series of femoro-popliteal shunts, including 15 patients suffering a severe lower limb arterite (level III, even IV) and for whom the saphenous vein could not be used, was reported by Campbell in 1976 [20]; the patency rate at 8 months was 87%. These ePTFE prostheses made surgeons very enthusiastic and at least one of them, Veith [21], argued in their favour through an impressive Fig. 5. Vascular prosthesis made of micoporous polytetrafluoroethylene, also known as expanded polytetrafluoroethylene. 392 C. Baquey et al. Fig. 6. Tubular conduit made of expanded polytetrafluoroethylene wrapped into a thin sheath, which is also made of polytetrafluoroethylene; the photograph shows the ability of the sheath to detach from the main wall surface. clinical experience. Few cardiac surgeons attempted to use these prostheses for aortocoronary bypass, but they gave up very soon with this practice. The analysis of microporous Teflon-based arterial prostheses, which were retrieved along autopsies or along revision surgeries, confirmed the excellent biostability of these devices insofar as they had been carefully implanted. Few ruptures or tears were observed but had been likely caused either by a bad handling or by fibrosis expansion, the latter being more frequent for nonsheathed devices (Formichi et al. [22,23]). Taking into account the lack of stability of the prosthesis wall, the two major makers made tremendous efforts to improve this situation. W.L. Gore chose to fit their prostheses with a very thin external sheath, made also of microporous PTFE but almost impervious (Fig. 6). 4.2. How to improve the functional patency of ePTFE-based prostheses? These prostheses need to be improved in at least two respects: their haemocompatibility that must be increased if they are to be used for the replacement of small diameter artery (f<4.5 mm) on the one hand, and their dynamic mechanical properties on the other. To resolve the first issue, two strategies that in fact do not apply specifically to ePTFE-based prostheses have been proposed. According to a first strategy, the triggering of the blood coagulation cascade, which generates thrombin as soon as blood comes into contact with the artificial material, cannot be avoided, and the latter must be endowed along appropriate chemical modifications, with the ability to catalyse the inhibition of thrombin by its naturally circulating inhibitor, that is, the so-called antithrombin. Among the proposed modifications, one can distinguish the covalent binding of either heparin [24], Fluorinated Biomaterials for Cardiovascular Surgery 393 a specific glycosaminoglycan of which the catalytic effect on the thrombin- antithrombin reaction is well known, or synthetic polymers that are functionalised along a further stage to endow them with heparin-like properties [25]. A second strategy aims at avoiding the triggering of the blood coagulation cascade by preventing in a non-specific way, the adsorption of the so-called contact phase proteins and their conformational changes upon adsorption on a surface as hydrophobic as PTFEs, these conformational changes being responsible for their activation. Pre-adsorption of human serum albumin has been shown empirically to be somewhat efficient in this respect. According to a more rational approach, irreversible adsorption of proteins in general, and more particularly of proteins belonging to the coagulation system, can be prevented by the presence at the surface of the PTFE of a hydrophilic layer of which the main constituent may be polyethyleneglycol molecules. The latter can be bound to the PTFE insofar as it has been previously adequately functionalised; a plasma treatment, as described in a further section, allows such a functionalisation [26]. However, the expected best way to prevent blood to clot upon its contact with prostheses wall is to coat the latter with endothelial cells, which are used to regulate the blood-vessel wall relationship. To carry out this coating, the material surface has to be endowed with pro-adhesive properties towards endothelial cells; such properties may be brought by peptidic ligands able to be specifically recognised by specialised membrane receptors (integrins) sitting at the surface of the cells. These ligands are characterised by the presence in their sequence of the RGD (arginin-glycin-aspartic acid) triade [27], the latter being also included in the sequence of extracellular matrix proteins (collagen, fibronectin, vibronectin, etc.). Thus, such tripeptides may be also brought onto a prosthetic surface by coating the latter with an aqueous solution of collagen or of any other extracellular matrix protein. To control their availability and their superficial distribution density, proadhesive synthetic peptides may be used, as reported in a subsequent section. Endothelial cells anticoagulant properties are partly due to their ability to express at their membrane, thrombomodulin (TM) a glycoprotein, which tightly binds thrombin. So TM works as a direct anticoagulant by inhibiting the thrombin cleavage of fibrinogen, the first step of the fibrin clot formation; more importantly, TM is the essential cofactor that promotes thrombin cleavage of protein C; the resultant activated protein C inactivates factors Va and VIIIa and thus shuts down coagulation and haemostosis. This explains the choice made by Vasilets et al. [28] who proposed to immobilise TM onto PTFE previously grafted with acrylic acid (AA) through a microwave CO2 plasma initiated process. Considering the second requirement, that is, good dynamic mechanical properties ePTFE-based arterial prostheses must satisfy to improve their functional patency, there are not so many ways to reach this goal. Unfortunately, and due to the intrinsic mechanical characteristics of PTFE, the mechanical behaviour of these prostheses cannot be easily modified. However, different ways have been explored; on the one hand, an optimisation of the design of the prostheses 394 C. Baquey et al. has been attempted; on the other, the replacement of PTFE by other fluorinated polymers with a lower Young's modulus has been envisaged. As far as the design of the prostheses is concerned, the replacement of strictly cylindrical conduits, by tapered ones that better conform to the anatomic realty, has been proposed and deeply documented by theoretical and experimental studies [29]. ePTFE-based tapered arterial prostheses have been commercialised, but did not appear to bring any clinical benefit. The design of prostheses with an oval section, instead of a circular one, offers a way to get a gain in compliancy as the section area of such prostheses increases via a simple change of its shape (oval ! circular) as blood pressure increases, without any change of its circumference. However, to our knowledge, no arterial prosthesis designed according to this concept has ever been commercialised. The poor ability of ePTFE to reversibly stretch is not compatible with the making of arterial substitutes with a good compliancy; thus, specialists considered other polymeric materials combining the chemical inertia and the biostability of PTFE with a mechanical behaviour similar to that of elastomers, and their interest moved towards polyvinylidene difluoride (PVDF) and even more towards copolymers of vinylidenedifluoride and hexafluropropylene (HFP), which may have pseudo-elastomeric properties. Until now, only PVDF has been processed into yarns [while yarns of P(VDF-HFP) copolymers are not commercially available] from which tubular conduits, prefigurating vascular prostheses, have been woven (see Section 4.3). Even if the mechanical behaviour of these woven PVDF-based conduits, when they are experimentally exposed to a pulsatile flow with characteristics analogous to that of blood flow, is better than that of ePTFEbased prostheses or PET-based ones, it is far from conforming specialists' expectations. Nevertheless, the faisability of the chemical modification of PVDF to improve its haemocompatibility, according to the previously described principles, has been investigated. A further step will concern the modification of P(VDF-HFP) copolymers (hopefully, the same procedure as the one used with PVDF will be applicable), as soon as corresponding yarns from which tubular conduits demonstrating the expected mechanical behaviour could be woven, will be available. 4.3. Chemical modifications of fluorinated polymers: A way to the improvement of their haemocompatibility This section will successively deal with the treatment of PTFE, the treatment of PVDF and the treatment of P(VDF-HFP) copolymers. 4.3.1. PTFE case Because of its high chemical inertia, the chemical modification of PTFE may appear as a challenge. However, although this polymer resists to acidic or alkaline attacks, Fluorinated Biomaterials for Cardiovascular Surgery 395 it is vulnerable to the action of ionising radiations and to gaseous plasmas. Unfortunately, when PTFE is exposed to g-rays or to accelerated electrons beams, it degrades even if the adsorbed doses (a few kilograys) are relatively low; its molecular weight and its tensile strength decrease dramatically, as a lot of structural bonds are broken in the whole bulk of the material. Plasma treatment offers the opportunity to break bonds that belong only to the very first layers of macromolecules sitting at and under the surface of the material, without any noticeable bulky effect. Among others authors, Vasilets et al. [28] already quoted and Baquey et al. [26] demonstrated the interest of such an approach to introduce some functionality at the surface of ePTFE. After their paper, Baquey et al. exposed ePTFE samples to a Radio Frequency Glow Discharge fed with an argon/oxygen mixture (flow rate ratio 1:1) in a classical reactor. The latter was fitted with two internal aluminium electrodes, one being grounded and the other powered by a 13.56 MHz generator and acting as a sample holder. The pressure was set at 100 mTorr, and the treatments were driven at 100 W for 1 min. Then the samples were exposed to air atmosphere for 1 h before further grafting by AA via their immersion in an aqueous Acrylic Acid (AA) solution (25%, v/v) contained in glass flasks; following vigorous degassing, the flasks were sealed and kept for 5 h in a water bath at 65C. The AAgrafted samples were taken out of the flasks, and appropriately washed to remove any adsorbed homopolymers. Along a further step, the carboxylic groups available at the surface of the AA-grafted samples were exploited for the coupling of bNH2PEG, which is intended to be used as an anchor arm between the surface and peptidic molecules of interest via amide bonds. In this respect, Baquey et al. [26] chose a tetrapeptide, containing the RGD sequence and being, for that reason, a potential ligand for integrins (adhesion molecules), which sits at the membrane of cells, and particularly, of endothelial cells. The different steps of the procedure were monitored by X-ray photoelectron spectroscopy (XPS) quantitative analysis. It appeared that after plasma treatment (according to the above described protocol here) the oxygen content of the material surface was significantly increased, this being possibly attributed to the formation of peroxides. The latter were supposed to give rise upon heating, to peroxyl radicals able to induce the grafting of AA. In fact, the oxygen content of the material surface further increased after AA-grafting, and the presence of carboxylic groups was confirmed by a colorimetric assay based on the reactivity of these groups towards toluidine blue. So was confirmed the coupling of the AA-grafted surface with bNH2PEG, as the presence of nitrogen could be detected as significant by XPS. The final coupling of the RGDC tetrapeptide (Arg-Gly-Asp-Cys) was confirmed, as well as the presence of sulfur due to its cysteine amino acid component, and could be detected by XPS also. As far as their biological properties are concerned, the treated ePTFE samples showed their ability to better induce the adhesion of endothelial cells than does the pristine material. The number of cells adhered to the material 396 C. Baquey et al. after 2 h of culture in the absence of serum were four times larger for the treated ePTFE than for the pristine material; the mechanism of this adhesion was specific as the phenomena could be inhibited by the introduction of soluble RGDC peptides in the immersion medium of the samples containing the cells. 4.3.2. PVDF case PVDF is mainly obtained by radical polymerisation of 1,1-difluoroethylene; `head to tail' is the preferred mode of linking between the monomer units, but according to the polymerisation conditions, `head to head' or `tail to tail' links may appear. The inversion percentage, which depends upon the polymerisation temperature (3.5% at 20C, around 6% at 140C), can be quantified by 19F or 13C NMR spectroscopy [30] or FTIR spectroscopy [31], and affects the crystallinity of the polymer and its physical properties. The latter have been extensively summarised by Lovinger [30]. Upon recrystallisation from the melted state, PVDF features a spherulitic structure with a crystalline phase representing 50% of the whole material [32]. Four different crystalline phases (a, b, g, d) may be identified, but the a phase is the most common as it is the most stable from a thermodynamic point of view. Its helical structure is composed of two antiparallel chains. The other phases may be obtained, as shown by the conversion diagram (Fig. 7), by applying a mechanical or thermal stress or an electrical polarisation. The b phase owns ferroelectric, piezoelectric and pyroelectric properties. The interest for this polymer came as already said, from its relatively high chemical inertia, although lower than that of PTFE, and its lower Young's modulus (1.45 GPa) in comparison to that of PET (10.56 GPa) and PTFE. In addition, the availability of multifilament yarns obtained by extrusion from bulky PVDF offers the possibility to weave or to knit, as it is the case for PET yarns, tubular conduits usable as vascular prostheses (Fig. 8). Moreover, threads made of PVDF have long been actually used in surgery for suturing purposes [33] and have demonstrated a clinical biocompatibility [34] equivalent to that of other non-biodegradable polymeric materials used for this application. In parallel, the possibility to endow this polymer with `heparin-like' properties was demonstrated [35-37]. Briefly, the polymer available as 25-mm-thick films was grafted with polystyrene along a first step including its irradiation either with g-rays delivered by a 137Cesium source, or with swift heavy ions (SHI; mainly Argon) available from the GANIL (Grand Acce le rateur National d'Ions Lourds) facility in Caen, France. Different grafting yields (Y %) were obtained according to the type of radiation that was used, the adsorbed dose and the time of exposure to the vinylic monomer, that is, styrene; then the phenyl rings of the grafted polystyrene were chlorosulfonated and the chlorosulfonate groups reacted with the aspartic acid dimethylester; lastly, an alkaline treatment regenerated the carboxylic groups of the aspartic acid residues and generated sulfonate functions from the unreacted chlorosulfonate. Fluorinated Biomaterials for Cardiovascular Surgery 397 High T (high T ?) High P Any T Melting High T annealing Low T stretching High P oTnhiKnBlaryer a High T stretching b High T annealing Polarisation under very high E Polaris ation under high E High T annealing (phase e) (high P annealing ?) Polarisation under very high E Stretching g Very high P annealing d High T annealing DME, DMA or DMSO Solution MCB/DMF cyclohexanone Fig. 7. Polyvinylidene difluoride conversion diagram. Cyclohexanone Knowing the deleterious effects of ionising radiations on PTFE, much attention was paid on their effects on PVDF although the latter had been told to behave well under irradiation. As an example, PVDF multifilament yarns can be g irradiated up to the absorption of 80 kGy without any effect on their Young's modulus [38]. However, the structure of the polymer was somewhat modified as its energy to break kept constant and even increased by about 50% while the adsorbed dose was less than 8 kGy but decreased for higher adsorbed doses, down to 1/3 of its maximum value (1/2 of its initial value) when the adsorbed dose reached 81 kGy. To avoid these bulky effects, the interest of 398 C. Baquey et al. Fig. 8. Tubular conduit made of woven polyvinylidene difluoride. Fig. 9. Scheme of a swift heavy ion latent track. the irradiation by SHI has been investigated. Instead of being homogeneously distributed in the whole bulk of the irradiated material when g-rays are used, the energy (or the absorbed dose) brought by heavy ions is deposited very locally along so-called latent tracks (Fig. 9) related to their very short range inside the Fluorinated Biomaterials for Cardiovascular Surgery 399 material. According to the fluence (i.e. the average number of ions crossing a 1 cm2 section) of the heavy ions beam that is operated, these latent tracks may be either completely separated or overlap with one another. Moreover, due to their high Lineic Energy Transfer (LET), SHI are rapidly stopped; thus, their interactions with the iradiated polymer only concern the very superficial layers of the latter. As a matter of fact, the subsequent grafting of polystyrene can only occur onto the related surface microdomains, where the density of precursors of polymerisation initiators is relatively high. This appears clearly on microphotographs obtained by Scanning Electron Microscopy (SEM) of treated films which show the presence of circular islands (Fig. 10), the diameter of which depends upon the adsorbed dose. In addition, the elemental analysis of these films by Energy-Dispersive X-ray Analysis (EDXA) evidenced a decrease of the relative concentration of fluorine related to an increase of the grafting yield, and this decrease being maximum when the microprobe targets the centre of the above mentioned islands. Fourier Transform IR, transmission and internal reflection spectroscopies have been used to calculate the PS grafting yields at different depths; the observed gradient is higher in the case of g-ray-induced grafting than in that of a SHI one. This might be explained by the fact that the PS growing chains diffusion is accelerated in the latent tracks formed after irradiation with SHI. The existence of a grafting can be linked to the monomer ability to diffuse towards the grafting centres. The subsequent steps of the treatment aimed at endowing the PVDF with heparin-like properties lead as well, to a non-homogenous distribution of the related functional groups; as a matter of fact the hydrophobicity of the material surface depends upon the coordinates of the point around which the wettability is measured. In fact, the surface has acquired a mosaic-like structure; in other words, it consists of two classes of microdomains more or less delimited, respectively characterised by the original hydrophobicity of PVDF for some of them, and by a relative hydrophilicity for the others. According to the concept developed by Okano et al. [39], such surfaces, insofar as they are properly designed in terms of size and specific characteristics of their constitutive microdomains, could express a low thrombogenicity as they could suppress platelet adhesion, and not induce any activation of the coagulation cascade. In spite of these very promising perspectives, there was a lot of work to carry out to apply this concept to the processing of PVDF multifilament yarns. So and considering practical reasons (i.e. the necessity to rapidly obtain tubular conduits which could be experimentally implanted in vivo as arterial substitutes), Marmey et al. [37] decided to initiate the chemical functionalisation of this material through its irradiation with g-rays; even under such conditions, the resulting functions are homogeneously distributed at the surface of the material. To evaluate the effect of the treatment on the haemocompatibility of the PVDF yarns, the so-called thrombin time (TT) of human plasma was measured, whether a given amount of PVDF yarns, either treated or not was, immersed into a plasma aliquot or not. The immersion of pristine PVDF did not change the value 400 C. Baquey et al. Fig. 10. Scanning electron microscopy microphotographies of the surface of different polystyrene-grafted polyvinylidene difluoride (PVDF) surfaces; the grafting was performed upon irradiation with Argon ions with various fluences or absorbed doses. (a) PVDF-gAr-PS (Y 2.5%), D 3.72 kGy, Ft 1.1109 ions/cm2; (b) PVDF-gAr-PS (Y 19%), D 3.72 kGy, Ft 1.1 109 ions/cm2 and (c) PVDF-gAr-PS (Y 12%), D 37.2 kGy, Ft 1.1 1010 ions/cm2. of TT in comparison with the value (18 s) measured for plasma alone, while the immersion of treated PVDF dramatically increased the TT up to values greater than 120 s. Thus, a first requirement seemed to be fulfilled before knitting haemocompatible tubular conduits from chemically modified PVDF multifilament yarns; unfortunately the available yarns had a too big diameter, which rendered impossible the Fluorinated Biomaterials for Cardiovascular Surgery 401 making of enough supple tubular conduits able to be used as vascular substitutes. Except for this application, such yarns seem to not find any other commercial application, which explains the lack of interest from specialised companies to transform PVDF into multifilament yarns. 4.3.3. P(VDF-HFP) case A particular copolymer for which the molar fractions of the two constitutive monomers were 93% and 7%, respectively was available as films prepared by MS Techniques (France) with a 1.78 g/cm3 density. The interest for this copolymer comes from its mechanical properties, which should render it better adapted for making compliant tubings, and from its relatively high radiation resistance. Unfortunately, the availability of multifilament yarns is a bigger concern than it is for PVDF. Nevertheless, the faisability of the modification of this copolymer to endow it with heparin-like properties has been investigated according to the same protocol. During the grafting stage, the styrene can diffuse more easily into this copolymer than it does through PVDF as the latter has a higher level of crystallinity [Fig. 11 clearly shows the presence of 1-mm-large spherulites at the surface of PVDF, whereas such features do not appear at the surface of the P(VDF-HFP)]. In fact, swelling measurements performed with styrene at 60C on pristine and irradiated polymers, show that the diffusion coefficient is almost 15 times smaller for PVDF than for P(VDF-HFP), this result being attributed to the difference of crystallinity between the two materials [36]. At the same time, the plasticising effect of HFP increases the Fig. 11. Comparison of PVDF (a) and P (VDF-HFP) (b) surface respective morphologies as shown by scanning electron microscopy. 402 C. Baquey et al. mobility of the radicals created upon irradiation and their ability to recombine, which explains a lower global grafting yield of styrene on P(VDF-HFP) in comparison to the grafting yield on PVDF following the same absorbed dose. The previously mentioned authors [36] have investigated in details the role of different parameters: radiation kind (g or SHI) adsorbed dose or fluence for SHI, duration of exposure to the monomer, on the distribution of the grafted polystyrene. The latter may consist in separated islands, when SHI are used at low fluence and the exposure to the monomer is short (Fig. 10), or in a continuous and more or less thick film, which confers to the polymer surface a smooth appearance when g-rays are used and the grafting yield is high (Fig. 12). 5. CONCLUSIONS More than 30 years after it has been proposed for the manufacture of arterial substitutes, microporous PTFE stands more than ever among the biomaterials that are widely used by vascular surgeons. As it may be transformed into tubular conduits, they use the latter to replace arterial segments, or to build femoropopliteal by-pass, or even to build arterio-venous shunts for patients needing recurrent haemodialysis. Its biostability has been established along many years of clinical use, and according to manufacturers, more than 2 millions of microporous Teflon-based vascular prostheses have been implanted all over the world since they have been launched in the market. In the meantime, the original products have suffered very few modifications. Its wall has been made thinner to make its implantation easier, and a gelatin coating may be applied to prevent any bleeding through suture stitches. However, the relative success of such devices is beyond any rational analysis; their compliancy is rather poor and their integration into the host tissues is uneven; moreover, their internal surface may be colonised in vivo but without any positive bioactivity as it may turn thrombogenic again upon biochemical or mechanical stimulation [40]. In fact, despite spectacular clinical results, microporous Teflon-based vascular prostheses do not objectively perform better than the autologous venous graft, which still stands as the gold standard. Clinical studies do not establish as well that these prostheses perform better than polyester-based ones when they are used to build a femoro-popliteal by-pass. If one considers more demanding applications such as the replacement or coronary arteries, the lack of performant prostheses is still pending, and the only chance to fill the gap is to consider other polymeric materials (including other fluorinated polymers) and new strategies aimed at designing vascular substitutes. Among these strategies, those which are based on tissue engineering concepts appears as very promising, and almost ready to be developed. The availability of more compliant fluorinated polymers or copolymers than ePTFE has been evoked in this chapter as well as the availability of methods allowing the functionalisation of their surface to endow the latter with Fluorinated Biomaterials for Cardiovascular Surgery 403 Fig. 12. Scanning electron microscopy microphotographies of different polystyrene grafted polyvinylidene difluoride (PVDF) surfaces; the grafting was performed upon gamma irradiation with various absorbed doses; the grafting yield (Y ) was also modulated by the time of exposure of the irradiated surfaces to the styrene. (a) PVDF-gg-PS (Y 6%), D 10 kGy; (b) PVDF-gg-PS (Y 20%), D 10 kGy; (c) PVDF-gg-PS (Y 50%), D 30 kGy. pro-adhesive properties towards endothelial cells. It is just necessary to develop the appropriate processing techniques, enabling the manufacture of compliant small diameter tubular conduits from these materials, these conduits being able to be sutured by the surgeons to the natural vessels. 404 C. Baquey et al. REFERENCES [1] T. Gluck, Die modern chirurgie des circulations apparates, Berl. Klim 120 (1898) 1-29. [2] A.B.Ja. Woorhees, A.III. Jaretzki, A.H. Blakemore, The use of tubes contracted from vinyon =N? cloth in bridging arterial defects, Ann. Surg. 135 (1952) 332-336. 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Eloy, Macromolecular, histological, ultrastructural and immunocytochemical characteristics of the neointima developed within PTFE vascular grafts. Experimental study in dogs, J. Biomed. Mater. Res. 17(4) (1983) 623-636. Note from the Editors Partially adapted from ``Biomateriaux fluores pour la chirurgie cardio-vasculaire'', C. Baquey and R. Guidoin, Actualite Chimique, No. 301-302, November 2006. Actualite Chimique and Socie te Franc aise de Chimie are acknowledged for authorization. FINAL June 13, 2023 RE: Technical Support Document in Response to ECHA Annex XV Restriction Proposal for PFAS, Gujarat Fluorochemical's RAC Comment Letter OVERALL COMMENT In response to the Annex XV Restriction Report, proposal for a restriction on per- and polyfluoroalkyl substances (PFAS), we offer the following comments. Overall, we find the proposal to be overly broad with respect to "PFAS", and scientifically distorted as it relates to fluoropolymers. The goal of reducing risks to the environment and human health from exposure to PFAS and/or their degradation products can be achieved without requiring a restriction on PFAS as single class - especially with PFAS having a broad range of chemical functional groups and physical/chemical properties. Furthermore, by essentially equating risk with persistence, the proposal significantly oversimplifies the approach to both hazard identification and risk assessment that has been central to risk management approaches under REACH and other EU regulatory frameworks for many years (see REACH Annex XIII). Fluoropolymers should be excluded from the proposed risk management option because they are not bioaccumulative, not mobile, and not toxic, and, therefore, do not pose a risk to the environment or human health. SPECIFIC COMMENTS 1. Persistence alone is not an appropriate measure of potential human health or environmental risk. Some PFAS have been described as persistent because they degrade or transform to "terminal" persistent compounds. As stated in the restriction proposal (p.24), "[t]he persistence as the core concern of PFASs has also been pointed out by scientists for instance in the Helsingr Statement on PFASs (Scheringer et al., 2014) as well as the follow up Madrid statement (Blum et al., 2015)." The proposal omits an important detail, which is that neither of these statements refer to fluoropolymers. Scheringer et al. (2014) specifically referred to non-polymer perfluoroalkyl acids (PFAS) - perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonic acids (PFSAs), including perfluorooctanesulfonic acid (PFOS). Likewise, Blum et al. (2015) references scientific studies that are exclusively on non-polymer perfluoroalkyl acids (PFAAs), rather than fluoropolymers. As described in REACH Annex XIII, several regulatory frameworks in Europe require the assessment of "persistent, bioaccumulative, toxic" (PBT) properties of chemicals, including refined classifications such as "very persistent and very bioaccumulative (vPvB)". Substances with PBT/vPvB properties combine the characteristics of strong persistence with the potential to accumulate in the environment and biota (Moermond et al., 2012, p. 2). Dating back to the Stockholm Convention on Persistent Organic Pollutants, the objective for evaluating PBT as combined characteristics is the "protection FINAL of the environment and humans from substances that may harm these entities, either locally or globally, by accumulation in organisms where they then exert toxic effects" (Solomon et al., 2013, p. 1). Inherent in this objective is the understanding that the toxicity of a substance is contingent on the level present in the organism, and that chemicals with a lower bioaccumulation potential will present a lower risk. Persistence in the environment does not indicate that the substance would accumulate in organisms, nor that environmental levels would rise to such an extent that exposure would result in toxicity. According to ECHA, substances that persist for long periods of time in the environment and have a high potential to accumulate in biota are of specific concern because their long-term effects are rarely predictable1. Importantly, the PBT criteria established under REACH has always considered the characteristics of both persistency and bioaccumulation together, as indicators of potential risk (i.e., toxicity). Potential for bioaccumulation is defined by REACH criteria (EC-1907-2006) as the condition when the bioconcentration factor (BCF) in aquatic species is higher than 2000. PBT criteria have been applied consistently under numerous EU regulatory frameworks. The following are examples of applications of PBT concepts in regulatory programs over the past three decades (based on Table 3 from Moermond et al., 2012): Time Period Late 1990s 1998 2001 2003 2004 2006 Regulatory Program that Adopted or Applied PBT Concept Criteria Expert Group for Persistent Organic Pollutants develop criteria for categorization of POPs (Solomon et al. 2013) United Nations Economic Commission for Europe, the Convention on Long-range Transboundary Air Pollution (LRTAP) Stockholm Convention OSPAR Convention for the Protection of the Marine Environment of the Northeast Atlantic EU directives on Human & Veterinary Pharmaceuticals International Maritime Organization (IMO) International Convention for the Control and Management of Ship's Ballast Water and Sediments Registration, Evaluation, Authorisation and Restriction of Chemicals, (REACH) Across each of these regulatory frameworks, the combination of chemical properties that comprise PBT criteria are consistently evaluated: a. The chemical is evaluated for its persistence (P/vP) in the environment based on its half-life in environmental media (e.g., water, sediment, soil); and, b. The chemical is evaluated for bioaccumulation (B/vB) in biota based on its BCF, octanol/water coefficient (log KOW), or monitoring data; and, c. The chemical is evaluated for toxicity (T) to biota based on observed adverse effects at concentrations exceeding specific exposure thresholds, or evidence of 1 https://echa.europa.eu/understanding-pbt-assessment FINAL carcinogenicity, mutagenicity, reproductive toxicity, or specific target organ toxicity after repeated exposure. While there are differences in the specific criteria applied during PBT/vPvB evaluation, each regulatory framework makes clear that no standalone criteria, whether it be P/vP, B/vB, or T, is sufficient cause for PBT/vPvB status or environmental concern. In all cases, at least two of these three properties (P and B) must be established to identify a chemical as PBT/vPvB. In fact, there is precedent within EU chemical legislation for not restricting chemicals based on persistence alone. For example, vinyl neodecanoate was evaluated by the PBT Working Group and classified as "P/vP" but "not fulfilling PBT and vP/vB criteria". Specifically, the assessment report states that vinyl neodecanoate: "is not considered to be a PBT substance. It does not meet the B criteria and does not meet the screening criteria for T. It does meet the screening criteria for P (and vP)."2 2. Fluoropolymers are not bioaccumulative. Available data indicate that fluoropolymers are not bioaccumulative. Bioaccumulation potential is generally assessed based on a prediction using the octanol-water coefficient (e.g., log KOW > 3) or measurements in tissue and exposure media (e.g., BCF > 2000). Fluoropolymers such as polytetrafluoroethylene (PTFE, CASRN 9002-84-0), polyvinylidene fluoride (PVDF) homopolymer (CASRN 24937-79-9), perfluoroalkoxy alkane (PFA, CASRN 26655-00-5 and 31784-04-0), and fluoroelastomer (FKM, CASRNs 9011-17-0, 26424-79-6, and 25190-89-0) are insoluble in octanol and water (Henry et al., 2018; Korzeniowski et al., 2022). Therefore, the bioaccumulation potential of fluoropolymers cannot be reliably predicted from a log KOW. Measured biota tissue, water, and sediment concentrations indicate there is a low bioaccumulation potential for fluoropolymers in aquatic food webs. Researchers examining benthic invertebrate exposure to PTFE and other polymers demonstrated that there was no evidence of bioaccumulation through the aquatic benthic community from lower trophic level filterfeeders and grazers to higher trophic level omnivores and predators in the Arctic (Sfriso et al., 2020) and in Norway (Bour et al., 2018). 3. Fluoropolymers are not environmentally mobile. The restriction proposal argues that the continuous release of PFAS will lead to the accumulation of these compounds in the environment, such that unknown toxicity thresholds will be exceeded at some unknown point in the future. Moreover, the proposal also suggests that "PFAS" as a class will be found in all environmental media. Neither of these arguments apply to fluoropolymers. Fluoropolymers are not water soluble and will not likely result in widespread groundwater impacts or exposures from drinking water. If released to the environment, fluoropolymers are likely to remain in the environmental matrix they contact following release, such as terrestrial soil or aquatic sediment. Because fluoropolymers are chemically inert, they cannot partition and are not chemically mobile between water and soil/sediment. Any potential movement of fluoropolymers in the environment will occur via mechanical 2 https://echa.europa.eu/documents/10162/6af350f6-e259-4545-859f-293ce8515cb3 FINAL transport processes, such as overland flow from precipitation events (e.g., rainfall flows carrying fluoropolymers from soil to sediment via runoff). Indeed, Feng et al. (2022) recently demonstrated that PTFE in modelled tidal sediments showed enhanced retention and low likelihood of resuspension into the water column. Given their chemical inertness, non-volatility, and lack of water solubility, fluoropolymers are not highly mobile in the environment. 4. Fluoropolymers present in the environment are not toxic to humans or ecological receptors. Toxicity studies on fluoropolymers indicate that adverse effects are unlikely following exposure by human or ecological receptors to levels of fluoropolymer that may be present in the environment. A summary of available laboratory bioassays examining the toxicity of PTFE on test animals is provided by Radulovic and Wojcinski (2014). Given that fluoropolymers such as PTFE are insoluble in water and non-volatile, the most likely exposure route for PTFE is ingestion. In fact, acute oral toxicity of PTFE in rats is low, with a reported LD50 > 11,280 mg/kg. Researchers also found there were no observed adverse effects in rats exposed to up to 25% PTFE in rat diet for up to 90 days (Naftalovich et al., 2016; Radulovic & Wojcinski, 2014). The lack of toxicity of PTFE at 25% of the diet level fed to rats for 90 days was subsequently validated by peer review by the Scientific Review Panel of the Hazardous Substances Data Bank (TOXNET) (Naftalovich et al., 2016). Additionally, a four-week repeated dose study exposed mice to PTFE via their diet and reported no effects at any dose level, and no PTFE was detected in mice blood (Lee et al., 2022). The study supports an unbounded no-observed-adverse-effect-level (NOAEL) of 2,000 milligrams per kilogram (mg/kg) in mice, equivalent to approximately 9,720 mg/kg for a 60 kg human adult. The lack of toxicity from ingestion of PTFE and other fluoropolymers is attributed to their extremely high molecular weight, which renders absorption via the gastrointestinal tract negligible, and the fact that they are chemically inert compounds and not metabolized under physiological conditions (Naftalovich et al., 2016). Manufacturer Material Safety Data Sheets indicate that dermal contact with PTFE does not cause skin irritation in rabbits or humans. PTFE is not considered genotoxic and is so inert it has been used in genotoxicity protocols or test methodologies for Salmonella typhimurium mutagenicity testing of the US EPA Mobile Reaction Chamber (Naftalovich et al., 2016). The World Health Organization's International Agency for Research on Cancer concluded that organic polymeric materials (such as fluoropolymers) as a group are not classifiable as to their carcinogenicity to humans (Group 3) (IARC, 1999). 5. The "P-sufficient" approach is novel and precedent setting, worldwide. The Annex XV Restriction of all "PFAS" would be the first of its kind globally. The Restriction Report (p.24) references California EPA, Department of Toxic Substances and Chemicals (DTSC) as an example of established regulatory precedent, where a state regulatory agency has placed restrictions on all PFAS as class3. The referenced journal article (Blan et al., 2021) written by California DTSC staff specifically refers to PFAS present in specific consumer products. It would be inaccurate to conclude from this one example that 3 The Restriction report says: "It is noted that the first example of regulation of PFASs as a chemical class according to the P-sufficient approach has been introduced in California. Here a regulation of PFASs as a class is in place for certain consumer products under the California Safer Consumer Products Program (Balan et al., 2021)." FINAL California has adopted the P-sufficient concept as a PFAS risk management strategy. Indeed, an examination of recent legislative developments in California clearly shows that the state is actually pursuing a targeted risk management strategy: 1. PFAS in fire-fighting foam o Effective 1 January 2022, this legislation prohibits the use of class B firefighting foam containing intentionally added PFAS chemicals in California. 2. PFAS in textiles o Effective 1 January 2024, will prohibit the sale of PFAS-containing textile articles and require least toxic alternatives when replacing PFAS. 3. PFAS in cosmetics o Effective 1 January 2025, prohibits sale of cosmetic products that contain intentionally-added PFAS. 4. PFAS in plant-based food packaging and cookware o Effective 1 January 2023, prohibits sale of various plant fiber-based food packaging that contains PFAS. o Requires disclosure of certain chemicals, including PFAS, in cookware starting January 2023. Importantly, none of these legislative actions apply to industrial PFAS uses, where fluoropolymers are primarily utilized. Furthermore, these initiatives clearly demonstrate that California is pursuing targeted restrictions on PFAS used in specific consumer products. Moreover, Blan et al. (2021) inappropriately include fluoropolymers under their Psufficient approach based solely on one false statement and a second statement that lacks important context: 1. "Fluoropolymers are characterized by large molecular sizes and do not degrade to PFAAs under typical environmental conditions, although they have been observed to release [perfluorocarboxylic acids] PFCAs, including [perfluorooctanoate] PFOA, when heated to temperatures between 180 C and 800 C (Schlummer et al. 2015; Feng et al. 2015)." This statement, while correct regarding the large molecular weight of fluoropolymers, is incorrect with regard to the release of PFCAs such as PFOA. When heated to temperatures greater than 300 C, the potential transformation products of PTFE include trifluoroacetic acid (TFA, CASRN 76-05-1), hydrofluoric acid (CASRN 766439-3), tetrafluoroethylene (TFE, CASRN 116-14-3), hexafluoropropylene (CASRN 116-15-4), or perfluoroisobutylene (CASRN 382-21-8) (Ellis et al., 2001; Radulovic and Wojcinski, 2014; Henry et al., 2018; Tolkach et al., 2020). Heating PVDF homopolymer to temperatures greater than 300 C may result in the formation of hydrogen fluoride (HF, CAS No. 7664-39-3) and oxides of carbon (Arkema, 2011). Similarly, thermal decomposition of PFA at temperatures exceeding 300 C can produce HF, carbonyl difluoride (CASRN 353-50-4), carbon monoxide (CO, CASRN 630-08-0) and carbon dioxide (CASRN 124-38-9) (Inoflon Fluoropolymers, 2018). The potential transformation products of these fluoropolymers do not include PFCAs such as PFOA at intended use and end of life conditions. FINAL 2. "PFAAs are used in the manufacture of fluoropolymers and can occur as impurities in the final product." PFAAs such as fluorinated polymerization aids (FPAs), also referred to as fluorosurfactants, are currently used by some chemical manufacturers, albeit to a lesser extent, to facilitate the polymerization reaction that forms the final fluoropolymer product (Ameduri et al., 2023). PFOA and hexafluoropropylene oxide dimer acid (HFPO-DA, or GenX) are examples of these FPAs that have garnered widespread environmental concern. Furthermore, the substitution of non-fluorinated polymerization aids (NFPAs) for FPAs in the manufacture of the three main fluoropolymers by volume - PTFE, PVDF, and FKM - allows for the complete manufacture of these fluoropolymers without the use of FPAs and any resulting minor impurities (Ameduri et al., 2023). Therefore, by implementing the widespread use of NFPAs in fluoropolymer manufacturing, environmental contamination can be reduced to the maximum extent practicable. Residual impurities from non-polymeric PFAS entrained in the final fluoropolymer product, such as low molecular weight (<1000 Da) leachables and residual monomers, are quantifiably low: <1 ppm in PTFE and <50 ppb in PFA (Henry et al., 2018). This low leaching potential is what allows PTFE to meet the requirements for use in the food and beverage, pharmaceutical, medical, and semiconductor industries (Olabisi and Adewale, 2015). The following table summarizes the numerous regulatory safety standards that fluoropolymers meet for US and EU regulations, demonstrating their safety for use across drinking water, food contact, and medical industries: Regulation EC 10/2011 21CFR 177.1550 2011/65/EU USP Class VI 3-A 20-27 Umwelt Bundesamt (UBA) Regulatory Program Description EU Commission Regulation No 10/2011 of 14 January 2011 safety requirement on plastic materials and articles intended to come into contact with food (EU, 2011a). US food contact regulation for perfluorocarbon resins (CFR, 2023). Restriction of hazardous substances in electrical & electronic equipment (EU, 2011b). Biocompatibility testing requirements from the U.S. Pharmacopeia (USP). Includes safety standards for plastic, polymers, and elastomers to be applied in medical devices and surgical equipment. Testing includes acute systemic toxicity test, intracutaneous test, and implantation test (USP, n.d.). Sanitary standards for multiple-use plastic materials as a product contact or cleaning solution contact surfaces in equipment for production, processing, and handling of milk and milk products. Test criteria includes their ability to be cleaned, to receive effective bactericidal treatment, and to maintain their essential functional properties (3-A, 2011). German Environmental Agency (UBA) evaluation criteria for any plastic and rubber products that come in contact with drinking water (UBA, 2022). FINAL Sanitary Conformity Certification (ACS) Water Regulations Approval Scheme (WRAS) French mandatory certification for any device in contact with drinking water during production, treatment, storage, and distribution (ANSES, 2013; FR, n.d.). United Kingdom's accreditation body for approval process of water fittings. It aims to prevent the misuse, waste, excessive consumption, and inaccurate measurement of water and, ensure that drinking water is free from contamination. Includes products used only after the time of supply (WRAS, n.d.). References: 3-A Sanitary Standards (3-A). (2011). 3-A Sanitary Standards for Multiple-Use Plastic Materials, Number 20-27. Accessed May 2023. Ameduri, B., Sales, J., & Schlipf, M. (2023). Developments in fluoropolymer manufacturing technology to remove intentional use of PFAS as polymerization aids. International Chemical Regulatory and Law Review, 6(1). Arkema. (2011). Material Safety Data Sheet, Kynar Homopolymer. Blan, S. A., Mathrani, V. C., Guo, D. F., & Algazi, A. M. (2021). Regulating PFAS as a Chemical Class under the California Safer Consumer Products Program. Environmental Health Perspectives, 129(2), 025001. https://doi.org/10.1289/EHP7431 Blum, A., Balan, S. A., Scheringer, M., Trier, X., Goldenman, G., Cousins, I. T., Diamond, M., Fletcher, T., Higgins, C., Lindeman, A. E., Peaslee, G., de Voogt, P., Wang, Z., & Weber, R. (2015). The Madrid Statement on Poly- and Perfluoroalkyl Substances (PFASs). Environmental Health Perspectives, 123(5). https://doi.org/10.1289/ehp.1509934 Bour, A., Avio, C. G., Gorbi, S., Regoli, F., & Hylland, K. (2018). Presence of microplastics in benthic and epibenthic organisms: Influence of habitat, feeding mode and trophic level. Environmental Pollution, 243, 1217-1225. https://doi.org/10.1016/j.envpol.2018.09.115 FINAL Code de la Sant Publique [Public Health Code] (FR). (n.d.). Article R1321-48: Materials in contact with water. Last updated: 1 January 2023. Accessed May 2023. Available online at: https://www.legifrance.gouv.fr/codes/article_lc/LEGIARTI000006909569 Ellis, D. A., Mabury, S. A., Martin, J. W., & Muir, D. C. G. (2001). Thermolysis of uoropolymers as a potential source of halogenated organic acids in the environment. 412. European Union (EU). (2011a). Commission Regulation (EU) No 10/2011 of 14 January 2011 on plastic materials and articles intended to come into contact with food (text with EEA relevance). Official Journal of the European Union. 14 January 2011. Accessed May 2023. Available online at: https://eur-lex.europa.eu/legalcontent/EN/ALL/?uri=celex%3A32011R0010 European Union (EU). (2011b). Directive 2011/65/EU of The European Parliament and Of The Council of 8 June 2011 on the restriction of the use of certain hazardous substances in electrical and electronic equipment (recast). Official Journal of the European Union. 8 June 2011. Accessed May 2023. Available online at: https://eur-lex.europa.eu/legalcontent/en/TXT/?uri=CELEX:32011L0065 Feng, Q., Chen, Z., Greer, C. W., An, C., & Wang, Z. (2022). Transport of Microplastics in Shore Substrates over Tidal Cycles: Roles of Polymer Characteristics and Environmental Factors. Environmental Science & Technology, 56(12), 8187-8196. https://doi.org/10.1021/acs.est.2c01599 French Agency for Food, Environmental and Occupational Health and Safety (ANSES). (2013). Materials and objects in contact with water, products and processes used for treating water for public distribution. Accessed May 2023. Available online at: https://www.anses.fr/en/content/materials-and-objects-contact-water-products-andprocesses-used-treating-water-public FINAL Henry, B. J., Carlin, J. P., Hammerschmidt, J. A., Buck, R. C., Buxton, L. W., Fiedler, H., Seed, J., & Hernandez, O. (2018). A critical review of the application of polymer of low concern and regulatory criteria to fluoropolymers: Fluoropolymers PLC. Integrated Environmental Assessment and Management, 14(3), 316-334. https://doi.org/10.1002/ieam.4035 IARC (Ed.). (1999). Surgical implants and other foreign bodies. IARC. Inoflon Fluoropolymers. (2018). PFA Fluoroplastic Resin SDS. https://www.inoflon.com/pdf/PFA_Powder_Eng.pdf Korzeniowski, S. H., Buck, R. C., Newkold, R. M., kassmi, A. E., Laganis, E., Matsuoka, Y., Dinelli, B., Beauchet, S., Adamsky, F., Weilandt, K., Soni, V. K., Kapoor, D., Gunasekar, P., Malvasi, M., Brinati, G., & Musio, S. (2022). A critical review of the application of polymer of low concern regulatory criteria to fluoropolymers II: Fluoroplastics and fluoroelastomers. Integrated Environmental Assessment and Management, ieam.4646. https://doi.org/10.1002/ieam.4646 Lee, S., Kang, K.-K., Sung, S.-E., Choi, J.-H., Sung, M., Seong, K.-Y., Lee, J., Kang, S., Yang, S. Y., Lee, S., Lee, K.-R., Seo, M.-S., & Kim, K. (2022). In Vivo Toxicity and Pharmacokinetics of Polytetrafluoroethylene Microplastics in ICR Mice. Polymers, 14(11), Article 11. https://doi.org/10.3390/polym14112220 Moermond, C. T., Janssen, M. P., de Knecht, J. A., Montforts, M. H., Peijnenburg, W. J., Zweers, P. G., & Sijm, D. T. (2012). PBT assessment using the revised annex XIII of REACH: A comparison with other regulatory frameworks. Integrated Environmental Assessment and Management, 8(2), 359-371. https://doi.org/10.1002/ieam.1248 Naftalovich, R., Naftalovich, D., & Greenway, F. L. (2016). Polytetrafluoroethylene Ingestion as a Way to Increase Food Volume and Hence Satiety Without Increasing Calorie Content. Journal of Diabetes Science and Technology, 10(4), 971-976. https://doi.org/10.1177/1932296815626726 FINAL Radulovic, L. L., & Wojcinski, Z. W. (2014). Encylopedia of Toxicology; PTFE (Polytetrafluoroethylene; Teflon) (Vol. 3). Elsevier Inc. Scheringer, M., Trier, X., Cousins, I. T., de Voogt, P., Fletcher, T., Wang, Z., & Webster, T. F. (2014). Helsingr Statement on poly- and perfluorinated alkyl substances (PFASs). Chemosphere, 114, 337-339. https://doi.org/10.1016/j.chemosphere.2014.05.044 Sfriso, A. A., Tomio, Y., Rosso, B., Gambaro, A., Sfriso, A., Corami, F., Rastelli, E., Corinaldesi, C., Mistri, M., & Munari, C. (2020). Microplastic accumulation in benthic invertebrates in Terra Nova Bay (Ross Sea, Antarctica). Environment International, 137, 105587. https://doi.org/10.1016/j.envint.2020.105587 Solomon, K., Matthies, M., & Vighi, M. (2013). Assessment of PBTs in the European Union: A critical assessment of the proposed evaluation scheme with reference to plant protection products. Environmental Sciences Europe, 25(1), 10. https://doi.org/10.1186/2190-471525-10 Tolkach, P. G., Basharin, V. A., Chepur, S. V., Gorshkov, A. N., & Sizova, D. T. (2020). Ultrastructural Changes in the Air--Blood Barrier of Rats in Acute Intoxication with Furoplast Pyrolysis Products. Bulletin of Experimental Biology and Medicine, 169(2), 270-275. https://doi.org/10.1007/s10517-020-04866-x Umweltbundesamt [German Environment Agency] (UBA). (2022). Annexes to evaluation criteria document for plastics and other organic materials in contact with drinking water (KTWBWGL) - Polymer-specific Part. Bad Elster, Germany. Accessed May 2023. Available online at: https://www.umweltbundesamt.de/sites/default/files/medien/3521/dokumente/polymersp ezifische_anlagen_der_bewertungsgrundlage_fur_kunststoffe_und_andere_organische_ materialien_en.pdf U.S. Code of Federal Regulations (CFR). (2023). Code of Federal Regulations Title 21, Volume 3, 21CFR177.1550: Title 21--Food and Drugs, Chapter I--Food and Drug FINAL Administration, Department of Health and Human Services, Subchapter B - Food for Human Consumption (Continued), Part 177 -- Indirect Food Additives: Polymers. Last Updated: 28 March 2023. Accessed May 2023. Available online at: https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-177/subpart-B/section177.1550 U.S. Pharmacopeia (USP). (n.d.). Chapter 88: Biological Reactivity Tests, in Vivo. Accessed May 2023. Available online at: http://www.pharmacopeia.cn/v29240/usp29nf24s0_c88.html Water Regulations Approval Scheme (WRAS). (n.d.). Regulation 31. Accessed May 2023. Available online at: https://www.wrasapprovals.co.uk/approvals/products_and_materials_directory/regulation _31/#:~:text=The%20Water%20Regulations%20Advisory%20Scheme%20(WRAS)%20i s%20concerned%20with%20products,distribution%20of%20public%20water%20supplie s. 1.3.2C Fluorinated Biomaterials DAV I D W. G R A I N G E R 1,2 1Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, United States 2Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, Salt Lake City, UT, United States Introduction Fluorinated biomaterials have a long history of biomedical device and biomaterials applications. These materials are generally carbon-based polymers, liquids, and gas precursors to films that all contain large amounts of chemically bonded fluorine (i.e., perfluorocarbons). Fluorinated materials can be solids, liquids, thin films, coatings, or gels, depending on their chemistry, processing, and mode of use. Fluoropolymers in general are thermoplastic polymers analogous to hydrocarbon-based polyethylene (PE), but highly fluorinated; some or all of the hydrogen atoms attached to the PE carbon polymer chain are replaced by fluorine (F) or fluorinated alkyl (perfluorocarbon) side groups. In some cases, other halogen atoms (e.g., chlorine, Cl) are also included with F to slightly modify polymer properties (Drobny, 2005). Notably, fluoropolymers show unique properties not achievable by other polymer materials, including chemical inertness, extreme hydrophobicity and solvent resistance, low coefficients of friction, high design tolerances for device fabrication, and temperature resistance (Drobny, 2005). These properties facilitate fluoropolymer use in specific technologies where most hydrocarbon-based materials do not perform well, either in device manufacturing or their applications. Nevertheless, as with all biomaterials, fluoropolymers perform best only in certain biomedical applications, and often carry a considerably greater cost than their hydrocarbon analogs into medical device designs. Just 2 years after the first commercial launch of completely fluorinated polytetrafluoroethylene (PTFE), as DuPont's now well-known Teflon product, after World War II ended, this new polymer was implanted in animals for the first time (Leveen and Barberio, 1949). However, early PTFE materials processing difficulties limited device capabilities. In 1963, Japanese researchers reported a new process for expanding PTFE films to produce highly uniform, continuous fibrous porous structures that, after thermal processing, retained this microstructure with vastly improved mechanical strength (Oshige, 1967). In 1972, this expanded fibrous material was first used experimentally as a venous graft substitute (Soyer et al., 1972), and a year later as an arterial bypass implant (Matsumoto et al., 1973). Several years later (1976), expanded PTFE (ePTFE) was refined to production scales by Gore, allowing increased access and clinical use of this more versatile PTFE form in commercialized biomedical products (Gore, 1976). This enabled fluorinated biomaterials to be employed in biomedical applications both inside and outside the living host, facilitating entry as an important class of polymeric biomaterials that are seen in the field today. Biomedical interest in fluorinated biomaterials focuses on several unique properties: lubricity; high sizing tolerances for device fabrication; and select aspects of reasonable biocompatibility resulting from both unique chemical and morphological properties. Understanding certain aspects of fluorinated chemistry is important to appreciate their material properties and broad utility in biomedical products. Interesting Fluoropolymer Chemical and Physical Properties Derived From Their Polymer Chemistry, Molecular Structure, and Bonding Replacing large amounts of hydrogen in C-H and C-C bonds in organic materials with fluorine as C-F chemistry, using several different chemical means, results in dramatic changes to the fluoromaterial's physical and chemical properties. Technologically desirable characteristics of perfluorinated materials are identified from how they interact distinctly with other media (e.g., heated fabrication machines and device-extruding dyes, as well as tissue, blood, proteins, and other polymers). Single fluorine bonds with carbon are the strongest carbon bonds, some 25 kcal/mol-1 stronger than C-Cl (Smart, 1994). Fluorination also strengthens adjacent aliphatic bonds: the CF3-CF3 bond is 10 kcal/ mol-1 stronger than the CH3-CH3 bond (Smart, 1994). This makes alkyl fluorides 102-106 times more stable than 125 126 S E C T I O N 1 . 3 Classes of Materials Used in Medicine the corresponding alkyl chlorides in solvent and thermal reactions (Smart, 1994). Exceptional thermal and chemical stabilities observed for perfluorinated materials then result. Fluorine's high ionization potential energy and low polarizability provide relatively weak intermolecular forces, low interfacial energies, and low refractive indices in fluorinated materials. This is important to interfacial applications (see section on Surfaces Modified by Fluorination Treatments later). Fluorine's larger atomic radius compared to hydrogen provides a rational basis for the observed structural differences between perfluorocarbons and hydrocarbons; chain movement energies (i.e., C-C chain rotational barriers) for various fluorine-substituted bonds are significantly higher than barriers in analogous hydrocarbon systems (Smart, 1994). Partially fluorinated commercial polymers, polyvinylidene fluoride (PVDF), and ethylene-trifluoroethylene copolymer, have zigzag polymer chain conformations with different C-F dipole alignments along the chain (Smart, 1994), while perfluorocarbons with only C-F bonds (e.g., PTFE, see later) assume helical chain orientations with C-F dipoles distributed axially around the chain helix (Doeff and Lindner, 1989; Zhang et al., 1989; Sun et al., 1994a, 1994b; Kobayashi and Owen, 1995; Bar et al., 1997; Stone et al., 1998). PTFE, for example, as a model for high molecular weight perfluorocarbon chains, is known to have a rich phase diagram of several distinct helical solid phases (Scheirs, 1997). This polymer helix basically encases the inner carbon-carbon polymer backbone with a tight outer shell of fluorine groups, protecting the carbon bonds from reactants, and also contributing to unique chain-chain interactions in PTFE and helical fluorinated polymers. Although most fluoropolymers share unique properties (e.g., thermal and chemical stability, lubricity), their mechanical properties are slightly different, depending on whether they are fully fluorinated or contain a number of hydrogen atoms. Generally, partially hydrogenated fluoropolymers (e.g., PVDF, see later) exhibit higher stiffness than fully fluorinated polymers (i.e., perfluoropolymers). Perfluoropolymers exhibit greater elongation and higher maximum service temperatures that benefit device engineering and thermal processing. Distinguishing the Different Fluoropolymers Fluoropolymers can be classified into homopolymers and copolymers by the monomer(s) used in their polymerization. They are divided into either "partially fluorinated" or "perfluorinated" (i.e., 100% C-F bonds) based on the amounts of fluorine in the polymer chain. Fig. 1.3.2C.1 lists currently available commercial biomedical fluoropolymers. Polymer chemical composition affects the resulting materials' properties; only certain fluoropolymers exhibit properties attractive for biomedical products. As one selection criterion, Fig. 1.3.2C.2 (Scheirs, 1997) compares some selected mechanical properties for different biomedical fluoropolymers (Drobny, 2005). Figure 1.3.2C.1 Abbreviated names and molecular structures for some biomedical fluoropolymers. Figure 1.3.2C.2 Comparison of mechanical properties of some select biomedical fluoropolymers, FEP, Fluorinated ethylene propylene; PTFE, polytetrafluoroethylene; PVDF, polyvinylidene fluoride. (Adapted by permission from Modern Fluoropolymers. Scheirs, J. (Ed.), John Wiley & Sons, Ltd., copyright 1997). Polytetrafluoroethylene PTFE (DuPont tradename Teflon) is perhaps the most commonly analyzed fluoropolymer. As described previously, fluorine's large size and mutual repulsion of adjacent fluorine atoms causes PTFE macromolecule chains to exhibit a twisting helix, comprising 13 CF2 groups per 180-degree turn, distinct from the classic planar zigzag chain typical for PE (Bunn and Howells, 1954). Fig. 1.3.2C.3 shows this important conformational chain distinction that imparts certain unique physical properties to the fluoropolymer. Helical PTFE chains are often of very high molecular weight (>106) from their polymerization by reactive tetrafluoroethylene (TFE) gas. The helical polymer chains pack into solid CHAPTER 1.3.2C Fluorinated Biomaterials 127 Figure 1.3.2C.3 (A) Polytetrafluoroethylene (PTFE) twisted zigzag chain compared to polyethylene (PE) molecular zigzag chain; (B) side space-filling views and (C) top views of PTFE chain versus hydrocarbon chain (PE). (Adapted by permission from Macmillan Publishers Ltd: Bunn, C.W., Howells, E.R., 1954. Structures of molecules and crystals of fluoro-carbons. Nature 174, 550, http://www.nature.com/npg/ indexnpg.html). BOX 1.3.2C.1 Sir John Charnley and the PTFE Replacement Hip Bearing Convinced that hip joint repair could not use metal-on-metal bearings, Professor Sir John Charnley's early work on hip arthroplasty techniques in the early 1950s used a Teflon-onTeflon solid bearing to resurface the arthritic femoral head and acetabulum. These Teflon-on-Teflon bearings failed within 2 years from mechanical creep and particulate issues. His further innovations created a femoral stem and metal head articulating against a Teflon cup socket inserted into the acetabulum. High Teflon wear occurred with joint articulation, producing severe osteolysis, loosening in the surrounding bone, and, as a result, requiring many revision surgeries. Teflon's poor performance in this articulating joint application prompted the adoption of high molecular weight polyethylene as a better bearing surface--an innovation that persists today. crystallites like long, parallel, stiff molecular rods; individual PTFE polymer molecules can slip on each other as quasicylinders sliding under shear stress. Tight helical packing and chain-chain slip make PTFE the most lubricious polymer available, with a low coefficient of friction (0.1). This is a major selection criterion for manufacturing fluoropolymer tubing for catheters. Unfortunately, this also makes PTFE solids very susceptible to cold flow (creep) under stress--a major reason for their contraindication in mechanical applications (i.e., poor bearing and joint surfaces) (Box 1.3.2C.1). Mutual repulsive forces of adjacent fluorine atoms keep the PTFE chain backbone from bending. Low-energy barriers to chain-chain slip events result from low chain-chain interaction energies. PTFE's very high bulk solid fractional crystallinity means that it scatters most visible light wavelengths, resulting in its characteristic opaque white color. PTFE's high molecular weight and rigid helical chain conformation also produce high melt viscosities (e.g., 1012 Pa/s), 6 times higher than most thermoplastic polymers. This viscosity is excessive for conventional melt processing fabrication methods for thermoplastic medical devices (e.g., extrusion and injection molding). This requires a high continuous service temperature (260C) for processing PTFE into devices. Therefore, as PTFE does not dissolve in any solvents, PTFE processing technologies are similar to those of powder metallurgy. This involves form casting of prepolymerized PTFE granulated powders or latex formulations, followed by mold compression and thermal sintering. PTFE's high thermal stability is key to success under the extreme processing conditions required for molded device parts (Drobny, 2005). Fluorinated Ethylene Propylene Fluorinated ethylene propylene (FEP) is a copolymer of TFE and hexafluoropropylene (HFP), first produced by DuPont in 1956 (Teflon FEP) to reduce PTFE's high crystallinity and melt viscosity. This improves FEP processing characteristics while maintaining high perfluorination. Bulky FEP perfluoromethyl groups produce defects in solid fluoropolymer crystallites, reducing polymer melting point, impeding chain slip, and reducing solid cold flow (Drobny, 2001). 128 S E C T I O N 1 . 3 Classes of Materials Used in Medicine FEP combines the unique mechanical and chemical properties of PTFE with the melt processability of more conventional polymers. FEP has a maximum service temperature of 204C, and a slightly higher coefficient of friction than PTFE. It is used in biomedical devices in place of PTFE. Polyvinylidene Fluoride PVDF is a homopolymer of the vinylidene monomer (CH2CF2), and is sold as Kynar. PVDF has the highest flexural modulus of all fluoropolymers, due to the interpenetration of larger CF2 groups crystallizing with adjacent smaller CH2 groups on adjacent chains. Unlike other fluoropolymers, PVDF is soluble in highly polar solvents (dimethylformamide, tetrahydrofuran), acetone, and esters (Drobny, 2005). PVDF's unique high dielectric constant, high dielectric loss factor, and interesting piezoelectric behavior under certain conditions result from this chemistry and result in solid-state structures. Fluorine's shielding effects to all neighboring CH2 groups provides PVDF with good chemical resistance and thermal stability (Scheirs, 1997; Drobny, 2001). These are all valuable properties sought in specific medical device applications. Fluoropolymer Melt Processing Because most perfluorinated polymers do not dissolve in many solvents, their biomedical products are often made by melt extrusion, where polymers develop flow upon melting in normal extrusion equipment. This technique, common to all polymer devices and chemistries, exposes fluoropolymers to very high temperatures to reduce their viscosity and improve flow characteristics for extended device production runs and product lengths. Fluoropolymers FEP and PVDF will readily melt flow when heated, typically above 260C. This permits uninterrupted feed of fluoropolymer resin into the parts extruder to produce long continuous lengths of product (i.e., medical tubing). By contrast, PTFE extrusion is limited due to difficulties in its materials handling, size of the stock preforms, and tubing. However, PTFE's poor melt processing presents an important opportunity: PTFE tubing can be manufactured to very small dimensions, with wall thicknesses as small as 2.54 10-3 cm and tolerances of 1 10-3 cm. This engineering benefit is largely due to PTFE's inability to melt flow, allowing more precise control over its use in small-dimensional, high-tolerance extrusion forms. This unique PTFE property is essential for producing medical products requiring tight size tolerances, such as small diameter and multilumen tubing with multiple precision passages for advanced catheters. Original Gore-Tex and Generic Equivalents PTFE film extrusion under anisotropic loading conditions produces expanded Teflon (ePTFE). Its microarchitecture exhibits pores axially aligned along the stretch direction, resulting in a unique fluoropolymer fabric material (A) (B) (C) Figure 1.3.2C.4 (A) Scanning electron micrograph (SEM) of expanded polytetrafluoroethylene (ePTFE) showing regular node-fiber open materials structure (scale bar, lower right corner = 10 microns) (B. Wagner, W. L. Gore & Associates, Flagstaff, USA, is acknowledged for ePTFE micrographs). (B) SEM of solid Teflon showing the crosssectional porous structure resulting from the compressed sintering of PTFE particles (P. Hogrebe, SEM micrographs). (C) Dense continuous top surface (scale bar = 25 microns). with an oriented microporous architecture. This was originally commercialized as the fabric-like Gore-Tex material (Gore, 1976). ePTFE's porous structure is characterized by regular PTFE nodes interconnected by PTFE fibrils (Fig. 1.3.2C.4A), distinct from solid PTFE shown in Fig. 1.3.2C.4B. In ePTFE, internodal spacing or distance (i.e., PTFE fibril length between solid PTFE nodes) is important to control device implant behavior (McClurken et al., 1986), and this can be controlled from 1 to 100 microns (Santiago et al., 1981) while retaining some properties similar to PTFE, e.g., biological adsorption, low tensile strength, low modulus of elasticity, water penetration control, and easy sterilizability. Porous ePTFE structures also allow important mechanical modulus-matching properties in tissue sites better than other polymers for many soft biological tissue applications (Mole, 1992). Porosity also importantly CHAPTER 1.3.2C Fluorinated Biomaterials 129 TABLE Surface Energies for Perfluorocarbons Versus 1.3.2C.1 Analogous Hydrocarbonsa Substance Solid Interfacial Energy c (mN/M) Perfluorocarbon Hydrocarbon PTFEb 18.5 31 PVDF 25 31 HDPEc 18.5 31 n-Pentane 9.4 15.2 n-Hexane 11.4 17.9 n-Octane 13.6 21.1 Decalin 17.6 29.9 Benzene 22.6 28.5 HDPE, High-density polyethylene; PTFE, polytetrafluoroethylene; PVDF, polyvinylidene fluoride. aSmart, B.E., 1994. Characteristics of C-F systems. Chapter 3. In: Banks, R.E., Tatlow, J.C., Smart, B.E. (Eds.), Organofluorine Chemistry: Principles and Commercial Applications, Plenum Press, New York, NY, Chapter 3. bc values. cl/v values. encourages in-growth of tissue, and hence moderate levels of tissue mechanical fixation. Bulk PTFE does not exhibit this property. The micropores also present active sites for stable blood clotting, an important property for conditioning implanted vascular graft surfaces to limit their chronic blood coagulation. Surfaces Modified by Fluorination Treatments (Grainger and Stewart, 2001) Bulk perfluorinated materials' intrinsically higher costs and often substandard mechanical properties limit their applications. When only fluorinated polymer interfacial properties are desired, then fluorinated surface layers can be chemically deposited or coated over other mechanically superior substrates to impart fluorinated properties only at the surface. This surface application limits bulk fluorocarbon costs and their performance liabilities. As developed further later, fluorinated surfaces can be produced by plasma deposition of gaseous precursor monomers, direct solid powder or solution overcoating and casting/evaporation, and solution phase fluorinated component blooming. High surface fluorocarbonation produces unique interfacial properties, imparting specific, technologically attractive features, including low solid-state surface free energy (or low water wettability and permeability), surface lubricity, and chemical resistance and durability, to device surfaces. Table 1.3.2C.1 shows that perfluorinated polymer surfaces exhibit low interfacial energies (indicated by Zisman c values), correlating directly with their utility as low-adhesion, low-water-wetting, and low-friction surfaces. Substituting either hydrogen or another halogen for fluorine along the polymer backbone results in significant increases in c values (as seen in comparisons of PTFE with high-density polyethylene [HDPE]); PVDF:poly(CH2CHF) has a c 25 mN/m, approaching that for polyethylene (HDPE, see Table 1.3.2C.1). Another important outcome of this low interfacial fluoromaterial energy is that fluorinated species thermodynamically prefer to coat a material's surface exposed to air. Hence fluorinated components will migrate from deep inside fluid coating mixtures to "bloom" and enrich as a coated overlayer at the solid-air interface. Surface-enriched films of fluorinated components reside at surfaces even if fluorinated components are doped only at trace or minority components into bulk coating materials. Therefore fluorinated surfaces can be fabricated using minority fluorinated components added to a bulk material if they are allowed to move to that material's surface (e.g., from coating solutions), offsetting the intrinsically high costs of fluorinated materials. Emphasis on surface-fluorinated coatings and films has therefore increased as technological needs drive new, improved, and less expensive methods to put this chemistry over biomaterial surfaces. Several coating strategies have sought to create, organize, and orient -CF3 and -SF5 terminal groups from films over any surface to provide such properties. High surface density and organization of these groups is necessary to achieve their technological properties. Alignment of perfluorinated chains terminating in this -CF3 or -SF5 chemistry at the surface is required. Orienting the side chains in fluoroalkyl side chain acrylate and methacrylate films enriches surfaces with side chain-terminating -CF3 groups (Bunn and Howells, 1954; Clark and Muus, 1962; Russell et al., 1986; Naselli et al., 1989), and lowers solid interfacial energies. Perfluoroalkylgrafted polysiloxanes also exhibit side chain orientation of their perfluorinated chemistry, sometimes with spontaneous perfluorinated group organization as a film or coating (Hare et al., 1954; Pittman, 1972; Schneider et al., 1989; Tsao et al., 1997; Clark, 1999). Gas plasma-deposited thin fluorinated coatings are also well developed for this purpose (D'Agostino, 1990), representing a mature industry and biomedically relevant materials treatment (e.g., for vascular devices and intraocular lenses; Ratner, 1995). Biomedical Applications Biomedical applications of fluoropolymers, fluorocarbon coatings, and perfluorinated fluids and gels all include clinical interventional and luminal access devices (catheters in many forms), and more permanent implants (cardiovascular (Stanley, 1982), dental (Ratner, 1993), ocular (Legeais et al., 1998), craniofacial (Valdevit et al., 2000), urological (Reid et al., 1995), and abdominal (Grannis and Wagman, 1995) applications) as well as substantial nonimplanted medical tubing and biotechnology components (protein blotting and filtration membranes). Annually, millions of perfluorinated polymer components are used worldwide in biological milieu both in vitro and in vivo. PTFE (Teflon) and ePTFE (Gore-Tex) are widely used in medical tubing, 130 S E C T I O N 1 . 3 Classes of Materials Used in Medicine TABLE Fluorinated Biomaterials Biomedical 1.3.2C.2 Applications Decade Biomedical Applications 1970s Implantable vascular grafts, peripheral catheters, and catheter introducers 1980s Guiding catheters, protein blotting membranes, tissue meshes, tubing 1990s Endoluminal stents, blood substitutes 2000s Drug-eluting stents advanced catheters, vascular grafts, meshes, sutures, and other medical implants. PVDF is used for biotechnology blotting/separation membranes. Table 1.3.2C.2 provides biomedical applications of more popular fluoropolymers. Clinically, ePTFE vascular grafts, including dialysis-access grafts, and Teflon-FEP catheter components are the most widely used fluorinated material medical devices. Other biomedical applications are described next. Fluorinated Material Biological Response Fluoropolymers are often regarded as chemically inert under most biological conditions. As noted earlier, they have some mechanical shortcomings under cyclic or continuous shear (creep). This makes applications in loadbearing situations (i.e., joint replacement, wear surfaces) difficult. Additionally, fluoropolymer surfaces are not inert to host biological reactions, including protein adsorption and blood clotting, either in vitro or in vivo. In fact, extremely tight binding of serum albumin to fluoroplasma-deposited surfaces (Kiaei et al., 1992), high levels of fibronectin and hemoglobin on PVDF (Paynter and Ratner, 1985) and various serum proteins (Dekker et al., 1991), including significant fibrinogen (Chandy et al., 2000), and high levels of both fibronectin and albumin (Grainger et al., 2003) on PTFE are observed in vitro. Importantly, protein adsorption to fluoropolymers is also observed in vivo (van Wachem et al., 1985; Roald et al., 1994), including fibrinogen activation, fibrin deposition, and platelet activation from blood, often deliberately promoted to stabilize blood reactivity on ePTFE vascular graft materials in vivo (Hoffman et al., 1986; Callow, 1988; Roald et al., 1994). Therefore nonspecific protein adsorption is significant, often irreversible, on fluoropolymer surfaces, leading to their desired utility as efficient protein-blotting membranes. But different proteins from different media (i.e., serum vs. plasma vs. blood) produce different interfacial reactions to fluorinated surfaces. From serum in vitro, for example, substantial amounts of albumin adsorption hinder serum-mediated cell attachment to fluoropolymers. This albumin passivation against further biological reactivity helps render the surface biofouling resistant. Clinical human cell-based vascular graft endothelialization to improve their blood compatibility is also generally poor on nonporous fluoropolymer chemistries (Kempczinski et al., 1985; Callow, 1988; Dekker et al., 1991; Schmidt et al., 1991; van Kooten et al., 1992; Roald et al., 1994; Legeais et al., 1998). This poor cell-fluoropolymer attachment has often been interpreted as "biological inertness," but results instead from substantial plasma protein adsorption on fluoropolymers (Baier et al., 1984) that does not support cell attachment and growth. Serum albumin, the most abundant protein in blood, blocks most cell attachment and other protein binding (Kesler et al., 1986; Zilla et al., 1989). Fibronectin, collagens, and other trace matricellular proteins (e.g., osteopontin, laminin, vitronectin) are celladhesive proteins. The observed general inability of nonporous fluoropolymers to support cell attachment has been related to excessive adsorption of albumin over cell-adhesive proteins (e.g., fibronectin) from serum--a medium lacking clot-forming fibrinogen (Grainger et al., 2003). Preadsorption of specific cell-adhesive proteins (e.g., collagen or fibronectin) to fluoropolymers is used to promote reliable cell adhesion (McClary et al., 2000; Koenig et al., 2003). Therefore little evidence suggests that fluoropolymers can be intrinsically "biologically inert." In fact, the opposite is true; solid fluoropolymers are intrinsically reactive and adsorptive to almost every protein studied, and the nature of what types of proteins are adsorbed dictates the fluoropolymer's biological reactivity. For example, porous fluoropolymers with 60-80 m voids, including ePTFE, can facilitate rapid blood clotting and cell and bacterial in-growth in blood. These interactions occur by blood-based protein adsorption, clotting, and cell/bacterial adhesion, with additional physical integration and engagement into the ePTFE pores (Clark et al., 1974; Clowes et al., 1986). PTFE (Teflon) Mesh and Fabric Vascular Implants The innovation that enabled the spinning of PTFE paste into a fiber that could be woven or knitted into fabric or mesh produced a fabric-like fluorinated material (Berry, 1951). Attracted by solid PTFE's reported "blood compatibility" claimed in early animal acute in vivo studies, PTFE weaves were applied early in vascular grafts (Edwards, 1959). However, these early woven vascular grafts exhibited both high early failure rates and substantial late failure rates. Graft thrombosis was the most frequent early complication, accompanied by a high mortality rate (Boyd and Midell, 1971). Gore-Tex (ePTFE) vascular grafts supplanted these earlier PTFE weaves in this application and are discussed next. Thrombosis is a general property of fluoropolymer meshes and weaves in blood, passivating surfaces rapidly for acute short-term use, but limiting long-term blood-contacting applications. ePTFE and Teflon Soft Tissue Repair Meshes Teflon fibrous mesh has been used to repair abdominal wall defects (Ludington and Woodward, 1959) and hernias (Gibson and Stafford, 1964; Snijders, 1969; Kalsbeek, CHAPTER 1.3.2C Fluorinated Biomaterials 131 BOX 1.3.2C.2 ePTFE Hernial Mesh Nearly a million hernial repairs are performed annually in the United States. Clinically, hernial repair meshes are implanted to bulk the abdominal wall at the herniated site. Tissue in-growth and organized fibrogenesis are deliberately promoted in these meshes to stabilize them in the abdominal tissue. ePTFE meshes and their combinations with polypropylene meshes are clinically available as a hernial repair product. However, ePTFE's lack of resistance to infection and inability to effectively engage tissue, promote on-growth, and organize fibrogenesis makes these meshes inferior to more popular polypropylene and polyester synthetic polymer meshes. 1974). However, it does not reliably integrate into body tissues, is not sufficiently infection resistant, and exhibits wound complication rates too high for routine hernia or abdominal repair use. ePTFE mesh is clinically used to repair hernias of many types (DeBord, 1998), reducing risks of several complications (DeGuzman et al., 1995; Lo Monte et al., 2009) (Box 1.3.2C.2). Infection and intestinal obstructions remain an issue for ePTFE mesh. However, they are better controlled with antibiotic therapies without mesh removal. ePTFE meshes have also been used as abdominal surgery barriers against surgical adhesions (Tulandi, 1997; Morris-Stiff and Hughes, 1998). ePTFE is also Food and Drug Administration (FDA) approved for many different plastic surgical facial defect reconstructions and augmentations, but is contraindicated in cosmetic lip augmentation, temporomandibular joint reconstruction, cardiovascular defects, and dermal placement (Levine and Berman, 1995). Nonetheless, commercial sources for these plastic surgery materials are discontinued. ePTFE Vascular Implants Because of abundant protein adsorption, ePTFE's porous inner surface is often claimed in vascular implants (blood) to clot blood rapidly to stabilize further surface coagulation and promote formation of a host "pseudointimal lining" that maintains blood compatibility under high-flow, high-shear applications. Its porous outer surface promotes perigraft cell and tissue infiltration that mechanically stabilizes the prosthesis in place, preventing kinking (White, 1988). Unlike most animal models, humans do not reliably form stable cellular "neointimal" endothelial cell linings in these grafts, limiting their success. ePTFE is currently used most widely to fabricate medium-sized (4-10 micron internode) vascular grafts for use in specific clinical blood vessel replacement indications (Kannan et al., 2005), including major vessels affected by disease or trauma, and arteriovenous hemodialysis grafts (Jenkins, 1976; Konner, 2005). ePTFE vascular prostheses are most clinically successful in high blood flow, low -resistance conditions (i.e., large peripheral arteries >5-6 mm diameter, such as the descending aorta). They are generally not suitable for smaller arterial reconstructions (e.g., coronary circulation and peripheral vascular placements) under high-resistance, low-flow conditions that allow continued clotting and loss of patency. Typically, ePTFE suffers from thrombosis, poor healing, lack of compliance, and excessive intimal and anastomotic hyperplasia leading to stenotic complications. Their routine placement in high-flow vascular environments allows them to remain patent despite their thrombus generation (Box 1.3.2C.3). Arteriovenous ePTFE Grafts for Dialysis Access Hemodialysis--essential for patients with end-stage renal disease--often requires regular, repeated (weekly) access to large blood vessels capable of producing high flow rates through an external artificial kidney device. Hemodialysis patients typically undergo cannula puncture of skin, underlying tissue, and vasculature to provide this access to the external artificial kidney. Repeated trauma to patient skin, tissue, and blood vessels from 13- to 17-gauge access needles produces notable complications, including hyperplasia, thrombosis, hematoma, occlusion, infection, and other morbidities. Vascular access complications remain the main reason for hemodialysis patient hospitalization. Synthetic ePTFE arteriovenous (A-V) grafts are surgically placed across the basilic vein and brachial artery to permit cannula access and reduce tissue trauma complications. A-V prosthetic graft failure rates are substantial (>50%), leading to increasing use of native fistulas and catheters (Li et al., 2008). However, synthetic grafts reliably provide high blood flow rates shortly after placement, as they do not require maturation before use. In A-V ePTFE grafts, stenosis occurs most commonly at the graft-venous anastomosis. Histologically, macrophages are seen in large numbers in the adventitial and medial layers in the anastomotic tissues from A-V ePTFE grafts (Kapadia et al., 2008) (Box 1.3.2C.4). Multilumen Catheters Fluoropolymers are important for biomedical tubing, and are central to advanced multilumen small-gauge medicalgrade tubing required in many new minimally invasive catheters. These catheters permit surgeons to perform several invasive procedures through several lumens in a single inserted catheter device without removing one entire catheter to insert another. Catheter in vivo exposures are usually short term, typically using endoluminal access, and are increasingly minimally invasive. As described earlier, PTFE's unique properties and stable thermal processing methods allow PTFE multilumen tubing precision manufacture unlike any other material, and this is a very important fluoropolymer in this particular use. Guiding Catheters An important clinical device with a long track record, the guiding catheter helps the clinician deliver stents and other devices endoluminally. Central to the guiding catheter is a 132 S E C T I O N 1 . 3 Classes of Materials Used in Medicine Figure 1.3.2C.5 Drug-eluting stent (DES) implantable medical device: (A) metallic DES stent mounted on cardiovascular catheter, with fluoropolymer matrix coating around the struts incorporating a drug payload for local delivery to the vascular tissue bed adjacent to the implant, assisting stent biocompatibility; (B) expanded stent postdeployment; (C) cross-section view of the XIENCE (Abbott Vascular) stent design with CoCr metal struts, poly(butyl methacrylate) (PBMA) primer interlayer, and polyvinylidene fluorideco-hexafluoropropylene fluoroelastomer drug-releasing matrix overlayer; (D) magnified view of expanded stent struts showing conformal integrity of polymer coating after expansion. (Courtesy: Abbott Vascular). Figure 1.3.2C.6 (A) Polyvinylidene fluoride-hexafluoropropylene fluoropolymer coating molecular struc- ture, and (B) everolimus drug. BOX 1.3.2C.3 Notable Clinical Success for Fluoropolymer Coatings on Cardiovascular Stents Stent coatings comprising one or more polymers with a drug are widely used on coronary and peripheral DESs and deemed essential for producing controlled drug release kinetics to locally influence vascular site tissue healing, stent thrombogenicity, and stent patency. Among several patient factors, including health status, cardiovascular disease, and physiological factors, stent coating designs are known to influence stent blood compatibility, local tissue healing, and chronic inflammatory responses. Many durable and biodegradable polymers are used as coatings, combined with an equally diverse selection of drugs released from these polymers (Fig. 1.3.2C.5). Two different fluoropolymer coatings are currently used in the majority of cardiovascular stents deployed clinically. Abbott Vascular's XIENCE family of endovascular coronary stents is the world's leading DES, with twice as many implants as any other DES. First introduced in 2006, this stent model has undergone several design changes and product improvements to now represent four different XIENCE stents. Each XIENCE stent employs polymers PBMA as a primer layer and PVDF-HFP overlayers in conformal wire stent coatings (6-7 microns thick). PBMA base primer over the metallic stent metal wires (struts) adheres the stent to the overlying fluoropolymer polymer-drug coating. PVDF-HFP is employed in the drug matrix layer to hold the drug everolimus on the stent and control its release, as well as ease its release from the deploying catheter expansion balloon. PVDF-HFP is a semicrystalline fluorinated copolymer of vinylidene fluoride and hexafluoropropylene monomers (Fig. 1.3.2C.6). CHAPTER 1.3.2C Fluorinated Biomaterials 133 BOX 1.3.2C.3 Notable Clinical Success for Fluoropolymer Coatings on Cardiovascular Stents--cont'd The PVDF-HFP copolymer backbone is comprised of entirely saturated carbon-carbon single bonds, >50% of which are fluorinated, resulting in unusual -CF2 main chain and -CF3 side group polymer dipole properties and polymer hydrophobicity. Significantly, the PVDF-HFP copolymer exhibits high elasticity and fatigue resistance attributed to its low glass transition temperature, Tg (-29C), and semicrystallinity. It is considered a durable coating as it is resistant to hydrolytic, oxidative, or enzymatic breakdown. Introduction of the HFP comonomer to the PVDF polymer chains restricts polymer crystal content, forming nanosized crystalline domains that alter polymer interchain distances and dipolar mobility, and reducing the polymer Tg. This allows this fluoropolymer the requisite mechanical properties (polymer elongation 600%-750%) to expand as the metallic stent is expanded in vivo, retaining a conformal, adherent, and defect-resistant coating character important to its biocompatibility. XIENCE's drug is everolimus (Fig. 1.3.2C.2B; 100 g/cm2 stent surface area loading on-stent). The PVDF-HFP copolymer drug matrix controls drug release to 80% in 1 month. Like many other blood-contacting polymers, fluoropolymer surfaces are hydrophobic. They are recognized to elicit a unique biological response in contact with plasma or blood known as "fluoropassivation," reducing fibrin deposition, platelet reactivity, thrombogenicity, and inflammatory responses, and enhancing more rapid, reliable vascular neointimal healing (Lavery et al., 2017; Xie et al., 2010; Chin-Quee et al., 2010; Garfinkle et al., 1984; Kiaei, 1988; Massa et al., 2007; Lin et al., 2000). Preferential affinity of fluorinated surfaces for albumin, with respect to fibrin, fibrinogen, or fibronectin, and the inhibitory effect of materials fluorination on platelet adhesion/activation or leukocyte recruitment while encouraging more rapid neointima formation and endothelialization, are proposed mechanisms to explain this consistently observed phenomenon (Grainger et al., 2003; Szott et al., 2016). Commercially available (currently only in CE-mark countries) fluoropolymer-based peripheral stents (FP-PESs, Eluvia) are now sold by Boston Scientific. The Eluvia FP-PES uses the same duallayer polymer coating as XIENCE, comprising the primer layer PBMA to promote adhesion to the stent of an active polymer layer comprising a combination of drug, paclitaxel (concentration is 167 g/cm2 stent surface area), and PVDF-HFP, controlling drug release for 12 months upon deployment (Gasoir et al., 2017). Another fluoropolymer stent coating, Polyzene-F (PzF; CeloNova BioSciences, Inc., TX, USA) is a formulation of poly[bis(trifluoroethoxy) phosphazene], an inorganic hydrophobic polymer possessing a backbone of alternating nitrogen and phosphorus atoms bearing trifluoroethoxy side groups. The COBRA-PzF (CeloNova BioScience, Inc.) coronary stent system is a cobalt chromium metallic stent design using this Polyzene-F polymer coating without drug, and was recently approved by the FDA for clinical use (Richter and Stampfl, 2005; Hiroyoshi et al., 2018). Importantly, as stents undergo substantial mechanical manipulations, structural change, and deformation during expansion and deployment in vivo, coatings must adapt to the stent deformations with structural integrity and reliable metal-polymer adhesion. Select fluoropolymers seem to exhibit superiority in this regard, withstanding mechanical deformations required for stent assembly, deployment, expansion, and placement without any adverse effect on the mechanical and biological functionality of the coated device. The majority of struts on the XIENCE PVDF-HFP fluoropolymer coating lacked coating defects after stent in vivo explantation at 180 days. This coating also has been shown to remain intact at maximum stent postdilatation without exhibiting any mechanical constraints on stent final dimensions (Yazdani et al., 2016). The ability of the fluoropolymer coating to remain intact without defects, exhibit reliable fluoropassivation in blood, and deliver drug is a clear stent performance advantage. Recent metaanalyses have established that durable fluoropolymer (PVDF-HFP)-coated everolimus-eluting stents (FP-EESs) have lower rates of stent thrombosis and target vessel revascularization than bare metal stents (BMSs) or thick-strut biodegradable polymer drug-eluting stents (BP-DESs). Additionally, preclinical ex vivo porcine shunt data confirmed superior acute thromboresistance for FP-EES versus BMS and BP-DES (Otsuka et al., 2015; Torri et al., 2018). PTFE inner liner with its superior lubricity and low friction coefficient that slides within an outer lumen. Lubricity is so critical to this device function that FEP, as the secondmost lubricious material available, is insufficient as a catheter liner. During catheter construction, PTFE is chemically bonded onto the tube's outer diameter to enable slip. Bonding is accomplished by using an FEP heat-shrinkable fusing sleeve. After depositing PTFE over the liner the FEP mold is removed from the device, leaving a smooth outer PTFE jacket on the liner within the catheter outer liner. PTFE Catheter Introducers Now over three decades old, the PTFE "introducer" facilitates catheter insertion into a patient's vein, taking full advantage of PTFE's endoluminal lubricity and precision tubing processing. Once the catheter is inserted, the PTFE outer sheath can be removed from the patient, leaving the implanted catheter behind. The introducer exploits PTFE processing that molecularly orients the fluoropolymer material in the tubing-based sleeve over the catheter. This allows PTFE tubing to be readily split and torn longitudinally from the catheter in situ, enabling the surgeon to remove a PTFE introducer from a patient while the primary catheter remains in place. Perfluorocarbon Liquids and Emulsions as Oxygen-Carrying Blood Substitutes Low molecular weight perfluoro-fluids can be aspirated into the lungs directly or injected as submicron-sized emulsion droplets into the blood to facilitate oxygen transport, exploiting their high oxygen-carrying capacities (Winslow, 2005). Liquid perfluorocarbons in the lung eliminate the gas-lung interface, acting to reduce tension in the lung alveolus, and reducing mechanical work required to breathe during respiratory distress and lung surfactant deficiency. Emulsions made from dispersing perfluoro-fluids into water using interfacial droplet stabilizers (emulsifiers) create submicron perfluorodroplets, much smaller than red blood cells. This provides 134 S E C T I O N 1 . 3 Classes of Materials Used in Medicine BOX 1.3.2C.4 The ePTFE Vascular Graft and a Bizarre and Costly Patent Dispute The 1974 patent filing from W. L. Gore & Associates, Inc. for the invention of the vascular graft resulted in the eruption of one of the most expensive and notorious medical device patent disputes in history. To challenge Gore's patent validity, a competing company started from former Gore employees and consultants-- International Medical Prosthetics Research Associates, Inc. (IMPRA)--filed their own competing patent based on work from a pediatric heart surgeon, Dr. Goldfarb, investigating ePTFE at Arizona State University. IMPRA also agreed to fund Goldfarb's research in exchange for exclusive rights to Goldfarb's patent. But, after an extended period without IMPRA support, Goldfarb dissolved his IMPRA ties. Eventually, IMPRA returned patent rights to the doctor, but not without a nasty struggle. Goldfarb then licensed his still-pending patent to the C. R. Bard medical device company, seeking to obtain a piece of the vascular graft market from Gore and IMPRA. In 1995, the US Patent and Trade Office Interference Board declared that the Goldfarb patent (still pending) invalidated the Gore patent on the vascular graft--a decision upheld twice in the US appeals court. Goldfarb was finally awarded his patent in 2002, still licensed to C. R. Bard, invalidating the Gore patent. But Gore continued to sell its ePTFE vascular grafts until Bard filed suit in 2003. The trial, first "settled" in 2007, found Goldfarb to be the rightful graft inventor, that his patent was valid, and that Gore had willfully infringed the patent in its vascular products. But it was not over yet: in 2009, Gore's claims of inequitable conduct against Bard were denied, and damages against Gore were increased to a total of $410 million. Gore then appealed this verdict (Frankel, 2009). In 2012, citing "substantial evidence" that Gore infringed a patent for vascular grafts, the US Court of Appeals upheld assessed penalties on Gore for past interest, royalties, and fees. Resolution of the case was estimated to have yielded about $1 billion for Bard from Gore, and is among one of the largest settlements in patent litigation history. Interestingly, the judgment also allowed Gore to keep selling their products on the markets as it was in the public interest to allow competition in the medical device arena. enormous oxygen-carrying capacity in blood to supplement normal oxygenation in microcirculation. Several commercial products have been clinically available, most recently Oxygent (Alliance Pharmaceutical, USA), consisting of two different perfluorocarbon fluids stabilized as a microemulsion using egg phospholipids. The product is eliminated from the blood after injection by macrophage/monocyte clearance, and is exhaled eventually from the lung. Fluorinated Liquids in the Eye as Experimental Vitreous Substitutes Detached retinal repair and other ophthalmic surgeries require oxygen-permeable viscous liquid vitreous substitutes. Perfluorinated oils and polymers have intrinsic high oxygen permeabilities and solubilities with suitable viscosity control. Perfluoropolyethers, perfluorinated alkanes, and perfluorinated silicone oils have all been studied in ocular vitreous applications, but still lack convincing safety, toxicity, or efficacy to date to produce an approved product in this context. Fluorinated (Meth)Acrylates and (Meth) Acrylated Perfluoroalkyl Silicones as CrossLinked Polymer Cores for Soft Contact Lenses Exploiting the intrinsic high oxygen permeability well known for perfluorinated materials, rigid gas permeable contact lenses (RGPs) have used many variations on crosslinked perfluorinated acrylates and perfluorinated polyether silicone gels as lens cores to improve extended-wear contact lens on-eye performance. Increased ocular acuity under high-throughput inexpensive but precise lens fabrication methods, with high lens oxygen transport, is sought. Many patents describe many fluorinated polymer gels in this regard, with most major lens manufacturers developing these lens core materials. Fluorinated Materials as Antifouling Coatings for Intraocular Lenses General cellular reactions to implanted polymer intraocular lenses (IOLs) replacing cataracts can result in cell migration onto, and adhesion to, the lens, with optical interference (clouding) requiring IOL replacement. To prevent cells from migrating onto and coating the IOL's optical lens surface (typically a thermoplastic), thin optically transparent plasma-deposited fluorocarbon films or layers of other fluorinated polymers are deposited on the IOL rear surface. Several patents describe this approach and application. PTFE Paste Injectable Bulking Agent Teflon particles formulated as an injectable paste have been reported for the treatment of vesicoureteric reflux (VUR) (Puri, 1995), corrected by subureteric injection of a PTFE paste (Puri and O'Donnell, 1984). Subureteric paste injection by endoscopy has successfully addressed primary and secondary VUR in children for nearly two decades (Le Guillou et al., 1984; Dodat and Paulhac, 1987; Puri, 2000). Similarly, PTFE paste was introduced nearly four decades ago to treat female stress urinary incontinence (Beckingham et al., 1992; Politano, 1992; Meschia et al., 2002). However, this device does not have regulatory approval, due to high risks for PTFE microparticle migration and granuloma induction, especially in lymph nodes, kidneys, lungs, and brain (Aaronson et al., 1993). Applications of Teflon paste injection are still reported (Harrison et al., 1993; Lopez et al., 1993; Herschorn and Glazer, 2000), but its side effect concerns limit clinical use. Ligament Replacement The Gore-Tex ligament prosthesis comprises a single long fiber of ePTFE woven into loops. Mechanical testing shows that the resulting ultimate tensile strength is 3 times that of the human anterior cruciate ligament (ACL). Creep and bending fatigue testing validate this ePTFE device as a strong synthetic ACL replacement material (Bolton and Bruchman, 1985). The Gore-Tex ACL prosthesis is CHAPTER 1.3.2C Fluorinated Biomaterials 135 currently FDA approved for use in patients with failed autogenous intraarticular graft procedures (Mascarenhas and Macdonald, 2008). However, while acute performance shows promising stability in the knee, extended use and implant time produce significant ligament loosening, and other knee stability problems. Sutures PTFE also finds limited use as a suture fiber in various forms. Both PTFE monofilament and ePTFE fibers are surgically proven, with clinically accepted surgeon-handling and lubricity properties. Additionally, PTFE is blended into other common surgical sutures used for myocardial heart valve prostheses fixation. Poly(ethylene terephthalate) (polyester)braided sutures are impregnated with PTFE polymer to limit wrinkling of the braid and consequent swelling. PTFE hydrophobic properties likely help protect the polyester braid from water uptake and hydrolysis (Bhat, 2002). The Money Joint Most biomaterials used for jaw joint reconstruction were introduced to markets prior to the 1976 Medical Devices Amendment Act that required device manufacturers to prove that their devices were safe and effective. A legal loophole that required manufacturers only to prove that their devices were "substantially equivalent" to a pre-Amendment device allowed temporal mandibular joint (TMJ) implants marketed soon after 1976 to enter the market without testing. Two designs widely used as TMJ replacement surfaces were Dow Corning's Silastic and Vitek's Proplast-Teflon product. Vitek developed and sold Proplast sheeting (Teflon FEP film laminated with a porous composite material of PTFE and carbon) in the 1970s. Implants modified in the 1980s comprised Teflon film laminated to PTFE and aluminum oxide. These implants, 1 cm2 in size, were cut from sheets in the operating room and sutured into the TMJ joint. In 1983, the FDA allowed Vitek to market a precut disc because, under the law, the company needed only to convince the FDA that its device was "substantially equivalent" to Dow's Silastic disc marketed years earlier. In 1986, several reports of catastrophic biomechanical failure of the PTFE implant were linked to a giant cell reaction leading to bone resorption and pain. Further analysis documented device failure rates of 10%-25%. By 1992, implant success rates below 20% were reported. Animal studies performed only after failures in humans began showed complete erosion of the TMJ implant within a "few months." In early 1990, with implant failures increasing, the FDA recalled Vitek's products. Predictably, Vitek declared bankruptcy with its rising product litigation costs, but continued to market their TMJ implants. Surgeons continued to implant them until eventually the FDA seized all products from Vitek, as well as its subsidiaries. Summary Due to their unique chemistry, fluorinated materials, primarily fluoropolymers, have attractive properties of biomaterials interest, including chemical stability, low adhesion/friction, nonwetting, high protein adsorption, high oxygen permeability, and precision tubing manufacturing. Low cell adhesion in serum and high intrinsic blood coagulation in plasma and blood both result from distinct media-dependent protein adsorption treatments and the physical form of the material. Expanded PTFE provides fabric-like properties with controlled pores and high surface area to alter device-related mechanics, processing, and tissue responses, while promoting rapid blood clotting. Solid fluoropolymers also have attractive precision-engineering and device-processing properties essential to producing several medical device classes where fine dimensional tolerances and biocompatibility are required. This enables fabrication of multilumen, high-tolerance, small-dimensional tubing for advanced catheters. Glossary Blooming a term used to describe the spontaneous enrichment of certain chemistries at the surface of a bulk matrix, usually associated with surface enrichment by low surface energy chemistry-like fluorinated materials. This phenomenon is used to promote a surface enriched in trace components like expensive added fluorinated chemistry by allowing them to spontaneously diffuse from the bulk material to the surface. Blotting membrane a thin, porous, hydrophobic, high proteinbinding capacity polymer membrane (e.g., PVDF) used to transfer proteins from a gel electrophoresis separation process for further probing with antibodies to identify the proteins as a blot or spot. Drug-eluting stent small mesh tubes inserted into arteries to maintain patency after a procedure called angioplasty. The mesh is coated with a polymer/drug combination that deploys with the stent placement and elutes drug to the vascular bed adjacent to the stent for weeks to months. ePTFE expanded polytetrafluoroethylene, produced from PTFE films under anisotropic stretching to yield a unique node-fibril microporous morphology in a fabric-like sheet form deemed important to biomedical utility in implanted biomaterials. Fluorinated biomaterial a material intended for a biomedical application made from a base material that contains significant amounts of chemically bonded fluorine. 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A tremendous amount of research and developments are being carried out on polymers in healthcare applications because of their non-toxicity and biocompatibility. Since there was always been a need for cost-efficient and improved healthcare facilities. The journey of biomaterials which was started from metals and ceramics has now reached to the era of smart biocompatible synthetic and natural polymers. Any material which has to be used for biomedical applications has to satisfy specific criteria. Biocompatibility is the most crucial among all these criteria. The word biocompatible referred to the biologically acceptable material which can be utilized to interact with the human system to assess, modify, treat, supplement and replace any tissue or organ without any adverse effect on the human body. An assortment of definitions for the term "biocompatibility" is given as follows: IUPAC defines the "Capability of a material to be in contact with a living framework without creating any adverse effect " (Vert et al., 2012) as biocompatibility. William explained biocompatibility in his dictionary as the "Capability of any substance to perform with an appropriate host response in a particular application" (Willaims, 1999). Biocompatibility can also be defined as the capacity of a prosthesis embedded in the body to exist incongruity with tissue without causing harmful changes in the international dictionary of medicine and biology (Becker and Landau, 1986). According to the guidelines of Food and Drug Administration (FDA) and International Organization for Standardization (ISO), any material to be used in the medical and pharmaceutical area has to qualify various in vivo and in vitro tests such as genotoxicity, cytotoxicity, mutagenicity, hemocompatibility, immunogenicity, teratogenicity, toxicity, irritation, etc (Bernard et al., 2018). Materials such as metals, ceramics, composites, and polymers are considered as biomaterials due to their various advantages and biocompatible nature. Metals are susceptible to corrosion in the presence of enzymes and acids in the biological system, thus sometimes causing toxicity in the body. Shape maintenance is difficult with ceramics (zirconia, alumina, pyrolitic carbon etc.), whereas the involvement of high-cost and brittleness are the major disadvantages for the composites (Shanmugam and Sahadevan, 2018). Out of these biomaterials, biocompatible polymers have extensively been explored in the medical field owing to their wide array of advantages. The desired physical and chemical properties of the biocompatible polymers can be designed effortlessly by changing the monomer concentration during homopolymerization and copolymerization (Tang et al., 2014). Therefore, this article emphasizes on classification, properties, synthesis, and various applications of biocompatible polymers. Classification of Biocompatible Polymers Biocompatible polymers are mainly classified into biodegradable (Balaji et al., 2017; Pandey et al., 2017) and non-biodegradable polymers (Shastri, 2005) based on the susceptibility of their backbone towards environmental degradation: Biodegradable Biocompatible Polymers Biodegradable, biocompatible polymers contain polymeric chains that undergo deterioration and complete degradation into small soluble degradation products in the presence of microorganisms, aerobic, and anaerobic conditions (Table 1). Based on the source, biodegradable, biocompatible polymers have been categorized as follows: (1) Natural biodegradable biocompatible polymers (2) Synthetic biodegradable biocompatible polymers Natural biodegradable biocompatible polymers Polymers obtained from natural sources like plants, animals, and microorganisms fit into the category of natural polymers. It includes polysaccharides like chitin, chitosan, cellulose, alginate, and hyaluronan. The collagens, gluten, and gelatin are examples of protein-based polymers. Polymers derived from natural sources offer several benefits due to their biological relevance, availability, non-toxicity, non-immunogenicity, non-carcinogenic, and bioadhesive properties. Most of these polymers are the components of various living organisms and a part of their structural tissues. Owing to their lower mechanical properties, higher degradation rates, and hydrophilicity, they are either structurally modified or used in combination with other synthetic polymers or ceramic. 1contributed equally. Encyclopedia of Materials: Plastics and Polymers doi:10.1016/B978-0-12-820352-1.00044-4 1 2 Biocompatible Polymers and its Applications Table 1 Sources and applications of some selected natural biodegradable biocompatible polymers 1. Biodegradable biocompatible polymers A. Natural polysaccharides based polymers Chitin Source: Sea animals, insects, and microorganisms. Applications: Delivery of drugs, tissue engineering, and fabrication of suture threads. Chitosan Source: Sea animals, insects, and microorganisms. Applications: Medicine, pharmacy, agriculture, the food industry, cosmetics, flocculants, and antipollution agents. Alginate Hyaluronan Source: Brown algae cell walls e.g., Macrocystis pyrifera, Laminaria hyperborea, and Ascophyllum nodosum. Applications: As humectant stabilizer, thickener, emulsifier, and film former, in the food industry, in biomedical as a corneal wound healing agent, drug delivery, and for the arthroscopic application for the increase in production growth of cartilage. Source: Skin, umbilical cord, synovial fluid of animals rooster comb, and bacteria. Applications: In skin aging treatment, osteoarthritis treatment, artificial intraocular lens implantation, and also used as culture media for in vitro fertilization during embryo implantation. A. Natural protein-based polymer Collagens Gluten Gelatin Source: Tissues, ligaments, bones, skin blood vessels, cartilages, lungs, and cornea. Applications: Treatment of arthritis, antiaging creams, in food, and beverage industry, root canal filling, wound dressings, photography, and as ophthalmic collagen shields. Source: Flour, wheat, oats, barley, and rye. Applications: Food industry, adhesive tapes, medical bandages, removing ink from waste paper, binding heavy metals in industrial processes, in cosmetic industries, and solidifying waste oils. Source: Cattle bones, animal skin, mammals, and fishes. Applications: Foaming agents, emulsifier agents, gelling agents, and in pharmaceuticals, food industries, cosmetic industries, and photography. Synthetic biodegradable biocompatible polymers Polymers obtained from the chemical or enzymatic polymerization of monomers fall under this category. These polymers can be synthesized and processed in convenient ways as compared to natural polymers. Their mechanical, chemical and physical properties are tailored to meet up various purposes like drug delivery, tissue engineering, implants, etc. They can be designed to meet up specific applications and have synthetic reproducibility, secondary processability, and reasonable cost. Some examples of Biocompatible Polymers and its Applications 3 Table 2 Sources and applications of some selected synthetic biodegradable and biocompatible polymers B. Synthetic biodegradable biocompatible polymers: Polycaprolactone (PCL) Source: Polycondensation of 6-hydroxyhexanoic acid, and ring-opening polymerization of -caprolactone. Applications: Root canal filling, tissue engineering, drug delivery, suture fabrication. Polyglycolic acid (PGA) Poly(N-isopropylacrylamide) (PNIPAAm) Source: Ring-opening polymerization of glycolide, azeotropic condensation polymerization of glycolic acid, direct polycondensation polymerization of synthetic glycolic acid from the acid-catalyzed reaction of bromo or chloroacetic acid, carbon monoxide and formaldehyde. Applications: Drug delivery, and tissue engineering. Source: Radical polymerization of N-isopropyl- acrylamide (NIPAM). Applications: Biosensors, thin films, tissue engineering and drug delivery. Poly(lactic-co-glycolic acid) (PLGA) Source: Direct polycondensation of lactic acid and glycolic acid. Applications: Delivery vehicles for proteins, drugs, and various other macromolecule e.g., DNA, RNA and peptides, tissue, and bone regeneration. Polylactic acid (PLA) Source: By condensation of lactic acid monomer, starch fermentation, and ring-opening polymerization. Applications: Tissue engineering, wound management, drug delivery, and orthopedic device. synthetic biodegradable polymers are polycaprolactone (PCL), polyglycolic acid (PGA), poly(lactic-co-glycolic acid) (PLGA), poly (N-isopropylacrylamide) (PNIPAAm), polylactic acid (PLA) (Table 2) etc. Non-Biodegradable Biocompatible Polymers Polymeric materials that are resistant to degradation come under this class (Shastri, 2005). Poly(dimethylsiloxane) (PDMS), Poly (ether-urethanes) (PU), Poly(tetrafluoroethylene) (PTFE) and Ethylene-co-vinylacetate (EVA) etc., are the examples of non-biodegradable biocompatible polymers (Table 3). These polymers can be used for long term applications such as prosthesis, catheters, etc. Property Considerations for Biocompatible Polymers Any material introduced into our body as a drug carrier or implants, biological systems will consider them as foreign material and will treat them accordingly. Biocompatible materials should not produce an immune response or byproducts that are difficult to eliminate or might get absorbed by the body. Cells are sensitive to their local environment to which they are contacted, so cell response will depend on surface properties like surface roughness, surface energy, wettability, electrostatic effects, protein adsorption, and chemical functions of the polymeric materials. Even though synthetic polymers have compatibility and degradability, some of them lack surface properties. Surface modifications are necessary for particular applications so the biological system can accept them. Polymeric materials with hydrophilic surfaces show lower protein adsorption, hemocompatibility, and cell adhesion (Rabinow et al., 1995; Lee et al., 2002; Chen et al., 2018). Hydrophilicity can 4 Biocompatible Polymers and its Applications Table 3 Sources and applications of some selected non-biodegradable biocompatible polymers 2 Non-biodegradable biocompatible polymers: Poly(dimethylsiloxane) (PDMS) Source: By the reaction of dimethyldichlorosilane and water. Applications: Delivery of drugs, contact lenses, shampoos, food, lubricants, and heat-resistant tiles. Poly(ether-urethanes) (PU) Source: By the reaction of di- or triisocyanate with polyo. Applications: Constructions of buildings, transportation, packaging, manufacturing furniture, textiles, electronics appliances, footwear, apparel, in medicine as an implant in medical devices. Poly(tetrafluroethylene) (PTFE) Source: Free-radical polymerization of tetrafluoroethylene. Applications: Non-stick coating for pans and other cookware, coating on catheters, and lubricants. Ethylene-co-vinylacetate (EVA) Source: Copolymerization of ethylene and vinyl acetate. Applications: Packaging, textile, in coatings formulation, and drug delivery. be improved or introduced by various techniques like chemical treatments, plasma discharge, or by radiation grafting. The mechanical properties such as impact resistance, durability, and strength will depend mainly on their water uptake and absorption rates. For certain implants, surface roughness is also crucial because of its role in cell adhesion and osteo formation. Surfaces with higher surface roughness will eventually increase the macrophage adhesion due to the increased contact area (Teo et al., 2016; Hrub et al., 2019). Key properties like solubility, crystallinity hydrolytic/enzymatic stability, and degradability are governed by the chemical composition of the polymers. Polymers with a hydrolytic backbone such as polyanhydrides, polyesters, polyurethanes, polycarbonates, polyamides, etc., are prone to hydrolytic degradation (Bernard et al., 2018; Song et al., 2018). The time scale of degradation can vary from hours to months. Molecular weight, crystallinity, and comonomer composition also play an important role in the determination of the degradation rate of the polymer. The rate of degradation of high molecular weight polymer is less than low molecular weight polymer. The amorphous region is more susceptible to hydrolytic degradation as a result of higher free volume than the crystalline region, so highly crystalline polymer will take a longer time for degradation. Synthesis of Biocompatible Polymers Commonly Used Natural Biocompatible Biopolymers Proteins Collagen: Collagen is the most abundant protein present in mammals. It is one of the main structural proteins present in the extracellular matrix (ECM), fibrous tissue of various connective tissues, and musculoskeletal tissues (Balaji et al., 2017). They have a molecular weight of 300,000 and 300 nm length with a rod-shaped morphology (Fig. 1). They have a triple-helical structure of three polypeptide chains, consisting of Gly-X-Y (Gly- Glycine X- proline,Y- hydroxyproline) amino acid sequence. More than twenty-nine types of collagen are discovered so far, Type I-IV being the most common. They are differentiated based on their structural variation, length of the helix, and carbohydrate groups attached. Type I, II, and III contribute to 80% of total collagens found in the body. Type II collagen is highly water interactive by virtue of its large carbohydrate groups. Collagenbased biomaterials can be classified based on the type of processing. First is the collagen that is derived from the extracellular matrix (ECM) that are separated and isolated by chemical method. The method involves treatment with chemical solutions followed by a detergent treatment, which helps the cell disruption without any structural damage. The second one is extracted in Biocompatible Polymers and its Applications 5 Fig. 1 Schematic representation of collagen fiber and components. Fig. 2 Structure of gelatin. the form of collagen or gelatin through chemical and/physical methods. Being a structural component of the body makes it nonimmunogeneticin addition to their ability for tissue restoration by providing adequate structural support makes it an apt material for in vitro as well as in vivo tissue engineering applications. For specific applications like implants, solubility and adsorption have to be minimized. In order to attain that, chemical or physical crosslinking of collagen is commonly used. Chemical crosslinking with formaldehyde or glutaraldehyde is preferred. Even though chemical crosslinking improves the stability of the collagen, the main challenge is that their residues after in vivo degradation can be cytotoxic. Ultraviolet (UV) light and dehydrothermaltreatment (DHT) are commonly used for the physical crosslinking of collagen. Collagen is mainly used for drug delivery, tissue engineering, and wound healing (Sell et al., 2010; Cheema, Ananta et al., 2011; Chattopadhyay and Raines, 2014). Gelatin: Gelatin belongs to the class of natural water-soluble polymer. The general structure of gelatin is represented in Fig. 2. Denaturation and controlled hydrolysis of collagen yields gelatin (Balaji et al., 2017; Akilbekova et al., 2018). Their properties depend on collagen from which they are extracted and on the conversion method. Mainly collagen derived from pig skin, fish, mammals, and cattle bones are used for the preparation of gelatin. Acid, base, or enzymatic treatment are commonly used for gelatin isolation. The primary structure of gelatin comprises of 18 amino acids. Almost all gelatin has a similar primary structure. Secondary structure consists of mainly three polypeptide chains(a, g, and b). Gelatin is isolated from the collagen by two-step process, a thermal treatment followed by hydrolysis. The collagen extracted from the various sources undergoes thermal treatment at 401C in the presence of water to break the interaction (hydrogen, electrostatic) existing in the collagen Hydrolysis involves the breakage of the intramolecular bond between the helical structure. After hydrolysis, different forms of gelatin can be obtained based on the bonds retained between the chains. Gelatin based hydrogels are used for wound dressing, drug delivery, and tissue engineering applications owing to their ability to promote cell adhesion and proliferation (Devi et al., 2016; Balaji et al., 2017; Jaipan et al., 2017). Gelatin nanoparticles are also a promising candidate as a drug and gene carrier. Polysaccharides Chitin and chitosan: Chitin is the second-most abundant natural polymer. It is the main constituents of the cell wall of all fungi, and are found on the exoskeleton of crustaceans, mollusks, and arthropods. However, commercial chitin is obtained from shrimps. It is an inelastic, rigid nitrogenous hydrophobic polysaccharide consisting of N-acetyl-2-amino-2-deoxy-D-glucose and 2-amino-2-deoxy-D-glucose residues as repeating units (Rodrguez-Vzquez et al., 2015; Balaji et al., 2017). N-acetyl glucosamine units are joined by b (1-4) glycosidic linkages and are distributed as blocks or in a random fashion. Chitin possesses more N-acetyl-glucosamine (450%), while chitosan has more number of N-glucosamine units (450%) (Fig. 3). Chitosan is 6 Biocompatible Polymers and its Applications Fig. 3 Structure of chitin and chitosan. Fig. 4 Structure of Alginate. obtained by partial deacetylation of chitin via alkaline or enzymatic hydrolysis. Strong hydrogen bonds between the chains reduce the solubility of chitin in most solvents. Amino groups of the D-glucosamine units in chitosan get protonated, thereby improving its solubility in dilute acidic aqueous solutions at pH o6 (Ivanova et al., 2014). However, its aqueous solubility is pH-dependent. Amino acid when protonated acts as polycation and forms ionic complexes with natural and synthetic anionic species. DNA, proteins, and lipids, proteins are some of the natural anionic species, and poly(acrylic acid) belongs to synthetic anionic species. Amino and alcohol groups of chitosan chains can undergo various chemical reactions like reduction, etherification, and esterification, thus introducing various functionalities on chitosan structure. Chitosan shows excellent antimicrobial property due to their cationic nature of glucosamine part at pH 6. The interaction between positively charged chitosan and negatively charged cell membrane of microorganisms causes the rupture of cell membrane and, ultimately, cell death. Chitosan is susceptible to chemical modifications and activation due to reactive amino and hydroxyl groups in the structure. Chitin and chitosan have potential applications in tissue engineering, wound management, drug delivery, etc., and they can be easily processed to gels, nanoparticles, nanofibers, membranes, and scaffolds (Jayakumar et al., 2010; Azuma et al., 2014; Rodrguez-Vzquez et al., 2015). Alginate: Alginates are a group of linear anionic polysaccharide is widely seen in the cell wall of brown algae. Their structure consists of b-D-mannuronic acid and 1,4-a-L-guluronic acid residues that are joined by 1,4-linkage arranged in homogenous or heterogenous block-like fashion (Fig. 4) (Dang and Leong, 2006; Jana et al., 2011). Depending on the sources, the length of mannuronic and guluronic acid residues in alginates varies. With increased guluronic content, alginate becomes stronger and brittle. Owing to the presence of free carboxyl groups, they have excellent mucoadhesive property. Free carboxyl groups help to form hydrogen and electrostatic bonds through which polymer interacts with the mucin. Carboxyl groups can also undergo a chemical reaction with cations such as Ca 2 hence providing different functionality and property to the alginates (Ivanova et al., 2014). For example, sodium alginate (NaC6H7O6), potassium alginate (KC6H7O6) are soluble, but alginic acid and calcium alginates are insoluble. Monovalent ions like in sodium alginate are replaced with divalent ions, thereby changing its physical property, i.e., low viscous liquid to a gel-like structure. Viscosity is pH-dependent, and maximum viscosity can be attained at a pH of 3 where protonation of carboxyl groups occurs, leading to hydrogen bond formation. Alginates are crossed linked via chemical or physical methods to prepare hydrogel. Alginate hydrogel is used for diverse applications such as controlled drug delivery, tissue engineering and wound healing (Lee and Mooney, 2012; Szekalska et al., 2016). Biocompatible Polymers and its Applications 7 Synthesis of Commonly Used Synthetic Biocompatible Biopolymers Chemical synthesis of polymers has been majorly carried out by following polymerization methods (Balaji et al., 2017): (1) Addition polymerization: This polymerization involves the addition of monomers without loss of any atom or molecules. These reactions may proceed by free radical cationic or anionic mechanisms. Addition polymerization is classified into four types: Bulk, solution, emulsion, and suspension. (2) Condensation polymerization: In this polymerization, a monomer having a reactive group joins each other by releasing small molecules. Condensation polymerization is classified into three types: Melt, solution, and azeotropic dehydration. (3) Ring opening polymerization: It is also known as chain-growth polymerization. In this type of polymerization terminal end of polymer attack on cyclic monomer to form a polymer chain. It can follow cationic, anionic, radical, and coordination or insertion mechanism. Polycaprolactone: Polycaprolactone (PCL) is a synthetic biodegradable biocompatible, hydrophobic, and semicrystalline thermoplastic polymer. It is an aliphatic polyester with hexanoate repeating units. At 601C, PCL starts melting and changing from rigid to soft at 601C (Tg glass transition temperature). It can be utilized for diverse applications by tuning its various processing properties such as flexibility, toughness, tear strength, and compression set. Generally, synthesis of this polymer has been carried out by utilizing two chemical reactions, polycondensation and ring-opening reaction. Condensation of 6-hydroxyhexanoic acid and continuous removal of water under vacuum during reaction produced PCL. Ring opening polymerization of -caprolactone/2-methylene-1,3-dioxepane in presence of catalyst and initiator afforded PCL (Guarino et al., 2017). Various metallic (alkali, alkali earth, transition and rare earth metals), organic and enzymatic catalytic systems have been explored for ring-opening polymerization (Fig. 5). Out of all metals, tin octoate has been extensively used due to its high activity. Various eco-friendly enzyme-catalyzed (lipase, cutinase, and esterase) reactions have also been reported for the PCL synthesis. Recently, ultrasonication, supercritical CO2 technologies, and microwave irradiation are also used to synthesize PCL (Labet and Thielemans, 2009; Balaji et al., 2017). Polylactic acid (PLA): PLA is one of the most popular and comes under the thermoplastic aliphatic polyester family. Lactic acid is used as a precursor for the synthesis of PLA, which is obtained from the renewable agricultural source. They have a glass transition temperature of 651C and a melting point ranging from 150 to 1601C. PLA exists as amorphous as well as semicrystalline form, depending on their stereochemical configurations. PLA is obtained from the condensation reaction of lactic acid or ring opening polymerization of lactide or by enzymatic polymerization or by azeotropic dehydration. Lactic acid exists as an optically active compound in its two enantiomeric form L and D. Both D, and L forms of lactic acid can be achieved by fermentation of carbohydrates, proteins, starch and other nutrients in the presence of microorganisms of Lactobacillus species, while the racemic mixture of DL lactic acid can be produced by the hydrolysis of lactonitrile (Fig. 6) (Masutani and Kimura, 2014). The polycondensation reaction of lactic acid either by solution or bulk produced low molecular weight polymers. Lactides (D lactide, L lactide, mesolactide, and racemic lactide) undergo ring opening polymerization to produce high molecular weight polymer (Fig. 7) (Lee and Hang, 2014). Various conditions have been screened out for achieving high molecular weight polymers with the desired polydispersity by selecting the catalysts (metals or organic), initiators, techniques (bulk or solution), and Fig. 5 Various polymerizations for the synthesis of polycaprolactone. 8 Biocompatible Polymers and its Applications Fig. 6 Structure of various lactic acids and lactides. Fig. 7 Synthesis of polylactic acid. Fig. 8 Synthesis of polyglycolic acid. polymerization mechanisms (cationic, anionic, or coordination insertion) as reported in the literature (Avrous, 2008; Lee and Hang, 2014). Polyglycolic acid (PGA): Polyglycolic acid is a synthetic biocompatible, biodegradable linear aliphatic polyester of glycolic acid. Polyglycolide melts at a temperature ranges from 200 to 2251C, and its glass transition temperature varies from 35 to 401C. Its high tensile modulus and lower solubility in organic solvents are attributed to its high crystalline nature, which varies from 45% to 55% (Singh and Tiwari, 2010). Polyglycolic acid has been synthesized at various conditions such as temperature, solvent catalyst, reaction time. Low molecular weight PGA has been prepared by polycondensation of linear glycolic acid, whereas ringopening polymerization of cyclic glycolides yields high molecular weight PGA (Fig. 8) (Sanko et al., 2019). The major drawbacks of the ring opening polymerization are the requirement of high reaction time and the use of costly monomer. These drawbacks have been overcome by azeotropic distillation method where the use of inexpensive monomer such as glycolic acid, Biocompatible Polymers and its Applications 9 Fig. 9 Triflic acid mediated synthesis of polyglycolic acid. Fig. 10 Synthesis of poly(lactic-co-glycolic acid). Fig. 11 Synthesis of poly(N-isopropylacrylamide). low reaction time, high yield, simple reaction condition make it useful for industrial production (Sanko et al., 2019). Schmidt et al. devised a novel method for the synthesis of high molecular weight polyglycolide by using diglycolide as the monomer, stabilizer free supercritical CO2 as a reaction medium, tin(II) ethyl hexanoate as catalyst and 1-dodecanol as initiator. They obtained the highest Mn of polyglycolide (31,200 g mol1) at 1201C temperature and 530 atmospheric bar pressure in 5 h (Schmidt et al., 2014). Reyhanoglu et al. (2019) reported cationic polymerization of trioxane (source of formaldehyde) and carbon monoxide in the presence of triflic acid in dichloromethane at 1701C, under 800 psi pressure afforded polyglycolic acid (Fig. 9). Poly (lactic-co-glycolic acid) (PLGA): Poly(lactic-co-glycolic acid) (PLGA) is a copolymer polyester of polylactic acid (PLA) and polyglycolic acid (PGA). Copolymer properties such as solubility, degree of crystallinity, melting point and degradation depend on the ratio of PLA and PGA in the polymer. Properties of poly(D,L-lactide-coglycolide) can be tuned according to the desired properties (Gentile et al., 2014; Sun et al., 2017). Bulk or solution polycondensation of PLA and PGA and ring opening polymerization (ROP) of lactide and glycolide in presence of catalyst and initiator have been utilized for the synthesis of PLGA (Fig. 10) (Moon et al., 2004; Gentile et al., 2014). ROP of lactide and glycolide in the presence of lipase from Pseudomonas has also been reported (Huijser et al., 2006). Poly(N-isopropylacrylamide): Free radical polymerization of N-isopropylacrylamide (NIPAM) monomer has been employed for the synthesis of thermoresponsive poly(N-isopropylacrylamide) polymers (Fig. 11) (Schild, 1992). Besides biocompatibility, this polymer specifically gains the attention of researchers due to the unique property of undergoing coil-to-globule transition at its lower critical solution temperature (LCST) at B321C. NIPAM reversibly undergoes from its hydrophilic form to hydrophobic form above 321C. Since this temperature is near to the human body temperature, so it is used for biomedical applications such as drug delivery and tissue engineering. Jadhav et al. (2016) reported the distillation precipitation polymerization (DPP) technique for the synthesis of different molecular weight of poly(N-isopropylacrylamide) polymers from N-Isopropyl- acrylamide monomer (NIPAM) in the presence of azobisisobutyronitrile (AIBN) initiator in ethanol. 10 Biocompatible Polymers and its Applications Fig. 12 Synthesis of poly(dimethylsiloxane). Fig. 13 Synthesis of poly(tetrafluoroethylene). Fig. 14 Synthesis of poly(ethylene-vinyl acetate). Poly(dimethylsiloxane) (PDMS): Poly(dimethylsiloxane) or dimethylpolysiloxane (PDMS) is a silicon-based nondegradable biocompatible inorganic polymer (Ninago et al., 2009). These polymers are hydrophobic and amorphous in nature. The length of the chain, nature of cross-links, molecular weight of polymer etc., are responsible for the mechanical properties of the polymer. Low molecular weight poly(dimethylsiloxane) is liquid in nature and used as antifoaming agent, lubricant, and hydraulic fluid while high molecular weight poly(dimethylsiloxane) is soft rubbery and used in various biomedical applications. Linear and cyclic poly(dimethylsiloxane) can be synthesized conventionally by the hydrolysis and condensation of dimethyldichlorosilane. Poor control on achieving desired molecular weight limits the scope of these methods. Anionic or cationic ring opening polymerization of cyclic siloxane has provided better control to afford high molecular weight poly (dimethylsiloxane) (Fig. 12). Poly(ether-urethanes) (PU): Poly(ether-urethanes) is non degradable biocompatible polymer. It gained attention due to its various properties, such as flexibility, elasticity, haemocompatibility, and nontoxicity. Poly(ether-urethanes) containing aliphatic chains are found to be soft, which makes them attractive to be used inside the body. Poly(ether-urethanes) has been synthesized from the polycondensation of diols or polyols and diisocyanates (Lligadas et al., 2007). To obtain low molecular weight poly(ether-urethanes), ethylene glycol (ED), 1,4-butanediol (BD), 1,6-hexanediol (HD) has been used as diols,whereas polyethylene glycol has been used as polyols in high molecular weight poly(ether-urethanes) (Bouchemal et al., 2004). Poly(tetrafluoroethylene) (PTFE): Poly(tetrafluoroethylene) is a thermoplastic fluoro-polymer, also known as Teflon. Attributed to its diverse properties such as high thermal stability, mechanical strength, hydrophobicity, thermal conductivity, lubricity, chemical and biological inertness, and nondegradability, PTFE is endorsed for various applications. Its high melting point (3271C) is attributed to its high thermal stability. Manufacture of poly(tetrafluoroethylene) has been carried out by radical polymerization mechanism of tetrafluoroethylene via addition polymerization in the presence of an initiator, additives, with or without surfactant in an aqueous medium (Fig. 13). Two different methods: suspension and emulsion polymerizations have been used for the synthesis of two different products i.e., granular resin and fine powder products. In the suspension method, polymerization is carried out in the presence of a very small amount or absence of surfactant under brisk stirring conditions while in emulsion polymerization, an ample amount of surfactant and mild stirring conditions are maintained (Dhanumalayan and Joshi, 2018). Ethylene-co-vinylacetate (EVA): Poly(ethylene-vinyl acetate) (PEVA) or Ethylene-co-vinylacetate (EVA) is a thermoplastic copolymer of ethylene and vinyl acetate. It is flexible, transparent, chemical resistant, and rubber-like. Its good low-temperature flexibility is due to its low glass transition temperature (Tg). Free radical polymerization of ethylene and vinylacetate in the presence of initiator at high pressure and temperature afford poly(ethylene-vinyl acetate) (Fig. 14) (Demarteau et al., 2015). Biocompatible Polymers and its Applications 11 Applications of Biocompatible Polymers Biosensors Nowadays, living in a pollution-free environment, maintaining a healthy lifestyle, having unadulterated food, living secure, and safe life became challenging. Every day we are facing various new threats such as outbreaks of novel microbes like covid19 viruses, epidemic, pandemic, non-epidemic diseases, chemical/biological wars, environmental and food-related issues so there is a strong need to develop handy, but sensitive and selective analytical devices that can sense all issues and thus preventing their spread. The word "Biosensor" was first coined by Cammann (Mehrotra, 2016). According to the IUPAC, a biosensor can be defined as "A device that uses specific biochemical reactions mediated by isolated enzymes, immunosystems, tissues, organelles or whole cells to detect chemical compounds usually by electrical, thermal or optical signals." Generally, biosensor refers to the analytical device which is used for detection or the estimation of biological analytes. The basic structure of biosensor devices, as depicted in Fig. 15, comprised of four components: Bio-receptor, which interacts with the analyte or sample to be detected. Base material, a significant part of a biosensor that provides a surface to attach with biomolecules. Transducer and Electronic system,convert biochemical reaction into a measurable signal. Biosensors show diverse applications in the area of medical, environment, and food analysis. In recent years several attempts have been made to develop a variety of materials for fabricating biosensors. It includes various biomaterials such as glass, silica, metals, paper, carbon nanotubes, graphene, and polymeric materials (Tavakoli and Tang, 2017). Out of these, biocompatible polymeric materials have been used extensively as discussed below: Chitosan based biosensor Chitosan is a polysaccharide-based biopolymer. Properties like hydrophilicity biocompatibility, non-toxicity, mechanical strength, stability, film forming ability and immobilization with other biomolecules make it useful for biosensing applications. Solanki et al. devised a nanobiosensor for the detection of Vibrio cholera bacteria. It consists of dual antibodies immobilized chitosan surface which was used to encapsulate nickel oxide, that was deposited on indium titanium oxide modified glass substrate. The detection of this device is based on electrochemical and optical techniques. The use of chitosan not only increases the dispersion of nickel oxide nanoparticles but also increase the loading of the capacity of antibodies (Solanki et al., 2015). Synthesis of chitosan- and quantum dot based nanogel biosensor has been reported by Maxwell et al. The chitosan layer of the quantum dot was functionalized with folic acid and fluorescein isothiocyanate. Folic acid functionalization helps the probe to attach with the folic acid receptor, while fluorescein isothiocyanate is used for tracking the path of biosensors. This biosensor was found to be nontoxic and effective against cancer-targeting agents (Fig. 16) (Maxwell et al., 2015). The innovative rapid and Fig. 15 Schematic representation of biosensors. Reproduced from Tavakoli, J., Tang, Y., 2017. Hydrogel based sensors for biomedical applications: An updated review. Polymers 9 (8), 1-25. doi:10.3390/polym9080364. 12 Biocompatible Polymers and its Applications Fig. 16 Chitosan- and quantum dot based nanogel. Reproduced from Maxwell, T., Banu, T., Price, E., et al., 2015. Non-cytotoxic quantum dot-chitosan nanogel biosensing probe for potential cancer targeting agent. Nanomaterials 5 (4), 2359-2379. doi:10.3390/nano5042359. sensitive copper nano cubes and chitosan modified copper nanocubes biosensor have been developed for the detection of mefenamic acid and indomethacin in human plasma by using voltammetry technique (Feyziazar et al., 2020). Cellulose based biosensors Cellulose is a biocompatible polysaccharide-based polymer with good electrical, tensile mechanical, and optical properties that make it useful for sensing applications. Novel tyrosine immobilized/cetyltrimethylammonium bromide modified nano cellulose (CTAB-NCC)/3-mercaptopropionic acid-modified quantum dots (MPA-QDs)/carbon electrode (SPCE) have been employed for phenol detection. Hybridization of CTAB-NCC and MPA-QDs improves the biocompatibility, permeability, conductivity, and immobilization of tyrosine. This hybrid biosensor was found to be selective, sensitive, and stable up to one month for detection. This biosensor can be utilized for the detection of phenolic samples in the environment (Fig. 17) (Manan et al., 2019). Novel glucose oxidase immobilized porous cellulose microspheres have been developed for the detection of glucose in blood serum. For the fabrication of glucose biosensor, the insertion of acidic functionality on the cellulose matrix was carried out by plasma-induced graft polymerization of acrylic acid. Further, attachment of amino group of Glucose oxidase to carboxy cellulose was carried out by ethyl-3-(3-dimethylaminopropyl)-carbodiimide(EDC)/N-hydroxysuccinimide (NHS) cross-linking reaction. This probe provides visual detection of glucose by changing the color of the mixture from colorless to yellow, whereas in the presence of starch,color of the mixture was amaranth. This biosensor works efficiently, even at a low concentration of glucose (0.003 M) in 4 min (Lin et al., 2012). Effective and sensitive disposable cellulose acetate fiber-based biosensor for detecting Vitamin-D3 has also been developed. An immune electrode was fabricated by depositing cellulose acetate fibers (CAEF) by using the electrospinning technique on conducting paper substrate (RCP) (CAEF/RCP). Further CAEF-decorated RCP electrode was Biocompatible Polymers and its Applications 13 Fig. 17 Cellulose modified biosensor for phenol detection. Reproduced with permission from Manan, F.A.A., Hong, W.W., Abdullah, J., Yusof, N.A., Ahmad, I., 2019. Nanocrystalline cellulose decorated quantum dots based tyrosinase biosensor for phenol determination. Materials Science and Engineering C 99 (January 2018), 37-46. doi:10.1016/j.msec.2019.01.082; Copyright 2019 Elsevier. Fig. 18 Cellulose acetate fiber modified biosensor. Reproduced with permission from Chauhan, D., Solanki, P.R., 2019. Hydrophilic and insoluble electrospun cellulose acetate fiber-based biosensing platform for 25-hydroxy vitamin-D 3 detection. ACS Applied Polymer Materials 1 (7), 1613-1623. doi:10.1021/acsapm.9b00179; Copyright 2019 American Chemical Society. immobilized with monoclonal antibody specific to vitamin D3, and bovine serum albumin to block nonspecific sites. Detection of attachment of vitamin D3 is based on chronoamperometry techniques (Fig. 18) (Chauhan and Solanki, 2019). Polyethylene glycol based biosensors Polyethylene glycol (PEG) is hydrophilic, biocompatible, and biodegradable material. Due to its low interfacial energy, it resists protein and cell surface adhesion and shows excellent antifouling properties, hence quite attractive for biosensing. Electrochemical immunosensor for the detection of brucellosis antibody in whole serum was developed. Fabrication of biosensor was carried out by deposition of polyethylene glycol and hyaluronic acid-modified Fe3O4@Au nanoparticles on the carbon electrode (Fig. 19) (Lv et al., 2018). Rahman et al. developed a polyethylene glycol-modified carbon nanotubes biosensor for the detection of L-glutathione (GSH). Three different composites of polyethyleneglycol modified carbon nanotubes (oxidized CNTs, octadecylamine modified CNTs, pristine CNTs) were synthesized and deposited on glass carbon electrode using nafion binder for the fabrication of electrodes. This electrode was found to be selective and sensitive against GSH detection than the existing ones (Rahman et al., 2017). 14 Biocompatible Polymers and its Applications Fig. 19 Polyethylene glycol biosensor for the detection of brucellosis. Reproduced with permission from Lv, S., Sheng, J., Zhao, S., Liu, M., Chen, L., 2018. The detection of brucellosis antibody in whole serum based on the low-fouling electrochemical immunosensor fabricated with magnetic Fe3O4@Au@PEG@HA nanoparticles. Biosensors and Bioelectronics 117, 138-144. doi:10.1016/j.bios.2018.06.010; Copyright 2019 Elsevier. Fig. 20 Poly (L-aspartic acid) based biosensor for the detection of xanthine in food product. Reproduced with permission from Yazdanparast, S., Benvidi, A., Abbasi, S., Rezaeinasab, M., 2019. Enzyme-based ultrasensitive electrochemical biosensor using poly(L-aspartic acid)/MWCNT bionanocomposite for xanthine detection: A meat freshness marker. Microchemical Journal. 149, 104000. doi:10.1016/j.microc.2019.104000; Copyright 2019 Elsevier. Other biocompatible polymers based biosensor The carbon based biosensor is sensitive to use in protein-rich environments for a long period because of their susceptibility in biofouling. The coating of biocompatible polymers suppresses the adsorption of protein, thus restricting the fouling. Biocompatible polymeric brushes of poly(2-methacryloyloxyethyl phosphorylcholine) have been grown on the carbon electrode surface. This modified biosensor has been successfully employed without adsorption of protein up to 8 h for the detection of the neurotransmitter dopamine in blood serum. The sensitivity of the polymeric brush coated glass electrode is found to be better than the bovine serum albumin coated glass electrode (Uen et al., 2020). Xanthine oxidase immobilized nanocomposite of carbon nanotube and biocompatible poly(L-aspartic acid) based glass carbon electrode has been developed for detecting xanthine in food products. The determination of xanthine in fish or meat products can be carried out by using differential pulse voltammetry at different storage temperatures (Fig. 20) (Yazdanparast et al., 2019). Tissue Engineering Tissue engineering is an interdisciplinary field that deals with the improvement and replacement of biological tissue and its functions. With the main focus on restoring and repairing damaged tissue or a whole organ, it combines support (scaffold), living cells, and a biological signaling molecule to rebuild the damaged cells (Ivanova et al., 2014; Song et al., 2018). Regenerated cell/ tissue will have a similar function, structure, and mechanical properties. Scaffolds are three-dimensional porous frame work possessing a crucial role in this process. The human body has an extracellular matrix (ECM) whose main role is to provide structural and mechanical support to various tissues and to regulate cellular activity and wound healing. An ideal tissue engineering scaffold, replicate the structure and function of ECM. Apart from mimicking the biological function of ECMs, they must provide structural and mechanical support to the regenerating tissue as well as helps in the seeding and proliferation of new tissue. They should have tunable degradation rates and should not have degradation products that are harmful to the biological system. Both synthetic and natural polymers are widely used as scaffold owing to their biocompatibility, biodegradability, noncarcinogenicity and non-immunogenicity (Table 4). Synthetic polymers such as polyglycolic acid (PGA), poly(lactide-co-glycolide) (PLGA), polyanhydrides, polylactic acid (PLA), poly(e-caprolactone) (PCL), etc., are commonly used for tissue engineering. Natural polymers such as chitosan, alginates, collagen, and elastin are commonly used as materials for fabricating the scaffolds (Ivanova et al., 2014). These materials are often used as blends or as composite.Synthetic polymers have functional groups (esters, anhydrides, amides, orthoesters) or chemical bonds in their backbone that are labile to the hydrolysis. PGA can be utilized for the regeneration of cartilage and blood vessels, often with other natural and synthetic polymers. Kobayashi et al. (2013) have studied the performance of PGA-Collagen nanocomposite and was found that after 5 days of implantation, it was completely occupied and vascularized. Implants like orthopedic devices, rods, screws, are made out of PLA. Lin et al. fabricated and studied the performance of hydroxyapatite (HA) mineralized on chitosan-coated PLA nanofibers for bone regeneration. It was found that this Biocompatible Polymers and its Applications 15 Table 4 Advantages and disadvantages of biocompatible polymers Advantages Naturally occurred polymers Biodegradable and nonimmunogenic Abundant availability Possess inherent specific cell-binding site that provides cell attachment and proliferation Synthetic polymers Easily tailored to complex architectures Control over chain length, structure, degradability, porosity, physical and chemical properties Easy to fabricate and possess a long shelf life Supply is inadequate Disadvantages Low mechanical strength and higher hydrophilicity Faster degradation Difficult to tailor for specific applications Difficult to control properties like mechanical strength, pore size Expensive Uncontrollable shrinkage Lacks cell-binding site and cell recognition signals Some of them cause an immune response and exhibit local toxicity Note: Nicolas, J., Mura, S., Brambilla, D., Mackiewicz, N., Couvreur, P., 2013. Design, functionalization strategies and biomedical applications of targeted biodegradable/ biocompatible polymer-based nanocarriers for drug delivery. Chemical Society Reviews 42 (3), 1147-1235. doi:10.1039/c2cs35265f. Ivanova, E.P., Bazaka, K., Crawford, R.J., 2014. Natural polymer biomaterials: Advanced applications. In: New Functional Biomaterials for Medicine and Healthcare. Woodhead Publishing, pp. 32-70. doi:10.1533/ 9781782422662.32. Teo, A.J., Mishra, A., Park, I., et al., 2016. Polymeric biomaterials for medical implants and devices. ACS Biomaterials Science and Engineering 2 (4), 454-472. doi:10.1021/acsbiomaterials.5b00429. Balaji, A.B., Pakalapati, H., Khalid, M., Walvekar, R., Siddiqui, H., 2017a. Natural and synthetic biocompatible and biodegradable polymers. In: Biodegradable and Biocompatible Polymer Composites: Processing, Properties and Applications. Elsevier Ltd, pp. 3-32. doi:10.1016/B978-0-08-100970-3.00001-8. combination can work as an excellent material for bone regeneration and have structural and biological similarities with the natural bone (Lin et al., 2014). Another study was done by Mi et al. who has prepared a scaffold using thermoplastic polyurethane (TPU) and polylactic acid (PLA) nanocomposite. PLA was incorporated as a sphere into the TPU matrix (Mi et al., 2013). The results indicated that this could be used as synthetic scaffolds for bone regeneration due to its good mechanical property, biocompatibility, and surface roughness. Polycaprolactone (PCL) is another bioabsorbable, biodegradable polyester. Uma Maheshwari et al. (2014) had fabricated a nanocomposite comprising of polycaprolactone (PCL)/polyvinyl alcohol (PVA) bilayer nanofibers with hydroxyapatite nanoparticles (HAp) for repair and regeneration of bone. The obtained results confirmed that this composition is suitable for biocompatible scaffolds for bone tissue engineering. Poly(lactic-co-glycolic acid) PLGA can also be used in tissue engineering. Poly(lactic-co-glycolic acid)/nano-hydroxyapatite (PLGA/nHA) scaffolds were fabricated by Qian et al. (2014). They found that modulus of this biomorphic scaffolds was enhanced because HA incorporation reduced the crystallinity of PLA. It is well known that the human body responds and reacts to electrical signals. This works as the general principle of neural communication. Role of electrical charges in stimulating the use of conducting polymers (CPs) like polyaniline (PANI), polypyrrole (PPY), and polythiophene (Guo and Ma, 2018). They are mainly used as bioactive materials for tissue engineering. They are biocompatible and can enhance cell adhesion and cell proliferation. Cell interactions and responses will vary according to the chemical structures of the polymer and on their macroscopic forms like membranes, fibers, films, etc. They provide better mechanical strength, compatibility, and structural property than conventional electronic materials. For the fabrication of electrically sensitive tissues like cardiac muscles, skin, nerves, and skeletal, CPs are especially useful. Most of these polymers are brittle and have poor processability. Therefore, they were used as conductive polymeric composites or as blends with a biocompatible biodegradable polymer. Polymers, including PLA, PCL, chitosan, and silk fibroin were blended with common conducting polymers like PANI, PPY. Wang et al. had prepared PLA/PANI based conductive nanofibrous sheets that can efficiently be used for cardiac tissue engineering. The sheet possess higher cell viability, promotes differentiation and cell-cell interaction (Wang et al., 2017). Conductive materials are efficient in enhancing cellular activities, activating fibroblasts and keratinocytes. Guo et al. fabricated antibacterial nanofiber composites constituting poly(aniline-co-aminobenzenesulfonic acid), poly(vinyl alcohol), and chitosan for skin wound healing (Guo and Ma, 2018). PANI showed good antibacterial property and was successful in healing the wound within 15 days. This conductive nanofiber sheet enhanced collagen and granulation, making it suitable for wound healing. As discussed earlier, natural biopolymers possess inherent biocompatibility and can serve as an intrinsic template for cell attachment and proliferation. Many of these polymers have extracellular ligands in their structure, which can bind to various cell receptors. They also have some drawbacks. Due to their lower temperature resistance, they may get degraded before reaching their melting point, and it is challenging to fabricate them into complex structures. Among natural polymers, chitin, chitosan, collagen, etc., are commonly used. Chitosan and its derivatives are widely used for wound management and as scaffolds due to its blood compatibility and less immune response (Dang and Leong, 2006; Akilbekova et al., 2018). It can be used for the fabrication of porous scaffold or hydrogel. The presence of N-acetylglucosamine groups in their structure can accelerate tissue repair and prevent scar formation of the skin. Chitosan and chitin are used as films, membranes, gels, sprays, woven, or non-woven dressings to treat burns, ulcers, and skin grafts. Chitin/Chitosan sprays are found to be effective for superficial lesions, while gels are efficient in treating shallow injuries. Littlejohn et al. investigate the hemostatic potential of chitosan-based gauzes, and their results demonstrated that gauzes help to form the mucoadhesive barrier of chitosan by cross-linking of red blood cells (Bennett and 16 Biocompatible Polymers and its Applications Littlejohn, 2014). These gauzes are apt for the healing of epidermal wounds. Chitosan based tissue scaffolds are highly in demand by virtue of its processability and degradability. Chitosan is non toxic and can undergo enzymatic hydrolysis resulting in Nglucosamine that exists in the extracellular matrix of eukaryotes. Chitosan can be used for the regeneration of hard tissues like bone and cartilage. But in the hydrated state, chitosan scaffolds lack adequate mechanical strength; therefore, they require structural modifications or some additives to enhance its mechanical stability. Composites, such as hydroxyapatite/Chitosan, nano-calcium zirconate/Chitosan, and strontium-modified CS/montmorillonite composites were designed to meet the end applications. For example, hydroxyapatite improves the compressive strength of chitosan. CS/chondroitin/nano-bioglass-based polyelectrolyte composite was fabricated with better bioactivity, such as accumulation of apatite and in vivo osseointegration of the scaffold (Rodrguez-Vzquez et al., 2015). Regenerating cartilage has been a challenge considering the lack of blood vessels in its tissue, so the scaffold material must be capable of stimulating the regeneration in avascular conditions. Chitosan has structural similarity to sulfated glycosaminoglycans and can provide a suitable environment for the synthesis of the extracellular matrix, chondrogenesis, and chondrocyte proliferation (Pandey et al., 2017). Collagen is the structural component of native ECM, making it an excellent material for the scaffold for repair and reconstruct tissues of the skin, cardiovascular tissue, musculoskeletal system, and nerves. Collagen types I, II and III can form collagen fibers having comparable structural and biological properties of the natural collagen ECM. Pure collagen scaffold has limited application by virtue of its poor mechanical strength and structural stability. To improve its properties, collagen can be cross linked by physical or chemical treatment. ultraviolet (UV) irradiation and gamma radiation are usually used for physical treatment in the scaffold (Cheema et al., 2011). Chemical modification can be done by incorporating amine/imine linkages. Scaffolds made of collagen with synthetic/natural polymer blend can also enhance its properties. Collagen/chitosan blend has shown good cytocompatibility along with adequate mechanical and biological properties. Cellular behavior on PCL/collagen fibrous scaffolds was studied and results indicated that they can promote adhesion and growth of fibroblasts. Collagen/PLA hybrid scaffold with 3D-porous structure showed better mechanical strength, due to PLA and showed a higher stiffness than pure collagen (Cheema et al., 2011; Chattopadhyay and Raines, 2014; Ivanova et al., 2014). Implants Implants are materials or devices that are inserted into the body for therapeutic, diagnostic or prosthetic purposes. Examples include knee, hip prosthetics, heart valve, pacemakers, spine screws, rods, intrauterine devices (IUD) breast implants, artificial lenses etc (Fig. 21) (Teo et al., 2016). Polymeric materials are used both as a substrate for the fabrication of implants and as packaging the device (Table 5). Implants can be prosthetics designed to replace a missing body part, a device for medication, or to monitor various body functions (Dang et al., 2014). Implants are mainly classified as biodegradable and non-biodegradable implants. For cardiovascular applications, synthetic polymers like polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), and modified polyurethane are extensively used. Often the polymeric substrate is coated with proteins like collagen or albumin to avoid any immune response. Polytetrafluoroethylene (PTFE) is commonly used for the fabrication of vascular grafts, heart valves ring, and sutures for mitral valve repair (Teo et al., 2016; Dhanumalayan and Joshi, 2018). Owing to its characteristics, such as flexibility low thrombogenicity, hemocompatibility, and biphasic nature (crystalline and elastomeric nature). PU is utilized for heart valve applications. Modified PU, like polycarbonate urethane (PCU), can offer a low degree of degradation, improved strength, and oxidation stability (Wheatley et al., 2000; Lam and Wu, 2012). Polydimethylsiloxane (PDMS) grafted PU have also been used for Fig. 21 Examples of implants. Biocompatible Polymers and its Applications 17 Table 5 Applications of some selected biocompatible polymers in biomedical applications Name of polymers Typical biomedical applications Polyethylene (PE) Polypropylene (PP) Polysulfone (PS) Polyethertherketone (PEEK) Polyvinyl chloride (PVC) Polytetrafluoroethylene (PTFE) Polymethylmethacrylate (PMMA) Polydimethylsiloxane (PDMS) Polyurethane (PU) Catheters, orthopedic sutures, hip prostheses Sutures, heart valves, plasmapheresis membrane Heart components and valves, penile prosthesis Dentistry products, rigid tubing Plasmapheresis membrane, blood bags, and tubing Surgical sutures, catheter linings Dental implants, dentures, intraocular lenses Artificial blood vessels, neuroprosthetics, breast testicular Artificial heart, pacemaker leads, catheters prostheses Note: Lee, H.B., Khang, G., Ho Lee, J., 2002. Polymeric biomaterials. In: Biomaterials: Principles and Applications. CRC Press. doi:10.1201/b15739-9. Dang, T.T., Nikkhah, M., Memic, A., Khademhosseini, A., 2014. Polymeric biomaterials for implantable prostheses. Natural and Synthetic Biomedical Polymers. Elsevier Inc. doi:10.1016/B978-0-12-396983-5.00020-X. Teo, A.J., Mishra, A., Park, I., et al., 2016. Polymeric Biomaterials for Medical Implants and Devices. ACS Biomaterials Science and Engineering 2 (4), 454-472. doi:10.1021/acsbiomaterials.5b00429. the heart valves to improve its hydrophobicity and reduce calcification (Dabagh et al., 2005). Drug-eluting stents (DES) are vascular stents that release drugs in a controlled manner and prevents narrowing of arteries. However, expanded PTFE or e-PTFE (formed by stretching the above its melting point) are generally used as vascular graft and bypass graft due to its porosity, improved mechanical integrity, and ability to support tissue growth (Cassady et al., 2014). The drug is incorporated in the polymer matrix, surrounded by the metallic stents. Polymers like polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), are extensively used to coat the metallic substrate (Strohbach and Busch, 2015). Bioresorbable drug-eluting stents surpass the drawbacks of conventional stents such as thrombosis and surgical removal. The use of polymeric materials in dentistry is increasing thus paving the way for advanced research in this field. The materials used for prostheses must have similar physical, mechanical properties of natural teeth. PMMA is one of the commonly used polymers in dentistry. PMMA posses biocompatibility, excellent mechanical strength as well as wear resistance. They do not impart any odor or taste and are resistant to microbial agents (Gautam et al., 2012). Other synthetic polymers like UHMWPE, PTFE, and PET are also used for various dental implants (Teo et al., 2016). Ophthalmology mainly uses polymers for the fabrication of intraocular lenses. Polymers such as PMMA or polypropylene are widely used for the lenses for their outstanding optical clarity. For keratoprosthesis, PMMA is a common choice. Polymeric implants are used to replace degenerated part in the case of vertebral injuries. For this purpose, composite of bioglass/PU, bioglass/polystyrene, carbon-fiber-reinforced polystyrene were used for the replacement and bone grafting purposes (Dang et al., 2014). Polymeric biomaterials such as PE, PU, and PET/SR are used for artificial disks. UHMWPE and its composite can be utilized for the fabrication of hip and knee replacement components owing to their strength, stiffness, and wear resistance (Bracco et al., 2017). As discussed earlier, biodegradable and non-degradable implants can also be used as drug-releasing vehicles. Non degradable implants have to be removed after completing their function. These implants are specially used for treating chronic diseases that require long term medications. Synthetic polymers like silicones, poly(urethanes), poly(acrylates), etc., are commonly used for these purposes. Monolithic type implants are fabricated where a drug is homogeneously dispersed in the matrix while reservoirtype implants have a compact non-biodegradable membrane coated with a drug. Non-biodegradable implantable drug delivery systems are widely studied for contraceptive delivery due to its structural resilience and lifetime. The main drawback of these implants is that they must be removed once the drug load is finished or released. Biodegradable implants are fabricated with tailored degradation kinetics. Polymers like PLA, PLGA, PCL are commonly used for this. The main advantage of these implants is that they are degradable in our body, eliminating the need to remove it. The degradation products are either converted to metabolites that are easily eliminated by the kidney or are absorbed by the body (Stewart et al., 2018). Implants must meet up their functions and lifetime as designed. If they fail, it can lead to severe side effects, which may even cause death.Often there is a packaging film that acts as barrier material between the device and the biological system during its operational period. The protective film prevents any waste materials that can be released from the device to be in contact with the biological environment. Implant packagings are mainly done using biocompatible and biostable polymers. The polymer should possess good gas permeability and water permeability and ensure the safety of the electronic circuit from moisture and ions. Also, the material should possess excellent tensile strength and shelf life. Synthetic polymers like polyvinylidene fluoride (PVDF), polyethylene (PE), polydimethylsiloxane, polytetrafluoroethylene, poly(methyl methacrylate), polyimide, and polyurethane have been successfully used as biomaterials for biomedical packaging (Qin et al., 2014). PMMA is used in implants like the intraocular lens and cranioplasty. PTFE (Teflon) has limited use as a substrate for medical devices due to their low gamma resistance, which is required during procedures like sterilization. However, expanded PTFE or e-PTFE (formed by stretching the above its melting point) are generally used as vascular graft and bypass graft due to its porosity, improved mechanical integrity, and ability to support tissue growth (Cassady et al., 2014). Urinary catheters are coated with PTFE to reduce bacterial infections (Wang et al., 2019). For targeted drug delivery in specific tissues, a microporous PTFE catheter is utilized, since the drug can be released by diffusion at the targeted zone through the pores. Polyimides are commonly used as encapsulation and insulation materials for 18 Biocompatible Polymers and its Applications medical devices. It was found that they have long term efficiency and can sustain in for 20 months in phosphate buffer at 601C without any loss of their mechanical property. Polyimide-based MEMS device was developed by Hasenkamp et al. (2013) for artificial knee implants. Polyimide is also used as a protective coating and can be fabricated with various micro apertures for accelerating the diffusion of gases during the sterilization process of leads. Drug Delivery A large number of biocompatible polymers have been developed to be used as drug delivery systems (Liechty, 2010; Calzoni et al., 2019). Biocompatible polymers are used as a matrix to enhance drug stability and to modify drug release profiles. These polymercarriers help to control the temporal and spatial release of drugs by controlling dissolution rate, carrier degradation rate, and drug diffusion. Encapsulation of drug also improves in vivo solubility of lipophilic and hydrophobic drugs. Natural biocompatible polymers and synthetic biocompatible polymers, both are used as drug delivery carriers (Jana et al., 2011; Mogoanu et al., 2016). The biocompatible polymers are commonly utilized for drug delivery systems in following different forms: (1) Micro and nanoparticles (2) Micelles (3) Micro/nanogels Micro and nanoparticles Microparticles and nanoparticles are the most widely used drug delivery systems (El-Say and El-Sawy, 2017; Lengyel et al., 2019). These microparticles can be introduced into dosage in different forms such as solids (e.g., tablets and capsules), semisolids (e.g., creams, pastes, and gels) and liquids (e.g., solutions and suspensions). These particles protect the drug from the environment, reduce the unpleasant taste of drug and help to tune the drug release profile under various conditions. The drug release from the microparticles is highly affected by various parameters such as size and shape of the particles, e.g., to study the effect of particle's shape on drug release profile, PEG-PCL block copolymer was synthesized by ring opening polymerization of e-caprolactone using mPEG as an initiator and worm-like nanoparticles were prepared from PEG-PCL block copolymer which was used as a carrier of anticancer drug methotrexate (Gharebaghi et al., 2017). These non spherical worms like particles showed a slow and controlled release of methotrexate in comparison to spherical particles. Electrohydrodynamic jetting technique provides good control over the particle's shape (from cup to disk shape particles) as reported by Ifra et al. (Ifra and Saha, 2019), and the drug can be directly encapsulated by mixing it in polymer jetting solution with 100% encapsulation efficiency. Similarly, core shell particles that were composed of poly(lactide-co-glycolide) core and poly(lactide) shell having different sizes (2-280 mm) were fabricated via one-step solvent evaporation method. Encapsulated Metoclopramide monohydrochloride monohydrate (MCA) released faster with an increase in particle size due to faster degradation of the particles (Fig. 22) (Lee et al., 2012; Saha and Loo, 2015a,b). To further explore the drug delivery systems, janus particles were introduced which are composed of two compartments having two different chemical compositions and also exhibit different physical and chemical properties (Aiswarya and Saha, 2020; Tran et al., 2014; Su et al., 2019). These different compartments can be utilized to incorporate two different drugs into two different parts, e.g., Parthipan et al. (2018) have fabricated disk-shaped bicompartmental particles composed of poly(lactide-co-glycolide) (relatively hydrophilic and amorphous) and polylactide (completely hydrophobic and semicrystalline) via electrohydrodynamic co-jetting technique. They have loaded two different drugs (levodopa and carbidopa) in two different compartments and observed 80% release of drugs within 5 h which shows the potential application of the particle as a dual drug delivery system (Fig. 23(A)). Similarly, Romanski et al. (2012) have fabricated janus particles consisting of two phases (polymer-lipid phase), which were utilized to load two different anticancer drugs, doxorubicin and curcumin (Fig. 23(B)). These dual drug-loaded particles were Fig. 22 Drug release profile of different sized PLGA-PLA core shell particles encapsulated with Metoclopramide monohydrochloride monohydrate (MCA). Reproduced with permission from Lee, W.L., Seh, Y.C., Widjaja, E., et al., 2012. Fabrication and drug release study of double-layered microparticles of various sizes. Journal of Pharmaceutical Sciences 101 (7), 2271-2280. doi:10.1002/jps; Copyright 2012 Elsevier. Biocompatible Polymers and its Applications 19 Fig. 23 (A) PLGA-PLA bicompartmental particles encapsulated with levodopa and carbidopa (B) Polymer-lipid phase separated particles encapsulated with anticancer drugs doxorubicin and curcumin to treat lungs tumor. (C) PLGA/PLLA/hydrophobic pactitaxel (PTX) multilayer particles containing doxorubicin in core and shell. Reproduced with permission from (A) Parthipan, A.K., Gupta, N., Pandey, K., 2018. One-step fabrication of bicompartmental microparticles as a dual drug delivery system for Parkinson's disease management. Journal of Materials Science 54 (1), 730-744. doi:10.1007/s10853-018-2819-x; Copyright 2018 Springer Nature. (B) Romanski, F.S., Winkler, J.S., Riccobene, R.C. Tomassone, M.S., 2012. Production and characterization of anisotropic particles from biodegradable materials. Langmuir 28 (8), 3756-3765. doi:10.1021/la2044834; Copyright 2012. (C) Lee, W.L., Guo, W.M., Ho, V.H., et al., 2014. Inhibition of 3-D tumor spheroids by timed-released hydrophilic and hydrophobic drugs from multilayered polymeric microparticles. Small 10 (19), 3986-3996. doi:10.1002/smll.201400536; American Chemical Society, Copyright 2014 Wiley. delivered to the lungs of mice with an orthotopic model of human lung cancer which helped to prevent the growth of lung tumors. Instead of janus particles, multilayered particulate systems can also be utilized to load more than one drug as reported by Lee et al., (2014). They have developed dual drug loaded multilayer particles to encapsulate hydrophilic doxorubicin HCl and hydrophobic paclitaxel (PTX) into (poly(dl-lactic-co-glycolic acid)) PLGA and (poly(l-lactic acid)) PLLA which resulted in a trilayer particle consisting of a separate layer for PTX and doxorubicin in PLGA shell and core, respectively (Fig. 23(C)). Recently, Biswal et al. have also extended the application of these multi-layered particles in the area of food packaging (Biswal and Saha, 2019a,b; Biswal and Saha, 2020). They have demonstrated the fabrication of multilayer particles composed of Poly(l-lactic acid) (PLLA) and Poly(dllactic-co-glycolic acid) PLGA via emulsion solvent evaporation technique. Fabricated bi-layered (PLGA/PLLA: shell/core) particles from high viscous PLGA and tri-layered (PLGA/PLLA/PLGA: shell/middle/core) from low viscous PLGA particles were loaded with antibacterial (benzoic acid in PLGA) and antioxidant (tocophorel in PLLA) where release rates of dual actives significantly increased in trilayer particles in comparison to bilayer particles and both the particles exhibited antibacterial and antioxidant effect over a period of 60 days. Polymer micelles Polymeric micelles are formed by the self assembly of block copolymers into nanoaggregates on dissolving the polymer chains above Critical Micelle Concentration (CMC) and solution parameters (Xu et al., 2013). These micelles consist of a hydrophobic core and hydrophilic shell (Fig. 24). The most commonly used hydrophilic shell is poly(ethylene glycol) (PEG) or poly(ethylene oxide) (PEO) while common hydrophobic cores are poly(lactic acid), poly(glycolic acid), poly(glycolide-co-lactide), poly(L-amino acids) and poly (e-caprolactone) etc (Jhaveri and Torchilin, 2014). Drugs can be loaded into polymer micelles via physical entrapment, chemical conjugation or polyionic complexation. The drug loading capacity is highly dependent on the compatibility between core and drug molecule which can be adjusted by optimizing the chemical structure of the core. Various polymer micelles have been reported for drug loading, e.g., three different types of PEGylated block copolymers i.e., poly(ethylene glycol)-block-poly(gluconamido ethyl methacrylate) (PEG113-b-PGAMA20), poly(ethylene glycol)-block-poly(styrene)-block-poly(gluconamido ethyl methacrylate) (PEG113-b-PS50-b-PGAMA20) and poly(ethylene glycol)-block-poly(2-(diethyl 20 Biocompatible Polymers and its Applications Fig. 24 Polymeric micelles. Reproduced with permission from Jhaveri, A.M., Torchilin, V.P., 2014. Multifunctional polymeric micelles for delivery of drugs and siRNA. Frontiers in Pharmacology 5, 1-26. doi:10.3389/fphar.2014.00077; Copyright 2014 Frontiers. amino) ethyl methacrylate)-block-poly(gluconamido ethyl methacrylate) (PEG113-b-PDEA50-b-PGAMA20) were prepared via atom transfer radical polymerization to load anticancer drug, bortezomib by hydrophobic interaction or pH-induced covalent bonding (Zhang et al., 2018). They have observed that (PEG113-b-PGAMA20) block copolymers exhibit the fastest release among the three while PEG113-b-PS50-b-PGAMA20 showed the sustained release in comparison to (PEG113-b-PGAMA20) because of the stable micellar structure(due to the presence of non-responsive PS middle block), however, (PEG113-b-PDEA50-b-PGAMA20) block copolymer showed fast release in comparison to PEG113-b-PS50-b-PGAMA20 block copolymer because of the presence of PDEA middle block (pH-responsive segment). Polymeric hydrogels Hydrogels are 3-dimensional, cross-linked networks made from a water-soluble polymer and can hold a large amount of water which helps to release the loaded drug in a controlled manner. The gels may be porous or nonporous and the porosity of the hydrogel can be controlled easily by tuning the density of cross-links. The porosity of the hydrogel allows drug loading inside the hydrogel. Hydrogels can be prepared by two types of crosslinking; hydrogels having covalent crosslinking are called chemical gel, whereas hydrogels having noncovalent interactions are called physical gel (Mishra et al., 2017). Drug loading in hydrogels can be carried out by two different methods. In the first method, the polymer (which is required for hydrogel formation) is mixed with an initiator, a cross-linker, and a drug; then the system is allowed to polymerize in which a matrix loaded with the drug is resulted in. In the second approach, an already synthesized hydrogel is taken and allowed to swell in a drug solution, which results in drug loading into the hydrogel (Parajapati et al., 2016). The polymer is dried after drug loading in both the procedures. The drug loading into the hydrogel matrix is affected by various parameters such as polymer-solvent interaction, porosity (crosslinking density) of the hydrogel matrix, type of solvent etc. These parameters directly affect the swelling of hydrogel and thus affect the drug loading capacity. Various types of drug loaded hydrogels have been synthesized to load the drugs e.g., poly(ethylene glycol) hydrogel was synthesized from PEG vinyl sulfone which was crosslinked with PEG-diester-dithiol for protein delivery and cell encapsulation (Zustiak and Leach, 2011). Summary Significant advances and innovative research has facilitated the tremendous growth and development of the biomedical field. Extreme importance has always been given for material selection for any of the biomedical applications. Metals and ceramics were widely used once, but they had major drawbacks like corrosion, weight, degradability, and availability. So there was a need for a material with excellent properties that can replace these materials surpassing the drawbacks of metals and ceramics. Biocompatibility is the most important aspect of any material to be used in any of the biomedical applications. Biocompatible polymers are ideal materials where the properties can be tailored and designed to meet up the end applications without compromising their non toxic response in the biological environment. Considering their cost and availability in addition to their benign nature, biocompatible polymers have made a strong place in biomaterials research. Starting from macro to nano dimensions, biocompatible polymers can find them in wide range of biomedical application areas ranging from implant such as contact lens, pacemakers, etc., to drug delivery. Biocompatible Polymers and its Applications 21 Future Scope Though many of the existing biocompatible polymers have been used since decades, only a limited number of polymers are FDA approved for biomedical use and scaled up for commercialization. Extensive researches are being carried out for the synthesis and fabrication of new type of biocompatible polymers and devices which can also be made to responsive to the biological environment. Most of these polymers are non degradable but biocompatible. However, biodegradable polymeric materials with various functionality would definitely be worth considering as the primary choice for biomedical applications owing to their degradable nature. But, functionalized biodegradable polymers are scarce and require multiple steps to synthesize, thus making them economically unattractive. Therefore, current research from our group, as well as others is focused upon the easy synthesis techniques of biodegradable biocompatible polymers which can be easily modified to meet the desired applications. If suitably designed, these polymers can find their potential applications not only in the biomedical area but also other areas such as food packaging (Biswal et al., 2018; Biswal and Saha, 2019a,b; Biswal and Saha, 2020; Biswal et al., 2019), ground water remediation, etc (Pandey and Saha, 2020). Acknowledgments Department of Material Science and Engineering (DMSE), Indian Institute of Technology (IIT), Delhi, Council of Scientific and Industrial Research, Department of Science and Technology (DST) are appreciated for providing research and teaching funds. References Aiswarya, T.T., Saha, S., 2020. 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Hydrolytically. XIENCE family of drug eluting stent (DES) is a permanent implant and used for treating blocked or narrowed coronary and below-the-knee arteries. The drug everolimus is mixed with polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), and the drug/polymer coating is applied on the cobalt-chromium metal stent. For a representative 3 x 18mm XIENCE stent, PVDF-HFP/everolimus coating contains approximately 420 g of PVDF-HFP. The primary function of PVDF-HFP is to control release of everolimus for >90 days. PVDF-HFP contains no chemically active groups. Therefore, the polymer will not chemically alter the drug everolimus or bind to biomolecules in vivo. PVDF-HFP is a semi-crystalline polymer with a balanced hardness and elongation. These properties minimize coating damage during the manufacture process, and the coating are resistant to the delamination and breaking during stent delivery and deployment, even in the calcification lesion. High elongation property of PVDF-HFP eliminates the coating cracking after the stent expansion (typically 100% elongation and up to 200% elongation) Different from other drug eluting stents, XIENCE stent has demonstrated anti-thrombogenic property1. Autopsy study showed that XIENCE stent has anti-inflammatory properties compared to its counterpart bare metal stent2. These properties are largely due to fluoropassivation property of PVDF-HFP3,4. Fluoropassivation is a term that describes a blood implant inter- surface phenomenon, where good proteins such as albumin is preferentially retained on the surface. As a DES gold standard, XIENCE is the most clinically studied drug eluting stent, i.e., over 120 clinical trials with over 125,000 patients studied and the most implanted drug eluting stent, i.e., approximately 10 million implantations in Europe and over 20 million implantations worldwide (data through end of 2022). XIENCE product has demonstrated long term patient safety. ISAR- TEST 4 randomized trial compared three drug eluting stents, i.e., Yukon Choice PC sirolimus/bioresorbable polymer coated stent (n=1299), XIENCE everolimus/PVDF-HFP coated stent (n=652) and Cypher sirolimus/permanent polymer coated stent (n=652). At 10 years follow-up5, XIENCE demonstrated statistically lower major adverse cardiac events (MACE) and lower definite stent 1 Jinnouchi H; et al `Comparison of Thromboresistance Between Everolimus-Eluting Fluoropolymer Stent and Currently Available Drug-Eluting Stent in an Ex Vivo Swine Shunt Model Under Only Single Antiplatelet Therapy'. J Am. College of Card. 2019; V 74(13) Suppl, B290, 2 Hiroyoshi M; et al `Very Late Pathological Responses to Cobalt-Chromium Everolimus-Eluting, Stainless Steel Sirolimus-Eluting, and Cobalt-Chromium Bare Metal Stents in Humans'. J. Am Heart Assoc. 2017; 6 (11) p.e007244- e007244 3 Mori H; et al 'Clinical implications of blood-material interaction and drug eluting stent polymers in review' EXPERT REVIEW OF MEDICAL DEVICES, 2017 https://doi.org/10.1080/17434440.2017.1363646 4 Szott LM, et al `Blood compatibility assessment of polymers used in drug eluting stent coatings'. 2016; 029806-1 Biointerphases 11(2) 5 Kufner S., et al `Ten-Year Clinical Outcomes From a Trial of Three Limus-Eluting Stents With Different Polymer Coatings in Patients with Coronary Artery Disease Results from the ISAR-TEST 4 Randomized Trial'. Circulation. 2019; 139:325-333 thrombosis than Cypher stent, and trends better than Yukon Choice PC stent in terms MACE and definite thrombosis. XIENCE also improves patient's quality of life6. In addition, XIENCE has passed all ISO10993 biocompatibility tests including carcinogenicity and reproductive toxicity tests. Additional information on XIENCE product can be found in the following website https://www.cardiovascular.abbott/int/en/hcp/products/percutaneous-coronary-intervention/xience- family/xience-sierra.html 6 Zanchin C, et al. JACC Cardiovasc Interv. 2019;12(17):1665-1675. Serruys P, et al. N Engl J Med. 2010;363:136-146. Shiomi H, et al. JACC Cardiovasc Interv. 2019;12:637-647. Baron SJ, et al. J Am Coll Cardiol. 2017;70:3113-3122 CHAPTER 7 IMPLANT MATERIALS ARNOLD S. BREITBART AND VALERIE J. ABLAZA The history of implant materials can be traced to 3000 b.c., when the Incas of Peru used gold and silver to repair trephination defects. Petronius offered an early description of the use of alloplastic materials in 1565 when he described closure of a cranial defect with a gold plate. Over the next 300 years, the use of implants was sporadic and often complicated by infection. The use of synthetic materials as bioimplants did not become widespread until after the 1940s, when advances in biomaterial science led to the development of numerous materials suitable for implantation. Alloplastic implantation is indicated for the stabilization of fractures and for the reconstruction or augmentation of soft tissue defects or bony deformities. The ideal implant material produces no foreign-body inflammatory response, does not support the growth of microorganisms, and should be sterilizable, nontoxic, nonallergenic, noncarcinogenic, and biologically compatible. Other criteria for the ideal implant material include resistance to strain and deformation, ease of removal, ease of shaping into the desired form, and, in certain circumstances, radiolucency. The selection of a particular implant depends on the specific requirement for its use. Certain implants are more appropriate for soft-tissue augmentation, whereas others are used for bone contouring or reconstruction. The possibility of encapsulation or tissue ingrowth is also relevant to the choice of an implant. For example, the strength of integrated polypropylene mesh and the rigid incorporation of a bone substitute are often desirable, whereas the encapsulation of a silicone Hunter rod allows for free gliding of a subsequent tendon graft. The use of autologous tissue, particularly vascularized autologous tissue, may be more appropriate in many circumstances, especially when conditions for implantation are not optimal. These include a history of radiotherapy, marginal blood supply of the surrounding tissue, or tenuous soft-tissue coverage over the implant. In these circumstances, the risk of implant-related complications, including infection and implant extrusion, are significant, and the use of an alloplastic implant should be avoided. Implants are less likely to tolerate overlying wound-healing problems than autologous tissue, and in such circumstances may require removal of the implant when a reconstruction with autologous tissue might have been salvaged. In addition, because the complications of alloplastic materials may develop long-term, one must not make early assumptions about the safety of these implants. Implants, however, can be used as alternatives to autogenous tissue in selected cases, and as such, have the advantages of avoiding operative time for graft harvesting, the absence of donor site morbidity, and an unlimited supply. Unlike autologous tissue, implants can be fabricated in such a manner that they undergo no resorption, and therefore may be preferable to autologous grafts in certain cases. In particular, implants have been used as bone graft substitutes with much success in orbital floor reconstruction, cranioplasty, and maxillofacial reconstruction. The basic classification of implant materials most commonly used includes metals, calcium ceramics, polymers, and biologic materials (Table 7.1). METALS Metals are primarily used in plating systems for craniomaxillofacial internal fixation and hand surgery, and as Kirschner wires (K-wires), cranial plates, hemoclips, rods, and artificial joints. Stainless steel, cobalt-chromium, and titanium are the principal metals currently available for biologic implantation. Characteristics of a desirable metal implant include biocompatibility, strength, resistance to corrosion, and imaging transparency. Stainless steel is an alloy composed of iron, chromium, nickel, molybdenum, manganese, and silicone; it was first used in biomedical implants in the 1920s. Although all of the metals are biocompatible, stainless steel miniplates for rigid fixation in craniofacial surgery were found to undergo corrosion with the potential for implant failure after several years. With regards to magnetic resonance imaging (MRI), stainless steel may have the potential to cause artifacts or movement. The development of Vitallium (Howmedica, Rutherford, NJ) helped to overcome the problem of corrosion. Vitallium is composed primarily of cobalt and chromium, with molybdenum, nickel, manganese, and silicone added to increase strength. The superior corrosion resistance of Vitallium is partially a result of the surface formation of a protective oxide film. Although Vitallium alloys have the greatest tensile strength of the metals in terms of fracture and resistance to fatigue, they are difficult to bend or shape. Compared to stainless steel, Vitallium has no magnetic properties and causes less artifact on computerized tomography (CT) or MRI scans than does stainless steel. Titanium is the most recently developed alloy and has generally replaced the use of stainless steel and Vitallium in craniofacial plating systems. It is available as pure titanium, as well as a stronger alloy of titanium in combination with aluminum and vanadium. In the unalloyed form, titanium is more malleable than stainless steel or Vitallium, which facilitates easy and precise molding to fit the contours of the facial skeleton. Despite its malleability, titanium's tensile strength is similar to that of Vitallium. The protective oxide layer that forms on the surface of titanium makes it the least corrosive metal for implantation. It also induces significantly less scatter on CT and MRI scans than either stainless steel or Vitallium, thereby allowing for postoperative imaging with minimal bone distortion. Gold has also been used as an implant material, but with limited applications. Although gold is resistant to corrosion, its lack of strength and high cost has generally made it a suboptimal choice as an implant. It is, however, used as an upper eyelid weight in cases of facial nerve dysfunction. 58 Copyright 2007 by Lippincott Williams & Wilkins, a Wolters Kluwer business. Grabb and Smith's Plastic Surgery, Sixth Edition by Charles H. Thorne. TABLE 7.1 IMPLANT MATERIALS Metals Stainless steel Vitallium (cobalt-chromium) Titanium Gold Calcium ceramics Hydroxyapatite Tricalcium phosphate Hydroxyapatite cement Bioactive glass Polymers Silicone Polymethylmethacrylate Hard tissue replacement (HTR) polymer Polyesters (Dacron, Mersilene) Biodegradable polyesters (polyglycolic acid, poly-l-lactic acid) Polyamides (Supramid, Nylamid) Polyethylene (Medpor) Polypropylene (Prolene, Marlex) Cyanoacrylates Polytetrafluoroethylene (Teflon, Gore-Text) Biologic materials Collagen AlloDerm Discontinued materials Polyurethane Proplast Metals are also used as osseointegrated implants to attach dental and facial prostheses. Most of the available implants are composed of titanium. Because bone grows into the implant and bonds to its surface, the implant becomes rigidly fixed (osseointegrated) and is resistant to infection. The development of osseointegrated implants was pioneered in Sweden by Branemark. They have been used as bone anchors to which epitheses are secured, most commonly for dental, auricular, ocular, and nasal restoration. CALCIUM CERAMICS Calcium phosphate ceramics are extensively used as bone graft substitutes. They are biocompatible, can be fabricated into different shapes, and, depending on the porosity, are osteoconductive, providing a scaffold for bone ingrowth. The primary calcium phosphate ceramics in clinical use are hydroxyapatite, tricalcium phosphate, and calcium phosphate bone cements. Hydroxyapatite [Ca10(PO4)6(OH)2] is converted as a replica from naturally occurring calcium carbonate coral by a hydrothermal exchange process. Its porous structure has parallel channels and interconnecting fenestrations and has a macroscopic architecture resembling that of human cancellous bone (1). It is commercially available in both block form and as granules (Interpore, Cross International, Irvine, CA) and does not resorb. Tricalcium phosphate [Ca3(PO4)2] is prepared synthetically, and its pore structure is more random than that of hydroxyapatite. Unlike hydroxyapatite, tricalcium phosphate is resorbable, with resorption rates ranging from 30% to 85% by 6 months, depending on the porosity and implantation con- Chapter 7: Implant Materials 59 FIGURE 7.1. Secondary reconstruction of post-traumatic frontal bone deformity with onlay hydroxyapatite cement. ditions. Tricalcium phosphate is also available in block form and in granules, and has been used clinically in the repair of traumatic defects of long bones. Hydroxyapatite has been widely used as a bone graft substitute, most successfully as an interpositional graft. It has also been used in its block form as an onlay graft, but with somewhat less success. Hydroxyapatite granules, when mixed with blood and microfibrillar collagen to form a paste, have been used for craniofacial skeletal augmentation. The principal disadvantages of calcium phosphate ceramics are that they are brittle, have low tensile and compressive strength, and may be difficult to fix into position. However, because they are osteoconductive, they are incorporated into surrounding tissue by both bone and fibrous tissue ingrowth, and become vascularized. Calcium phosphate bone cements are among the most recently developed bone graft substitutes (2). These materials can be used in the repair of cranial defects and in the restoration or augmentation of bony contours of the craniofacial skeleton for non-stress-bearing applications (Fig. 7.1). The commercially available materials (Norian CRS Bone Cement, BoneSource, and Mimix) are supplied as variations of calcium phosphate powders, which are mixed intraoperatively with a solution to form a puttylike substance. These substances can then be used to fill cranial defects or as onlay materials for craniofacial augmentation or restoration. It generally hardens within 5 to 10 minutes to become a structurally stable osteoconductive implant. Norian CRS Bone Cement (Synthes, Paoli, PA) is comprised of a powder of monocalcium phosphate monohydrate, -tricalcium phosphate, and calcium carbonate, which is mixed intraoperatively with sodium phosphate solution. It hardens within 10 minutes and forms dahllite, the primary mineral component of bone. BoneSource (Stryker-Leibinger, Kalamazoo, MI) is similarly prepared by mixing calcium phosphate salts and sodium phosphate solution, and converts to hydroxyapatite. Mimix (W. Lorenz Surgical, Jacksonville, FL) is a mixture of tetracalcium phosphate and tricalcium phosphate, which is mixed with citric acid to form a hydroxyapatite material. The calcium phosphate-based bone cements undergo a limited degree of resorption and replacement with bone at the periphery. These bone cements are also used in conjunction with resorbable miniplates (see Biodegradable Polyesters below) in order to provide additional structural stability in the reconstruction of larger cranial defects. Calcium phosphate ceramics have been combined with bone growth factors in an attempt to increase the amount of bone Copyright 2007 by Lippincott Williams & Wilkins, a Wolters Kluwer business. Grabb and Smith's Plastic Surgery, Sixth Edition by Charles H. Thorne. 60 Part I: Principles, Techniques and Basic Science ingrowth within the implant. This improves both the incorporation and fixation of the implant. Tricalcium phosphate combined with osteogenin, one of the bone morphogenetic proteins, has potential as a bone graft substitute because it is replaced by new bone ingrowth as the tricalcium phosphate resorbs. Experimentally, tricalcium phosphate-osteogenin composite maintains its volume over time, while being replaced by new bone (3). Bioactive glass is a related material; it forms a surface layer of apatite in vivo, which promotes the formation and attachment of bone. Nova Bone (Porex Surgical, Fairburn, GA) is a synthetic bioactive glass consisting of 45% sodium oxide, 45% silica dioxide, 5% calcium, and 5% phosphate. This material is osteoconductive and promotes bone formation at the bioactive glass-bone interface. It has been used for periodontal and alveolar ridge repair, orbital floor reconstruction, and, when mixed with autogenous bone particles, for cranial vault reconstruction (4). POLYMERS Polymers are the most extensively used alloplastic materials and have applications in both bone and soft-tissue reconstruction and augmentation. The structure of polymers consists of long chains of repeating basic units that can reach high molecular weights. Commonly used polymer biomaterials include silicone, polymethylmethacrylate, polyesters, nylon, polyethylene, polypropylene, cyanoacrylates, and polytetrafluoroethylene. Silicone Silicone, or dimethylsiloxane, consists of a monomer backbone of interlinked silicone and oxygen molecules, with methyl and, occasionally, vinyl or phenyl side groups, in a varying number of repeating units. This material is very stable, highly biocompatible, nontoxic, and insoluble in body fluids. Although silicone is considered biologically inert, it does elicit a mild foreign-body reaction, which is followed by encapsulation, but without tissue ingrowth. The viscosity of silicone is determined by the extent of polymerization. Short polymer chains result in liquid silicone with less viscosity, lengthening of the chains results in gel-type substances, and cross-linking of the polymer chains results in highviscosity silicone rubber. Liquid silicone was developed in 1963 and used for augmentation of the breast and face prior to the development of a purer grade of injectable silicone, which was available for investigational purposes. This new formulation was in the process of being considered as an investigational new drug by Dow-Corning in 1976, when the accumulation of reported adverse effects, including inflammation, induration, discoloration, ulceration, migration, and silicone granuloma formation led Dow-Corning to withdraw its application. Liquid silicone is not Food and Drug Administration (FDA) approved and its use should be condemned. The polymerization of dimethylsiloxane into longer chains results in silicone gel. This form of the polymer has been used primarily for filling breast implants, and has also been used in buttock implants and in the correction of contour deficiencies. The use of silicone gel, however, has been surrounded by the controversy related to concerns about migration, toxicity, and an unproven association with human adjuvant disease, leading to restriction of the use of silicone gel implants by the FDA in 1992. As they await FDA approval for unrestricted use, silicone gel breast implants are currently available in the United States only as part of a protocol for use in breast reconstruction, or in cases where implant-related complications necessitate implant replacement. Although the initial clinical experience and early data related to the newer generation of silicone gel breast implants are quite favorable, additional longer-term data are currently being accumulated. Cohesive gel implants, made with a higher-viscosity silicone gel have also been developed, and, although available in Europe and elsewhere, are not yet FDA approved for use in the United States. The cross-linking of polymerized chains of dimethylsiloxane results in a silicone rubber elastomer. This high-viscosity silicone is used for fabricating tissue expanders, the outer shell of both saline-filled and silicone gel-filled breast implants, and as an onlay material for the augmentation of the bony skeleton and soft tissues. Solid silicone implants are commonly used for chin and malar augmentation, and have been used in nasal, chest, and calf augmentation, as well as in joint replacement and tendon reconstruction. The use of silicone elastomer implants has been associated with capsule formation and contracture, particularly with breast implants, which may lead to implant distortion and hardness. Texturing of the implant surface was thought to minimize this potential for capsular contracture, but it is still not clear if it offers any advantage. Silicone synovitis is a recognized complication of silicone implant arthroplasty, which usually requires removal of the implant. Polymethylmethacrylate Polymethylmethacrylate (PMMA) is a high-molecular-weight polymer used as a replacement for bone. It is biocompatible, biologically inert, and rigid. When liquid methylmethacrylate monomer is added to powdered granules of methylmethacrylate polymer, a moldable dough forms as the monomer polymerizes and binds together pre-existing polymer particles, which hardens in about 10 minutes. Because the polymerization process results in an exothermic reaction that can generate high temperatures, saline irrigation should be used to cool the surrounding tissues during the curing process. PMMA can be custom-made preoperatively or prepared intraoperatively. PMMA is a widely used alloplastic material for cranial bone reconstruction (5). It can be used alone or in combination with wire or mesh reinforcement (Fig. 7.2). The immobility and relatively low stresses intrinsic to the calvarium are responsible for the low morbidity of PMMA cranioplasty. Most of the potential complications are related to the exothermic reaction produced during the curing process, which may result in local tissue damage, including bone necrosis and soft-tissue injury. Local and systemic allergic reactions have on occasion been observed and are attributed to the toxic effects of the unbound monomer. Hard tissue replacement (HTR) polymer (W. Lorenz Surgical, Jacksonville, FL) is a nonresorbable composite of PMMA beads fused with polyhydroxyethylmethacrylate, which is then coated with calcium hydroxide. HTR polymer is biocompatible and demonstrates remarkable compressive strength in spite of its extensive porosity. Although it has not been widely used, applications for HTR include chin and malar augmentation, as well as correction of the temporal "hourglass" deformity following postsurgical temporalis atrophy. It has also been used as a prefabricated computer-generated implant based on threedimensional CT scan images for cranial defect reconstruction (6). Polyesters (Dacron, Mersilene) Dacron (polyethylene terephthalate) is a biocompatible, flexible, nonabsorbable polymer that is used as a suture material, Copyright 2007 by Lippincott Williams & Wilkins, a Wolters Kluwer business. Grabb and Smith's Plastic Surgery, Sixth Edition by Charles H. Thorne. Chapter 7: Implant Materials 61 A B FIGURE 7.2. Reconstruction of cranial defect with titanium mesh-reinforced polymethylmethacrylate. A: Placement of titanium mesh. B: Polymethylmethacrylate applied to mesh. as a prosthetic material for arterial replacement, and as a mesh (Mersilene mesh, Ethicon, Inc., Somerville, NJ). It is a suitable implant for applications requiring both tensile strength and stability, and has been used for abdominal and chest wall reconstruction, as well as for chin and nasal augmentation. Biodegradable Polyesters (Polyglycolic Acid, Poly-L-Lactic Acid) In contrast to the aromatic polyester Dacron, the biodegradable polyesters are aliphatic compounds that are more susceptible to hydrolysis. Polyglycolic acid (PGA) and poly-l-lactic acid (PLLA) are two of these polymers that are degraded in the body at physiologic pH over the course of several months. These resorbable polymers are available as mesh sheets for body wall reconstruction, and as rods for the internal fixation of fractures and osteotomies. Biodegradable polyesters have been widely used in the fabrication of resorbable miniplates and screws for the fixation of bones of the craniofacial skeleton, and as orbital floor implants (7). They are especially indicated for use in pediatric craniofacial fixation, because the potential for intracranial migration (as sometimes seen with permanent metallic plates, screws, and wires) is avoided (Fig. 7.3). These biodegradable polymers have also been used as components of resorbable craniofacial distraction devices. LactoSorb (W. Lorenz Surgical, Jacksonville, FL) plates and screws are composed of a copolymer of 82% l-lactic acid and 18% glycolic acid. They retain most of their strength for 6 to 8 weeks and absorb within 12 months. Similar resorbable fixation devices fabricated from a copolymer of 70:30 poly (l-lactide-co-D, l-lactide) are also commercially available (Macropore Biosurgery, San Diego, CA). Endotine Forehead fixation device and Endotine Midface ST 4.5 (Coapt Systems, Inc., Palo Alto, CA) consist of 82% PLLA and 18% PGA and are easy to use, bioabsorbable implants designed to create sutureless soft-tissue fixation during brow lift and midface suspension surgery. The absorbable tines of both these devices allow for multiple points of contact to grasp and elevate soft tissue, holding it in position until the soft tissues adhere to the underlying bone. PGA has also been applied in the fabrication of resorbable matrices in the tissue engineering of both cartilage and bone, and as tubes for guided nerve regeneration. PGA implants seeded with chondrocytes or genetically modified mesenchymal stem cells have been used as scaffolds in the tissue engineering of articular cartilage (8). PGA matrices seeded with cultured periosteal cells have been used in the tissue-engineered bone repair of calvarial defects (9). Polyamide (Supramid, Nylamid) The polyamide compound nylon is available as a woven mesh implant (SupraFOIL, Sepramesh, S. Jackson, Inc., Alexandria, VA). It consists of long chains of amide units that are twisted and then woven. Nylamid is biocompatible, can be easily shaped and sutured, possesses stability as a result of fibrous tissue ingrowth, and has been used successfully as an implant for the repair of orbital floor defects. Polyamide compounds do, however, undergo resorption over time, limiting their applications in facial reconstruction and augmentation. Polyethylene, Polypropylene (Medpor, Prolene, Marlex) Polyethylene is an inert material with a high degree of biocompatibility. There are several types of polyethylene compounds available with different biochemical properties, based on the density of the material. Chemical resistance, tensile strength, and hardness increase with increasing density from the low-density polyethylene, to the ultrahigh-molecularweight polyethylene. Medpor (Porex) is a high-density porous polyethylene implant that is used in facial reconstruction. It is nonantigenic, nonallergenic, nonresorbable, highly stable, easy to fixate, and is available in a wide variety of preformed shapes (Fig. 7.4). It is produced through a sintering process that produces a contiguous porous polyethylene framework. This porosity allows for vascular and soft tissue ingrowth with incorporation of the implant. Medpor is most commonly used in the restoration or augmentation of bony contour in the craniofacial skeleton for both reconstructive and aesthetic applications (Fig. 7.5). Medpor has been used as malar, chin, nasal, orbital rim, orbital floor, and cranial implants, as well as an auricular framework in postburn ear reconstruction (10). Complications of Medpor are unusual, but include exposure and infection. Although the ingrowth of fibrous tissue offers the advantage of positional stabilization, it also creates difficulty should the implant need to be removed. The substitution of one methyl group for a hydrogen atom in each polyethylene unit results in a loosely woven, highdensity polypropylene polymer with biologic properties similar Copyright 2007 by Lippincott Williams & Wilkins, a Wolters Kluwer business. Grabb and Smith's Plastic Surgery, Sixth Edition by Charles H. Thorne. 62 Part I: Principles, Techniques and Basic Science A B C FIGURE 7.3. Fixation of reconstructed skull with resorbable plates for correction of metopic synostosis. A: Trigonocephalic appearance of metopic synostosis. B: Fixation of advanced fronto-orbital segment with resorbable plates and screws. C: Appearance of patient before (left) and 1 year after (right) surgical treatment of metopic synostosis using resorbable fixation. to polyethylene. Polypropylene is one of the most inert biomaterials used in surgery, and is available as a woven mesh (i.e., Marlex, Prolene). It is easy to suture, has good tensile strength, and demonstrates early fibrous tissue ingrowth that serves to fix and incorporate the mesh. Polypropylene mesh is commonly used to repair abdominal fascial defects. It is also used in the reconstruction of chest wall defects, either alone or sandwiched around a polymethylmethacrylate core (Fig. 7.6). Cyanoacrylates The cyanoacrylates are quick-setting, biodegradable, polymeric tissue adhesives that have become useful tissue-bonding agents. They form a strong, durable bond with most human tissue, particularly those tissues containing a large amount of protein, such as skin and tendon. In addition to their role in bonding tissues, these polymers are also used as hemostatic and embolic agents. The cyanoacrylate tissue adhesives polymerize by an exothermic reaction in the presence of water and hydroxyl groups on the wound surface, and thus are effective on moist surfaces. The first of the cyanoacrylate compounds to be synthesized was methyl-2-cyanoacrylate, which was followed by the development of other adhesives, including ethyl-2cyanoacrylate (Krazy Glue), isobutyl cyanoacrylate (Bucrylate), and butyl-2-cyanoacrylate (Histoacryl). Experimental and clinical applications of cyanoacrylates in plastic surgery include sutureless skin closure for incisions and lacerations, fixation of bone and cartilage grafts, fixation of craniofacial fractures, tendon repair, and tarsorrhaphy. The FDA approval of Dermabond (2-octyl cyanoacrylate, Ethicon, Inc., Somerville, NJ) as a topical skin adhesive in 1998 has contributed to the increased use of the polymeric tissue adhesives. The liquid polymerizes within minutes after Copyright 2007 by Lippincott Williams & Wilkins, a Wolters Kluwer business. Grabb and Smith's Plastic Surgery, Sixth Edition by Charles H. Thorne. Chapter 7: Implant Materials 63 FIGURE 7.4. A variety of Medpor implants, including (clockwise from top left) auricular framework, auricular helix, mandibular angle/body, orbital floor, chin, enucleation, and malar implants. chemically inert polymer with favorable handling characteristics. The main application for Teflon has been in the reconstruction of orbital floor defects. Gore-Tex (W.L. Gore, Flagstaff, AZ) is an expanded synthetic polymer composed of solid PTFE nodes with interconnecting thin PTFE fibrils that form a grid pattern. It is a pliable, durable, inert, biocompatible material that demonstrates some tissue ingrowth, little inflammatory reaction, and almost no encapsulation. It is available as sheets that are easily contoured or stacked to a desired thickness, as well as solid blocks (SAM Facial Implant, W.L. Gore, Flagstaff, AZ) that can be carved to customized shapes (11). Applications of GoreTex in plastic surgery include abdominal fascial reconstruction (Fig. 7.7); chest wall reconstruction; soft-tissue filler for lip, nasal, chin, and malar augmentation; and as treatment for nasolabial and glabellar creases. Composite sheets of polypropylene mesh and expanded PTFE are also available for abdominal wall reconstruction. In this application, the PTFE side is placed on the side in closest proximity to the bowel so as to avoid the adherence of the polypropylene mesh to the underlying bowel. application to the skin, setting as a thin film that covers the wound edges and peels away in 7 to 10 days. In vitro studies show Dermabond to be an effective barrier against the penetration of bacteria. Indermil tissue adhesive (n-Butyl-2cyanoacrylate, U.S. Surgical, Norwalk, CT) received FDA approval in January 2004, with the additional claim that it acts as a barrier to microbial penetration as long as the adhesive film is intact. Polytetrafluoroethylene (Teflon, Gore-Tex) The basic unit of the polytetrafluoroethylene (PTFE) polymer consists of an ethylene monomer backbone with four covalently bound fluorine molecules. This material is inert and highly biocompatible. Teflon is synthesized from the polymerization of tetrafluoroethylene gas under high temperature and pressure. It is a BIOLOGIC MATERIALS (COLLAGEN, ALLODERM) Collagen is a large, rod-shaped protein composed of three polypeptide chains arranged in a triple-helix configuration. It is the most common protein in the body and is a widely used biologic implant material (see Chapter 45). AlloDerm (LifeCell Corp., Branchburg, NJ) is an acellular, structurally and biochemically intact human dermal graft that is used for cosmetic and reconstructive soft-tissue augmentation. Donated human skin is denuded of epithelium, freeze-dried, and decellularized through a special process that preserves the bioactive components without damaging the extracellular dermal matrix and basement membrane architecture. The resulting graft serves as a framework to support cellular repopulation, revascularization at the surgical site, and softtissue regeneration by the recipient's own cells (12). Animal studies demonstrate that AlloDerm is nontoxic with no elicitation of an inflammatory response. It has a shelf-life of up to 2 years under standard refrigeration and is rehydrated immediately before use with normal saline or lactated Ringer solution. The most common uses for AlloDerm include fascial defect repair, wound coverage, lip enhancement, dorsal nasal augmentation, correction of depressed scars and liposuction defects, and nipple augmentation. Depending on the degree of softtissue replacement needed, AlloDerm can be used as a single layer or stacked in multiple layers. The graft can be pulled through subdermal tunnels created through small incisions. Cymetra (LifeCell Corp., Branchburg, NJ) is a particulate form of AlloDerm delivered by injection and is most commonly used (as is collagen and hyaluronic acid) for lip augmentation and the filling of prominent nasolabial folds. FIGURE 7.5. Medpor implant used to reconstruct orbital floor. Orbital rim fracture has been repaired with titanium plates. DISCONTINUED IMPLANT MATERIALS The polyurethanes and Proplast are implant materials that are no longer available for clinical use but deserve mention for historical reasons. The polyurethanes are a group of polymers consisting of a diisocyanate and an alcohol. An intense foreignbody giant cell reaction, followed by tissue adhesion, was responsible for the connective tissue ingrowth that resulted in the low capsular contracture rates seen with polyurethanecovered breast implants. Concerns regarding the effect of Copyright 2007 by Lippincott Williams & Wilkins, a Wolters Kluwer business. Grabb and Smith's Plastic Surgery, Sixth Edition by Charles H. Thorne. 64 Part I: Principles, Techniques and Basic Science A B FIGURE 7.6. A: Exposure of heart and lungs following resection of ster- num and ribs for recurrent chest wall sarcoma. B: Reconstruction of chest wall with Marlex-polymethylmethacrylate sandwich. C: Coverage with free C rectus myocutaneous flap. Copyright 2007 by Lippincott Williams & Wilkins, a Wolters Kluwer business. Grabb and Smith's Plastic Surgery, Sixth Edition by Charles H. Thorne. Chapter 7: Implant Materials 65 infection, and extrusion related to Proplast temporomandibular joint implants, resulted in the removal of all forms of Proplast from American markets by the FDA in 1990. FIGURE 7.7. Abdominal fascial reconstruction with Gore-Tex sheet following harvest of transverse rectus abdominis myocutaneous flap. toluene-diamine, the breakdown product of polyurethane, resulted in the FDA request for a voluntary delay of production and sales of polyurethane-covered breast implants in 1991, and production was subsequently discontinued. Proplast I (Vitek, Houston, TX) was introduced as a highly porous, black Teflon and carbon composite with a spongy consistency. Proplast II, a more rigid, white Teflon and alumina compound, was developed as an alternative to Proplast I. Although Proplast was previously regarded favorably, with a wide variety of applications including the correction of bony deformities of the face, skull, and rib cage, the subsequent accumulation of reports of biomechanical failure, intense inflammation, References 1. Bucholz RW, Carlton A, Holmes RE. Hydroxyapatite and tricalcium phosphate bone graft substitutes. Orthop Clin North Am. 1987;18:323. 2. Burstein FD, Cohen SR, Hudgins R, et al. The use of hydroxyapatite cement in secondary craniofacial reconstruction. Plast Reconstr Surg. 1999;104:1270. 3. Breitbart AS, Staffenberg DA, Thorne CHM, et al. Tricalcium phosphate and osteogenin: a bioactive onlay bone graft substitute. Plast Reconstr Surg. 1995;96:699. 4. Gosain AK, PSEF DATA Committee. Bioactive glass for bone replacement in craniomaxillofacial reconstruction. Plast Reconstr Surg. 2004;114:590. 5. Manson PN, Crawley WA, Hoopes JE. Frontal cranioplasty: risk factors and choice of cranial vault reconstruction material. Plast Reconstr Surg. 1986;77:888. 6. Eppley BL, Kilgo M, Coleman JJ. Cranial reconstruction with computergenerated hard-tissue replacement patient-matched implants: indications, surgical techniques, and long-term follow-up. Plast Reconstr Surg. 2002;109:864. 7. Eppley BL, Morales L, Wood R, et al. Resorbable PLLA-PGA plate and screw fixation in pediatric craniofacial surgery: clinical experience in 1883 patients. Plast Reconstr Surg. 2004;114:850. 8. Mason JM, Breitbart AS, Barcia M, et al. Cartilage and bone regeneration using gene-enhanced tissue engineering. Clin Orthop Rel Res. 2000;379S:171. 9. Breitbart AS, Grande DA, Kessler R, et al. Tissue engineered bone repair of calvarial defects using cultured periosteal cells. Plast Reconstr Surg. 1998;101:567. 10. Yaremchuk MJ. Facial skeletal reconstruction using porous polyethylene implants. Plast Reconstr Surg. 2003;111:1818. 11. Schoenrock LD, Chernoff WG. Subcutaneous implantation of Gore-Tex for facial reconstruction. Otolaryngol Clin North Am. 1995;28(2):325. 12. Terino EO. AlloDerm acellular dermal graft. Applications in aesthetic softtissue augmentation. Clin Plast Surg. 2001;28:83. Copyright 2007 by Lippincott Williams & Wilkins, a Wolters Kluwer business. Grabb and Smith's Plastic Surgery, Sixth Edition by Charles H. Thorne. BVMed Bundesverband Medizintechnologie e.V. Berlin, 25.05 2023 Zi 255-32 E-Mail: @i3vrned.de BVMed-Stellungnahme zum Anhang XV Report zur Beschrnkung der Herstellung, des Inverkehrbringens und der Verwendung von Per- und Polyfluoralkylsubstanzen (PFAS) unter der Verordnung (EG) Nr.1907/2006 (REACH). A. Vorbemerkung Der BVMed vertritt als Wirtschaftsverband ber 310 Industrie- und Handelsunternehmen der Medizintechnik-Branche in der Bundesrepublik Deutschland. Im BVMed sind u. a. die 20 weltweit grten Medizinproduktehersteller im Verbrauchsgterbereich organisiert. Mit diesem Papier nimmt der BVMed Stellung zum o. g. Beschrnkungsvorschlag, adressiert Kritikpunkte und identifiziert Fragen, die der Vorschlag aufwirft. B. Kommentierung Wenngleich wir das Ziel des Beschrnkungsvorschlags hinsichtlich des Gesundheits- und Umweltschutzes grundstzlich untersttzen, haben wir doch erhebliche Bedenken, dass der Vorschlag den Besonderheiten der Medizintechnik als Teil der Gesundheitswirtschaft hinreichend Rechnung trgt. Die Anwendung von Beschrnkungen fr die Verwendung von chemischen Stoffen nach der REACH-Verordnung auf den Sektor der Medizintechnik muss aufgrund der potentiellen Auswirkungen auf die Gesundheitsversorgung wie die ffentliche Gesundheit in einem breiteren Kontext betrachtet werden. Whrend unter anderem Arzneimittel von der Beschrnkung ausgenommen sind, sollen Medizinprodukte vollumfnglich unter die Beschrnkung fallen. Das erscheint unangemessen und unverhltnismig. Zugunsten der vorgeschlagenen Ausnahmen vom Anwendungsbereich wird argumentiert, die ausgenommenen Produktgruppen wie Wirkstoffe in Arzneimitteln seien in den jeweils fr sie geltenden europischen Verordnungen adressiert. Wir weisen darauf hin, dass Medizinprodukte mit der europischen Medizinproduktverordnung (Verordnung EU 2017/745; nachfolgend MDR) einer eigenstndigen, strikten und in sich geschlossenen EURegulierung unterliegen. Damit setzt sich der Beschrnkungsvorschlag nicht auseinander und enthlt auch im brigen keine schlssige Begrndung fr die Benachteiligung von Medizinprodukten gegenber Arzneimitteln. Die Benachteiligung erscheint daher inkonsistent und willkrlich. Der Geltungsbereich der Beschrnkung ist sehr weit gefasst und umfasst mehr als zehntausend Einzelsubstanzen. Eine Risikobewertung der einzelnen Stoffe oder zumindest einzelner Gruppen von Stoffen mit homogenen Eigenschaften liegt nicht vor. Die fr den Vorschlag verantwortlichen Behrden sttzen ihren weitreichenden Beschrnkungsvorschlag in erster Linie auf die Persistenz der Stoffe. Persistenz allein stellt jedoch keine Gefahr oder ein ,,unannehmbares Risiko" im Sinne von Art. 68 (1) REACH dar. Durch das Fehlen spezifischer Seite 2 | BVMed-Stellungnahme zum PFAS-Beschrnkungsvorschlag Bewertungen fr die einzelnen Stoffe oder mindestens fr jede PFAS-Gruppe ist kein ,,unannehmbares Risiko" belegt, so dass die Anforderungen eines Risikonachweises gem Artikel 68 (1) oder Anhang XV, Teil 3 REACH nicht erfllt sind. Vor allem aber wird in dem Beschrnkungsvorschlag an keiner Stelle nachgewiesen und belegt, welche konkreten und ,,unannehmbaren" Gesundheitsrisiken sich aufgrund der Exposition des Menschen durch PFAS-haltige Medizinprodukte ergeben. Vielmehr werden Gesundheitsrisiken allgemein vermutet oder unterstellt. Diesen potenziellen Gesundheitsrisiken stehen aber sehr konkrete Gesundheitsrisiken entgegen, die durch eine Verschlechterung der Gesundheitsversorgung aufgrund eines Wegfalls von bewhrten Therapieoptionen entstehen. Dies zeigt sich beispielsweise tagtglich bei lebenserhaltenden Produkten fr hunderttausende Patienten mit Nierenversagen, war aber auch bei der Beatmung von COVID-Patienten hchst relevant. Diese Risiken und die sich daraus ergebenden soziokonomischen Nachteile werden in dem Beschrnkungsvorschlag nicht hinreichend bercksichtigt. Indem der Regelungsvorschlag Medizinprodukte wie ein herkmmliches Alltagsprodukt behandelt, wird er der soziokonomischen Bedeutung ihrer Anwendung nicht gerecht. Medizinprodukte mssen in Anbetracht dessen entsprechend dem ,,Essential-use"-Ansatz als integrale Bestandteile der Gesundheitsversorgung auf gleicher Ebene wie Arzneimittel betrachtet und generell von der Beschrnkung ausgenommen werden. Dabei mssen die vorgelagerten Produktionsschritte und die fr die Herstellung von Medizinprodukten ntigen Zwischenprodukte und -erzeugnisse eingeschlossen werden. Auch in Zusammenhang mit den vorgeschlagenen Ausnahmeregelungen fr einzelne Medizinprodukte ist unverstndlich, dass fr die notwendigen Vor- und Zwischenprodukte (Verarbeitungshilfsstoffe und Monomere) zur Herstellung der weiter erforderlichen Fluorpolymere keine ergnzenden Ausnahmeregelungen vorgesehen sind. Dies gilt vor allem auch fr die in der Medizintechnik wichtigen Polymere PTFE, PVDF und FKM, zumal diese von der vorgeschlagenen sehr engen und kurzen Ausnahmeregelung fr Polymerisationshilfsmittel in Nr. 5. a) explizit ausgeklammert sind. Der Ausschluss dieser Fluorpolymere von der Ausnahmeregelung fr Polymerisationshilfsmittel wird im Vorschlag damit begrndet, dass PFAS-haltige Hilfsstoffe fr die Herstellung dieser Polymere (angeblich) nicht mehr bentigt werden. Diese Aussage ist jedenfalls in Hinblick auf die Verwendung in Medizinprodukten falsch. Die erforderlichen hochmolekularen Ketten knnen whrend des Polymerisationsprozesses nur durch PFAS-haltige Prozesshilfsmittel erzeugt werden. Die vorgeschlagene, sehr eingeschrnkte Ausnahmeregelung fr Vorprodukte und Zwischenprodukte wrde bedeuten, dass selbst Medizinprodukte mit einer 13,5-jhrigen Ausnahmeregelung nach dem Auslaufen der Ausnahme fr Polymerisationshilfsstoffe nicht mehr in der EU hergestellt werden knnten. Die Hersteller wren somit gezwungen, die eigentlich zulssige und gewnschte Produktion von Medizinprodukten fr den EU-Binnenmarkt in Drittstaaten zu verlagern. Auch dieser Aspekt macht deutlich, dass eine berarbeitung des Beschrnkungsvorschlags in Bezug auf Medizinprodukte zwingend notwendig ist. Soweit es um etwaige Alternativen fr die Verwendung von PFAS in Medizinprodukten geht, muss beachtet werden, dass potenzielle alternative Stoffe nur dann eine angemessene Alternative sein knnen, wenn sie hinsichtlich der medizinischen Performance und Risikobewertung gleichrangig und auch in der Gesamtbetrachtung in Bezug auf Nachhaltigkeit, Energieverbrauch, Umweltaspekte und Arbeitssicherheit vergleichbar sind. Die Breite des von den fnf nationalen Behrden gewhlten gruppenbezogenen Ansatzes stellt gerade die Medizintechnik vor groe praktische Herausforderungen. Bereits die Analyse der Auswirkungen der vorgeschlagenen Beschrnkung ist fr Unternehmen (insbesondere fr kleine und mittlere Unternehmen (KMU)) im Medizintechniksektor sehr schwierig. Eine vollstndige Identifizierung, Bewertung und Kommunikation entlang der gesamten Wertschpfungskette in Hinblick auf jede einzelne der mehr als 10.000 Substanzen und fr jedes einzelne Medizinprodukt ist fr die betroffenen Unternehmen angesichts komplexer, globaler Lieferketten und oft begrenztem Zugang zu Geschftsgeheimnissen ber die Produkt- Seite 3 | BVMed-Stellungnahme PFAS-Beschrnkungsvorschlag zusammensetzung praktisch nicht mglich. Selbst wenn alle PFAS in Medizinprodukten und ihre jeweiligen Alternativen sofort identifiziert werden wrden, ist eine Umstellung innerhalb der vorgeschlagenen generellen 18-monatigen bergangsfrist oder der 6,5- bzw. 13,5-jhrigen Ausnahmefrist auf die Alternativstoffe nicht realisierbar. Selbst wenn die Umstellung dieser Medizinprodukte technisch zu bewerkstelligen wre, blieben noch enorme Herausforderungen in Hinblick auf die Anforderungen an das Inverkehrbringen ber die jeweiligen Verfahren zur Zertifizierung im Zuge der MDR, da derartige nderungen an Produkten entwickelt, beantragt und entsprechend geprft werden mssten, was innerhalb der bergangsfrist nicht mglich wre (dazu im Einzelnen weiter unten). PFAS werden in der Medizintechnik in unterschiedlichsten Anwendungen eingesetzt. Solche Verwendungen sind im vorliegenden Vorschlag allerdings nur teilweise bercksichtigt. Viele Medizinprodukte sind im Vorschlag hingegen nicht genannt oder ungenau definiert. Beispiele dafr sind invasive Medizinprodukte mit Blutkontakt unter anderem in der Apherese, Katheter, Fhrungsdrhte, Verpackungen von mit Ethylenoxid oder Gamma-Strahlen sterilisierte Medizinprodukten, Ophthalmika, implantierbare Medizinprodukte, Nahtmaterial, Wundauflagen, Reinigungsflssigkeiten, Abdeckungen und Textilien fr medizinische Anwendungen, aber auch Membranen, Filter etc. Die vorgeschlagene Einschrnkung muss sicherstellen, ggf. durch klarstellende Formulierungen, dass der gesamte Bereich der Medizinprodukte ordnungsgem identifiziert und in die erforderlichen Ausnahmeregelungen einbezogen wird, da sonst die Gefahr besteht, dass der Zugang zu diesen wichtigen Medizinprodukten in der EU nach der bergangszeit unmglich wird. Der Ansatz, der im Beschrnkungsvorschlag festgelegten Ausnahmen, erscheint somit in Hinblick auf die Medizinprodukte-Branche inkonsistent. Zudem weicht die Abgrenzung der verschiedenen Gruppen von Medizinprodukten von der Systematik der MDR ab ohne dass dafr im Beschrnkungsvorschlag ein Sachgrund dargelegt wird. So werden ohne jede Begrndung ,,Netze" aus der Produktgruppe der (ausgenommenen) implantierbaren Medizinprodukte herausdefiniert und nur speziell ,,Hernien-Netze" dann wiederum anders behandelt als alle anderen ,,Netze", selbst wenn sie in unmittelbarer Nhe im menschlichen Krper eingesetzt werden (z. B. gynkologische Netze). Dies zeigt nicht nur eine mangelhafte Analyse der Medizinprodukte im Beschrnkungsvorschlag, sondern widerspricht explizit Anhang VIII Kapitel III Nr. 5.4 der Medizinprodukteverordnung. Die Verordnung nennt dort im 7. Spiegelstrich explizit umfassend ,,chirurgische Netze" und ordnet diese den implantierbaren Medizinprodukten zu. Nach alledem ist unklar, ob die nationalen Behrden, die den Vorschlag fr die Beschrnkungen ausgearbeitet haben, sich in der erforderlichen Tiefe mit der Medizintechnik auseinandergesetzt haben. Es besteht ein sehr groes Risiko, dass wesentliche medizinische PFAS-Anwendungen bei der Definition der teils sehr kleinteiligen Ausnahmeregelungen bersehen werden. Ausschlaggebend fr die Festschreibung der erforderlichen Ausnahmeregelungen ist die Verfgbarkeit von ggf. technisch mglichen Alternativen. Bei der Festlegung der vorgeschlagenen Ausnahmen scheint das begrenzte Verstndnis der fnf nationalen Behrden im Hinblick auf die technisch mglichen Alternativen und deren Verfgbarkeit eine entscheidende Rolle gespielt zu haben. Der starre Ansatz der nationalen Behrden greift viel zu kurz und ist im Hinblick auf Medizinprodukte unzureichend. Vermeintliche oder tatschliche technische Alternativen mssen im Rahmen eines ganzheitlichen Ansatzes genau geprft werden, um sicherzustellen, dass sie im Hinblick auf Sicherheit und Wirksamkeit den derzeit auf dem Markt befindlichen Produkten mindestens ebenbrtig, wenn nicht sogar berlegen sind. berdies sind bei Medizinprodukten neben gesetzlichen Anforderungen, die sich aus der MDR ergeben, auch der technologische Reifegrad, aber vor allem auch der Patientennutzen und die Patientensicherheit zu bercksichtigen. Das Vorhandensein einer technisch mglichen Alternative bedeutet noch lange nicht, dass diese im Hinblick auf den Nutzen, die Sicherheit und Langlebigkeit des Medizinprodukts und dessen Funktionsfhigkeit tatschlich fr den Einsatz in der Medizin geeignet ist. Darber hinaus ist aus dem Vorhandensein einer Alternative auch nicht der Schluss abzuleiten, dass die Hersteller von Medizinprodukten einfach substituiert Seite 4 | BVMed-Stellungnahme zum PFAS-Beschrnkungsvorschlag werden knnen, weil dadurch der Zugang der rzte zu umfassenden Therapieoptionen zur bestmglichen Versorgung ihrer Patienten eingeschrnkt werden knnte. Sollte der Beschrnkungsvorschlag in seiner jetzigen Form angenommen werden, wre mit einer deutlichen Reduzierung der Verfgbarkeit von Medizinprodukten und einer damit verbundenen Verschlechterung der Patientenversorgung im EU-Binnenmarkt zu rechnen. Dies liegt nicht zuletzt an den vorgesehenen bergangsfristen, die fr Medizinprodukte unangemessen sind. Die generelle bergangsfrist von nur 18 Monaten fr Verwendungen, die nicht unter eine der wenigen und engen Ausnahmeregelungen fallen, schliet in jedem Fall aus, dass Substitutionsprodukte entwickelt, zugelassen und eingefhrt werden knnten. Nichts anderes gilt aber auch fr die im Beschrnkungsvorschlag vorgesehenen Ausnahmen und die dafr vorgeschlagenen bergangsfristen. Die beiden Ausnahmefristen (6,5 und 13,5 Jahre) scheinen willkrlich gewhlt, haben keine empirische Grundlage in Bezug auf die herkmmlichen Produktentwicklungs- und Zulassungszeitrume, insbesondere nicht im Hinblick auf Medizinprodukte. Der Vorschlag ignoriert nicht nur die Tatsache, dass extensive regulatorische Anforderungen fr das Inverkehrbringen von Medizinprodukten durch die MDR neu geregelt sind und eine umfassende (Neu-)Zertifizierung aller Medizinprodukte erfordern. Er lsst vielmehr auch auer Betracht, dass der bergangszeitraum bis zur finalen Implementierung der MDR aufgrund der Komplexitt des Zertifizierungsverfahrens sowie der Erkenntnis, dass aufgrund der bestehenden Kapazittsengpsse bei den zustndigen Benannten Stellen zustzliche Zeit fr die erforderliche (Neu-) Zertifizierung aller Produkte bentigt wird, gerade erst bis 2027/2028 verlngert worden ist. Die auf PFAS abzielende Beschrnkung wrde zudem weit ber die durch die MDR geschaffene Herausforderung hinausgehen. Medizinprodukte, die PFAS enthaltende Medizinprodukte substituieren, mssten nicht nur neu zertifiziert werden, sondern ihre gesamte Zusammensetzung wrde eine ganz neue Sicherheits- und Leistungsprfung erfordern. Die Zertifizierung fr eine materialbasierte Produktumgestaltung wrde Designkontrollaktivitten wie MaterialScoping, Materialentwicklung, Einrichtung und Qualifizierung von Lieferanten, Produktbernahme einschlielich der Entwicklung von Herstellungsprozessen, Leistungstests und Erstellung oder Aktualisierung der technischen Dokumentation, klinische Tests und die Zertifizierung durch Benannte Stellen umfassen. Zu den Arbeiten im Zusammenhang mit einer Produktumgestaltung/-nderung knnen auch Klrungen im Bereich Recht/IP und entsprechende Einreichungspflichten, zustzliche personelle Auswirkungen aufgrund der Umstellung von Rollen/Schwerpunkten, einschlielich potenzieller Schulungen und Personalgewinnung, organisatorisches nderungsmanagement und Projektmanagement sowie eine fortlaufende klinische Nachbereitung hinzukommen. Umfassende Anforderungen wie diese knnen pro Medizinprodukt bzw. Produktlinie bis zu 20 Jahre dauern. Es sollte allen Beteiligten klar sein, welche Herausforderungen der Beschrnkungsvorschlag fr die Industrie beinhaltet und welche Risiken fr die Industrie und Gesellschaft damit verbunden sind. Im Interesse der Patientinnen und Patienten in der EU stehen die Mitglieder des BVMed, aber auch die europischen und nationalen Behrden in der Verantwortung, diese Risiken zu mindern. Eine unbefristete, generelle Ausnahmeregelung fr Medizinprodukte wre dafr das geeignete Instrument. Unabhngig von den vorstehenden Aspekten sieht der BVMed den weiten gruppenbezogenen Ansatz des Beschrnkungsvorschlags als kritisch an. Zur Begrndung verweisen die fnf nationalen Behrden neben der Persistenz auf die Bioakkumulation, die Mobilitt, das Potential eines Transports ber weite Distanzen, die Anreicherung in Pflanzen, das Erderwrmungspotenzial und die (ko-)toxikologischen Auswirkungen. Dies trifft allerdings nur auf einige, aber nicht alle Stoffe zu, die als PFAS definiert sind. So haben insbesondere Fluorpolymere ein vllig anderes Gefahrenprofil. Sie weisen die oben genannten Eigenschaften nicht auf. Fluorpolymere sind eine eigene Klasse innerhalb der weitreichenden Gruppe der PFAS. Hochmolekulare Fluorpolymere wie z.B. Polytetrafluorethylen (PTFE) sind ungiftig, extrem stabil, zu gro, um bioverfgbar zu sein, und haben nicht das Potenzial, sich in der Umwelt zu verbreiten. Dementsprechend erfllen PTFE und mehrere andere Fluorpolymere die 13 Kriterien, die von der Seite 5 | BVMed-Stellungnahme PFAS-Beschrnkungsvorschlag OECD fr wenig besorgniserregende Polymere (sogenannte ,,polymers of low concern") entwickelt wurden. Deren Auswirkungen auf Umwelt oder menschliche Gesundheit werden als geringfgig angesehen. Sie knnen auf verantwortungsvolle Weise hergestellt, verarbeitet, genutzt und entsorgt werden, indem bewhrte Verfahren fr industrielle Kontrolltechnologien eingesetzt werden (z. B. thermische Oxidationsanlagen und Granulatkohlefilterbetten, wie in einem neuen BVT-Merkblatt im Rahmen der Industrie-Emissions-Richtlinie beschrieben). Daher ist es sachgerecht, Stoffe wie die hier genannten Fluorpolymere generell aus dem Anwendungsbereich des Beschrnkungsvorschlags herauszulsen. Zudem muss beachtet werden, dass bei Anwendungen im Bereich der Medizintechnik vielfach keine oder keine relevante direkte Umweltexposition einhergeht. Viele (Einmal-)Produkte werden nach ihrer Benutzung im Krankenhaus als kontaminierter Abfall verbrannt, weswegen keine PFAS in die Umwelt gelangen, da eine umweltgerechte Entsorgung ber Abfallschlssel AS 18 01 02 erfolgt. Dies werden unsere Mitgliedsunternehmen in eigenen Stellungnahmen darlegen. In diesen Fllen ist ein Verbot umso weniger gerechtfertigt, weil unverhltnismig. Abschlieend weisen wir darauf hin, dass unabhngig vom Nachweis der NichtSubstituierbarkeit einzelner Produktgruppen auf der Rechtsgrundlage des Artikels 68 Absatz 1 REACH-VO zunchst eine tatschliche Bewertung des Risikos einschlielich der Exposition in den verschiedenen Verwendungen fr den Erlass der Beschrnkungsverordnung erforderlich ist. Dies ist bei Medizinprodukten erkennbar nicht erfolgt. Hinzu kommen Inkonsistenzen in der unterschiedlichen Behandlung von Medizinprodukten und Arzneimitteln sowie mit der Systematik der Produktgruppen-Einteilung der Medizinprodukteverordnung. Wir erwarten daher auch im Interesse der Rechtssicherheit eine grundlegende berarbeitung des Beschrnkungsvorschlags. C. Vorschlge zur Verbesserung des Beschrnkungsvorschlags - Die finale Beschrnkung sollte objektiv zwischen den einzelnen PFAS differenzieren und diejenigen Stoffe einschrnken, die nachweislich ein ,,unannehmbares Risiko" darstellen (Art. 68 (1) REACH). Aus Sicht des BVMed ist es sachgerecht, Stoffgruppen, die nachweislich kein ,,unannehmbares Risiko" darstellen, wie z. B. Fluorpolymere, von dem Beschrnkungsvorschlag auszunehmen. Dies gilt umso mehr, als das angestrebte Ziel der Emissionsminderung in diesen Fllen auch auf anderem Wege erreicht werden kann (z. B. ber die IndustrieEmissions-Richtlinie). Im Einklang mit der REACH-Verordnung sollte ein Verbot das letzte Mittel sein und bleiben. - Wie bei pharmazeutischen Produkten muss auch die Medizintechnik inklusive aller vorgelagerten Produktions- und Prozessschritte als gesamter Industriesektor aus dem Beschrnkungsvorschlag herausgenommen werden, bis fr die einzelnen Verwendungen Alternativen verfgbar sind, bei denen der Nachweis erbracht wurde, dass sie mindestens ebenso sicher und wirksam sind, wie die derzeitigen, unter Verwendung von PFAS hergestellten Produkte. Die Alternativen mssen bedenkenlos wie auch ohne wesentliche Abstriche in Bezug auf das Nutzen-Risiko-Verhltnis und die Sicherheit im besten Interesse der Patienten in den relevanten Produkten einsetzbar sein. Sollte der EU-Gesetzgeber diesem Vorschlag folgen, steht es ihm ohnehin frei, regelmig zu evaluieren, wie weit die Suche nach Alternativen in der Medizintechnik fortgeschritten ist. Auf dieser Basis kann dann ggf. eine entsprechende Folgeregulierung eingeleitet werden. Das stellt einen hinreichend geeigneten Anreiz fr die Medizintechnik dar, sich auch in Zukunft intensiv um Alternativen zu bemhen. Gleichzeitig wrde der Zugang zu denjenigen Produkten erhalten bleiben, fr die zum aktuellen Zeitpunkt keine vergleichbar hochwertigen Alternativen zur Verfgung stehen. Es wrde auch den vorgelagerten Lieferketten die Zeit geben, sich entsprechend anzupassen, Seite 6 | BVMed-Stellungnahme zum PFAS-Beschrnkungsvorschlag damit sie die Nachfrage decken knnen und die Patienten letztlich kontinuierlich Zugang zu u.U. lebensrettenden Technologien haben. Eine zeitlich unbefristete Ausnahme von der endgltigen Beschrnkung wre auch im Hinblick auf die in der Entwicklung befindlichen PFAS-basierten Innovationen in der Medizintechnik gerechtfertigt, die einen hohen soziokonomischen Mehrwert versprechen. Darber hinaus ist zu bercksichtigen, dass die in der Medizintechnik verwendeten PFASMengen bereits jetzt uerst gering sind, wie die Eingaben unserer Mitgliedsunternehmen ausfhrlich beschreiben. Ein Verbot wrde daher im Bereich der Medizintechnik nur zu einer geringen Emissionsreduktion fhren, die in keinem Verhltnis zu dem durch das Verbot bedrohten hohen Patientennutzen, der derzeit im Binnenmarkt verfgbaren Medizinprodukte steht. - Auch fr die Rohstoffe/Monomere, Verarbeitungshilfsstoffe und Zwischenprodukte in der gesamten Lieferkette sowie in den Produktionsanlagen mssen entsprechende Ausnahmen verankert werden, damit die Medizintechnik weiterhin in der EU produzieren kann. Es muss sichergestellt werden, dass die Medizintechnik nicht in Drittstaaten auerhalb der EU abwandern muss. - Damit die Medizintechnik berhaupt eine Chance htte, eine endgltige Beschrnkung vollstndig umzusetzen, wre es zwingend erforderlich, die vorgeschlagene bergangsfrist von 18 Monaten auf mindestens 15 Jahre zu verlngern und in dieser Zeit eine Neubewertung nach Anhang XV vorzunehmen. Schlielich zielt die vorgeschlagene Verordnung nicht auf eine begrenzte Anzahl einiger weniger Stoffe ab, wie dies normalerweise der Fall ist, sondern umfasst mehr als 10.000 Stoffe. Vor diesem Hintergrund muss den Unternehmen ein angemessener Zeitraum eingerumt werden, um sich auf die vernderten Rahmenbedingungen fr diese Flle von Stoffen einzustellen. - Die derzeit dem Beschrnkungsvorschlag zugrunde gelegten Annahmen und die daraus hergeleiteten Regelungen legen nahe, dass es sinnvoll sein knnte, zustzliches technisches und anwendungsbezogenes Fachwissen von Dritten (u. a. Industrie, medizinisches Fachpersonal, Wissenschaft, NGOs) einzubeziehen. Die Korrektur unzutreffender technischer Annahmen wrde die berarbeitung des Beschrnkungsvorschlags sicherlich erleichtern und frdern. Der BVMed spricht sich daher dafr aus, ber die Konsultationsphasen hinaus Mglichkeiten zu schaffen, die Expertise sachkundiger Akteure transparent in den Prozess einzubinden. Der BVMed untersttzt vollumfnglich den Beitrag seiner Mitglieder zur laufenden Konsultation der ECHA zum laufenden Regulierungsvorhaben und ist bereit, sich in die weitere Diskussion konstruktiv einzubringen, um einer ausgewogenen, zielgerichteten PFASBeschrnkung den Weg zu ebnen, die der Umwelt und Gesundheit der Menschen in der EU gerecht wird. Zusammenfassend begrt der BVMed, dass die fr den Vorschlag verantwortlichen nationalen Behrden die bedeutsame Rolle von Medizinprodukten anerkennen. Gleichzeitig sind wir der Ansicht, dass sie die Gefahren oder ,,unannehmbaren Risiken" der gesamten Bandbreite an PFAS nicht angemessen herausgearbeitet bzw. begrndet haben. Wir sind auerdem der berzeugung, dass die im Vorschlag fr die Beschrnkung vorgeschlagenen Ausnahmeregelungen unzureichend sind, da sie die Anforderungen der Entwicklung, Prfung und Vermarktung eines alternativen, nicht PFAS-haltigen Medizinprodukts nicht angemessen bercksichtigen. Vor diesem Hintergrund ist es nicht mglich, die im Beschrnkungsdossier vorgeschlagene Ausnahmeregelung von 13,5 Jahren fr die meisten Anwendungen von Medizinprodukten einzuhalten. Die Belastung durch diesen langwierigen, ressourcenintensiven Prozess zur Entwicklung, Prfung und Vermarktung neuer Medizinprodukte in Verbindung mit der Nichtverfgbarkeit von technisch oder wirtschaftlich machbaren Alternativen fhrte zu einem Beschrnkungs- Seite 7 | BVMed-Stellungnahme PFAS-Beschrnkungsvorschlag szenario, das fr die Industrie unbeherrschbar wre und zu Engpssen bei kritischen, lebensrettenden Technologien fhren wrde. Aus diesen Grnden fordern wir eine generelle und unbefristete Ausnahme fr Medizinprodukte einschlielich Verarbeitungshilfsstoffe, Rohstoffe, Monomere und Zwischenprodukte. Mindestens aber erwarten wir eine berprfung der Ausnahmeregelungen, um Ausnahmen fr wichtige Materialien wie Fluorpolymere und alternativlose Verwendungen (einschlielich aller Vorstufen) ohne zeitliche Befristung oder mit angemessen langen bergangsfristen zu ermglichen. Bei Rckfragen stehen wir gerne zur Verfgung. Mit freundlichen Gren BVMed - Bundesverband Medizintechnologie e. V. Dr. Christina Ziegenberg Stellv. Geschftsfhrerin Leiterin Referat Regulatory Affairs PRODUKT KANZLEI. Memorandum Date 22.03.2023 Author Martin Ahlhaus Dr. Dominik Strobl To European Chemicals Agency Martin Ahlhaus Dipl.-Verwaltungswirt (FH) Rechtsanwalt ProvinostraBe 52 86153 Augsburg T: +49 (0) 821 899823-20 F: +49 (0) 821 899823-99 M: +49 (0)160 88 678 04 M @produktkanzlei.com Az. 59/23, MA, D3-23 Legal Observations Proposal for a restriction of Per- and polyfluoroalkyl substances (PFAS) according to Regulation (EC) No.1907/2006 (REACH) submitted by BAuA, Federal Institute for Occupational Safety and Health Bureau REACH, National Institute for Public Health and the En- vironment (RIVM) Swedish Chemicals Agency (KEMI) Norwegian Environment Agency The Danish Environmental Protection Agency Version 2.0 Date: 22.03.2023 prepared for and on behalf of Gujarat Fluorochemicals GmbH Produktkanzlei ProvinostraBe 52 86153 Augsburg Ahlhaus Handorn Niermeier Schucht Rechtsanwaltsgesellschaft mbH Geschaftsfuhrer Martin Ahlhaus, Rechtsanwalt Dr. Boris Handorn, Rechtsanwalt Dr. Florian Niermeier, Rechtsanwalt Dr. Carsten Schucht, Rechtsanwalt Tel. +49 (0)821 899 823-0 Fax. +49 (0)821 899 823-99 @produktkanzlei.com www.produktkanzlei.com Amtsgericht Augsburg HRB 34009 Zugelassen bei der Rechtsanwaltskammer fur den Oberlandesgerichtsbezirk MOnchen USt.-ID: DE325991634 Bankverbindung Stadtsparkasse Augsburg Konto: 251 80 59 58 BLZ: 720 500 00 IBAN: DE82 7205 0000 0251 8059 58 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 -- Page 1/44 Table of Contents A. EXECUTIVE SUMMARY..............................................................................................................................3 B. STARTING POINT .......................................................................................................................................5 I. Gujarat Fluorochemicals Limited............................................................................................................................5 II. Background ...................................................................................................................................................................5 C. LEGAL ASSESSMENT..................................................................................................................................7 I. Fluoropolymers in the restriction proposal ........................................................................................................7 II. Objections against the inclusion of Fluoropolymers ......................................................................................8 1. Failure to meet the prerequisites established in Article 68 REACH: hazard to human health / environment ....................................................................................................................................8 a) Failure to conduct proper hazard assessment........................................................................8 aa) Hazard assessment as a mandatory starting point for restriction proposals ...........................................................................................................9 bb) No alternative approach available ............................................................................... 10 cc) No hazard property beyond persistence identified for Fluoropolymers.........11 b) Hazard to human health ...............................................................................................................11 c) Hazard to environment.................................................................................................................14 aa) General considerations ....................................................................................................14 bb) Assessment of environmental hazard properties of Fluoropolymers..............16 cc) Failure to establish persistence as such as (environmental) hazard................. 17 d) Need to provide evidence for a hazard to human health or the environment for every subgroup.........................................................................................................................19 e) No ,,justified" uncertainties and incorrect handling of uncertainties ............................ 19 f) Insufficient hazard assessment regarding new hazard classes ....................................... 21 2. Failure to meet the prerequisites established in Article 68 REACH regarding risk assessment .................................................................................................................................................... 22 a) Insufficient evidence regarding exposure to Fluoropolymers. ....................................... 23 b) Deviation from principles for risk assessment ..................................................................... 23 3. Unlawful grouping ...................................................................................................................................... 25 a) Deviation from available guidance .......................................................................................... 25 b) Grouping not justified with respect to PFAS definition established by OECD.......... 27 aa) PFAS definition according to OECD ........................................................................... 27 bb) OECD definition not based on hazard or risk assessment ................................. 29 cc) Deviating scope of the restriction proposal does not justify grouping approach.............................................................................................................................. 30 dd) Violation of OECD guidance on PFAS ....................................................................... 32 4. Breach of principle of proportionality .................................................................................................. 33 a) Availability of less onerous measures ..................................................................................... 33 b) Inappropriate assessment of the alternatives available.................................................... 36 5. Infringement of the principle of good administration ................................................................... 37 6. Breach of precautionary principle ......................................................................................................... 39 7. Infringement of right to be heard / right to comment ...................................................................41 III. Reference to other parts of the submission.................................................................................................... 42 IV. Conclusion .................................................................................................................................................................. 44 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 2/44 A. Executive Summary (1) The legal basis for the Proposal is Article 68(1) REACH. This provision requires, that an unacceptable risk to human health or the environment, arising from the manufacture, use or placing on the market of the substance(s) within the intended scope is demonstrated. The Proposal substantially deviates from applicable legal prerequisites and principles. It is, therefore, flawed from a factual, technical and legal perspective as far as Fluoropolymers are included in the scope. (2) The scope of the Proposal, in essence, is based on the OECD definition of PFAS established in 2021. This definition also includes Fluoropolymers. (3) Insofar, however, the Proposal does not meet the requirements for a grouping approach under REACH. This would require that all substances within the scope share the key property in combination with the exposure that causes the risk leading to the proposal of a restriction. The Proposal is based on the assumption that all PFAS qualify as persistent and do have other hazard properties in addition to their persistence. The Proposal, however, lacks a mandatory risk assessment to demonstrate that Fluoropolymers share the same or similar hazard properties with other PFAS. In particular it needs to be noted that Fluoropolymers do not meet the criteria for being bioaccumulative, mobile or toxic. It follows already from scientific evidence that Fluoropolymers should not be included in the grouping approach. (4) Furthermore, the Proposal fails to demonstrate that there is an unacceptable risk to human health or the environment with respect to Fluoropolymers. Insofar, any proposal for a restriction needs to be based on a hazard assessment. Mere reference to the OECD PFAS definition is not sufficient as the definition is not established on the assessment whether a compound is harmful or not. Moreover, the assumption that all PFAS qualify as persistent is not sufficient, as persistence as such does not even qualify as a hazard criterion, which is already acknowledged by the Proposal. (5) Restricting Fluoropolymers as supported by the Proposal does also not align with the precautionary principle. A correct application of that principle presupposes identification of the potentially negative consequences of the proposed use of Fluoropolymers as well as a comprehensive assessment of the associated risks based on the most reliable scientific data available and the most recent results of international research. The Proposal lacks sufficient evidence in this regard and is based on a mere hypothesis rather than on a scientifically substantiated risk assessment. This specifically holds true for Fluoropolymers, for which no respective hazard and, consequently, no corresponding risk can be identified. (6) Moreover, the Proposal breaches the principle of proportionality with respect to Fluoropolymers. Due to the fact that any emission in connection with the entire life-cycle of Fluoropolymers from manufacturing to use until the end-of-life stages are to be consid- 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 3/44 ered de minimis if fluorinated polymerisation aids are restricted, a restriction of Fluoropolymers as such would not be necessary at all against the background of the principle of proportionality. (7) In addition, the Dossiers Submitters erroneously have chosen the restriction procedure under REACH for an intended approach which, in fact, is structured with significant similarity to an authorisation proceeding. The contemplated process to accept potential applications and to decide on potential for exemptions or derogations basically establishes a requirement for stakeholders to provide any and all evidence to substantiate a corresponding request within a unreasonable short time period and, therefore, shifts the burden of proof to stakeholders contrary to the legal perquisites defined in Article 68 REACH. (8) All in all, and irrespective further concerns on the Proposal demonstrating infringements of e.g. the principle of good administrative behaviour or the right to be heard and the right to comment, Fluoropolymers manufactured without the use of fluorinated polymerisation aids should be exempted from the scope of the Proposal. Without a corresponding exemption or derogation significant market distortion are to be expected as critical products, technologies or applications will no longer be available if removed from the market due to the contemplated restriction. 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 4/44 B. Starting Point I. Gujarat Fluorochemicals Limited (9) Gujarat Fluorochemicals Limited (hereinafter referred to as "GFL") is an Indian Chemicals Company with over 30 years of expertise in Fluorine Chemistry. GFL holds domain expertise in Fluoropolymers, Fluorospecialities, Refrigerants and Chemicals, catering to the material requirements of modern world. GFL leverages its competencies in Fluorinebased products through product innovation and customer partnerships in diverse enduse markets. Impacting mobility, telecommunications, healthcare and architecture, GFL constantly challenges itself to find solutions to some of the most demanding applications. (10) GFL is committed to sustainable operations and corporate social responsibilities. Focus on clean processes, continuous development of new applications, customised solutions and consistent services make GFL one of the reliable strategic partners for our clientele globally. II. Background (11) GFL commissioned Produktkanzlei - Ahlhaus Handorn Niermeier Schucht Rechtsanwaltsgesellschaft mbH (hereinafter referred to as ,,Produktkanzlei") to assess the proposal for a restriction of Per- and polyfluoroalkyl substances (individual substances and/or the group of substances hereinafter referred to "PFAS", unless explicitly specified otherwise) according to Regulation (EC) No. 1907/2006 (hereinafter referred to as "REACH") as submitted by the German Federal Institute for Occupational Safety and Health (hereinafter referred to as "BAuA"), the Dutch Bureau REACH, National Institute for Public Health and the Environment (hereinafter referred to as "RIVM"), the Swedish Chemicals Agency (hereinafter referred to as "KEMI"), the Norwegian Environment Agency and the Danish Environmental Protection Agency (hereinafter jointly referred to as the "Dossier Submitters"). (12) This memorandum summarizes the findings of the legal assessment with a special focus on general legal concerns as well as legal implications due to the fact that the intended restriction shall, in general, also cover Fluoropolymers. (13) The legal assessment is based on the aforementioned proposal as submitted on 13 January 2023 and initially published by the European Chemicals Agency (hereinafter referred to as "ECHA") on 7 February 2023. As the Dossier Submitters provided an updated version of the proposal, i.e. Version 2.0, as of 22.03.2023 (hereinafter referred to as "Proposal"), only this version is considered. (14) Following the prerequisite according to Article 69(6) REACH, ECHA has started the public consultation on the Proposal on 22 March 2023. Submissions can be made until 25 September 2023. 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 5/44 (15) This legal assessment of the Proposal is drafted to supplement a broader submission of GFL within the public consultation. Produktkanzlei explicitly confirms that GFL is entitled to use this memorandum for this purpose. (16) We respectfully request to consider this submission in connection with the further proceeding to avoid further procedural flaws. We understand that the process to develop opinions at level of the Committee for Risk Assessment ("RAC") and the Committee for Socio-Economic Analysis ("SEAC") will be initiated already prior to the end of the period granted for submissions in the public consultation. While we further understand that the time period for opinion development as established in Articles 70, 71(1) REACH does require immediate action at committee level, we submit that any and all submissions need to be taken into consideration. The mere fact that opinion development has been initiated prior to the end of the consultation period should not result in a scenario that substantial submissions are not sufficiently considered. Therefore, we respectfully request ECHA, RAC, SEAC and the Dossier Submitters to consider the concerns raised with this submission and the further arguments as brought forward and supported by the broader submission of GFL to avoid procedural shortcomings which might give rise to further legal concerns. 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 6/44 C. Legal Assessment (17) From a legal perspective, it needs to be assessed whether the Proposal meets the applicable requirements for restrictions according to Title VIII of REACH from a procedural, scientific and legal perspective taking into account the scope of the Proposal as well as the underlying justification. Insofar, the following submissions need to be made on the Proposal. I. Fluoropolymers in the restriction proposal (18) In general, we understand that Fluoropolymers qualify as PFAS within the (new) OECD definition on PFAS and would, therefore, be within the scope of a restriction according to the Proposal. (19) This is already acknowledged in the Proposal insofar as Fluoropolymers are explicitly addressed, including but not limited by means of specific derogations for Fluoropolymers and the related use of polymerisation aids as set out in Nos. 5a), 6, 7 and 8 (cf. Proposal, p. 4 et seqq.). (20) This notwithstanding, the proposal also underpins the fact that the Dossier Submitters consider Fluoropolymers to be a distinct group of PFAS. This view is supported by many sections of the Proposal in which Fluoropolymers are discussed separately, which indicates their independent and distinct position within the group of PFAS. (21) The proposed restriction following Restriction Option 2 (cf. Proposal, p. 4) contains a specific series of time-limited derogations for certain uses of Fluoropolymers in Column 2, No. 6. According thereto, the restriction shall not apply to Fluoropolymers and perfluoropolyethers for the use in food contact materials for the purpose of industrial and professional food and feed production until 6.5 years after entry into force ("EiF"); implantable medical devices (not including meshes, wound treatment products, tubes and catheters) until 13.5 years after EiF; tubes and catheters in medical devices until 13.5 years after EiF; coatings of Metered Dose Inhalers (MDIs) until 13.5 years after EiF; protonexchange membrane (PEM) fuel cells until 6.5 years after EiF and fluoropolymer applications in petroleum and mining industry until 13.5 years after EiF. (22) Furthermore, according to the proposed entry in Column 2, No. 8, importers and downstream users of Fluoropolymers and perfluoropolyethers making use of any of the derogations shall establish a site-specific management plan which shall include information on the identity of the substances and the products they are used in, a justification for the use and details on the conditions of use and safe disposal. Additionally, the management plan shall be reviewed annually and kept available for inspection by enforcement authorities upon request. (23) Of the many other sections in the proposal where specific reference is made to Fluoropolymers, the most important one is, that Fluoropolymers are the only group of PFAS 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 7/44 for which a separate assessment is provided within the environmental hazard assessment set out in Annex B to the Proposal (cf. Proposal, Annex B, p. 219 et seqq.). II. Objections against the inclusion of Fluoropolymers (24) Even if one were to assume that the Proposal and the underlying aims and purposes are reasonable, the Proposal fails to demonstrate that the inclusion of Fluoropolymers would meet the requirements according to Article 68(1) REACH and general principles of law which need to be adhered to in connection with the introduction of a restriction under REACH. (25) First of all, it needs to be noted that Article 68(1) REACH establishes the prerequisites for a restriction under REACH as follows: "When there is an unacceptable risk to human health or the environment, arising from the manufacture, use or placing on the market of substances, which needs to be addressed on a Community-wide basis, Annex XVII shall be amended in accordance with the procedure referred to in Article 133(4) by adopting new restrictions, or amending current restrictions in Annex XVII, for the manufacture, use or placing on the market of substances on their own, in mixtures or in articles, pursuant to the procedure set out in Articles 69 to 73. Any such decision shall take into account the socio-economic impact of the restriction, including the availability of alternatives." (26) The Proposal, however, deviates from these requirements by broadly referring to the OECD definition of PFAS, including Fluoropolymers, without providing sufficient scientific evidence that there is an unacceptable risk to human health or the environment resulting from the manufacturing or use of Fluoropolymers. 1. Failure to meet the prerequisites established in Article 68 REACH: hazard to human health / environment (27) The proposal fails to meet the requirements arising from the wording of Article 68(1) REACH with respect to Fluoropolymers. The wording requires that there is an unacceptable risk to human health or the environment, arising from the manufacture, use or placing on the market of substances, which needs to be addressed on a community-wide basis. The basic requirement is therefore that there is a hazard to human health or a hazard to the environment. Only in a subsequent step it has to be examined whether, due to exposure, a risk arises as a result of this. However, the dossier is not able to prove that Fluoropolymers pose a hazard to health or environment at all. a) Failure to conduct proper hazard assessment (28) The Proposal is flawed from the very beginning since there is no hazard assessment conducted as required by REACH. As a mandatory prerequisite to adopt a restriction under REACH, Article 68(1) REACH requires that there is an unacceptable risk to human 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 8/44 health or the environment, arising from the manufacture, use or placing on the market of a substance, which needs to be addressed on a community-wide basis. The basic requirement is therefore that the substance under scrutiny has been identified to pose unacceptable risk to human health or the environment. Following the fundamental principles enshrined in the REACH Regulation, any corresponding risk assessment needs to be based on an assessment of the hazard properties of the substances involved. (29) If a corresponding risk assessment would have been initiated in accordance with applicable requirements, it would have been already obvious from the relevant results that Fluoropolymers should not be included in the scope of the Proposal. aa) Hazard assessment as a mandatory starting point for restriction proposals (30) It follows already from the legal prerequisites that a profound hazard assessment is a mandatory starting point for any restriction proposal under REACH. This fundamental principle already follows from Article 69(4) of REACH, as any dossier submitter needs to refer to any corresponding dossier, chemical safety report or risk assessment established under REACH for the substance at issue in the restriction proposal. Any such dossier, however, mandatorily contains details on the hazard properties of the substances under scrutiny. (31) We submit in this context, that the term dossier refers to any dossier prepared under REACH as Article 69(4) REACH does not limit its scope to certain types of dossiers. Therefore, the Dossier Submitters were required to take into consideration corresponding registration dossiers or any available dossiers already established in accordance with Annex XV for substances within the scope of the proposed restriction. It should be noted, however, that for both types of dossiers, the identification and assessment of hazard properties is essential and, moreover, a mandatory requirement. (32) First, this holds true for registration dossiers as hazard properties according to Regulation (EC) No. 1272/2008 ("CLP") need to be indicated for any substance subject to registration requirements. This follows directly from Annex V Section 4 to REACH, but also hazard properties as defined in Annex XIII to REACH have to be assessed in connection with standard information requirements applicable to the registration of substances under REACH according to Annex VII. (33) Second, also any dossier established in accordance with Annex XV to REACH needs to comprise an assessment of hazard properties. (34) This holds true for dossiers established to identify potential substances of very high concern. The details for such dossiers are outlined in Annex XV Section 2 to REACH. Corresponding dossiers need to demonstrate that the prerequisites as set out in Article 57 REACH read in conjunction with Article 59 REACH are met. Insofar, such dossiers only relate to hazard properties of substances from the outset. In addition, Article 58(1)(b) 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 9/44 REACH emphasizes that properties as referred to in Article 57 REACH are to be considered as "intrinsic properties". Insofar, Article 58(1)(b) REACH follows the general principle as set forth in the CLP Regulation that hazard classification is to be determined on basis of the intrinsic properties of a substance (cf. Judgment of the General Court of 23 November 2022, Cases T-279/20 and T-288/20). The explicit reference to intrinsic properties underpins the fact that the identification of substances of very high concern is based on an assessment of the hazard properties of a substance. (35) We further submit, that the same holds true for dossiers according to Annex XV aiming at a proposal to establish a restriction under REACH as referred to in Annex XV Section 3 to REACH. This specific section states that the corresponding dossier needs to contain information on hazard and risk, whereby the risks to be addressed with the restriction shall be described based on an assessment of the hazard and risks according to the relevant parts of Annex I to REACH and shall be documented in the format set out in Part B of that Annex for the Chemical Safety Report. Therefore, also restriction proposals, as in the case at hand on PFAS, need to contain a sufficient assessment of hazard properties as a basis for the identification and further assessment of related risks. (36) As far as Annex XV Section 3 to REACH refers to chemical safety reports according to Annex I to REACH, it should be taken into account, that these require, as a starting point, the consideration of information related to the hazards of a substance. The sub-paragraph following Section 0.5 explicitly states that "the information to be considered includes information related to the hazards of the substance". In addition, Section 0.6.1. of Annex I to REACH stipulates that the hazard assessment is the first step to perform a chemical safety assessment. (37) Moreover, Section 0.6.3 in Annex I to REACH clarifies that any risk characterization shall be based on an exposure assessment which need to relate to the identified hazard properties of the substance under scrutiny. (38) A hazard assessment is, therefore, a mandatory starting point for each and every proposal of a restriction under REACH. Only on that basis and in a subsequent step, it needs to be assessed if and to what extent a risk to human health or the environment arises from the corresponding hazards and relevant exposures. And only if the identified risk turns out to be unacceptable, a restriction according to Article 68(1) REACH is warranted (cf. Guidance for the preparation of an Annex XV dossier for restrictions, figure 4, p. 32). bb) No alternative approach available (39) We further submit, that a hazard assessment as an initial mandatory step cannot be replaced or circumvented by any other approach. Article 68(1) REACH read in conjunction with Annex XV to REACH and the corresponding guidance does not provide for any deviating option. This even holds true with respect to more generic options for potential restrictions as provided for in Article 68(2) REACH as such an approach mandatorily requires the identification of applicable hazard properties of the respective substances. 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 10/44 (40) It should also be noted that Article 68 REACH does not contain any provision similar to Article 57(f) REACH, so that a restriction proposal can be justified on basis of some sort of an "equivalent level of concern". While already Article 57(f) REACH would require a hazard assessment as set out in Section 2 of Annex XV to REACH, it goes without saying that Article 68 REACH does not contain any language that could support the view that a hazard assessment could be negligible. (41) Only if risks derived from hazard properties of a substance and related exposure can be established and proven to meet the further criteria laid down in Article 68(1) REACH, a restriction proposal on basis of a dossier according to Annex XV to REACH would meet applicable legal requirements. Contrary to the underlying assumption referred to in the Proposal, it is not sufficient to bring forward merely general assumptions about a substance being hazardous or giving rise to a specific or general concerns. cc) No hazard property beyond persistence identified for Fluoropolymers (42) According to the Proposal, persistence is the key property common to the thousands of substances defined as "PFAS" under the Proposal (cf. Proposal, p. 22). Apart from persistence, the Proposal identifies additional concerns that differ depending on the type of PFAS, including, among others, Long-Range Transport Potential ("LRTP"), Mobility, Accumulation in plants, Bioaccumulation, Ecotoxicty, Endocrine Activity / Endocrine Disruption and effects on human health (p. 22). However, data do not exist for each and every of the thousands of substances that fall within the scope of the Proposal as established on basis of the respective "PFAS" definition, including Fluoropolymers. Without corresponding data, the Proposal lacks sufficient evidence to substantiate that one or more of additional concerns, i.e. hazard properties, apply to the substances within the scope of the contemplated restriction. Also other scientific methods to extrapolate such hazard properties are not provided in the Proposal. Instead, the Dossier Submitters seem to take the position that a sufficient risk within the meaning of Article 68(1) REACH can legally and scientifically be based on the (presumed) persistence of all PFAS that remain within the scope, and the additional assumption that any PFAS is likely to have also other hazard properties, although these are only substantiated for a limited number of the thousands of substances defined as "PFAS". (43) This approach, however, does not meet the prerequisites of Article 68(1) REACH and it cannot be based on any other provision of the REACH Regulation. Consequently, the Proposal fails to provide evidence for a sufficient hazard assessment as required by the REACH Regulation. This specifically holds true with respect to Fluoropolymers, as no hazard properties can be identified beyond the persistence. b) Hazard to human health (44) The proposal itself already states on a general level (cf. Proposal, p. 29) that while there is a vast amount of literature published on the health effects of PFAS, most of the liter- 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 11/44 ature relates to the PFAA arrowheads PFCAs and PFSAs, especially PFOA and PFOS. Furthermore, according to the proposal, other PFAS (like Fluoropolymers) have been less well-studied. Accordingly, the human health hazard assessment in Annex B of the dossier states in its first two sentences, that the majority of available data on human health effects address the toxicity of PFAAs (mainly PFCAs and PFSAs; in particular PFOA and PFOS), while less or no data are available for other PFAS groups and that for the vast majority of PFAS (estimated >99%), no data on repeated-dose toxicity, carcinogenicity, or reproductive toxicity is available (Annex B, p. 141). (45) The proposal admits (cf. Proposal, p. 29) that some precursors to PFAAs may be of less direct concern with regard to human health effects and only indirectly add to the concern (due to degradation). In addition, the proposal states with regard to PFAAs that data available for less well-studied PFAA arrowheads and some PFAA precursors indicate that these PFAS can have similar effects as the well-studied ones mentioned above (cf. Proposal, p. 30). (46) In this respect, the proposal already shows on the summary level that there is no scientific evidence for the existence of a risk to human health for all substances covered by the restriction proposal. In particular, there is no such evidence regarding Fluoropolymers, which, according to the Proposal, have been less researched. (47) In particular, the dossier explicitly states with regard to polymeric PFAS, and accordingly for Fluoropolymers, that properties of the substances can vary considerably and that a clear assignment of the substance to health effects is complicated, because unique identifiers are often not available (cf. Proposal, p. 31). Additionally, the proposal states that the end-of-life fate of the polymers is uncertain (cf. Proposal, p. 31). According to the dossier, only a few studies with toxicological information are available for this diverse group of oligomeric and polymeric PFAS. Most available toxicological studies of oligomeric/polymeric PFAS investigated oligomeric PCTFE oils and pure PCTFE oligomers (cf. Proposal, p. 31). (48) Hence, there is no significant proof or evidence that polymers and in particular Fluoropolymers pose a risk to human health equal or similar to other PFAS within the scope of the proposed restriction or any risk at all. To the contrary, scientific articles on Fluoropolymers demonstrate that fluoropolymers satisfy widely accepted assessment criteria to be considered as "polymers of low concern" ("PLC"; e.g. Henry et al., Integrated Environmental Assessment and Management, 2018, p. 316 et seqq., DOI: 10.1002/ieam.4035, available at https://setac.onlinelibrary.wiley.com/doi/full/10.1002/ieam.4035; Korzeniowski et al., Integrated Environmental Assessment, 2022, p. 326 et seqq., DOI:10.1002/ieam.4646, available at setac.onlinelibrary.wiley.com/doi/ 10.1002/ieam.4646). Accordingly, the dossier sees no clarity on effects after repeated exposure of polymeric PFAS based on available data (cf. Proposal, p. 31). In the end, the proposal concludes that polymeric PFAS contribute to the overall risks of non-polymeric 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 12/44 PFAS because, according to the Proposal, they "may generate and/or release non-polymeric PFAS", in particular at the end-of-life. In itself, this is not sufficient to substantiate a hazard to human health, since the proposal indicates no certainty that non-polymeric PFAS are generated or released at any point. Moreover, the proposal itself states that the end-of-life fate of the polymers is uncertain (see above), therefore it is contradictory when it is stated a few sentences later that there "may" be a release of non-polymeric PFAS in particular at the end-of-life. (49) In this respect, we reiterate that available data demonstrates that Fluoropolymers meet the criteria for PLC (Henry et al., loc. cit.; Korzeniowski et al, loc. cit.). Although the Proposal takes note of the corresponding publication (Henry et al., loc. cit; cf. Proposal, p. 46), the respective findings are only discussed in connection with bioavailability of Fluoropolymers. The Dossier Submitters, however, should have taken note of the fact that available fluoropolymer toxicity data (including available human clinical data) demonstrate that Fluoropolymers do not pose a risk to human health equal or similar to other PFAS within the scope. Moreover, an analysis of Annex B to the Proposal also shows that the scientific data with regard to the hazard of Fluoropolymers to human health is very weak and does not establish sufficient scientific evidence to justify the inclusion of Fluoropolymers in the scope of the Proposal. As shown below, the evidence with regard to the main category of polymers is not given: - Regarding toxicokinetics/ADME, the proposal states that no studies are available on toxicokinetics of polymeric PFAS (Annex B.5.1.2, p. 154) - With regard to liver effects in experimental animals, the proposal sums up that there are only indications that oligomeric PFAS (not Fluoropolymers) can cause adverse liver effects and that clarity on liver effects of oligomeric/polymeric PFAS cannot be given on the basis of available data (Annex B B.5.2.1.1, p. 159). - As for kidney effects in experimental animals, the proposal sums up that there are only indications that low molecular weight oligomeric/polymeric PFAS can cause kidney effects but clarity on kidney effects of oligomeric/polymeric PFAS cannot be given on the basis of available data (Annex B.5.2.1.3, p. 163) Moreover, it is not considered that Fluoropolymers have negligible residual oligomer content. - For oligomeric/polymeric PFAS, no studies observing thyroid parameters are known (Annex B.5.2.1.4, p. 164). - Regarding immune effects in experimental animals, the proposal concludes that for oligomeric/polymeric PFAS immunotoxic effects were shown, but only states evidence concerning oligomeric PFAS. (Annex B.5.2.1.5, p. 165). - As for developmental effects and fertility effects in experimental animals, no studies observing developmental toxicity are known for oligomeric/polymeric PFAS (Annex B.5.2.2.1., Annex B 5.2.2.2, p. 168). 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 13/44 - With regard to carcinogenicity, the proposal on the one hand quotes studies that found carcinogenic effects regarding polymeric PTFE. On the other, however, there is no evidence for such effects for other Fluoropolymers and for PFAS in general the proposal states, that human relevance of carcinogenicity of most PFAS is unclear (Annex B.5.2.3, p. 169). - Regarding immune outcomes, the proposal sees evidence between PFAS and common infectious diseases, even though it states, "that more studies with objective measures of infections (not self-reports) are needed" and that "there are inconsistent findings" (Annex B, p. 171) regarding upper respiratory tract infections. In fact, this seems to be contradictory. (50) Moreover, the Proposal is not even able to justify a hazard to human health with regard to non-polymers, for which studies are available more commonly. It remains vague in various places and does not describe any clear scientific statements. For example, it is taken as evidence that absorption through the skin cannot be excluded, because small insignificant increases of plasma fluoride concentrations after dermal absorption of PCTFE oligomers were shown in rodent urine and plasma (Annex B.5.1.2, p. 155). (51) Against this background it needs to be concluded that the Proposal fails to demonstrate hazard properties of Fluoropolymers with respect to human health effects. Insofar, the prerequisites according to Article 68(1) REACH are not met. c) Hazard to environment (52) Also, there is no conclusive scientific evidence that Fluoropolymers have hazard properties with respect to effects to the environment. aa) General considerations (53) Regarding ecotoxicity, the main part of the Proposal only states that there is evidence for (just) a subset of PFAS and because of the large number of different substances with heterogenous properties (e.g. due to different functional groups) in the group of PFAS the assessment of their ecotoxicity is very complex (cf. Proposal, p. 28). On a more detailed level, Annex B of the Proposal concludes that the available data on adverse effects of PFAS in the environment is limited to a small number of substances (B.7.1.11, p. 202). According to the Proposal, conventional ecotoxicological tests may not be suitable to detect long term effects from exposure to PFAS and the small subset of PFAS, for which such information is available, contains PFOA and PFOS (B.7.1.11, p. 202). Accordingly, there is no evidence or proof that Fluoropolymers pose any risk to the environment at all. (54) In this respect, it is not sufficient or convincing that the proposal states, that due to certain properties of PFAS it is not possible to demonstrate safe use of PFAS (B.7.1.11, p. 202). Contrary to the dossier, it cannot be concluded that this warrants for a restriction. 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 14/44 To the contrary, Article 68(1) REACH clearly states that there has to be a risk to the environment and, as stated above, any such risk needs to be identified on basis of a sufficient hazard assessment. If a risk to the environment cannot be concluded from available scientific data regarding hazard properties of the substance(s) within the scope of a proposed restriction, the provisions of Article 68(1) REACH are not fulfilled. A restriction under REACH is not a legitimate legal consequence if based on mere assumptions. To the extent that the Proposal (B.7.1.11, p. 202 et seq.) also points to the fact that future contamination is irreversible, it evidently fails to recognize that mere irreversibility in itself does not represent an environmental hazard and is only relevant in connection with other hazards, which, however, are not identified on basis of relevant scientific evidence for Fluoropolymers. (55) With respect to the effects on wildlife, the proposal concludes that the available studies provide evidence, that PFAS can cause adverse effects on wildlife species at currently relevant concentrations (Annex B.7.2.8., p. 207). This is wrongful, since according to the proposal, due to the limitations of the studies, a clear link between PFAS measurements in the environment, or PFAS-body-burdens in the animals and the observed effects can rarely be established (ibid.). Furthermore, it is stated that laboratory studies that can plausibly link effects in these species to PFAS exposure would be needed but are in most cases not available (ibid.). This contradiction is justified by the Proposal with a precautionary approach. However, this consideration is not convincing, because the precautionary principle requires reliable scientific data and logical reasoning, leading to a conclusion which expresses the possibility of occurrence and the severity of a hazard's impact. Such an assessment has not been conducted in the present case, in particular not with respect to Fluoropolymers. (56) As to the atmospheric compartment, only fluorinated gases are considered to be problematic, i.e. no specific hazard property has been identified with respect to Fluoropolymers in this regard. (57) With respect to endocrine activity and endocrine disruption, the proposal summarizes, that "indications" of interactions of "some" PFAS with the endocrine system of environmental species, adverse effects (some occurring cross-generational), and "first observations of possible influences" of PFAS body-burden on hormone levels in wildlife raise concerns about the presence of PFAS in the environment (Annex B.7.5.3.4., p. 218) and that adverse effects "cannot be excluded" (cf. Proposal, p. 28). Again, the wording clearly shows, that there is no conclusive evidence for any hazard and especially no conclusive evidence for a hazard with regard to every substance within the scope of the proposal, e.g. Fluoropolymers. As before, the proposal argues for a hazard with the persistence of the substances. Insofar, the above stated considerations again apply mutatis mutandis. (58) With regard to LRTP, the dossier concludes that many PFAS have potential for longrange transport mainly due to their high persistence (p. 25; Annex B.4.2.8., p. 112). However, according to the dossier, for the majority of PFAS no data on transport pathways 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 15/44 or point sources are available and thus substantial uncertainties on the concern of the long-range transport potential remain (Annex B.4.2.8., p. 112). As for accumulation in plants, it is stated that studies on accumulation of PFAS in plants are lacking for the majority of PFAS and that, while it is indicated that PFAS have the property to enrich plants, it remains unclear if all substances/subgroups may have this property (Annex B.4.4., p. 134, 135). Available data (as summarized in Henry et al., loc. cit.) Fluoropolymers are insoluble in water and LRTP is completely ruled out. Accumulation of fluoropolymers in plants is unthinkable due to their unique properties. bb) Assessment of environmental hazard properties of Fluoropolymers (59) The proposal comments on the hazard characteristics of Fluoropolymers in a special section (B.7.6., p. 219 et seqq.) and states, that Fluoropolymers themselves can pose an environmental hazard. However, there is no sufficient evidence presented in this regard. For example, with regard to toxicity, conflicting studies are cited (see B.7.6.1., p. 220). Furthermore, the dossier admits, that the bioaccumulation potential for polymers in general is poorly understood so far and cell membrane penetration "cannot be excluded" (ibid.), while no further evidence is provided. (60) Apart from that, the dossier mainly refers to the hazard properties of microplastics, which is insufficient for several reasons. First, the dossier does not state any relevant intersections of Fluoropolymers and microplastics. This is quite astonishing because it is the only section in the entire dossier where reference is not made to specific PFAS or PFAS in general, but to a distinct category. Obviously, evidence presented for microplastics is not relevant in the current context, since there is no evident connection established between the category "Fluoropolymers" and the category "microplastics". Second, there has been a restriction process for microplastics in the past. Therefore, any evidence regarding microplastics seems to be brought forward either in the wrong restriction procedure or the Proposal at hand would result in an illicit double-regulation of the same matter. Third, and foremost, the current Proposal quotes the former RAC opinion regarding microplastics saying that, although there are uncertainties in the understanding of the hazard and risk of microplastics, there is sufficient evidence to conclude that they constitute an intrinsic hazard because of their persistence in combination with their potential to cause adverse effects. This consideration fails to meet the criteria and procedure set out in Article 68(1) REACH. Fourth, according to the dossier, several studies have investigated adverse effects of microplastics in general and no negative effects on population level have been demonstrated so far. Moreover, Microplastics are generated due to surface friction or abrasion whereas fluoropolymers like PTFE have the lowest coefficient of friction. Also, the concerns related to microplastics are connected to commodity uses of 100s of millions of tons of general plastics whereas fluoropolymers are mostly used in industrial applications and their global consumption is estimated at less than 350,000 tons. Comparison between microplastics and fluoropolymers is untenable, first due to the property of required friction and second due to the difference in consumption volumes particularly for commodity applications. 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 16/44 (61) In conclusion, the dossier fails to establish any relevant evidence that Fluoropolymers pose a risk to the environment. The mere persistence is not sufficient and moreover, the proposal states that persistence is only well known for some Fluoropolymers (B.7.6.3., p. 221 et seq.). Therefore, even according to the logic of the submitters, there is no evidence for hazard properties for the entire group of Fluoropolymers. cc) Failure to establish persistence as such as (environmental) hazard (62) Additionally, it needs to be noted that the Proposal is also unlawful insofar as it aims to establish risks to the environment by mainly referring to the persistence of the substances within the scope of the intended restriction. With respect to environmental hazards, the Proposal itself states that there is evidence for only a subset of PFAS and that, because of the large number of different substances with heterogenous properties in the group of PFAS, the assessment of their ecotoxicity is very complex (cf. Proposal, p. 28). Consequently, for the vast majority of PFAS, the only environmental property presented by the Proposal is "persistence" as defined in a broad and general manner. This approach, however, is unlawful for a variety of reasons. (63) Persistence as such does not qualify as a hazard property but is merely a physical and chemical property of a substance based on the identification of the degradation potential due to the half-life of a substance under various conditions. As a physical and chemical property, persistence alone does not qualify as an environmental hazard because persistence alone cannot cause or result in environmental effects. The mere persistence of a substance, therefore, simply means that a substance with this property exists for a long time. This finding also follows from the Proposal itself, i.e. is in line with the view of the Dossier Submitters. (64) With reference to the environmental aspects of any hazard assessment, testing will be used to determine the physical and chemical properties of a substance to identify and indicate the fate of the substance in the environment. This holds true for criteria like persistence, degradation or mobility. Only as a separate step, and with a set of different studies, potential environmental effects of a substance can be identified, like e.g. aquatic toxicity, mammalian toxicity, etc. The headings in Annex B to the Proposal only refer to defined environmental hazards such as ecotoxicity and effects on wildlife (cf. Annex B.7.), while persistence is discussed in the context of the "environmental fate properties" (cf. Annex B.4). Therefore, already systematically persistence is not considered as a hazard property relevant to the mandatory environmental hazard assessment. If mere persistence would already be considered as an environmental hazard, many other substances would also qualify for further regulatory measures. Such approach on a "P-only" basis is not supported by REACH or any other regulatory framework on EU level. Not even the most recent amendments under CLP support hazard classification on basis of the persistence of a substance, but only if further properties can be identified. 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 17/44 (65) As far as the Proposal attempts to justify the existence of e.g. potential ecotoxicity or effects on wildlife in the context of the environmental assessment (cf. e.g. Proposal, Annex B.7.5.3.4., p. 218), it does so on basis of the assumption that there is a need for action because all PFAS within the scope are considered to be persistent and, therefore, any consequences would be irreversible, while the Dossiers Submitters nonetheless acknowledge that there is insufficient evidence for relevant environmental hazards which can be attributed to any and all PFAS within the scope of the Proposal, including Fluoropolymers. (66) We therefore submit that the justification provided with the Proposal is invalid from a systematic point of view and does not support the inclusion of Fluoropolymers. The REACH Regulation does not contain any provision which states that the reversibility of a condition is important in connection with an environmental hazard assessment. Rather, it is the genuine task of the environmental hazard assessment to determine whether a given substance has intrinsic hazard properties. If this determination cannot be made, it is contradictory to presume environmental hazards simply because, in theory, a substance may be persistent and it may, in some respects, difficult to take countermeasures (referred to in the proposal as "threat of irreversible damage", cf. for example Annex B.7.5.3.4., p. 218). With this approach, the Proposal fails to demonstrate a sufficient hazard assessment as required for the preparation of a dossier in accordance with Annex XV to REACH and, consequently, no environmental hazards are demonstrated in an appropriate manner if the Dossier Submitters base their conclusion merely on the purported persistence of all PFAS alone. (67) Such an approach can also not be justified with a mere reference to the precautionary principle. It follows already from Commission Communication COM(2000) 1 of 2 February 2000 that the precautionary principle should be considered within a structured approach to the analysis of risk which comprises three elements: risk assessment, risk management and risk communication. It is commonly acknowledged that the precautionary principle comes into play subsequent to a risk assessment and, thus, where scientific information is insufficient, inconclusive, or uncertain and where there are indications that the possible effects on, inter alia, the environment may be potentially dangerous and inconsistent with the chosen level of protection. The precautionary principle, however, does not excuse the need for scientific information as a basis for a risk assessment in the first instance in favour of simply presuming that persistence equates to unacceptable risk. (68) As far as the Proposal (B.7.6.1., p. 219 et seq.) indicates that an intrinsic property results in a relevant hazard property due to mere persistency and additional further properties - as already supported in the restriction of microplastic - such argumentation has to be rejected as incorrect. (69) This argumentation fails because it deliberately circumvents the criteria of Article 68(1) REACH. It fails to recognize that there must be an unacceptable risk to the environment 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 18/44 for a restriction to be imposed in the first instance. If one were to dispense with this requirement, the result would be that a broad variety of substances could be restricted, because many substances are present in the environment in ever greater quantities due to continuous use and associated release, and for many of these substances there is also no possibility of removing them from the environment. In other words: If only the potential irreversibility of the condition and not the actual harmful effects on the environment are taken into account, Article 68(1) REACH would be interpreted in way which exceeds its actual wording. (70) We further submit in this context, that such an approach results in a deviation from the prerequisites set out in Article 68(1) REACH. Insofar, the Proposal also infringes the principle of good administrative behaviour as well as legitimate expectations of market actors as it would not be possible to reasonably foresee whether a substance could and potentially would be restricted. d) Need to provide evidence for a hazard to human health or the environment for every subgroup (71) It has, therefore, been shown that Fluoropolymers do not pose a risk to human health or the environment. As a precaution, it must be pointed out that the lack of corresponding scientific evidence for the identification of respective hazard properties and, as a consequence, the existence of a relevant risk within the meaning of Article 68(1) REACH, cannot be justified by the grouping approach. It is true that a restriction may regulate several substances at the same time, provided that the relevant requirements on grouping are met. However, this does not justify a deviation from the requirement to demonstrate compliance with the legal requirements for a restriction at least for each subgroup. The guidance document on groupings does not state at any point that lower evidence requirements apply in this respect. This applies in particular against the background that Fluoropolymers are treated in the proposal, as can be seen in Annex B.7.6 or the proposed Annex XVII entry, as a special PFAS category with special properties and circumstances that characterize them. While it may be justifiable with regard to the groupbased approach for individual substances to dispense the requirement for individual, substance-based evidence, such an approach cannot be considered permissible for a whole, high-profile subgroup. It is contradictory to the teleological background of the group-based approach that a group of substances, which is distinct from the other substances covered, is considered as belonging to a broader group so that the need to established a concrete proof of hazard properties is waived. e) No ,,justified" uncertainties and incorrect handling of uncertainties (72) As a precautionary note, it should also be noted that the absence of hazardous properties cannot be justified by the fact that uncertainties are concerned and that such uncertainties are quite legitimate in the context of restriction procedures. This is because, on 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 19/44 the one hand, in this respect the Dossier Submitters do not comply with ECHA's requirements for dealing with such uncertainties. (73) In this respect, it needs to be noted that the respective uncertainties are not uncertainties concerning the scientific evaluation of a certain question, i.e. hazard properties, but selfinflicted uncertainties which are solely due to the selected approach to cover a huge, non-homogeneous group of substances with the scope of the restriction proposal. For this reason, the Dossier Submitters cannot refer to the position that specific uncertainties are a regular part of every restriction dossier. (74) This notwithstanding, the Proposal contains a remarkably high number of uncertainties regarding the analysis and assessment of claimed hazards of PFAS, which are ultimately caused by the lack of sufficient scientific studies. When presenting these uncertainties, in some cases the Dossier Submitters did not adhere to the formal principles established by the document ,,Description of uncertainties in the evaluation of restriction proposals" by the Restriction Task Force (endorsed at the CARACAL-35 meeting on 31 March 2020, hereinafter referred to as "Guidance on uncertainties"). (75) Compliance with these formal requirements already by the Dossier Submitters is by no means a mere formality, since according to the guidance document, RAC and SEAC have to indicate in their opinions regarding the dossier whether and to what extent the existing scientific data do not allow for a complete hazard assessment. This, in turn, should enable the Commission in the further course of the procedure to apply the precautionary principle in an appropriate manner when deciding whether restriction measures should be taken. The dossier fails to comply with the respective document in some important respects, as shown as follows. (76) According to the Guidance on uncertainties, the Dossier Submitters should have clarified which elements are uncertain. This requirement relates to, inter alia, hazards, uses, emissions, availability of alternatives and technologies, and the assessment of the socio-economic impacts of the restriction (cf. Guidance on uncertainties, p. 2). In the present case, deficits are particularly evident in the case of Fluoropolymers. For example, the Dossier Submitters on the one hand admit that no studies are known on the persistence of Fluoropolymers under environmental conditions (Annex B, p. 219) but, on the other, proceed to regard persistence as already proven (for example Annex B, p. 218). This contradiction would have required a precise presentation of the uncertainties. The lack of such a precise presentation will consequently also have an impact on the quality of the opinions to be established by RAC and SEAC. (77) Furthermore, the Dossier should indicate the extent to which remaining uncertainties affect the conclusions drawn (cf. Guidance on uncertainties, p. 2). For example, regarding the mobility of PFAS, the dossier states that there is insufficient data, but it is not clear how this insufficient data is reflected in the subsequent conclusion (see Annex B, p. 79). 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 20/44 Insofar, the Dossier does not comply with the rules set out in the respective guidance document. (78) Another requirement for a dossier is to indicate the timeframe and costs to be expected in order to fill the identified gap through additional scientific studies (cf. Guidance on uncertainties, page 2). This is related to the consideration that, within the framework of the precautionary principle, the Commission could order further studies instead of deciding for a restriction. Again, the dossier fails to comply with this requirement. For example, within the conclusions for environmental monitoring in Annex B.4.2.7.10. (p. 104) it is made clear that "significant fractions of organofluorine in environmental samples are unknown and are therefore not captured by monitoring using only targeted PFAS analysis". Contrary to the requirements, however, it is not stated whether more precise findings on this are to be expected from further studies and, if so, what duration and costs are to be expected in this respect. There are also uncertainties regarding the toxicity of polymeric PFAS in animal experiments, which are due to insufficient data. However, the Dossier Submitters do not give an outlook on future data collection or its costs and duration (Dossier, Annex B p. 154). Furthermore, it is conceded that further studies are required, without specifying their predicted time span (Annex B, page 116). (79) Overall, the requirements laid down in the Guidance on uncertainties are not met for various reasons. This complicates the further proceedings, in particular because it is unclear which uncertainties are relevant and have to be solved, e.g. by commissioning further studies, and which uncertainties can remain as regular part of any science-based evaluation. However, the mere identification of uncertainties without further description or information can by no means suffice. f) Insufficient hazard assessment regarding new hazard classes (80) The aforementioned inconsistencies regarding the hazard assessment of PFAS within the scope of the Proposal, in particular with respect to Fluoropolymers, also hold true against the background that the proposal refers to the mobility of PFAS. The assumed mobility of PFAS is clearly not derived from the intrinsic properties of the substances within the defined scope, i.e. properties which the substances may have individually to varying degrees in and of itself. It is rather the exposure of the substances and their potential availability especially in water compartments that supports the criterion against the background of the outline provided with the Proposal. The mere fact that PFAS might emerge in the aquatic environment, however, is not linked to any intrinsic property of the substances but qualifies as a result of their (presumed) persistence and an assumed availability in the water cycle. The Proposal, however, fails to sufficiently consider the fact that Fluoropolymers do not dissolve in water and therefore are not mobile. (81) This also holds true with respect to the further considerations outlined in Recital (8) of Commission Delegated Regulation (EU) 2023/707. Nothing in this Delegated Regulation 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 21/44 can additionally support the Proposal. The aforementioned Delegated Regulation introduced, inter alia, new hazard classes for substances being identified as PMT (persistent, mobile, toxic) and vPvM (very persistent, very mobile). But according to the Recital (8) of the Delegated Regulation, PMT and vPvM criteria mainly focus on persistence and mobility, whereby the overall basis for the introduction of the corresponding hazard classes is the mere fact that such substances "can enter the water cycle, including drinking water, and spread over long distances. Many PMT and vPvM substances are only partly removed by wastewater treatment processes and can even break through the most advanced purification processes at drinking water treatment facilities. Such incomplete removal coupled with new emissions mean that the concentration of those PMT and vPvM substances in the environment increase over time. Once released into the environment, exposure to PMT and vPvM substances is difficult to reverse, which leads to cumulative exposure of both animals and humans via the environment. Any effects from this exposure are unpredictable in the long-term." (82) Insofar, the underlying justification for the introduction of the hazard classes PMT and vPvM is similar to the justification provided for in the Proposal. We submit, however, that this Delegated Act has been adopted by the Commission in misuse of powers conferred to the Commission according to the CLP Regulation and, therefore, the newly introduced hazard classes cannot justify the proposed restriction or support the risk assessment outlined therein. (83) The Commission is only empowered under the CLP Regulation to adopt delegated acts in accordance with Article 53a of CLP to amend Articles 6(5), 11(3), 12 and 14, 18(3)(b), 23, 25 to 29, 35(2) subparagraphs 2 and 3 and Annexes I to VIII of CLP for adaptation to technical and scientific progress, taking due account of the further development of the Globally Harmonised System ("GHS"), in particular any amendments at level of the United Nations relating to the use of information on similar mixtures, and taking into account developments in internationally recognized chemical programs and data from accident databases. The amendment of the CLP Regulation to introduce new hazard classes does not fall under these powers. (84) Although the Proposal does not specifically refer to the contemplated new hazard classes due to the fact that the respective delegated act was published in the Official Journal of the EU only on 31 March 2023 (OJ of 31 March 2023, L 93, p. 7) the corresponding prerequisites and criteria are nonetheless applied. Due to the misuse of powers, however, the Delegated Act cannot be used to justify or support the Proposal. This moreover as the Proposal was established even prior to the entry into force of Commission Delegated Regulation (EU) 2023/707. 2. Failure to meet the prerequisites established in Article 68 REACH regarding risk assessment 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 22/44 (85) As stated above, an unacceptable risk within the meaning of Article 68(1) REACH is formed of a hazard to human health or the environment and a relevant exposure. The dossier not only fails to proof such hazard and, therefore, any further risk assessment already lacks a sufficient basis. a) Insufficient evidence regarding exposure to Fluoropolymers. (86) Any risk assessment needs to be based on identified hazard properties and relevant exposure to the substance at hand. With respect to Fluoropolymers, the Proposal is already lacking a sufficient assessment of respective hazard properties. But also the identification of related exposures is not convincing. For example, according to the proposal, very little is known about the levels of polymeric PFAS in the environment (cf. Proposal, p. 45). As for human exposure assessment, the proposal states, that the bioavailability and thus the potential for human exposure to Fluoropolymers has been an issue for discussion (cf. Proposal, p. 46). Thus, according to the Proposal, it has been proposed that absorption of Fluoropolymers in humans is obstructed due to their large sizes (Henry et al., 2018). (87) Despite these findings, it has been argued that the production, processing, use, and endof-life treatment of Fluoropolymers lead to emissions of bioavailable compounds (ibid.). In sum, there seems to be no clarity regarding the exposure to Fluoropolymers. (88) And even if one would consider it appropriate to consider corresponding risks with respect to the use of fluorinated polymerisation aids used for the manufacture of Fluoropolymers, although the underlying hazard assessment is lacking sufficient evidence, it would have been possible and sufficient to propose a restriction for the use of fluorinated polymerisation aids qualifying as PFAS in connection with the manufacture of Fluoropolymers. The manufacture and use of Fluoropolymers as such, however, should not be included in the scope of the Proposal, i.e. an exemption or non-time-limited derogation would be justified. Also because more than 50% of commercially produced fluoropolymers do not require the use of any polymerization aids let alone fluorinated polymerization aids (cf. Sales et al., ICRL 2022, p. 13, 19 with further references). b) Deviation from principles for risk assessment (89) With respect to risk assessment requirements as set out in Article 68(1) REACH, the Proposal itself demonstrates a deviation from applicable principles. The Proposal states that the procedures in Sections 1 to 6 in Annex I to REACH are impracticable to describe the particular effects of PFAS within the scope of the restriction proposal, as the PFAS in scope are very persistent in combination with identified and possible other concerns. Therefore, the Proposal states that the respective risk is described on a case-by-case basis as reflected in Section 0.10 of Annex I to REACH. 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 23/44 (90) The Proposal, however, ignores the fact that already the wording of Section 0.10 of Annex I to REACH states that (only) in "relation to particular effects, such as ozone depletion, photochemical ozone creation potential, strong odour and tainting, for which the procedures set out in Sections 1 to 6 are impracticable, the risks associated with such effects shall be assessed on a case-by-case basis". Against this background, it is against the law that the entire risk assessment for all hazard properties and all corresponding exposures is carried out on a case-by-case basis. Moreover, a "case-by-case" approach according to Section 0.10 of Annex I to REACH is established as a more specific and tailored approach for certain effects. The corresponding section does not support the view that a deviation from Sections 1 to 6 of Annex I to REACH is also possible to establish a broad and generic restriction proposal and to circumvent a possible, although complex and potentially difficult assessment according to Sections 1 to 6 of Annex I to REACH. Rather, the wording of Annex I suggests that a case-by-case approach is only intended in justified individual cases and only for certain effects. These requirements are not met with respect to PFAS, not even in the view of the Dossier Submitters. (91) As is demonstrated with the further evidence provided as part of the broader submission of GFL, a risk assessment according to Sections 1 to 6 of Annex I to REACH would have resulted in the conclusion that manufacturing and use of Fluoropolymers do not entail a risk in accordance with Article 68(1) REACH. (92) But even if a case-by-case approach according to Section 0.10 of Annex I to REACH would be considered appropriate with respect to PFAS, including Fluoropolymers, it needs to be noted that "a full description and justification of such assessments" still would be required. Deviating from the general approach for a risk assessment in line with Section 1 to 6 of Annex I to REACH and applying a restriction-specific assessment cannot circumvent the requirement to establish sufficient scientific evidence and justification that environmental hazards actually are present. Mere presumptions and referenced possibilities do not qualify as a sufficient basis. Therefore, the Proposal erroneously follows a route for the hazard assessment, which is not supported by the REACH Regulation and, thus, cannot justify the proposed restriction. (93) Therefore, it must be concluded that the Proposal is lacking sufficient evidence and justification as to why all PFAS have intrinsic properties which result in environmental hazards. The Proposal does not comply with Article 68(1) REACH and erroneously deviates from applicable statutory requirements and established guidance. By doing so, the Proposal breaches the principle of good administration and legitimate expectations. (94) The Proposal and the underlying justification deviates from statutory prerequisites and established guidance. Due to this deviation, it is not only difficult to identify the specific scientific basis for the conclusion as to why any and all substances within the scope of the Proposal do have relevant hazard properties that result in a relevant risk as required by Article 68(1) REACH. Insofar, the Proposal infringes the principle of good administration due to inconsistency of the underlying administrative behaviour and a breach of 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 24/44 legitimate expectations of stakeholders and other market actors regarding the proceeding, the underlying assessment, and the intended decision-making process. 3. Unlawful grouping (95) Although various inconsistencies of the grouping as referred to in the Proposal are already demonstrated with respect to the hazard and risk assessment, as outlined above, we further submit that the grouping of all known and unknown PFAS as proposed by the Dossier Submitters is unlawful. a) Deviation from available guidance (96) In the respective guidance document, it is stated, that grouping could be considered "when the key property in combination with the exposure that causes the risk leading to the proposal of a restriction is shared by several related substances" (cf. Guidance for the preparation of an Annex XV dossier for restrictions, p. 23). As is apparent from the wording, the substances do not only need to share the same property or properties but also, in effect, the same risk. In the present case, the PFAS within the scope of the Proposal share, according to the Proposal itself, one single property, i.e. persistence, which as such does not even qualify as a hazard property. (97) While the Dossier Submitters emphasize that this is the relevant key property, we submit that persistence as such does not qualify as a hazard property nor as a risk. Therefore, persistence as such is not a sufficient basis for a grouping approach. According to the Proposal (cf. p. 22), the additional properties of PFAS differ and vary among the PFAS, while it is not even demonstrated that any and all PFAS within the scope of the Proposal have additional hazard properties beyond their persistence at all. A common hazard property and profile and, thus, any substantially similar risk shared by all substances within the scope of the Proposal cannot be established and the Proposal does not even claim to achieve the applicable prerequisites for grouping. Consequently, the requirement for grouping is not met, and the Proposal is further legally deficient on this basis. (98) Besides not meeting the criteria as laid down in the respective guidance document, the group-based approach is erroneously established for another reason. The background of this approach is that different substances can and should be examined together on the basis of similarities, in particular to improve the effectiveness of the restriction and the procedure (cf. Grouping of substances to be covered in a single restriction dossier (Restriction Task Force), p. 1). It is true that the PFAS within the scope of the proposal arguably all show some persistence. However, the numerous scientific uncertainties do not arise with regard to the question of persistence, but rather with regard to any potential additional hazardous properties. In this respect, the Proposal itself states that there are major differences between the PFAS covered (Proposal, p. 22). However, this undermines the conceptual origin of the group-based approach. Indeed, if no reciprocal 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 25/44 links can be established with respect to the issues at stake, there are no efficiency gains from the process. Moreover, the group-based approach in the present case leads to the conclusion that the properties of certain PFAS are related to the properties of other PFAS, without this being scientifically substantiated (cf., representative of many examples, for example Proposal, Annex B, page 181). Logically, such cross-references should take place precisely for the common property and precisely not with regard to such properties, which differ greatly. In this respect, the group-based approach is not persuasive. This specifically holds true with respect to the distinct sub-group of Fluoropolymers. (99) Against this background, the grouping can also not be justified by the fact that a regrettable substitution should be prevented. For example, with regard to Fluoropolymers, the extent to which such substitution behaviour would be possible at all has not been established. Furthermore, the consideration is not proportionate, especially with regard to substances that are still completely unresearched, because it does not make any gradation between more dangerous and less dangerous substances. It is evident that there are more dangerous and less dangerous PFAS. In this respect, in order to maintain proportionality, certain groups of PFAS could have been included in the restriction proposal with the aim of displacing the market and certain other PFAS, whose effects on humans and nature have been proven to be low, could have been excluded from the scope. This is especially true in light of the fact that certain persistent substances will continue to be needed in industry in the future. For these uses, a persistent alternative must inevitably be available, so that in terms of proportionality it should have just been enshrined to allow certain substitutions instead of restricting all PFAS with the argument of preventing any "regrettable substitution". (100) Moreover, specifically with respect to Fluoropolymers, it is impractical and ultimately erroneous to have them regulated together with other PFAS. This is because the dossier shows in several sections that it considers Fluoropolymers to be a special, distinct category of PFAS. An example of this is the specific environmental hazard assessment for Fluoropolymers in Annex B.7.6 (p. 219 et seqq.), in which it is significantly stated that the main problem of Fluoropolymers lies in the release of other PFAS. The dossier thus admits that Fluoropolymers as such do not have the same intrinsic hazard properties as other PFAS. In this respect, it is legally incorrect that Fluoropolymers are treated the same way as other PFAS and, thus, are subject to conclusions derived from hazardous properties of other PFAS due to the group-based approach. (101) This applies in particular against the background that Fluoropolymers - compared to all other PFAS - are partially treated as microplastics in the dossier. Furthermore, the proposal of the restriction text also shows the autonomy of the category of Fluoropolymers, because special derogations apply to them (cf. proposed restriction, Column 2, Nos. 6 and 8). In particular, according to Column 2, No. 8 of the proposed restriction, only Fluoropolymers are subject to certain further information requirements in the event that a derogation is used. This is contradictory in itself, because an exemption actually presupposes sufficient information. 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 26/44 (102) Above all, however, this distinct approach shows that there are obviously major knowledge gaps for Fluoropolymers. Against this background, too, it seems absurd to regulate Fluoropolymers together with other PFAS such as PFCAs, PFOA, for which corresponding information on the hazardousness is actually available. Due to the already acknowledged difference between Fluoropolymers and other PFAS, the principle of the rule of law requires that Fluoropolymers are regulated separately if a corresponding regulatory measure is justified at all. b) Grouping not justified with respect to PFAS definition established by OECD (103) The grouping approach as applied in the Proposal can also not be justified with the definition of PFAS as established with OECD guidance "Reconciling Terminology of the Universe of Per- and Polyfluoroalkyl Substances: Recommendations and Practical Guidance" ("OECD (2021)"). aa) PFAS definition according to OECD (104) Prior to the assessment of the justification of the grouping approach it needs to be noted that the perception and definition of PFAS as established by the OECD were subject to some major changes in recent years. (105) In Buck et al. (2011), PFAS were defined as "the highly fluorinated aliphatic substances that contain 1 or more C atoms on which all the H substituents (present in the nonfluorinated analogues from which they are notionally derived) have been replaced by F atoms, in such a manner that they contain the perfluoroalkyl moiety CnF2n+1-" (i.e. must contain at least -CF3). The definition highlights the presence of at least one fully fluorinated saturated carbon atom in the PFAS molecules. (106) PFAS were re-defined by the OECD in 2021 as follows: "PFAS are defined as fluorinated substances that contain at least one fully fluorinated methyl or methylene carbon atom (without any H/Cl/Br/I atom attached to it), i.e. with a few noted exceptions, any chemical with at least a perfluorinated methyl group (-CF3) or a perfluorinated methylene group (-CF2-) is a PFAS." (OECD (2021), Reconciling Terminology of the Universe of Per- and Polyfluoroalkyl Substances: Recommendations and Practical Guidance, OECD Series on Risk Management, No. 61, OECD Publishing, Paris, p. 8) (107) According to the OECD, the introduction of the new definition is triggered by two main reasons (cf. OECD (2021), p. 7, 18). First, the OECD/UNEP Global PFC Group prepared a new list of PFAS that may have been on the global market in 2018. In total, a set of substances with over 4.730 CAS numbers have been identified, including substances that contain fully fluorinated carbon moieties, but do not meet the PFAS definition in Buck et 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 27/44 al. (2011) due to a lack of a -CF3 group in the molecular structures. Second, according to the OECD, recent advancement of non-target screening analytical techniques using high-resolution mass spectrometry has enabled identification of many unknown substances in different environmental and product samples. Thus, the development and broaden of the definition is motivated by the identification of overlooked PFAS (cf. OECD (2021) p. 18) and the closing of identified gaps in the previous PFAS definition (cf. OECD (2021) p. 21, 23). (108) Furthermore, according to the OECD, the rationale behind the revision is to have a general PFAS definition that is coherent and consistent across compounds from the chemical structure point of view and is easily implementable for distinguishing between PFAS and non-PFAS, also by non-experts (OECD (2021), p. 8). The OECD claims, that the decision to broaden the definition is not connected to decisions on how PFAS should be grouped in regulatory and voluntary actions (ibid.) and that the intention of the revision of the PFAS definition is not to expand the PFAS universe, but to comprehensively reflect it (OCED (2021), p. 23). (109) The OECD states, that the term "PFAS" is a broad, general, non-specific term, which does not inform whether a compound is harmful or not, but only communicates that the compounds under this term share the same trait for having a fully fluorinated methyl or methylene carbon moiety (OECD (2021), p. 8). Accordingly, the general definition of PFAS is based on molecular structure alone and serves as a starting and reference point to guide individual users to have a comprehensive understanding of the PFAS universe and to keep the big picture of the PFAS universe in mind (ibid.) (110) The broadening of the definition is to be taken critically, since, in particular, it is contradictory and seems artificial. The justifications quoted above are subject to an error of logic. Ultimately, the OECD justifies the broadening of the definition by saying that PFAS overlooked by the former definition have been identified and that this gap is now to be closed. (111) In this respect, it is already linguistically illogical that a definition is supposed to have "gaps" just because certain substances are not covered by it. According to this logic, every definition of a group of substances would logically have a gap, because some substances are of course not covered by the definition. Consequently, every definition would need to be broadened. This train of thought shows that the OECD's justification is not correct in this respect and, therefore, cannot justify a grouping approach for a restriction proposal under REACH. (112) Moreover, the argument that new PFAS (!) have been identified in the meantime (e.g. by new screening methods) is illogical. After all, according to the definition applicable at the time, the substances identified were not PFAS by definition. (113) Consequently, it is not a matter of closing gaps, but of expanding the definition. This is already clear from the fact that, as the OECD itself admits, the revised definition now 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 28/44 covers significantly more substances than before. Against this background, it is not comprehensible that the OECD states that the amendment of the definition was not intended to expand the universe of PFAS. After all, this is exactly what has happened by changing the definition in such a way that certain substances that were previously not covered by the definition, for example due to the absence of a -CF3 group, are now covered. (114) As far as the OECD states that the new definition is necessary for a coherent and consistent distinction of PFAS, it fails to provide any evidence to what extent the previous definition was not coherent and not consistent. As already stated, the mere fact that certain, possibly even similar, substances are not covered by a definition does not make the definition inconsistent. On the contrary, it must be stated that the exclusion of certain substances from the definition has precisely shown that it functions and is therefore consistent and coherent. (115) Thus, the impression arises that the OECD, contrary to its attempts at explanation, has changed the definition precisely because it wanted to classify the newly discovered substances as PFAS. As shown, the attempts to explain otherwise are not convincing. In particular, the reference to the fact that classification is based solely on molecular structure is also not sufficient. After all, it has not been shown whether and to what extent the previous definition was deficient in this respect. Overall, therefore, the conclusion remains that the OECD has significantly expanded the definition of PFAS for reasons other than those listed in the paper. bb) OECD definition not based on hazard or risk assessment (116) Furthermore, it has to be noted, that the broadening of the PFAS definition is not at all connected to any scientific findings of hazards or risks of certain substances but only based on chemical considerations (cf. OECD (2021), p. 31: does not include [...] any other considerations beyond chemistry). This is remarkably, since the PFAS restriction proposal adopts (more or less) the definition and states that all substances within the scope of this definition are hazardous and thus must be restricted (Proposal, p. 22). (117) It already follows from this misinterpretation of the revised OECD definition that the Proposal is flawed from a scientific and legal perspective. While the Proposal, on the one hand, acknowledges that the "OECD definition of PFASs is based on chemical structure" and hazardous properties or risks are not part of it" (cf. Proposal, p. 19) and, thus, some substances are excluded from the scope due to the fact that "they will ultimately mineralize in the environment" (ibid.), it needs to be noted, on the other, that the Proposal only presumes that all PFAS that remain within the scope of the restriction proposal "share a common hazard and risk", while a lack of scientific data on hazards for PFAS within the scope is broadly acknowledged. In other words, the Proposal is essentially based on the PFAS definition as established by the OECD which does not consider any hazard properties or risks, and the Proposal does not substantiate or justify for all substances within its scope if and which specific hazard properties apply. Therefore, the 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 29/44 Proposal is based on a non-hazard-/non-risk-based definition of the scope. Such approach is infringing the basis for a restriction proposal as established in Article 68(1) REACH and cannot be used to justify a grouping approach. cc) Deviating scope of the restriction proposal does not justify grouping approach (118) For the purpose of the restriction proposal, the Dossier Submitters define PFAS -compared to the OECD - slightly different as substances that contain at least one fully fluorinated methyl (CF3-) or methylene (-CF2-) carbon atom, without any H/Cl/Br/I attached to it. For the purpose of the Proposal, the Dossier Submitters propose the following scope (cf. Proposal, p. 14): "Any substance that contains at least one fully fluorinated methyl (CF3-) or methylene (-CF2-) carbon atom (without any H/Cl/Br/I attached to it). A substance that only contains the following structural elements is excluded from the scope of the restriction: CF3-X or X-CF2-X', where X = -OR or -NRR' and X' = methyl (-CH3), methylene (-CH2-), an aromatic group, a carbonyl group (-C(O)-), -OR'', -SR'' or -NR''R'''; and where R/R'/R''/R''' is a hydrogen (-H), methyl (-CH3), methylene (-CH2-), an aromatic group or a carbonyl group (-C(O)-)." (119) Thus, the Proposal introduces an exception which concerns certain fully degradable PFAS subgroups that contain some specific structural elements. PTFE is a fluoropolymer and it uses TFE (Tetra Fluoro Ethylene) and HFP (Hexa Fluoro Propylene) as raw materials. While TFE is not a PFAS as per the definition, HFP is. Such anomalies exist for other fluorinated monomers used in the production of fluoropolymers. (120) Thus, the proposed scope of the restriction is a rather crude combination of the broad OECD definition and slight exemptions for subgroups which are considered to be not persistent by the Dossier Submitters. The derivation of the scope and its justification is, however, flawed for various reasons. (121) As can be seen from the Proposal, the starting point for the development of the scope for the proposed restriction remains the OECD definition of PFAS. According to the proposal, the substance scope is "additionally" considered to be a concern-based one, which wants to cover all PFAS that are persistent (cf. Proposal, p. 19). For this reason, the Dossier Submitters exclude identified non-persistent subgroups from the scope, while it is not demonstrated that any relevant hazard or risk profile can be established for the remainder of the substances considered to be within the scope. 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 30/44 (122) It follows already from these considerations that the PFAS definition cannot justify a grouping approach. If it would be correct to assume that all PFAS within the scope, i.e. within the scope of the definition as established by the OECD, qualify as being persistent, it should not be possible to exclude certain PFAS as they cannot be considered persistent. (123) But this notwithstanding, the Proposal only assumes that all PFAS, except for the few subgroups excluded from the scope, are persistent while this assertion is not substantiated in the justification of the scope of the Proposal or in any other section of the Proposal. To the contrary, the Dossier Submitters concede that they have no positive knowledge about the persistence of most substances, because they request stakeholders to prove that specific substances used by them are not persistent and can therefore be excluded from the scope (cf. Proposal, Annex B, p. 3). (124) However, this approach does not meet the requirements of a diligent elaboration on the scope of a restriction proposal. This applies in particular against the background that the OECD has stated in the context of the justification of its extremely broad definition that, on the one hand, the broad definition cannot be connected to the scope of possible regulatory measures (p. 8), and, on the other hand, the definition is only a "starting point" due to its broadness (p. 31). It is true that the narrowing down of the definition to persistent substances, basically, can be considered a plausible refinement of the OECD definition. However, it would have been necessary to prove to what extent the many thousands of substances still covered within the scope are persistent, as far as this is considered the "main concern" (cf. Proposal, p. 24). By merely making an unsubstantiated claim, the scope (with the small exception of substances known to be non-persistent) corresponds nearly to the extremely broad OECD definition, which is clearly not based on a hazard or risk assessment. (125) The aforementioned concerns especially hold true against the background that the OECD highly recommends that users clearly provide the context and rationale for selecting their PFAS working scope in order to provide transparency and avoid confusion by others (OECD (2021), p. 8). In the case at hand, such a rationale is not given except for the short statement that the aim is to address the concerns associated with the persistent nature of the substances (cf. Proposal p. 19). (126) As a matter of fact, the Dossier Submitters, when justifying the scope of the restriction proposal, did not even bother to change the wording of the OECD paper which introduced the new definition. As an example, we would like to emphasize that the sentence "(...)attracted much public attention since the late 1990s and early 2000s, when the hazards and ubiquitous occurrence in the environment of two PFAS, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), started to be reported and recognized", 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 31/44 is taken from pages 7 and 17 of the OECD paper and is repeated on page 18 of the Proposal without indicating that it is a citation from the OECD paper and without source citation. (127) Furthermore, it should be noted that the proposal only refers to persistence and not to hazards for humans or the environment. This is already questionable on the level of the elaboration of the scope, because persistence as such does not qualify as a hazard property as referred to in the REACH Regulation by reference to the CLP Regulation, and therefore not a suitable reference point for the mandatory risk assessment in accordance with Article 68(1) REACH. (128) The mere fact that the OECD paper assumes that a limitation for potential regulatory measures is possible, inter alia, on basis of the criterion of persistency (OECD (2021), p. 26). However, against the background of the clear wording of Art. 68 REACH, this cannot apply to a restriction under REACH. dd) Violation of OECD guidance on PFAS (129) Furthermore, the Proposal violates the underlying OECD guidance because its wording does not meet the requirements laid down in chapter 3 of OECD (2021). In chapter 3.2, OECD (2021) gives a practical guidance on how to identify and use suitable PFAS terms. As stated in the guidance, it is strongly recommended that the PFAS terminology be used in a clear, specific and descriptive manner which is due to the fact that the term "PFAS" does not inform whether a compound is harmful or not, but only communicates that the compounds under this term share the same trait for having a fully fluorinated methyl or methylene carbon moiety (cf. OECD (2021), p. 32). A clear and specific wording is necessary to prevent ambiguity or factual errors. Thus, the OECD asks regulators to use terms that most clearly describe the substance(s) referred to in their statement and provides for concrete examples (cf. ibid.). (130) The proposal violates these requirements in numerous points, of which only a few are listed below as examples. (131) For example, it is linguistically extremely unfortunate that the Proposal, when developing the scope, does indeed clarify that certain (non-persistent) substances are excluded from the scope of the Proposal. This results in the scope containing only a subset of the substances that are to be considered as PFAS according to the current OECD definition. Nevertheless, the proposal refers in some places to "all PFAS" (e.g. Proposal, p. 22: "All PFAS are considered to be very persistent (...)") and thus leaves great linguistic ambiguity as to which substances are meant. Moreover, the above quoted passage is also fundamentally wrong as the proposal itself states that some PFAS are not persistent. (132) A further linguistic inaccuracy is that in many places the term "some PFAS" is used (see e.g. Proposal p. 26, 35, 36, 48, 50; Annex B p. 133, 165, 208 and many more); in addition, sometimes a "subset of PFAS" is referred to (e.g. Proposal p. 28, 48). Both is entirely 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 32/44 insufficient against the background of the OECD's requirement to designate the respective substance or group of substances as accurately as possible. (133) In addition, there are passages in the proposal in which the properties of specific substances or groups are first discussed (in accordance with the OECD specifications) and then generalized in the course of consideration. For example, the mobility is first explained on the basis of concrete substances and 5 paragraphs later the generalizing statement is made that "Mobility of PFAS in water contributes to their long-range transport potential (...)" (cf. Proposal p. 25). (134) As a result, it must be stated that the Dossier Submitters did not comply with the requirements that emanates from the broad OECD definition. In many places they did not differentiate between PFAS in the sense of the definition and PFAS in the sense of the scope and, moreover, often made unnecessary generalizations. Insofar, the definition of PFAS as established with OECD (2021) and modified with the Proposal cannot justify the grouping approach due to the broad variety of inconsistencies. 4. Breach of principle of proportionality (135) Furthermore, the proposal infringes the principle of proportionality for various reasons. a) Availability of less onerous measures (136) The proposal is disproportionate as there would have been less onerous measures to achieve the intended aim and purpose. According to settled case-law, the principle of proportionality, which is part of the general principles of EU law, requires that EU measures do not exceed the limits of what is appropriate and necessary in order to attain the objectives legitimately pursued by the legislation in question; when there is a choice between several appropriate measures recourse must be had to the least onerous, and the disadvantages caused must not be disproportionate to the aims pursued (judgments of 8 July 2010, Afton Chemical, C 343/09, EU:C:2010:419, paragraph 45; of 21 July 2011, Etimine, C 15/10, EU:C:2011:504, paragraph 124; and of 1 February 2013, Polyelectrolyte Producers Group and Others v Commission, T 368/11, not published, EU:T:2013:53, paragraph 75). The clearly communicated objective of the restriction proposal is to eliminate PFAS from the market as far as possible. Regardless of the question to what extent this is a legitimate goal, there would have been less onerous measures in several respects that would have served the goal with equal effectiveness. (137) First, an authorization under Art. 55 REACH would have had to be considered. The ultimate aim of an authorization is that the use of substances of very high concern are replaced by suitable alternative substances or technologies where these are economically and technically viable (see judgment of 7 March 2013, Rtgers Germany and Others v ECHA, T 94/10, EU:T:2013:107, paragraph 134 and the case-law cited). 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 33/44 (138) Irrespective of the fact that the approach supported by the Dossier Submitters with the Proposal are in any case more similar to those of an authorization, an authorization obligation would have had the relevant advantage for stakeholders that they would have been provided with an orderly procedure for obtaining an authorization for their use. With the Proposal and the subsequent restriction procedure, stakeholders are now limited to requesting an exemption or derogation in connection with the consultation procedure. In this context it needs to be noted that the approach chosen by the Dossier Submitters leaves stakeholders in a less secured legal position. (139) Other than in a regular authorisation procedure, there is no specific decision which is directly addressed to the applicant and which can be subject to further legal action if considered necessary in case of deviations from the underlying application. In the case at hand, however, a rejection of a request for an exemption or derogation does not even result in a decision addressed to the respective stakeholder and, even worse, the REACH Regulation does not even establish any legal prerequisite that a further justification for such rejection is provided. As no decision is adopted to that effect, not even the general principle to justify decisions would apply although this is enshrined e.g. in Article 18 of the Code of Good Administrative Behaviour for the Staff of the European Chemicals Agency (adopted by Decision of the Management Board MB/11/2008 of 14 February 2008, as amended by Decision of the Management Board MB/21/2013 of 20 June 2013) and the European Code of Good Administrative Behaviour (cf. C(2000) 3614, OJ L 308, 8 December 2000, p. 26). (140) Even irrespective of the specific case at hand, which has the peculiarity that there must be different exceptions for many different uses, a restriction is generally the milder measure compared to the obligation to obtain authorization. It is true, however, that case law does not assume a special priority relationship between authorization and restriction in this respect. However, there is case law stating that a restriction is not (!) a less onerous measure compared to the identification of a substance for the candidate list (cf. Judgment of 25 September 2015, PPG and others vs. ECHA, Case T-268/10). (141) This implies that the route via an authorization must in principle be considered as less onerous. Since the objective of the authorization and the objective of the restriction are otherwise identical, namely, with the exception of substances that are exempt from the restriction or have to be authorized, market elimination is to be achieved, the path via an authorization would have been a more proportionate measure in the present case. (142) We understand that the Dossier Submitters identified various obstacles and regulatory shortcomings in connection with a potential authorisation approach for PFAS (cf. Proposal, Section 2.2.2.3, p. 69). We submit, however, that the aspects referred to in the Proposal in this context only address benefits for authorities as regards potential efforts which cannot justify deviations from the principle of proportionality. 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 34/44 (143) The Proposal already acknowledges that according to Article 58(3) REACH, priority for inclusion of SVHC in Annex XIV shall normally be given to substances with (a) PBT or vPvB properties, or (b) wide dispersive use, or (c) high volumes. While the Proposal also correctly states that only substances that were previously added to the Candidate List can be subject to authorisation requirements, the Proposal states that SVHC identification of all PFAS meeting the chemical definition would be very difficult (cf. Proposal, Section 2.2.2.3, p. 69). The Proposal, however, ignores the fact that already today a significant number of PFAS is included in the Candidate List (including but not limited to PFBS, PFHxS, PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFDoDA, PFTrDA, PFTeDA). In addition, the Proposal conceals the fact that it would be possible to include all PFAS in the candidate list on basis of Article 57(f) REACH. If a corresponding grouping approach is considered feasible for the proposed restriction (regardless further concerns in this regard as already outlined above), the same approach could be used for SVHC identification. To that end, the template for corresponding Annex XV reports explicitly refers to the option to propose SVHC identification on basis of grouping. (144) The same holds true for the prioritisation of SVHC for inclusion in Annex XIV as explicitly stated in ECHA's outline "General prioritisation approach: practical implementation examples" (Section 3, p. 4). Although no PFAS are listed in Annex XIV to REACH so far, nothing in the underlying procedural provisions would exclude this approach. The argument raised by the Dossier Submitters, that SVHC identification and subsequent inclusion in Annex XIV of all PFAS "fitting the chemical definition would be very difficult", is not convincing. (145) Moreover, we submit that a decisive aspect has not been considered by the Dossier Submitters. With respect to enforcement, authorisation requirements seem to provide relevant advantages as all market actors using a substance would need to either apply for an authorisation or submit a notification according to Article 66 REACH, i.e. need to identify themselves and their respective uses vis--vis authorities. Enforcement of restrictions and corresponding exemptions or derogations do not require proactive identification of market actors and uses, which creates a significant likelihood of non-compliance on side of market actors and insufficient enforcement and control measures on the side of authorities. (146) This notwithstanding, we further submit that with respect to Fluoropolymers any appropriate hazard assessment against the background of Article 57 REACH would have demonstrated that beyond the persistence no specific hazard properties can be identified for all Fluoropolymers in a way that would justify an identification as substances of very high concern or subsequent inclusion in Annex XIV. Therefore, an authorisation approach would have resulted in a regulatory approach excluding Fluoropolymers and, thus, would have been a less onerous approach for this subgroup of PFAS. (147) And even if the Dossier Submitters would have considered less onerous options only within the framework of a restriction under REACH, it would have been appropriate to 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 35/44 provide for an initially unlimited exemption for Fluoropolymers because there are at least uncertainties regarding the hazard and risk profile and, if considered necessary by the Dossier Submitters, to link this to a mechanism a review period for the Commission to assess whether and to what extent specific properties have been identified. Although there is no sufficient basis for such further review according to the information presented in the Proposal, such approach would qualify as a less onerous measure and a wellestablished approach in connection with multiple other restrictions. (148) In addition, such approach would also have supported any further assessment of specific uses and related alternatives. As far as an assessment of certain uses is not possible in connection with the decision on the Proposal, it would be possible to establish a review period for the Commission to assess whether suitable alternatives are available. In this respect, stakeholders would also have sufficient pressure to develop alternatives. However, it would not come to the scenario that the development of alternatives actually fails and thus, under certain circumstances, entire supply chains or industrial sectors are massively and possibly permanently disrupted by a certain deadline. (149) It is true that the Commission could subsequently amend the text of the restriction and thus react to this situation. However, experience shows that the Commission has not made use of this possibility even in justified cases. Therefore, such approach cannot be considered as suitable alternative. b) Inappropriate assessment of the alternatives available (150) The dossier breaches the principle of proportionality for another reason, as it makes an inappropriate assessment of the alternatives available. (151) The wording of Article 68(1) REACH already requires that a decision on a restriction has to take the availability of alternatives into account. Accordingly, Section 3 of Annex XV to REACH states that available information on alternative substances and techniques shall be provided, including information on the risks to human health and the environment related to the manufacture or use of the alternatives, availability (including the time scale) and technical and economic feasibility. The Guidance for the preparation of an Annex XV dossier for restrictions specifies these requirements and states that the respective aim is to provide information for the analysis of whether the equivalent function provided by the substance can be obtained by other substances or techniques (cf. Guidance, p. 68). (152) Furthermore, according to the guidance document, an alternative shall mean alternative chemical substances or alternative techniques (processes and technologies) or combinations thereof that can be used to replace (partially or totally) the substance of concern in a given use or a number of uses by providing the equivalent function that the substance delivers in those uses or by making the function redundant (cf. Guidance, p. 69). 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 36/44 (153) Moreover, the information on alternatives should be used to "defining a proportionate restriction that is targeted to the identified risk" (cf. Guidance, p. 68) and in developing the justification that the proposed restriction is the most appropriate measure (cf. Guidance, p. 69). Thus, the guidance document clearly states, that the evaluation of alternatives is a necessary and mandatory part of a proportionate restriction proposal. (154) In the present case, the assessment of available and, above all, future alternatives suffers from a decisive logical error. As can be seen in many passages, the assessment focuses on other substances that can have an equivalent function to PFAS. In this respect, the dossier adheres to the requirements of the guidance document, which specifies this as the definition of an alternative. However, the dossier fails to recognize that the decisive function of Fluoropolymers is precisely their persistence or their ability to persist in challenging environments like extremely high temperatures, inertness to highly reactive chemicals. Persistency in adverse environment is also the function of reliability or durability which is a requirement of many applications in particular aerospace, semiconductor, chemical process industry etc. In this respect, the dossier states in some passages that the common property of Fluoropolymers is their persistence and the dossier justifies the proposed restriction mainly with the fact that the substances are persistent. Other properties therefore play an additional role at best (cf., for example, Proposal, p. 22). (155) Against this background, it contradicts any logic of thought that alternatives are sought which possess the same decisive property, because according to the logic of the dossier, the alternatives would not be allowed at all and would consequently have to be restricted. In this respect, the analysis of existing and future alternatives should necessarily revolve around alternatives of use and not around alternatives of substance. (156) To that end, however, it needs to be submitted that, in general, no alternatives for Fluoropolymers are available. In addition, it is evident that for many applications there are no non-persistent alternatives available because Fluoropolymers are used precisely because of their unique properties, including persistence. This is especially true against the background that the Dossier Submitters want to prevent a "regrettable substitution". This consideration, however, is led ad absurdum if there is inevitably nothing that can be used as a suitable alternative. Consequently, persistent alternatives are not to be considered in the present case. Thus, on the one hand, there is a major error in the information about the alternatives, which makes the dossier disproportionate. On the other hand, the dossier is already disproportionate in general because it contains alternatives which are under scrutiny according to the logic of the dossier due to their persistence. 5. Infringement of the principle of good administration (157) The Dossier also infringes the principle of good administration due to further inconsistencies. The principle is codified in Article 41 of the Charter of Fundamental Rights of the European Union, the Rules of Procedure of the Commission and the European Code of 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 37/44 Good Administrative Behaviour. The principle comprises the general principle that authorities need to be consistent in their administrative behaviour and shall follow their normal practice, with the effect that legitimate expectations of the public are met. (158) A deficiency of the procedure results from the fact that, according to the dossier, the stakeholders are supposed to prove that specific PFAS are not hazardous or persistent (cf. Proposal, Annex B, page 3). This is the consequence of the group-based approach, by which a large number of individual substances are to be covered by the restriction, although for the vast majority of the substances no studies or evidence with regard to their hazard properties are available. (159) However, such a procedure violates the procedural rules for a restriction procedure under REACH with regard to the burden of proof. Articles 68 et seqq. REACH do not state at any point that the stakeholders, i.e. affected market actors, must provide evidence of the non-hazardousness of a particular substance. The hazard assessment described in the corresponding guidance document also explicitly provides only for such an assessment by the Dossier Submitters and not by the stakeholders (cf. Guidance, p. 34 et seqq.). Thus, in the context of the PFAS restriction, the German competent authority (BAuA) also stated that in the case of restriction, the burden of proof lies with the authority and, in contrast, in the case of authorization, the burden of proof lies with the industry (cf. BAuA webinar of 3 April 2023, presentation by Dr. Herkert, slide 5). By leaving concrete evidence with regard to the non-hazardousness of a concrete substance to industry, the present restriction procedure acts contrary to the applicable burden of proof rules. (160) This is particularly unacceptable in view of the fact that the individual stakeholders contrary to the Dossier Submitters - cannot opt for a group-based approach because they only use one or a few of the substances and thus have information on them. It is almost audacious that the Dossier Submitters admit that for many substances there is a lack of concrete scientific evidence for a hazardous property, but at the same time demand evidence for non-hazardousness from the stakeholders in connection with requests for exemptions or derogations. (161) Incidentally, it should be noted that the consultation process does not affect these considerations. It is true that the stakeholders have the opportunity to make a submission on the hazardousness or non-hazardousness of certain substances. However, they are not obliged to do so, so that the de facto reversal of the burden of proof is fully at their expense if they do not participate in the consultation procedure. (162) We further submit that the approach also infringes procedural rights of affected market actors. If the authorities would have chosen an authorisation process, affected market actors would have been in the position to prepare an application for authorisation typically within a time period of 18 to 24 months after inclusion of substances in Annex XIV to REACH. In connection with the determination of the respective last application date 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 38/44 (cf. Article 58(1)(c)(ii) REACH) a broad variety of factors need to be considered as estab- lished with the corresponding ECHA Practical Implementation document on Setting Lat- est Application Dates (cf. https://echa.europa.eu/docu- ments/10162/17232/recom_gen_approach_draft_axiv_entries_impl_doc_2020_en.pdf). It follows already from the details set out in this document that a complex ban as sup- ported with the Proposal would have resulted in a time period of 24 months after inclu- sion of substances in Annex XIV to REACH to set the last application date. (163) By illicitly initiating a restriction proceeding under Titel VIII of REACH, the time period for affected market actors to create convincing submissions to request and justify exemptions or derogations, including supporting data on alternatives, environmental fate and socio-economic considerations as requested in connection with the public consultation, is significantly shortened to roughly six months, i.e. the duration of the public consultation according to Article 69(6) REACH. (164) The burdens associated with this are also not compensated by the fact that the restriction proposal was already under discussion beforehand and affected actors could thus have prepared themselves at an early stage. It needs to be noted that the actual restriction proposal was initially published only on 7 February 2023 and the version currently subject of the public consultation was in fact only published on 22 March 2023, i.e. the date on which the public consultation was initiated. 6. Breach of precautionary principle (165) The Proposal does not align with the precautionary principle but has an arbitrary nature. (166) According to Article 191(2) TFEU, every REACH measure aiming at a Union policy on the environment has to take into account the precautionary principle. In contrary, such measures shall not be of an arbitrary nature. There is no definition for the precautionary principle in the EU treaties, but the Commission and case law have specified the content. (167) As already stated (cf. paragraph (67) above) the Commission has laid down its interpretation of the principle in a separate communication on the precautionary principle (cf. COM(2000) 1 final, dated 2 February 2000). According to this, the determination of appropriate action including measures based on the precautionary principle should start with a scientific evaluation to perform an as objective and complete as possible scientific evaluation to cast light on the existing objective evidence, the gaps in knowledge and the scientific uncertainties (cf. ibid, p. 16). In particular, the precautionary principle can under no circumstances be used to justify the adoption of arbitrary decisions (cf. ibid, p. 13). This requires reliable scientific data and logical reasoning, leading to a conclusion which expresses the possibility of occurrence and the severity of a hazard's impact (cf. ibid, p. 13). The limits of scientific knowledge may ultimately affect the foundation for protective or preventive action (ibid, p. 13). Particularly, this applies for the scenario, that scientific data are not sufficient and therefore cause-effect relationships are suspected 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 39/44 but have not been demonstrated (cf. ibid, p. 14). Furthermore, according to the Commission, the measures based on the precautionary principle must not be disproportionate to the desired level of protection and must not aim at zero risk (cf. ibid, p. 17). Accordingly, in some cases a total ban may not be a proportional response to a potential risk (cf. ibid, p. 17). (168) According to the ECJ, the precautionary principle entails that, where there is uncertainty as to the existence or extent of risks to human health, protective measures may be taken without having to wait until the reality and seriousness of those risks become fully apparent. Where it proves to be impossible to determine with certainty the existence or extent of the alleged risk because the results of studies conducted are inconclusive, but the likelihood of real harm to public health persists should the risk materialise, the precautionary principle justifies the adoption of restrictive measures (Judgement of 1 October 2019, Case C-616/17, ECLI:EU: C:2019:800, para. 43.). However, a correct application of that principle presupposes, first, identification of the potentially negative consequences for health of the proposed use of the substance at issue, and, secondly, a comprehensive assessment of the risk to health based on the most reliable scientific data available and the most recent results of international research (Judgement of 4 April 2019, Case T-108/17, ECLI:EU:T:2019:215, para. 281). (169) Measured against these criteria, the implementation of a general ban on (almost) all known and even currently unknown PFAS after the expiry of certain transitional periods, as proposed by the Dossier Submitters, would violate the precautionary principle, since it would be based to a large extent on a mere risk hypothesis and not on scientifically substantiated risk assessment. If the Commission were to follow the proposal, it would violate its self-imposed principles, according to which a restrictive measure may not be taken on the basis of the principle of general precaution alone, in order to limit a potential risk to zero, without any comprehensible, scientific evidence for this in detail. (170) There are numerous examples of such violations in the dossier. The group-based approach applied by the Dossier Submitters already raises fundamental concerns with regard to the precautionary principle (cf. Proposal, p. 21). Such an approach does not allow the exact determination of the possible risks of a certain substance, but is only able to draw conclusions, which cannot be scientifically justified in detail, from possible risks of certain substances belonging to a group to other substances of this group which have not been investigated. (171) By seeking to prevent substitutions with other PFAS, the Dossier Submitters are abandoning the principle of precaution and are pursuing a risk minimization to zero, which in fact is neither needed with regard to the precautionary principle, nor can it be justified by a mere reference to this principle. (172) Furthermore, the Dossier Submitters are not able to present logically comprehensible, scientifically based prediction tools for possible negative effects of Fluoropolymers in the 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 40/44 environment (cf. Proposal, p. 37). A substantiated risk assessment is not possible in this way; rather, the approach contradicts the requirements linked to the application of the precautionary principle as established by both, the Commission and the ECJ, according to which restrictions may only be made on the basis of a risk assessment based on the most reliable scientific data available and the latest results of international research, and not merely on a purely hypothetical risk assessment based on mere conjecture that has not yet been scientifically verified. (173) Although, as shown, for many PFAS except Fluoropolymers, there are no or only few scientific studies available with regard to their possible hazardousness, the dossier does not provide for the possibility of extending the maximum possible 13,5-year derogation if no alternative substances have been found within this period of time. Nor does the dossier take into account the fact that future studies could disprove or at least relativize the hazards of Fluoropolymers assumed by the dossier authors. The correct application of the precautionary principle, however, requires a consideration of such possibilities. Moreover, for Fluoropolymers available data already supports a non-time-limited derogation which is also not sufficiently reflected in the Proposal. (174) Further examples of violations of the precautionary principle can be found in Annex B. With regard to risk assessment, for example, it is described that a decreasing trend can be seen in humans, but in creatures the trends were inconsistent and (only) in some cases increasing (Annex B p. 97). However, the studies refer to PFSA and PFCA and precisely not to all PFAS and especially not to Fluoropolymers. The same applies, for example, to the immunological analysis, in which conclusions are drawn for all PFAS on the basis of studies on only specific PFAS without further justification (Annex B, p. 181). In this respect, the principle of caution is applied and not the precautionary principle as established by the Commission and the ECJ. In particular, there is an approach to achieve zero risk, which, as explained above, does not correspond to the precautionary principle. 7. Infringement of right to be heard / right to comment (175) The dossier infringes the stakeholders` right to be heard and right to comment. This follows from the fact that the proposed measure is, in effect, an authorization in the guise of a restriction. (176) In fact, the initial situation and the circumstances of the PFAS case strongly imply that the Dossier Submitters should rather have sought an authorization procedure. By failing to do so, they curtailed the participation rights and procedural rights enshrined in Article 59 REACH. In addition, if stakeholders were required to seek authorization, they would have a regulated process (namely, the authorization process) open to them in which they could argue socio-economically for certain uses in a regulated process. In contrast, the restriction process does not provide for mandatory participation; moreover, in contrast to the - necessarily individual - authorization decision, there is also no obligation 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 41/44 on the part of the authorities to deal with the specific use and to make an individual, judicially reviewable decision in the specific case. (177) The objective circumstances correspond to those of a potential authorization procedure. This is evident in particular from the fact that the Dossier Submitters obviously largely lack information on the concrete uses of the substances. After all, they themselves state that there are further uses not addressed in the dossier (cf. Information note on restriction report, Consultation on a proposed restriction on the manufacture, placing on the market and use of per- and polyfluoroalkyl substances (PFAS), p. 5). (178) Moreover, there is obviously only a rather low level of knowledge regarding the socioeconomic consideration. In particular, information on existing and future alternatives is largely lacking, which is now to be provided by stakeholders within the framework of the consultation procedure, as is already evident from the structure and content of the corresponding ECHA webform (cf. Information note on restriction report, Consultation on a proposed restriction on the manufacture, placing on the market and use of per- and polyfluoroalkyl substances (PFAS), p. 5). (179) This applies above all to Fluoropolymers. For this subgroup the level of knowledge is apparently so low that for them - in contrast to the other PFAS - it is even included in the proposed entry text of the restriction proposal (cf. Proposal No. 8) that (for the use of derogations already provided for) a management plan must be drawn up, from which, among other things, information on the substance and the product and a justification for the use must be provided. (180) However, it is precisely this initial situation that requires the issuance of an authorization procedure. After all, authorization and restriction must be differentiated on the basis of the fact that the burden of proof, especially for exemptions, lies with the authority for the restriction and precisely not for the authorization. If the authorities have so little information, particularly in the socio-economic dimension, as in the present case, this system dictates to consider an authorization and that the stakeholders should therefore have the opportunity to obtain exemptions in an orderly procedure. They were deprived of these rights due to the choice of the wrong measure, so that the participation and procedural rights were and are violated. III. Reference to other parts of the submission (181) As shown in detail above, the proposal is entirely insufficient from a legal point of view with regard to Fluoropolymers. As demonstrated above, the requirements of Article 68 REACH have not been met, in particular because, contrary to all known systematics and dogmatics, persistence was considered to be the key hazardous property. In addition, various superior legal principles were violated, in particular the principle of proportionality and the precautionary principle. 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 42/44 (182) Following on from this conclusion, it should be noted, that the Proposal cannot provide a detailed socio-economic consideration and an assessment of the exposure and hazard of the PFAS in question for all uses of PFAS. This can already be seen from the fact that the Dossier Submitters - as ECHA admits, cf. e.g. No. 6 of the Specific Information Requests - do not have knowledge of all use cases of PFAS and therefore could not include them in the Proposal. (183) Especially, regarding the socio-economic analysis, the Dossier Submitters seem to lack in particular an estimation of the expected costs of a possible replacement of products, including the immediate phase-out of products. Only with the help of such data, however, is it possible to conclude how this relates to, for example, the expected environmental impact costs. (184) Moreover, the Dossier Submitters did not conduct a hazard and risk assessment for each PFAS and not even for each PFAS group. This unlawful grouping results in the consequence that it is up to the stakeholders to contribute various information for their respective product or use and for the corresponding PFAS. In this respect, ECHA's webform on the consultation process and the corresponding guidance reveal that information is missing and what data should be provided by stakeholders for both known uses and as yet unknown uses. (185) Against this background, GFL submits further information as part of its broader submission. From a legal perspective, these additional studies, reports and papers precisely support the legal assessment at hand. In particular, the breach of the principle of proportionality, the breach of the precautionary principle and the conclusion, that the proposal fails to provide a sufficient socio-economic analysis for each substance concerned arise already from these papers. 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 43/44 IV. Conclusion (186) Against the background of the aforementioned arguments, a general exemption or derogation without any time limit for Fluoropolymers is warranted. Without a corresponding exemption or derogation, a restriction, if adopted, would constitute infringements of the prerequisites as set out in the REACH Regulation as well as fundamental principles enshrined in the European Union Charter of Fundamental Rights. We therefore suggest incorporating a corresponding section in the potential REACH Annex XVII entry regarding PFAS: "Paragraph 1 and 2 shall not apply to Fluoropolymers. This derogation does not apply to PFAS used as polymerisation aids for the production of Fluoropolymers." (187) In addition, the Proposal should be amended accordingly to ensure that no additional provisions as proposed with Nos. 5 a), 6, 7 and 8 of the contemplated entry to Annex XVII to REACH contradict the aforementioned derogation. (188) Therefore, we respectfully request ECHA, RAC, SEAC and the Dossier Submitters to consider the concerns raised with this submission and the further arguments as brought forward and supported by the broader submission of GFL to avoid procedural shortcomings which might give rise to further legal concerns. Augsburg, 21 June 2023 Produktkanzlei Ahlhaus Handorn Niermeier Schucht Rechtsanwaltsgesellschaft mbH Martin Ahlhaus Rechtsanwalt Dipl.-Verwaltungswirt (FH) 59/23, MA, Legal_Observations_PFAS_Proposal_Final 21.06.2023 - Page 44/44 REVIEW NiNater Environment Federation' the water quality people" Per- and polyfluoroalkyl substances thermal destruction at water resource recovery facilities: A state of the science review Lloyd J. Winchell,1'* Katherine Y. Bell John J. Ross ,1 Martha J. M. Wells ,2 Xavier Fonoll ,3 John W. Norton Jr,3 1 Brown and Caldwell, Walnut Creek, California 2 EnviroChem Services, Cookeville, Tennessee 3 Great Lakes Water Authority, Detroit, Michigan Received 2 July 2020; Revised 5 November 2020; Accepted 7 November 2020 Correspondence to: Lloyd J. Winchell, Brown and Caldwell, Walnut Creek, CA. Email: brwncald.com *All the authors are WEF members. Published online 31 December 2020 in Wiley Online Library (wileyonlinelibrary. com) DOI: 10.1002/wer.1483 2020 Brown and Caldwell. Water Environment Research published by Wiley Periodicals LLC on behalf of Water Environment Federation. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Abstract Per- and polyfluoroalkyl substances (PFAS) are a recalcitrant group of chemicals and can be found throughout the environment. They often collect in wastewater systems with virtually no degradation prior to environmental discharge. Some PFAS partitions to solids captured in wastewater treatment which require further processing. Of all the commonly applied solids treatment technologies, incineration offers the only possibility to completely destroy PFAS. Little is known about the fate of PFAS through incineration, in particular, for the systems employed in water resource recovery facilities (WRRF). This review covers available research on the fate of PFAS through incineration systems with a focus on sewage sludge incinerators. This research indicates that at least some PFAS destruction will occur with incineration approaches used at WRRFs. Furthermore, PFAS in flue gas, ash, or water streams used for incinerator pollution control may be undetectable. Future research involving full-scale fate studies will provide insight on the efficacy of PFAS destruction through incineration and whether other compounds of concern are generated. 2020 Brown and Caldwell. Water Environment Research published by Wiley Periodicals LLC on behalf of Water Environment Federation. Practitioner points Thermal processing is the only commercial approach available to destroy PFAS. Thermal degradation conditions required for destruction of PFAS during incineration processes are discussed. Fate of PFAS through water resource recovery facility incineration technologies remains unclear. Other thermal technologies such as smoldering combustion, pyrolysis, gasification, and hydrothermal liquefaction provide promise but are in developmental phases. Key words combustion; emissions; incineration; PFAS; products of incomplete combustion; residence time; temperature; thermal by-products; turbulence; wastewater INTRODUCTION PER- and polyfluoroalkyl substances (PFAS) encompass a wide range of compounds, numbering in the thousands, that have been used in a large variety of consumer and industrial products and, consequently, are widely distributed in the environment (Buck et al., 2011). As a result of the persistence and toxicity of these compounds, the Stockholm Convention, which manages risks of persistent organic pollutants through a global legally binding instrument, has restricted production of perfluorooctanesulfonic acid (PFOS) (UNEP, 2009) and banned the production of perfluorooctanoic acid (PFOA) (UNEP, 2019). Other actions are planned for perfluorohexane sulfonyl fluoride (PFHxSF) (UNEP, 2018). The United States Environmental Protection Agency (USEPA) Water Environment Research 93: 826-843, 2021 followed suit by releasing the PFAS Action Plan: Program Update (USEPA, 2020b), which is the first time in USEPA's 50-year history that it has tapped all program offices to address an emerging contaminant of concern. As a result, many of the major fluoropolymer and telomer manufacturers have committed to phasing out long-chain polyfluorinated substances through public or private initiatives. However, international production of PFAS continues in countries such as China (Swedish Chemical Agency, 2015) that have initiated production of perfluorohexane sulfonic acid (PFHxS) precursors and other PFAS compounds as replacement products, which may present concerns of their own. While global phase-outs are being implemented for some of the significant long-chain compounds, widespread distribution and health concerns (Buck et al., 2011a) have led government agencies to start regulating PFAS in drinking water. Although there are sufficient data for risk assessment of PFOA, PFOS, and several other PFAS, most PFAS detected in drinking water lack adequate data for proper risk characterization (ASTDR, 2018; Post et al., 2017). The European Union (EU) reached a provisional agreement in 2019 by setting a legally binding cumulative drinking water limit of 100 ng/L for the sum of 20 PFAS, and within 3 years regulators are mandated to develop testing protocols as well as establish a legal limit for 4,700 PFAS (The Greens/EFA in the European Parliament, 2019). In the United States (U.S.), the USEPA issued a health advisory level (HAL) of 70 ng/L for the sum of PFOA and PFOS in drinking water; however, because HALs are nonenforceable limits and USEPA's Maximum Contaminant Level (MCL) promulgation process is expected to take years, many U.S. states are establishing their own regulatory limits for PFOA, PFOS, and others that are well below USEPA's HAL (Cordner et al., 2019). Research focused on understanding the sources of these compounds in drinking water has identified municipal water resource recovery facilities (WRRF) as an important pathway (Clara et al., 2008). WRRFs provide several conduits for introducing PFAS to the environment: point source discharges of effluent, leakage or unintended releases from surface impoundments or sewer systems, air emissions, disposal of biosolids, and other by-products generated during the treatment process. PFAS are proven to exist in the effluent (Arvaniti & Stasinakis, 2015) and sludge (Eriksson et al., 2017; Hamid & Li, 2016; Lee et al., 2014) from WRRFs. Concentrations of selected PFAS increase during treatment and are generally higher in WRRF effluent than influent (Eriksson et al., 2017; Gallen et al., 2018; Kim Lazcano et al., 2019; Loganathan et al., 2007; Schultz et al., 2006; Venkatesan & Halden, 2013; Wang et al., 2018). The increases in concentration during treatment are attributed to the likelihood of precursors transforming in the wastewater treatment process (Eriksson et al., 2017; Loganathan et al., 2007). PFAS partition from wastewater and adsorb to the wastewater solids differentiated by hydrophobic and electrostatic interactions (Eriksson et al., 2017; Guo et al., 2010; Kim Lazcano et al., 2019; Loganathan et al., 2007; Nakayama et al., 2019; Pan et al., 2016). The composition of PFAS in wastewater or the solids derived thereof is a function of the WRRF treatment processes, the type and concentration of PFAS received by the WRRF, the biological and chemical transformation to intermediate and terminal degradation products, and the physical or Water Environment Research 93: 826-843, 2021 REVIEW chemical partitioning of congeners (Chen et al., 2013; Dimzon et al., 2017; Oliaei et al., 2013; Schultz et al., 2006). Because PFAS may be concentrated in solids captured in wastewater treatment processes (Rainey, 2019), WRRFs might introduce these compounds to the environment through the land application of biosolids, potentially allowing PFAS to enter surface water through runoff or infiltrate to groundwater (Lindstrom et al., 2011). What has not been well studied is the potential for sewage sludge incinerators (SSI) to act as a source of these compounds to the environment. In North America, there are more than 100 SSIs in operation that combust dewatered sewage sludge, or the solids generated during wastewater treatment. Thermal combustion has been reported as a critical method for destroying PFAS (USEPA, 2020c) and is important in processes such as regeneration of spent granular activated carbon (GAC) used in drinking water and in remediation treatment processes. In other words, SSIs may present a unique opportunity to destroy PFAS. Despite the highly oxidized nature of PFOA and PFOS, these and other PFAS display a relatively high thermal reactivity (Lee et al., 2012). The temperature used for thermal incineration of PFAS in carbon regeneration is usually higher than 1,000C (Lee et al., 2013); however, in laboratory studies, more than 99% of PFOS is degraded at 600C (Taylor & Yamada, 2003). Studies have shown the required degradation temperature increases with increasing perfluoroalkyl chain lengths (Rayne & Forest, 2009). While thermal combustion of PFAS has been studied for regeneration of spent activated carbon in oxygen-poor atmospheres, limited information is available on the fate of PFAS through SSIs. SSIs are expected to destroy at least some of the PFAS in wastewater solids, given the available research. For example, Takemine et al. (2013) observed 90% mineralization of PFOA in an airstream at 700C. Alkali addition enhanced destruction of halogenated compounds (Kamarehie et al., 2014; Takata et al., 2015; Yin et al., 2013), and laboratory-scale incineration of lime-conditioned sludge promotes fluorine mineralization from PFOS (Wang et al., 2013). Other chemical groups may serve as analogs to supplement PFAS-specific research. For example, full-scale waste incinerators and cement kilns have been reported to destroy chlorofluorocarbons at greater than 99.99% efficiency (Ueno et al., 1997; Urano et al., 2011). The extent of PFAS thermal destruction (i.e., thermal degradation by-product formation or complete mineralization) is also poorly understood. No published data currently exist on the overall fate of PFAS through an SSI, although limited information from other industries can be referenced. The primary point of release from an incineration system is the flue gas emitted from the stack, where any recalcitrant PFAS or by-products from the incineration process would be released directly to the environment. Some researchers have shown that off-gas from incineration of PFAS-containing textiles emitted no detectable PFOA (Taylor et al., 2014). Conversely, Garca et al. (2007) observed significant PFAS emissions, roughly 22% of the parent compound on a carbon basis, in laboratory-scale studies from thermal degradation of polytetrafluoroethylene (PTFE) under substoichiometric oxygen conditions at temperatures ranging 827 REVIEW from 750 to 1,050C. Recently, air concentrations of PFAS were determined at, and upwind of, municipal solid waste (MSW) incineration plants. Higher concentrations were found at the facilities than upwind (Wang et al., 2020). Tracking the fate of PFAS through any system is, in part, limited by available sampling and analytical methods. Agencies developing standardized methods for analyzing specific PFAS congeners include USEPA, American Society for Testing and Materials (ASTM), and the International Organization for Standardization (ISO). In the case of SSIs, these methods need to be adapted for the solids or aqueous phase samples that represent the inputs/outputs of the incineration process. Current analyses only measure a fraction of the PFAS present, partially due to the limited availability of analytical standards. Other nonquantitative or surrogate indicator approaches, such as nontargeted or total fluorine analyses, could be used to elucidate the fate of PFAS through an incineration system. This literature review aims to identify the current understanding regarding the fate of PFAS through SSI systems. With this review, the WRRF owners will have a comprehensive understanding of the state of the art of PFAS thermal behavior and of approaches likely to be useful in understanding their fate through SSIs. PFAS Diversity The following introduction to the PFAS chemical family is intended to help the reader better understand the fate of PFAS through an SSI. This introduction includes basic chemical structure, terminology, and classification within the PFAS family. Every PFAS contains a common structural element, the perfluoroalkyl group (CnF2n+1) (Buck et al., 2011b; Horst et al., 2018) and has a linear or a branched alkyl chain (Kissa, 2001). PFAS comprise an extensive family tree, the roots of which are illustrated in Figure 1. The USEPA has compiled a consolidated master list of nearly 8,000 chemicals that fit into the PFAS category (USEPA, 2020d). Beyond the scope of this review, more comprehensive schematics of PFAS families of compounds are found in the literature (ITRC, 2020; OECD, 2018; Wang et al., 2017). The primary familial classification is between the polymer and nonpolymer types of PFAS. Polymeric PFAS are potential precursors of nonpolymeric PFAS when they degrade. Nonpolymer PFAS are subdivided into perfluoroalkyl acids (PFAAs), PFAA precursors, and other potential PFAS (Figure 1). Two of the most well-known PFAA members are PFOA, an example of the perfluoroalkyl carboxylic acid (PFCA) family, and PFOS, an example of the perfluoroalkane sulfonic acid (PFSA) family. PFAS chemical structure and characteristics are diverse. Typical functional groups in PFAS include OH, CO2H, Cl, O, N, and SO3H. PFAS congeners exhibit many different chemical properties. PFAS can differ in polarity--polar or nonpolar; charge state--neutral, anionic, cationic, or zwitterionic; and volatility--volatile, semi-volatile, or nonvolatile. The alkyl carbon atoms in perfluoroalkyl substances are fully fluorinated, whereas they are not fully fluorinated in polyfluoroalkyl substances. In perfluoroalkyl substances, a hydrophilic functional group such as -CO2H or -SO3H links to the hydrophobic CnF2n+1 group; however, in polyfluoroalkyl substances, the CnF2n+1 group connects to at least one nonfluorinated alkyl carbon (-C-H) linking the perfluorinated Figure 1. PFAS family schematic. 828 Winchell et al. REVIEW group and the hydrophilic functional group (Dauchy, 2019; Pancras et al., 2016). Polyfluoroalkyl substances comprise a far more diverse group than the perfluoroalkyl substances (Ross et al., 2018), and polyfluoroalkyl substances can degrade into perfluoroalkyl substances (Dauchy, 2019). Another emerging subclass of PFAA compounds is the perfluoroether carboxylic acids; GenX, the ammonium salt of hexafluoropropylene oxide dimer acid (HFPO-DA) fluoride, introduced to the commercial market as a replacement for PFOA, is an example. Other PFAA precursors can generate PFAA compounds during processing and in the environment. One such subgroup is the fluorotelomers, which are polyfluorinated molecules with an ethyl (-CH2-CH2-) group between the fully fluorinated carbon chain and a variety of different functional groups. For example, the 8:2 fluorotelomer alcohol has a 2-carbon ethyl alcohol group attached to 8 fluorinated carbons. Thermal Processes Thermal processes utilize energy in the form of heat to transform materials. There are several types of thermal processes relevant to wastewater solids processing and which are typically identified by the involvement of oxygen in the process. Combustion entails a chemical reaction in which an oxidant, typically oxygen, reacts with a reducing agent (fuel). The chemical reaction breaks apart chemical bonds of the reactants to form more thermodynamically stable end products. In hydrocarbon combustion, the carbon (C)/hydrogen (H) fuel component combines with oxygen to form carbon dioxide (CO2) and water (H2O), If the reaction is exothermic, the released energy often is sufficient to self-sustain the process once the initial activation energy is provided. SSIs use combustion to process, or stabilize, wastewater solids. The term "incineration" generally refers to combustion of a waste product, so while wastewater solids are often utilized as an energy source, combustion of these solids is typically referred to as incineration. In the absence of oxygen, or at temperatures lower than required for combustion, materials will still break down when exposed to heat. In the strict absence of oxygen in the chemical reaction, the thermal process is called thermolysis. Calcination of limestone (CaCO3) to quicklime (CaO) using heat to drive off CO2 is a simple thermolysis example. Pyrolysis and gasification, examples of thermal processes in oxygen-limited environments, have been sparingly applied to wastewater solids. Table 1. Comparison of incinerator technology operating conditions INCINERATOR TYPE TEMPERATURE MHF FBF Rotary Kiln Liquid Injection Moving Grate Upper hearths - 300-500C Combustion hearths - 700-1,000C Bottom hearths - 150-300C Sand bed - 700-800C Freeboard - 800-900C Kiln - 650-1,300C Afterburner - 1,000-1,300C Burner - 800-1,200C Afterburner - 850C These processes are managed to generate simpler hydrocarbon substrates for subsequent use. Overview of Sewage Sludge Incinerators and Related Thermal Technologies Wastewater solids are currently processed by several thermal technologies while others are in development. The following describes the dominant combustion technologies employed at SSI facilities, industry analogs, and alternative technologies emerging in the industry. Incinerators Sewage sludge incinerators are a subset of incineration applications, including municipal solid waste incineration, cement kiln co-incineration, and hazardous waste incineration. Detailed discussions can be found in several sources (Albertson, 1992; Niessen, 2002; WEF, 2009). Municipal WRRFs typically have used two furnace technologies to combust solids captured from liquid treatment. Multiple hearth furnaces (MHF) have a long track record at WRRFs with installations first constructed in the 1930s. The first fluidized bed furnace (FBF) was installed at Lynwood, Washington, in 1965. Other furnaces types have been used, but MHF and FBF overwhelmingly represent the combustion technologies in service today at WRRFs. Table 1 summarizes the key operating characteristics of SSIs compared to other incinerators. The MHF consists of a cylindrical steel shell arranged vertically with refractory lining and multiple levels (Figure 2). Each level, or hearth, is constructed of firebrick. A central shaft extends the full height of the furnace and supports rabble arms extending to the periphery of each hearth. The rabble arms are fixed with plows or teeth to move material inward or outward. Dewatered solids are fed to a hearth near the top of the furnace and are either moved inward or outward (movement direction alternates on each subsequent hearth) to drop through holes onto the hearth below. Water associated with the solids evaporates before the volatile fractions are released and combustion initiates. The number of hearths, which account for evaporation or combustion, vary across installations to achieve different combustion conditions. Combustion control is achieved by the speed at which the rabble arms rotate to move the solids and by burners installed on selected hearths to provide RESIDENCE TIME Solids - approximately 1 h Gases - several seconds Solids - <1 min Gases - 6-10 s Solids - 1-1.5 h Gases - several seconds Gases - 0.3-2.0 s Gases - 2 s TURBULENCE Intense Extreme Intense Intense Moderate EXCESS AIR 50-125% 40% 50-200% 120-250% >200% Water Environment Research 93: 826-843, 2021 829 REVIEW Figure 2. Typical MHF section view. supplemental heat. Noncombustible material (i.e., ash) continues to the lower hearths, which is also where air is introduced. Combustion gases flow upward and out the exhaust ductwork on the top hearth. The MHF provides high solids and gas retention. The combination of the gas flow and mechanical mixing of the rabble arm teeth provide an intensely mixed environment. The temperature profile of an MHF increases from the upper hearths, where water evaporates, to the middle hearths where solids combust. As ash moves to lower hearths countercurrent to the combustion air, temperatures can drop to approximately 150C for easier handling of the ash. Combustion air requirements for acceptable performance are relatively high compared to an FBF. The higher combustion air volume, quantified as excess air 830 Figure 3. Typical FBF section view. which is calculated as that amount of oxygen provided in excess of stoichiometric combustion requirements, overcomes some of the comparably lower combustion efficiency in an MHF (from less turbulence) than an FBF. Most currently operating MHFs were modified after implementation of the Clean Water Act solids management rules in 1993, which lowered allowable emissions of products of incomplete combustion (PIC). Afterburners were retrofitted either externally, or by using one or more of the top hearths enabled by switching the dewatered solids introduction location to lower hearths. The afterburners typically use natural gas to elevate the flue gas temperature to Winchell et al. achieve complete combustion. The afterburners achieve temperatures of 820C or higher for 1-2 s. Fluidized bed furnaces differ significantly from MHFs in configuration (Figure 3). The FBF consists of a vertically oriented cylinder that expands in diameter with increasing height. Three major zones exist in an FBF starting at the bottom with the windbox, which acts as a plenum for the combustion air blown into the furnace. The windbox is capped by a distribution structure typically consisting of a ceiling penetrated by many tubes or tuyeres that extend through the ceiling. Head loss through the tuyeres provides uniform airflow distribution into the second zone, or sand bed, that uses the windbox ceiling as a floor. The flow of air through the three to six feet of sand creates enough drag force to fluidize the material, creating an extraordinarily turbulent or violent environment. Dewatered solids are injected into or immediately above the sand bed. Intense mixing of the sand bed facilitates heat transfer and fuel/air interaction to provide uniform temperatures and thus achieve efficient combustion. FBFs have two significant advantages over MHFs--the comparably lower excess air required, and the ability to operate without supplemental fuel, or autogenously, where dewatered solids provide all the heat needed to maintain temperatures. To operate autogenously, an FBF typically must be coupled with a heat exchanger that preheats combustion air using the waste heat from the furnace flue gas. The third zone in an FBF is the freeboard, which extends from the top of the sand bed to the furnace roof where an outlet duct exhausts the flue gas. Volatile compounds in the dewatered solids or fixed combustible material ejected from the sand bed combust in the freeboard, resulting in a higher temperature than in the sand bed. A well-operated FBF will maintain the freeboard temperature no more than 100C higher than the sand bed. The expanding shell of the FBF, most notably in the freeboard region, achieves high gas residence times. To protect downstream equipment, the FBF roof is equipped with spray water to drop the exhaust temperature to roughly 850C. FBFs achieve lower emissions than MHFs because of the highly turbulent sand bed and uniform temperatures that minimize localized cold spots that can result in incomplete combustion. The most recent federal regulations (Standards of Performance for New Stationary Sources & Emission Guidelines for Existing Sources, 2011) provide more stringent emission limits for FBFs compared with MHFs. From this, one can infer the performance differences from FBFs compared to MHFs. The dynamics in the FBF and MHF differ significantly from furnaces typically employed to treat hazardous or municipal solid wastes. Rotary kiln furnaces handle solid materials well and often are paired with an afterburner to combust volatile compounds. Operating conditions can be analogous to an MHF (Oppelt, 1987). Municipal solid waste can also be incinerated in a sloped moving grate-type furnace (USEPA, 2020a). The EU mandates temperatures shall reach 850C for 2 s (United Kingdom Department for Environment Food & Rural Affairs, 2013). Niessen (2002) provides an extensive discussion on grate type furnaces. Liquid injection hazardous waste furnaces spray or atomize particle-free waste into a burner flame Water Environment Research 93: 826-843, 2021 REVIEW or mix the waste with the supplemental fuel before the burner with operating conditions typical of those used in afterburners coupled with other incineration technologies (Oppelt, 1987). Neither the rotary kiln nor moving grate furnaces will match the turbulence of an FBF and may be more tranquil than an MHF. Long residence times and turbulent conditions in FBFs and MHFs favor more complete combustion. As a result, the combustion efficiency may be higher in SSIs for a given temperature compared with hazardous or municipal solid waste incinerators. Current incineration systems are required to meet emissions criteria with extensive air pollution control measures. All SSIs in the United States known to the authors employ some type of wet scrubber for air pollution control. Sandblom (2014) hypothesized that any PFAS compounds escaping the furnace would be captured in the wet scrubber due to their low pKa values. Many SSIs also include equipment to remove mercury from the flue gas, which requires an activated carbon or sorbent polymer composite (SPC) system. Activated carbon removal of PFAS is well accepted for drinking water applications, and removal can be expected from the gas phase, as well. The SPC mercury removal system has yet to be investigated for PFAS removal efficiency. Some facilities use wet electrostatic precipitators downstream of the wet scrubber to capture fine particulates that could include adsorbed PFAS compounds. Currently, no published work on PFAS removal within an incineration application across the stated pollution control equipment exists. Emerging thermal treatment techniques Several alternative thermal treatment processes for wastewater solids are currently in development or being implemented at a limited scale. Drivers for the evolution of these technologies have been the improved economics of wastewater solids management and energy efficiency; however, they are currently gaining increased attention for their potential as alternative PFAS destruction technologies. However, to date, none of these techniques have been proven to be commercially viable for widespread application with wastewater solids. Thermal drying with combustion systems Wastewater solids can be dried to reduce mass and create a beneficial reuse product. When dried, wastewater solids have a substantial heating value (14,000-21,000 kilojoules per kilogram), similar to that of low-grade coal (Heidrich et al., 2011; NACWA, 2010). Dried product furnaces have been installed in drying facilities to combust the dried product and capture the resulting heat for recycling back to the drying process. These systems contain a primary combustion chamber where dried product is combusted at temperatures of 760-980C, and typically postcombustion of the flue gas (at temperatures up to 1,150C) is performed before treatment and exhaust. The units currently are regulated under the same air emissions requirements as SSIs and require substantial air pollution control processes, typically including urea, alkaline, coke dosing, and textile filtration. Viswanathan et al. (2020) reported on progress in development of a laboratory-scale combustion reactor designed to simulate oxidative conditions similar to those 831 REVIEW occurring in a commercial dried product furnace to measure PFAS destruction, with publication of the results expected shortly. Pyrolysis and gasification Pyrolysis and gasification are thermal decomposition processes that convert solid carbon feedstocks into a combustible gas. Pyrolysis submits carbonaceous materials to high temperatures (200-1,100C) in the absence of oxygen and generates a carbon-rich, porous product called biochar. Gasification introduces a limited quantity of oxidant (typically air) at high temperatures (800-1,650C) to refine the volatile organic fraction through partial oxidation and reforming reactions while converting the solid mass to ash particles. Thermal treatment of wastes in a reductive environment has garnered interest from the waste management sector for its potential to guard against the formation of harmful oxidation by-products such as dioxins and furans (Maric et al., 2020; Rey et al., 2016). The basic pathway for thermal PFAS destruction in a reductive environment is hydrodefluorination (HDF). HDF is the conversion of a carbon-fluorine (C-F) bond into a carbon-hydrogen (C-H) bond and can be performed with a variety of reagents (and catalysts). For the reaction to proceed, the resulting element-fluorine bond formation must be sufficiently exothermic to generate the thermodynamic compensation required for the C-F cleavage, with common reagent elements including H, silicon, or boron (Kuehnel et al., 2013). The process requires a H source for the C-H bond, which often also serves as the fluorine acceptor (Kennedy et al., 1997; Kuehnel et al., 2013). H can be produced during pyrolysis through the steam reforming reaction, where the steam released from the moisture in feed materials generate H through reactions with primary pyrolysis decomposition products (Conesa & Font, 2001; Pinder, 2012; Rey et al., 2016). A variant on the pyrolysis process, called gas-phase reduction (GPR), introduces hydrogen gas directly into the thermal reactor and has been used to break down chlorinated hydrocarbons like polychlorinated biphenyls (PCB) (NRC, 1996). Laboratory-scale studies conducted in Canada to assess the effectiveness of applying GPR to dried biosolids successfully produced hydrogen-enriched methane gas but consumed a similar amount of H2 during the process, indicating that many of the energy recovery benefits of pyrolysis would be offset in GPR unless a well-functioning H recovery system was present (Pinder, 2012). Catalytic hydrogenation, reduction with metals or low-valent metal compounds, has also been proposed for hydrodefluorination of PFAS compounds (Alonso et al., 2002; Lee & Choi, 2002). Wang et al. (2015a) demonstrated transformation efficiencies upward of 80% when submitting a mixture of PFAS and calcium compounds to thermal treatment at temperatures at 600C and higher. Central to the potential for PFAS decomposition in pyrolysis and gasification systems is their ability to maintain PFAS within the hot zone of the reactor before volatilizing and exiting. Organic materials introduced into a pyrolysis reactor undergo various stages of thermal decomposition due to changing feedstock characteristics and moisture content. Studies show that 832 pyrolysis causes PFAS volatilization at temperatures below 450C, while the volatilization of organic feedstocks can require internal temperatures of up to 600C (Gao et al., 2020; Wang, Cousins, et al., 2015). Consequently, typical design parameters related to the residence time of organic feedstocks may not correlate to those required for PFAS destruction, and further study is required to investigate the potential for PFAS transformation concerning reactor design. Limited experimental data are available on PFAS removal during pyrolysis and gasification. Kim et al. (2015) conducted laboratory pyrolysis experiments with wastewater solids at 300 and 700C and found no significant change of residual PFAS concentration in the biochar; however, no discussion was provided on why PFAS were still detected, given general agreement in the literature that PFAS compounds volatilize at temperatures <700C. A pyrolysis technology supplier recently published biochar sampling data from a system operating at 850C that demonstrated PFAS removal to nondetect levels, indicating transformation or volatilization of the compounds (Bioforcetech, 2020). If the PFAS, or partial decomposition products, do volatilize and exit the reactor in the pyrolysis gas, they would likely be submitted to gas combustion applications for energy recovery resulting in further destruction or transformation. While syngas produced from simpler feedstocks such as woody waste and algal biomass has been refined to produce high-value gas or liquid fuels, wastewater solids generate a high load of inorganic contaminants that make internal combustion applications difficult. Consequently, demonstration and commercial scale systems have used a thermal oxidizer to combust the syngas and capture the heat for use in upstream drying processes or conversion to electricity through the organic Rankine cycle (ORC) process. Thermal oxidizers are typically operated to achieve temperatures of 850C or greater for more than 2 s and can achieve a greater degree of efficiency than incineration, given their ability to introduce process gases through or very near the ignition zone. Thermal oxidizers are often permitted for 99.99% emission reduction, and a recent test report of a thermal oxidizer used to control PFAS process stream emissions from an industrial facility demonstrated compliance with this requirement (Focus Environmental Inc., 2020). Consequently, the critical step for achieving PFAS control in pyrolysis and gasification systems may be the operation of the downstream thermal oxidizer. Hydrothermal liquefaction Hydrothermal liquefaction (HTL) subjects solids to high temperatures and pressures (250-350C, 10-25 mega Pascals [MPa]) to generate a liquid biocrude oil. The process is fed dewatered, slurried solids to generate biocrude, suitable for further refining into jet, diesel, and heavy fuels, while retaining an effluent stream with a high ammonia and chemical oxygen demand (COD) load that must be managed (Toor et al., 2011). During laboratory-scale HTL experiments with wastewater solids, Yu et al. (2020) demonstrated varying levels of PFAS degradation based on analysis of the functional groups of the compounds and operational parameters. Greater than 99% Winchell et al. REVIEW Table 2. Relevant bond energies adapted from Tsang et al. (1998) BOND ENERGY, KJ/MOL CF3F 552 CF2F 352 CFF 508 HF 569 FF 159 HOF 216 OF 220 CF3H 456 CF3CF3 408 CH3H 439 transformation efficiency was observed for PFAS compounds with carboxylate functional groups, specifically PFOA, fluorotelomer carboxylic acid (FTCA), and fluorotelomer unsaturated carboxylic acids (FTUCA). Conversely, less than 34% degradation was observed with the sulfonic acid compound PFOS, even when the temperature was elevated to 350C for 90 min. Both the original PFAS compounds and defluorinated intermediary products were found in the biocrude oil fraction, which presents a research need for understanding its resulting fate. The authors proposed potential application of reactive amendments to the HTL process to further promote destruction of recalcitrant PFAS compounds such as PFOS during HTL. Zhang et al. (2020) found that amending a plant biomassfed HTL process with potassium hydroxide (KOH) increased removal of perfluorosulfonic acids from <20% to 86%, indicating the potential efficacy of this strategy. Smoldering combustion Smoldering combustion propagates thermal oxidation by the diffusion of an oxidant (air) through the surface of a condensed liquid or solid fuel. The process can be engineered by mixing fuel with an inert media like sand to promote mass and thermal transfer and introduce a forced, upward airflow (Wang, 2017). Rashwan et al. (2016) reported that self-propagating smoldering combustion can be achieved with wastewater solids having a solids content as low as 20% by modulating the forced airflow to account for process and feed characteristic fluctuations. Major (2019) investigated smoldering combustion of PFAS-laden activated carbon and a simulated waste soil mixture in a Department of Defense (DoD) Strategic Environmental Research and Development Program (SERDP) study. Results reported all PFAS compounds as nondetect levels from the treated product. The process achieved temperatures over 1,000C for one to ten minutes based on separate tests and depending on the location in reactor column. Oxygen concentrations averaged 6%. Where emissions sampling was conducted for the simulated waste soil experiments, 82% of the available fluorine was captured as hydrogen fluoride (HF). The authors acknowledged the remaining available fluorine fraction indicated incomplete PFAS destruction. The presence of both parent PFAS compounds and fluorinated by-products with one less functional group was identified by emissions sampling. However, compounds over nine carbons were Water Environment Research 93: 826-843, 2021 BOND HH OHH CH3H CCl3Cl HCl HOCl ClCl CCl3H CCl3CCl3 ENERGY, KJ/MOL 436 499 439 288 431 235 242 392 301 attributed to material impurities and not by-products. A more recent study was conducted using municipal biosolids and demonstrated PFAS removal to nondetect levels in the solid by-product, although no gas-phase analysis was performed (Kinsman et al., 2020). Documented PFAS Thermal Behavior A significant body of literature exists on PFAS thermal behavior but focuses mostly on laboratory-scale experiments and only considers specific PFAS congeners given analytical limitations. The following organizes the available literature considering first the early theoretical work. Subsequently, this review presents laboratory work used as a basis for current incineration guidelines, full-scale incineration studies, and finally a summary of by-products observed during thermal processing. Theoretical combustion requirements For a combustion process to achieve complete PFAS thermal destruction (mineralization), PFAS compounds would have to be driven to their thermodynamic endpoints of CO2, H2O, HF, or sulfur compounds, if present. The introduction of additional chemical compounds such as salts, minerals, and halogens result in other end products, for example, HF as an end-product from organic fluoride compounds. Additionally, some inert fraction, or ash, of the fuel, or waste, remains as a solid product. The combustion process, while seemingly simple, involves thousands of elementary physical and chemical reactions, reaction kinetics, fluid dynamics, and heat transfer mechanisms (Burgess et al., 1995; Reed, 1978). Residence time, turbulence (mixing), and stoichiometry (the relative mixture of waste to fuel, oxygen, and other gas-phase constituents) within the flame zone all impact the completeness of the combustion process, and consequently, the temperature and destruction efficiency achieved (Lewis, 2008; Niessen, 2002). Given the dynamic nature of the incineration process as well as varying characteristics of input waste streams, operational parameters vary over time throughout the reactor (Lewis, 2008; Tsang et al., 1998). Additionally, the potential exists for flame zone failure modes, with the most notable being thermal quenching by pockets of cold unreacted material and inadequate mixing. Consequently, theoretical investigations into thermal destruction are often based on conservative operational 833 REVIEW assumptions accounting for the occurrence of nonideal conditions in operating systems (Tsang et al., 1998). These conditions lead to the formation of thermal degradation by-products, which are a primary concern in incineration processes. Early theoretical investigations into the potential for thermal destruction of fluorinated organic compounds focused on one- and two-carbon molecules, given the interest in their use as fire extinguishing agents (Burgess et al., 1995; Tsang et al., 1998). In these studies, thermochemical and kinetic data were compiled to develop a framework for future combustion simulation experiments. The thermal and chemical stability data show notably high bond strengths for both C-F and H-F bonds (relevant bond energies identified by Tsang et al. (1998) are provided in Table 2). A high degree of energy is required for cleavage of the C-F bond suggesting that stable fluorinated intermediary products may be produced. The relative stability of intermediary compounds results in less favorable reaction kinetics, which can interrupt or terminate flame chain propagating steps, resulting in the flame-retardant properties of PFAS. Additional research postulated that, due to the relative stability of the compounds, initial decomposition requires unimolecular bond cleavage because fluorinated organics would be less susceptible to bimolecular attack (Tsang et al., 1998). As the fluorinated organics become less saturated, they are more vulnerable to radical attack and reforming reactions. However, Tsang et al. (1998) showed fluorinated organics followed the rule of hydrocarbons in a homologous series--as larger compounds break down into smaller components, those compounds increase in stability. They calculated theoretical temperatures required to achieve 99.99% destruction of various intermediary products in 1 s via unimolecular decomposition, and perfluoromethane (CF4) resulted in the highest predicted temperature required at 1,441C. Destruction of CF4 has been noted in other studies to require temperatures ranging from 1,200 to 1,400C (Beu, 2005; USEPA, 2020c). Given this finding, CF4 has been proposed as a potential surrogate for monitoring emissions from fluorinated organics incineration. Although using CF4 alone may underpredict PFAS destruction efficiency, multiple surrogate compounds should be considered, with representatives covering the diverse chemical properties (i.e. volatility, polarity, and ionic charge) of the chemical family. Thermal destruction guidelines and experimental basis Most published research and industry guidance states that complete destruction of PFAS requires operation at the higher temperature ranges (>1,000C), as summarized in Table 3. Notably, this guidance is based on limited conceptual or laboratory-scale experiments and precedence on previous guidance established for hazardous waste incineration. The baseline research for these recommendations stems from USEPA and other international environmental agency activities. Under the Toxic Substances Control Act (TSCA), the USEPA worked to identify and reduce PFAS exposure from industry, including working with 3M to phase out the use of PFOS in products and facility emissions beginning in 2001 and continuing with the 2010/2015 PFOA Stewardship Program. After 3M's announcement to phase out the manufacture and use of PFOS, the U.S. and the United Kingdom led efforts within the Organization for Economic Co-operation and Development (OECD) to perform a hazard assessment of PFOS in cooperation with other member countries and industry. A final draft of the assessment was published in 2002 and noted that laboratory combustion studies were being conducted on PFOS and two polymeric formulations to assess combustion by-products over a range of temperatures (OECD, 2002). A final report was published the following year (Taylor & Yamada, 2003) discussing results of a simulated hazardous waste incineration experiment with limited air to account for nonideal combustion conditions. The chemicals were submitted in gaseous form to secondary combustion zone temperatures of 600 and 900C using methane as the fuel source (primary reactor temperatures of 1,250C were used to ensure volatilization). Experiments showed <0.4% and 0.05% of the PFOS fed to the reactor were detected in the exhaust at tests conducted at 600 and 900C, respectively, indicating a high degree of removal. While a variety of small molecular weight PICs were identified at 600C, the detection of perfluorinated alkanes was limited to C1 and C2 compounds. Two eight-carbon perfluoroalkyl sulfonamides were also studied to see if they acted as precursors for PFOS after combustion. No PFOS was detected, but some tests detected PICs identified as benzene, tetrafluorosilane, and difluorodimethylsilane. Taylor and Yamada (2003) Table 3. Recent guidance and literature basis for PFAS thermal destruction SOURCE TEMPERATURE NOTED Pancras et al. (2016) 1,000-1,200C Kucharzyk et al. (2017) 1,000C or greater USEPA (2020c) 1,000C UNEP (2019a) 1,100C Ross et al. (2018) ITRC (2020) 1,100C 1,000C or greater COMMENTARY High-temperature incineration is required for complete PFOS degradation High-temperature incineration is required to destroy PFAS adsorbed to spent activated carbon Studies found PFOA is removed to nondetect levels using laboratory-scale combustion experiments Combustion at hazardous waste incineration process parameters (2 s residence time at temperature) is the most appropriate way to handle PFOS waste High temperatures are required for destruction of gasphase PFAS PFAS destruction can be achieved at high temperature 834 Winchell et al. did not expect reformation of PFOS or other long-chain PFAS because the methane fuel provided hydrogen atoms to scavenge fluoride radicals. Yamada et al. (2005) later published a similar laboratory-scale study that considered the combustion of PFAS-impregnated textiles at 1,000C, 85% excess air, and a 2 s residence time. The focus of the study was to ascertain whether combustion of the PFAS-impregnated material would result in PFOA emissions. Neither PFOA nor PICs were detected under nonideal combustion performance measured by a high carbon monoxide emission of 650 part per million (ppm). HF was not detected, but silicon tetrafluoride (SiF4) was, suggesting the HF was reacting with the silica-based lining of the reactor. Consideration has also been given to incineration of activated carbon used for removing fluorinated alkyl compounds from water. A review conducted by Schultz et al. (2003) reported industry correspondence stating that incineration of the saturated activated carbon for 2 s with a combustion chamber reaching temperatures of 1,200C was sufficient for destruction, and the exhaust gas could be scrubbed to produce a solid CaF2 precipitate. Taylor et al. (2014) examined whether combustion of gasified fluorotelomer-based polymer would emit PFOA at 1,000C, in an oxidizing atmosphere, with a 2 s residence time to reflect municipal and medical waste incinerator conditions. No detectable quantities of PFOA were measured in the exhaust gas, and qualitative HF emission suggested complete mineralization occurred. Full-scale incineration studies A few full-scale studies have been published on the fate of PFAS compounds through incineration systems with only two considering an SSI. Loganathan et al. (2007) investigated eight PFAS compounds through two WRRFs. One of the facilities employed incineration, and while not stated in the published information, the furnace was most likely an MHF based on the facility geography. The PFAS compounds were measured in dewatered solids fed to the incinerator and in the ash. No mention was made on the operating conditions of the furnace or whether the bottom or fly ash was sampled. Findings indicated a significant removal of the measured PFAS compounds; however, some compounds were still detected in the ash in the range of single to double digit nanogram per gram concentrations. Concentrations of PFOS, PFOA, perfluorooctane sulfonamide (PFOSA), and perfluorodecanoic acid (PFDA) were all detected in the ash above method detection limits and ranged from 26% to 97% less than values measured in dewatered solids on a concentration basis, except in two samples. Interestingly, two of the ash samples yielded higher PFAS concentrations, one PFOS and one PFOSA, than in the dewatered solids. The authors did not speculate on the reasons for the increased concentrations for these two analytes. A second study is currently underway at an SSI facility employing an FBF (MacGregor, 2020). The temperature and gas residence time within the FBF were reported at 830C and 8 s, respectively. Samples were taken at all inputs and outputs of the SSI system and analyzed quantitatively for 28 PFAS. Only partial results were available at the time of this literature review, restricted to the solids and liquids streams around the SSI. Water Environment Research 93: 826-843, 2021 REVIEW Preliminary results show that mass flows were reduced through the SSI processes for all quantitated PFAS, with the exception of 6:2 fluorotelomer sulfonate. The degree of destruction was not characterized because water used in the air pollution control systems contained PFAS and may mask the levels emitted by the furnace. Release of the ambient air and stack emissions data in the near future will help to further determine the fate of PFAS through the SSI. The authors also noted that the inorganic fluoride content of the wet scrubber discharge water was over 10,000 times that of the influent flow plus the measured PFAS fed to the FBF, assuming mineralization. The authors suggest there are significant loads of nonmeasured PFAS being combusted through the SSI. No other studies have been published on SSIs, but limited information can be found in other industries. Two studies investigated the behavior of polymerized PFAS through incinerators. Lemieux et al. (2007) reported on the USEPA's study of feeding carpet treated with fluorotelomer products into a pilot-scale rotary kiln furnace operating at 952-998C. The emitted PFAS detected, primarily PFOA and perfluorohexanoic acid (PFHxA), did not change between operating with the carpet feed or on natural gas alone, suggesting contamination with fluoropolymers used in sampling or analytical equipment. Aleksandrov et al. (2019) investigated emissions from a pilotscale rotary kiln incinerator with a waste heat boiler and flue gas cleaning compliant with German emissions regulations. The incinerator was fed a mixture of PTFE and wood chips with supplemental natural gas. Two combustion conditions were evaluated with conditions in the afterburner ranging from 870C with 4 s of residence time to 1,020C and 2.7 s of residence time. In either condition, the combined rotary kiln and afterburner excess air was 143%. A total of 31 PFAS compounds were quantified, and 11 were detected in the air emissions but not at significantly different levels than that measured in control runs without PTFE, which suggests sampling and analytical contamination. The authors concluded that incineration of PTFE at the conditions studied would not release PFAS to the environment at measurable levels. Japan's Ministry of Environment (2013) released a report on PFOS behavior through a full-scale municipal solid waste incinerator operating at 1,100C in the rotary kiln and 900C in the afterburner with a combined gas residence time of 8 s and solids residence time in the rotary kiln of 1.0-1.5 h. Flue gas traveled through a wet scrubber and wet electrostatic precipitator to achieve emissions standards. Canisters of firefighting foam with known quantities of PFOS were fed to the incinerator. The overall PFOS destruction efficiency was over 99.999%, considering levels emitted in the flue gas, ash residues, or scrubber water discharge. The report also mentioned that flue gas emissions of fluoric carbons from the furnace, scrubber exhaust, or stack were undetectable, but did not define which compounds were analyzed. Sandblom (2014) sampled the various streams into and out of four municipal solid waste incinerators in Sweden operating at temperatures over 850C. Several of the nine PFAS compounds targeted were measured in the slag and fly ash streams in the single nanogram per gram (ng/g) range with 835 REVIEW perfluorononanoic acid (PFNA) consistently dominating. Levels observed in the wet scrubber discharge ranged from nondetect to single-digit ng/L concentrations. Stack emissions were not characterized. More recently, PFAS destruction of greater than 99.999% for five PFAS through a thermal oxidizer and four-stage scrubbing system was reported at a Chemours chemical facility in North Carolina (Focus Environmental Inc., 2020). The thermal oxidizer treated waste gas streams laden with PFAS at temperatures exceeding 1,000C, though neither residence time nor PICs were noted. A recent study investigating the incineration of PFAS contaminated soils observed extensive destruction (NRC Alaska LLC, 2019). Contaminated soils from a military installation in Alaska were incinerated through a rotary kiln fitted with a secondary combustion chamber. The kiln was operated at 425- 815C with the exact temperature depending on the soil characteristics. The secondary combustion chamber temperature ranged from 980 to 1,200C. No mention of retention times in either the kiln or secondary chamber was noted. Exhaust gases were quenched and filtered in a baghouse. One of the two trials included a packed bed scrubber after the baghouse. Samples of the contaminated and treated soil, exhaust gases, and flue gas scrubbing water were analyzed for specific PFAS compounds. For two test trials, the PFAS was typically nondetect in treated soil samples; however, a few samples did exhibit detectable levels of PFOS or PFHxS. Emissions from the incineration systems exhibited detectable levels of various PFAS but further evaluation found the XAD traps used in the sampling train and the supply water for the scrubbing system both contained background levels of PFAS. The authors concluded the emissions results were impacted and could not completely predict the background contamination in the reported results. Given the limited data provided in the report, a destruction efficiency could not be calculated. Interestingly, inclusion of the packed bed scrubber during the second test did not change PFAS emissions suggesting the PFAS evaluated are not captured in this type of emission control equipment. Solo-Gabriele et al. (2020) studied PFAS in landfill leachate; three leachates came from landfills dominated by MSW ash. A statistically significant correlation between the concentration of PFAS in the leachate from landfills with ash and the operating temperature range of the incinerator (R2 = 0.92, p = 0.008) was observed. The lowest total PFAS concentrations (<3,400 ng/L) were found in leachate from ash where the incinerators operated between 930 and 980C. The incinerator with the lowest operating temperatures (760-870C) exhibited the highest PFAS leachate concentrations (12,300-13,500 ng/L). The third landfill, dominated by MSW ash supplied by an incinerator operating in the range of 815-870C, had total PFAS from 8,400 to 8,700 ng/L. The main difference between the two leachates from ash originating from incinerators operating in lower temperature ranges was perfluorobutane sulfonate (PFBS). The four-carbon PFAS was highest (roughly 5,000 ng/L) in the low-temperature versus the mid-temperature incinerator by approximately 350 ng/L. The authors proposed the lower temperature incineration may be producing shorter 836 chain PFAS instead of proportionately destroying all PFAS. The study did not disclose the type of furnace used at these facilities or additional operating conditions beyond temperature. Where full-scale incineration of PFAS-laden wastes at hazardous waste conditions has been investigated, it is important to note that wastes are highly concentrated (e.g., spent activated carbon used for aqueous PFAS removal and aqueous firefighting foam). The Resource Conservation and Recovery Act (RCRA) labels a waste "hazardous" when it contains at least 0.1% percent of a halogenated organic chemical. For comparison, the highest levels of a PFAS compound (PFOS) identified in wastewater solids, given substantial contributions from an industrial discharger, is 0.0005% percent (Sun et al., 2011; USEPA, 2005; Yu et al., 2009). Thermal by-product formation Reports of PFAS treatment using thermal technologies on a variety of matrices provides some indication of potential thermal degradation by-products. Many bench and pilot studies have looked at the decomposition of specific PFAS congeners and by-product identification. By-product identification is complicated by the broad characteristics involving polar or nonpolar, anionic, cationic, or zwitterionic, and volatile, semi-volatile, or nonvolatile forms PFAS can take, so not all by-products can be detected. Several studies identified thermal PFAS degradation by-products as summarized in Table 4. These studies show that PFAS will decompose at temperatures relevant to operating conditions of SSIs although by-product formation will be a concern. These studies demonstrate that an array of by-products is possible during thermal treatment of PFAS. Given the diverse chemical species potentially formed as by-products, the currently available analytical methods based on a small number of targeted PFAS compounds are inadequate for following the fate of PFAS through thermal processes. Little is currently known regarding the formation pathways for by-products from PFAS combustion. Burgess et al. (1995) presented theoretical pathways for one- and two-carbon fluorinated species. Even when limiting consideration to these two simplest PFAS, the possible degradation products and intermediates are extensive. The study considered the formation of longer-chain compounds from simpler radicals suggesting reformation is possible. Garca et al. (2007) proposed PTFE would decompose to tetrafluroethene (C2F4) under reducing conditions and potentially reform as C3F6, which would then combust to CF4. No further discussion on reformation of PFAS or other compounds of concern from PFAS combustion was identified in available literature. The formation of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) in incineration systems may provide a valuable analogy, keeping in mind that the bond energies reported in Table 2 indicate large differences between C-Cl and C-F bonds. The PCDD/PCDF compounds are typically not present in wastewater solids but are often detected in incinerator emissions. McKay (2002) provides an extensive review of PCDD/PCDF emissions from municipal solid waste incineration. Formation of PCDD/PCDF Winchell et al. compounds was noted at approximately 400C, which is not a typical temperature for SSI operations unless the facility includes a waste heat boiler. Two formation pathways likely for PCDD/ PCDF formation include: (a) precursor compounds from incomplete combustion of chlorobenzenes and chlorophenols or (b) de novo pathway forming PCDD/PCDF from simpler compounds in the flue gas. Either pathway requires chlorine to halogenate the complex organic molecules. Furthermore, ash from wastewater incinerators has been shown to promote PCDD/PCDF formation if chlorine is present, or catalyze oxidation in its absence (Fullana et al., 2004). The complex chemistry in incineration systems may promote similar formations for PFAS-related compounds and will require further study to determine pathways to measured end products. Prospective SSI PFAS Fate Despite their reputation, PFAS compounds will combust during incineration. Early laboratory-scale work by Taylor and Yamada (2003) showed that PFOS will combust in a nonturbulent laboratory-scale reactor within the same temperature range that an SSI operates. Aleksandrov et al. (2019) conducted thermogravimetric analyses (TGA) of PTFE that exhibited complete destruction in <1 s at 800C, similar to SSI temperature regimes. Khan et al. (2020) calculated a PFOS half-life of 0.2 s at 726C. MacGregor (2020) reported PFAS is being destroyed through an FBF SSI (830C for 8 s) based on mass flows into and out of the incineration system though the stack emissions have yet to be characterized. At higher temperatures, more typical of hazardous waste incinerators, significant PFAS destruction has been reported for a variety of congeners (Focus Environmental Inc., 2020; Lemieux et al., 2007; Ministry of the Environment of Japan, 2013; NRC Alaska LLC, 2019; Taylor et al., 2014; Yamada et al., 2005). The existing published literature is too narrow to determine whether all PFAS combust under incineration conditions given analytical limitations. Further, the potential reduction in combustion efficiency of the studied PFAS at typical SSI temperatures has not been characterized. However, given the turbulent environments and long residence times of the FBF and MHF at least some destruction is expected to occur. The type of PFAS may also determine combustion efficiency within an incinerator. In contrast to the PFAS mentioned in the previous paragraph, CF4 may require over 1,400C for complete destruction (Tsang et al., 1998). In the case of the investigation by Loganathan et al. (2007), nonpolymeric PFAS (PFHxS, PFNA, PFOA, PFOS, PFOSA, PFDA, perfluoroundecanoic acid [PFUnDA], and perfluorododecanoic acid [PFDoDA]) would have likely dominated the incinerator feed, which resulted in some PIC levels in the ash. By comparison, both Lemieux et al. (2007) and Aleksandrov et al. (2019) studied systems deliberately incinerating polymeric forms of PFAS and did not observe any significant PIC formation. Likewise, Taylor et al. (2014) indicated the combustion of a fluorotelomer-based polymer produced no PICs. While there is inadequate information available to verify a trend, polymeric PFAS may combust more efficiently than nonpolymer forms. Water Environment Research 93: 826-843, 2021 REVIEW Formation of PICs during PFAS incineration at temperatures achieved in SSIs has not been well documented. In the SSI study by Loganathan et al. (2007), some ash samples reported higher levels of PFAS than that measured in the wastewater solids fed to the incinerator. If the volatile solids content of the wastewater solids fed to the incinerator was over 65% then despite the high concentrations in the ash the overall mass of each PFAS was reduced. Otherwise, this may be a result of sampling time and wastewater solid PFAS variability, transformation of precursor compounds to the measured PFAS, or sampling and analytical contamination. In studies of other combustion systems, contamination has been suggested as the source of quantifiable PICs in ash, air emissions, and scrubber water (Aleksandrov et al., 2019; Lemieux et al., 2007; NRC Alaska LLC, 2019). However, Sandblom (2014) and Solo-Gabriele et al. (2020) reported ash PFAS levels from MSW incinerators operating with similar temperature ranges as SSIs. SSIs, especially the FBF, will promote more turbulence than a typical moving grate incinerator used in MSW incineration and may therefore increase the relative level of PFAS destruction. Lastly, the available work only concerns PFAS that can be quantified, leaving unaccounted the vast majority of PFAS. Overall, no incineration system is 100% efficient, but the level of PICs released by SSIs is likely low compared to other environmental PFAS contamination pathways and whatever reduction occurs results in an overall reduction in global PFAS environmental discharge. Characterizing PICs will provide the necessary context for concern from both a public health and a greenhouse gas (GHG) perspective. For example, while CF4 has been identified as a potential PIC with a high GHG impact but no health concerns, potential emission rates from an SSI are low. If a large urban SSI facility processing 100 dry tons per day converted 50% of the PFAS load to CF4, the unchecked emissions would be equivalent to the emissions of one passenger vehicle. This estimate assumed the PFAS wastewater solids content based on New England Biosolids and Residuals Association (NEBRA) and New Hampshire Department of Environmental Services (NHDES) PFAS sampling data summarized by Rainey (2019). As environmental and legislative bodies have introduced calls to ban SSI operation due to concerns over the impact of PICs, understanding the makeup and levels emitted would provide necessary data for the developing regulatory landscape. The PFAS content of wastewater solids and characteristics thereof must also be taken into consideration in context to other incineration operations. Incinerating PFAS compounds with hydrocarbon-rich fuel sources may improve destruction efficiency. Narengerile et al. (2010) calculated the destruction of hydrofluorocarbons in thermal plasma with and without water. In the presence of water, which supplied hydrogen and oxygen radicals, fluorocarbon by-products were eliminated. Watanabe et al. (2018) observed more than a 20% increase in recovered mineralized fluorine when adsorbed to GAC compared with thermally treating the PFAS reagents alone at 700C in a nitrogen atmosphere. The chemistry with GAC or other hydrocarbon fuels may be responsible for the enhanced PFAS destruction. Wang et al. (2013) observed higher PFOS destruction rates 837 Winchell et al. 838 Table 4. PFAS thermal degradation by-products reported REFERENCE NRC Alaska (2019) PARENT PFAS PFOS and PFOA (measured in contaminated soil sample) Major (2019) PFOA, PFOS, PFHxS, PFNA, PFBS, and PFHpA TREATMENT TEMPERATURE 425-815C (kiln) 980-1,200C (secondary combustion) 1,000C Watanabe et al. (2018) PFOA, PFHxA, PFOS (on GAC) 700C Watanabe et al. (2016) Garca et al. (2007) Yamada et al. (2005) PFOA, PFHxA (on GAC) PFOS (on GAC) PTFE Fluorotelomer-based acrylic polymer (C0.33H 0.40O0.04F0.19Cl0.04) 800C 900C 1,000C 700-1,000C 750C 850C 950C 1,050C 600C 1,000C Krusic et al. (2005) Krusic and Roe (2004) Ellis et al. (2003) Taylor and Yamada (2003) Ellis et al. (2001) Treated polyester fiber (2% F by weight) PFOA Ammonium PFOA PTFE PFOS PTFE 725C 307C 355-385C 196-234C 550C 600C 900C 500C ATMOSPHERE Oxidizing Oxidizing Reducing Reducing Oxidizing Oxidizing Vacuum Vacuum Oxidizing Oxidizing Oxidizing Conesa and Font (2001) PTFE Simon and Kaminsky (1998) PTFE 700C 500-600C Oxidizing Reducing Reducing FLUORINATED BY-PRODUCTS NOTEDA PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFDoA, PFTeA, PFBS, FOSA, PFUnA, PFHxS, PFOS, NMeFOSAA, NEtFOSAA, 6:2 FTS PFBA, PFBS, PFPeA, PFHxA, PFHxS, PFHpA, PFOA, PFOS, PFNA, PFDA, PFUnA, PFDoA Incomplete balance suggests volatile organofluoro compounds PFPeA, PFBA PFBA None None CF4, C2F6, benzoyl fluoride CF4, C2F6 CF4, C2F6, C3F6, benzenepentafluoro CF4, C2F6, benzenepentafluoro Flurobenzene, difluorobenzene, CF3, CF2CH=CH2 CF3, CF2CH=CH2 CF3 Perfluoro-1-heptene 1-H-perfluoroheptane, perfluoro-1-heptene 1-H-perfluoroheptane fluoroacids CF4 or C2F6 (postulated), 1,1-difluroethene CF4 or C2F6 (postulated) Tetrafluoroethene, hexafluoropropene, trifluoroacetate, cyclo-octafluorobutane, CF3(CF2)nCOOH, CF3O(CF2)mCOOH, monofluoracetic acid, difluoroacetic acid C2F2, C2F4, CF4, CHF3, CH2F2, C2F6, CFO, CH2F2, cyclo-C4F8, C3F3 same Trifluroethylene, hexafluroproprene, cyclo-octafluorobutane (Continues) REVIEW Table 4. (Continued) REFERENCE Jun et al. (1995) Baker and Kasprzak (1993) PARENT PFAS PTFE PTFE TREATMENT TEMPERATURE 510-600C 400C ATMOSPHERE Reducing Oxidizing Reducing Vacuum Not identified Reducing Reducing FLUORINATED BY-PRODUCTS NOTEDA Tetrafluoroethylene, hexafluroproprene, cyclo-octafluorobutane Tetrafluoroethylene, hexafluropropylene, trifluoroacetyl fluoride, fluoroform, perfluoroisobutylene hexafluropropylene, perfluoroisobutylene Fluoroacetyl fluoride Perfluoroalkenes, hydrogen fluoride Perfluoroalkenes Carbonyl fluoride Tetrafluoroethylene Water Environment Research 93: 826-843, 2021 Blake and Tomlinson (1971) Sheppard and Sharts (1969), Kissa (2001) Scheel et al. (1968) Lewis and Naylor (1947) Fluoroacetic acid Perfluoroalkanoic acid Perfluoroalkanoic potassium salt PTFE PTFE 295-382C 550C 165-200C 550C 600-700C ACompound acronym definition can be found in the source reference. REVIEW when subjecting lime-treated wastewater solids to 300C compared with adding calcium hydroxide to PFOS alone (Wang et al., 2011). The authors speculated the enhanced thermal degradation could be due to catalyzing metals in the wastewater solids. Taylor and Yamada (2003) hypothesized that PFOS combustion with methane provides the required hydrogen atoms to scavenge fluorine radicals to prevent PFAS reformation. Yamada et al. (2005) observed combustion temperatures required for no PIC formation were lower with a PFAS-impregnated textile compared with the PFAS alone. Because the level of PFAS in biosolids is several orders of magnitude less than that required for RCRA hazardous waste classification and lower than MSW (Sanborn Head, 2019), PFAS destruction through an SSI may outperform other incineration industries, especially given the characteristics of the wastewater solids. For those SSIs using an adsorption technology for mercury removal (i.e., activated carbon or SPC), further PFAS removal is also expected. Activated carbon represents one of the main treatment technologies applied to aqueous streams (Horst et al., 2018). Activated carbon is widely used in incinerators, including SSIs, to remove organic pollutants such as PCDDs and PCDFs from flue gas (Niessen, 2002). The relatively new SPC technology marketed for mercury and sulfur dioxide removal may also remove PCDDs and PCDFs, which is just being explored (EnviroCare International & personal communication, 2020). The potential PFAS removal provided by these air pollution control technologies would further reduce environmental release from an SSI. Research Needs The current scientific knowledge on the behavior of PFAS through thermal processes is limited and requires additional study to understand how to best address public concerns and best practices for disposing of contaminated material. A nearterm study on the fate of PFAS through SSIs, like the study being finalized by MacGregor (2020) but looking at both MHF and FBF technologies is crucial and recommended. Sampling and analytical techniques that are available for identifying a broad spectrum of PFAS will be useful in developing a materials balance for such a study (Winchell et al., in review). While these initial full-scale studies will provide the gross fate of PFAS through SSIs and assist regulators and policy makers to respond to public pressure, additional research will be required to better understand the mechanisms behind the observed SSI performance and subsequently develop implementable solutions. One of the more basic areas of research needed is identifying the diversity of PFAS present in wastewater solids. As noted in Table 2, theoretical calculations (Burgess et al., 1995; Tsang et al., 1998) and laboratory data (Taylor & Yamada, 2003; Yamada et al., 2005) both illustrate the impacts of PFAS chemical structure on thermal degradation. Simply stated, thermal conditions for destruction will in part depend on the specific PFAS present. As analytical techniques develop, improved characterization of the PFAS in wastewater solids will provide the industry with key compounds to target in development and operation of treatment methods. 839 REVIEW Additional research must also focus on the nature of thermal degradation of PFAS under SSI operating conditions. Existing research has largely focused on operating conditions in hazardous waste incinerators, which differ from SSIs. Table 1 summarizes the different operating conditions between several types of incinerators. Although SSIs operate at lower temperatures than hazardous waste facilities, the SSI often use longer residence times and higher turbulence critical to PFAS destruction. Laboratory and pilot-scale research focused on MHF and FBF technologies, under controlled and representative conditions, would provide immensely valuable information on PFAS destruction efficiency. In part, these scaled down studies can evaluate different operating conditions for optimizing PFAS destruction without creating issues with other pollutant emissions or treatment goals. Additional research should also focus on the complex combustion chemistry resulting from use of wastewater solids as a fuel source. Several studies have indicated using hydrocarbon fuel sources increases PFAS destruction efficiency (Taylor & Yamada, 2003; Yamada et al., 2005). Others observed positive impacts from the addition of calcium (Wang et al., 2013). Further research may identify catalysts to enhance PFAS destruction and lead to engineered solutions. Emerging thermal treatment technologies, such as hydrothermal liquefaction or pyrolysis, operate under different conditions compared with existing SSIs. Given these technologies are under active development, their performance regarding PFAS destruction is also unknown. These technologies require separate research directives but can also be complementary to SSI research. Based on the emerging technologies discussed in this review, one key area differentiated from SSIs will be PFAS thermal degradation in the absence of or in substoichiometric oxygen conditions. Conclusions Thermal treatment of PFAS through an SSI represents a potential wastewater solids process for destroying PFAS; however, significant questions remain regarding both the destruction efficiency and potential formation of undesirable by-products. While nearly complete PFAS decomposition has been demonstrated at temperatures representative of SSI operation, byproducts have also been observed. Temperature is only one of the three primary parameters when assessing destruction capacity in combustion systems, the other two being residence time and turbulence. A well-functioning SSI will submit PFAS to greater residence times and mixing (or turbulence) than the laboratory-scale research performed to date, further promoting PFAS destruction. If PFAS parent compounds are recalcitrant or PICs are formed, they will be subjected to air pollution control equipment, which will likely capture an additional fraction of PFAS compounds. Consequently, a critical near-term need exists to evaluate the fate of PFAS through full-scale SSIs to understand the fate of the PFAS in the wastewater solids and identify PICs in stack emissions and air pollution control residual streams. Initial testing should focus on sites representative of SSI industry 840 operating conditions and configurations. Subsequent fullscale testing must consider operational changes or various air pollution control technologies to minimize PFAS emissions. Furthermore, an extensive database on PFAS content in wastewater solids at incineration facilities would inform the utilities of their PFAS loadings. Results should be compared among studied emissions to ascertain site-specific risks. Any of these research objectives must incorporate emerging analytical techniques to characterize the PFAS to the fullest extent, while using sampling techniques capable of collecting polar and nonpolar, as well as volatile, nonvolatile, and semi-volatile PICs. A comprehensive review of the sampling and analytical techniques available for utilizing these emerging techniques has been prepared separately (Winchell et al., in review). Conflicts of Interest In submitting this manuscript, the authors do not have any conflicts of interest or other considerations that would limit publication of the manuscript. Martha J.M. Wells is a chemical consultant to Brown and Caldwell and served in that role while assisting with preparation of this manuscript. Data Availability Statement Data sharing is not applicable to this article as no datasets were generated or analyzed during the current study. References Albertson, O. E. (1992). Sludge incineration: Thermal destruction of residues (manual of practice FD-19) (1st ed.). : Water Environment Federation. Aleksandrov, K., Gehrmann, H. J., Hauser, M., Mtzing, H., Pigeon, D., Stapf, D., & Wexler, M. (2019). Waste incineration of Polytetrafluoroethylene (PTFE) to evaluate potential formation of per- and Poly-Fluorinated Alkyl Substances (PFAS) in flue gas. Chemosphere, 226, 898-906. https://doi.org/10.1016/j.chemo sphere.2019.03.191 Alonso, F., Beletskaya, I. P., & Yus, M. (2002). 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Thermal degradation of fluorotelomer treated articles and related materials. Chemosphere, 61(7), 974-984. https://doi.org/10.1016/j.chemosphere.2005.03.025 REVIEW Yin, K., Gao, X., Sun, Y., Zheng, L., & Wang, W. (2013). Thermal degradation of hexachlorobenzene in the presence of calcium oxide at 340-400C. Chemosphere, 93(8), 1600-1606. https://doi.org/10.1016/j.chemosphere.2013.08.014 Yu, J., Hu, J., Tanaka, S., & Fujii, S. (2009). Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in sewage treatment plants. Water Research, 43(9), 2399- 2408. https://doi.org/10.1016/j.watres.2009.03.009 Yu, J., Nickerson, A., Li, Y., Fang, Y., & Strathmann, T. J. (2020). Fate of per- and polyfluoroalkyl substances (PFAS) during hydrothermal liquefaction of municipal wastewater treatment sludge. Environmental Science: Water Research & Technology, 6(5), 1388-1399. https://doi.org/10.1039/c9ew01139k Zhang, W., Cao, H., Mahadevan Subramanya, S., Savage, P., & Liang, Y. (2020). Destruction of perfluoroalkyl acids accumulated in Typha latifolia through hydrothermal liquefaction. ACS Sustainable Chemistry & Engineering, 8, 9257-9262. https://doi. org/10.1021/acssuschemeng.0c03249 Water Environment Research 93: 826-843, 2021 843 Interim Guidance on the Destruction and Disposal of Perfluoroalkyl and Polyfluoroalkyl Substances and Materials Containing Perfluoroalkyl and Polyfluoroalkyl Substances INTERIM GUIDANCE FOR PUBLIC COMMENT DECEMBER 18, 2020 The contents of this document do not have the force and effect of law and are not meant to bind the public in any way. This document is intended only to provide clarity to the public regarding existing requirements under the law or agency policies. This guidance is not intended to, and does not, create any right or benefit, substantive or procedural, enforceable at law or in equity by any party against the United States, its departments, agencies, or entities, its officers, employees, or agents, or any other person. Contents 1. Introduction.................................................................................................................................................... 1 1.a Statutory requirement.........................................................................................................................................1 1.b Scope, significance, and use of interim guidance document................................................................1 1.b.i PFAS and PFAS-containing materials identified in the FY 2020 NDAA.......................... 2 1.b.ii Guidance scope ...................................................................................................................................... 3 1.c Destruction and disposal technologies addressed in this interim guidance ................................4 1.d Summary of destruction and disposal interim guidance ......................................................................4 2. Description of PFAS-Containing Materials Identified in the FY 2020 NDAA ........................... 9 2.a Solid, liquid, or gas waste streams containing PFAS from facilities manufacturing or using PFAS ................................................................................................................................................................ ...................... 9 2.a.i Solid phase wastes ............................................................................................................................. 10 2.a.ii Liquid phase wastes .......................................................................................................................... 11 2.a.iii Gas phase wastes ................................................................................................................................ 11 2.b Aqueous film-forming foam ........................................................................................................................... 18 2.c Soils and biosolids.............................................................................................................................................. 20 2.d Textiles, other than consumer goods, treated with PFAS .................................................................. 22 2.e Spent water treatment materials................................................................................................................. 22 2.e.i Activated carbon ................................................................................................................................. 23 2.e.ii Ion exchange resins ........................................................................................................................... 23 2.e.iii High-pressure membranes (reverse osmosis and nanofiltration).................................24 2.f Landfill leachate containing PFAS ............................................................................................................... 24 2.g Summary ................................................................................................................................................................ 25 2.h References ............................................................................................................................................................. 25 3. Technologies for the Destruction and Disposal of PFAS and PFAS-Containing Materials ........................................................................................................................................................33 3.a Thermal treatment............................................................................................................................................. 33 3.a.i Types of thermal treatment............................................................................................................ 34 3.a.ii Ability of thermal treatment technologies to destroy PFAS .............................................39 3.a.iii Other thermal treatment byproducts of concern .................................................................. 41 3.a.iv Potential for releases for thermal treatment technologies ...............................................42 3.a.v Testing and monitoring....................................................................................................................43 3.a.vi Uncertainties/unknowns ................................................................................................................ 45 INTERIM GUIDANCE FOR PUBLIC COMMENT Introduction i 3.a.vii Treatment costs and commercial availability.........................................................................46 3.a.viii Summary ................................................................................................................................................49 3.a.ix References for Section 3.a ............................................................................................................... 50 3.b Landfills .................................................................................................................................................................. 55 3.b.i Types of landfills .................................................................................................................................56 3.b.ii Ability of engineered landfill components to contain PFAS..............................................58 3.b.iii Leachate discharge controls...........................................................................................................60 3.b.iv Landfill gas emission controls ....................................................................................................... 66 3.b.v Potential for releases during landfilling....................................................................................67 3.b.vi Testing and monitoring....................................................................................................................67 3.b.vii Uncertainties/unknowns ................................................................................................................ 68 3.b.viii Treatment costs...................................................................................................................................68 3.b.ix Summary ................................................................................................................................................ 71 3.b.x References for Section 3.b...............................................................................................................72 3.c Underground injection ..................................................................................................................................... 76 3.c.i Types of wells....................................................................................................................................... 76 3.c.ii Siting, engineering, and operational controls .........................................................................77 3.c.iii Availability and costs ........................................................................................................................79 3.c.iv Testing and monitoring.................................................................................................................... 81 3.c.v Uncertainties/unknowns ................................................................................................................81 3.c.vi Summary ................................................................................................................................................ 82 3.c.vii References for Section 3.c ............................................................................................................... 82 4. Considerations for Potentially Vulnerable Populations Living Near Likely Destruction or Disposal Sites .................................................................................................................83 4.a Potential releases from destruction and disposal facilities .............................................................. 83 4.b Potentially vulnerable populations............................................................................................................. 84 4.c PFAS and vulnerability..................................................................................................................................... 86 4.d Considering vulnerability................................................................................................................................ 87 4.d.i Identifying potentially vulnerable populations .....................................................................87 4.d.ii Incorporating vulnerability into risk assessment.................................................................87 4.d.iii Considerations for community engagement ...........................................................................88 4.e References ............................................................................................................................................................. 89 INTERIM GUIDANCE FOR PUBLIC COMMENT Introduction ii 5. Planned Research and Development on Destruction and Disposal Technologies for PFAS and PFAS-Containing Materials ..................................................................................................91 5.a Research needs.................................................................................................................................................... 91 5.b Current federal research and development activities......................................................................... 92 5.c Near-term EPA research and development initiatives ....................................................................... 93 5.d Longer-term EPA research and development initiatives................................................................... 96 5.e Data and information needs to inform future guidance updates ................................................... 96 5.f References ............................................................................................................................................................. 97 INTERIM GUIDANCE FOR PUBLIC COMMENT Introduction iii Tables Table 1-1. Destruction and Disposal Technologies Discussed in This Guidance, with Examples of PFAS-Containing Materials.................................................................................................................................................. 4 Table 2-1. Examples of PFAS Waste Streams by Industry Type ........................................................................12 Table 2-2. Examples of AFFF Users and Locations in the United States.........................................................19 Table 2-3. Biosolids Generation and Management in 2019 ................................................................................. 21 Table 3-1. Estimated Costs to Incinerate Different Types of Hazardous Waste (U.S. EPA, 2005a).....47 Table 3-2. Estimated Costs to Incinerate Different Types of Non-Hazardous Waste................................47 Table 3-3. Example Disposal/Reactivation Costs for Spent GAC for Drinking Water Treatment (Derived from U.S. EPA, 2020a).......................................................................................................................................48 Table 3-4. Required Environmental Controls by Landfill Type..........................................................................56 Table 3-5. Average PFAS Concentrations in Different Types of Landfill Leachate Reported in Published Studies ..................................................................................................................................................................57 Table 3-6. Existing Landfill Leachate Treatment Technologies for PFAS Removal or Destruction ....62 Table 3-7. Average MSW Tipping Fees per Ton for States and Regions (EREF, 2019) ............................69 Table 3-8. Average State-Level Wastewater Treatment Prices for Large Industrial Consumers with an 8-Inch Wastewater Meter (DOE, 2017)..................................................................................................................70 Table 3-9. Inventory of Permitted Class I Non-Hazardous and Hazardous Waste Wells in the United States (FY 2018; Source: EPA) .........................................................................................................................................80 INTERIM GUIDANCE FOR PUBLIC COMMENT Introduction iv Figures Figure 1-1. FY 2020 NDAA Section 7361. ...................................................................................................................... 1 Figure 1-2. Generation of PFAS materials identified in the FY 2020 NDAA.................................................... 2 Figure 3-1. Engineered landfill components and potential PFAS release pathways.................................59 Figure 3-2. Class I well.........................................................................................................................................................76 Figure 3-3. States with Class I non-hazardous or hazardous waste injection wells..................................79 Figure 4-1. Conceptual model providing examples of potential releases from destruction and disposal of PFAS-containing materials, which the technologies covered in this guidance could help to control...................................................................................................................................................................................84 INTERIM GUIDANCE FOR PUBLIC COMMENT Introduction v Abbreviations AFFF ARFF BEA BDL BLS BOHP/UV C CAA C2F6 C3F8 CaF2 C&D CaO Ca(OH)2 CDR CEPCI CF4 CFR CHF3 CIC CI/MS CKD DoD DOE DRE EIA EJ EPA ESTCP F FAA FBC FF FML FTIR FTOH FY 2020 NDAA GAC GCCS GDP GHGRP aqueous film-forming foam aircraft rescue firefighting Bureau of Economic Analysis below detection limit Bureau of Labor Statistics petitjeanite (Bi3O(OH)(PO4)2) microparticle ultraviolet Celsius Clean Air Act hexafluoroethane octafluoropropane calcium fluoride construction and demolition calcium oxide calcium hydroxide Chemical Data Reporting Chemical Engineering Plant Cost Index carbon tetrafluoride Code of Federal Regulations fluoroform combustion-ion chromatography chemical ionization mass spectrometry cement kiln dust Department of Defense Department of Energy destruction and removal efficiency Energy Information Administration environmental justice United States Environmental Protection Agency Environmental Security Technology Certification Program Fahrenheit Federal Aviation Administration fluidized bed combustor fabric filter flexible membrane liner Fourier transform infrared spectrometry fluorotelomer alcohol National Defense Authorization Act for Fiscal Year 2020 granular activated carbon gas collection and control system gross domestic product Greenhouse Gas Reporting Program INTERIM GUIDANCE FOR PUBLIC COMMENT Introduction vi H2O2 HAP HF HWC HWI kGal LFG LWAK MF MnO2 MSW MWC NADP NASA NESHAP NF ng/L NIOSH NMOC NPDES NSPS NTA ODS OECD OTM PAC PBPK PCB PFAA PFAS PFBS PFOA PFOS PVDF PIC PIGE PITT POTW ppmv PTFE RCRA RDF RO hydrogen peroxide hazardous air pollutant hydrogen fluoride hazardous waste combustor hazardous waste incinerator thousand gallons landfill gas lightweight aggregate kiln microfiltration manganese(IV) oxide municipal solid waste municipal waste combustor National Atmospheric Deposition Program National Aeronautics and Space Administration National Emission Standards for Hazardous Air Pollutants nanofiltration nanograms per liter National Institute for Occupational Safety and Health nonmethane organic compound National Pollutant Discharge Elimination System New Source Performance Standards non-targeted analysis ozone-depleting substance Organization for Economic Cooperation and Development Other Test Method powdered activated carbon physiologically based pharmacokinetic polychlorinated biphenyl perfluoroalkyl acid perfluoroalkyl and polyfluoroalkyl substances perfluorobutanesulfonic acid perfluorooctanoic acid perfluorooctane sulfonate polyvinylidene fluoride or polyvinylidene difluoride product of incomplete combustion particle-induced gamma emission spectrometry PFAS Innovative Treatment Team publicly owned treatment works parts per million by volume polytetrafluoroethylene Resource Conservation and Recovery Act refuse-derived fuel reverse osmosis INTERIM GUIDANCE FOR PUBLIC COMMENT Introduction vii SDA SDWA SERDP SSI STAR TOF TRI TSCA UF UIC U.S.C. USDW VOC WWTP XPS spray dryer absorber Safe Drinking Water Act Strategic Environmental Research and Development Program sewage sludge incinerator Science to Achieve Results total organic fluorine Toxics Release Inventory Toxic Substances Control Act ultrafiltration underground injection control United States Code underground source of drinking water volatile organic compound wastewater treatment plant X-ray photo-electron spectroscopy INTERIM GUIDANCE FOR PUBLIC COMMENT Introduction viii 1. Introduction 1.a Statutory requirement The National Defense Authorization Act for Fiscal Year 2020, Public Law No: 116-92 (hereafter, "FY 2020 NDAA"), was signed into law on December 19, 2019. Section 7361 of the FY 2020 NDAA (see text in Figure 1-1) directs the U.S. Environmental Protection Agency (EPA) to publish interim guidance on the destruction and disposal of perfluoroalkyl and polyfluoroalkyl substances (PFAS) and materials containing PFAS not later than one year from the date of enactment of the FY 2020 NDAA. This interim guidance fulfills that direction. EPA will review the interim guidance at least every 3 years and revise it, if appropriate based on the availability of new information or other factors. SEC. 7361. PFAS DESTRUCTION AND DISPOSAL GUIDANCE. (a) IN GENERAL.--Not later than 1 year after the date of enactment of this Act, the Administrator shall publish interim guidance on the destruction and disposal of perfluoroalkyl and polyfluoroalkyl substances and materials containing perfluoroalkyl and polyfluoroalkyl substances, including-- (1) aqueous film-forming foam; (2) soil and biosolids; (3) textiles, other than consumer goods, treated with perfluoroalkyl and polyfluoroalkyl substances; (4) spent filters, membranes, resins, granular carbon, and other waste from water treatment; (5) landfill leachate containing perfluoroalkyl and polyfluoroalkyl substances; and (6) solid, liquid, or gas waste streams containing perfluoroalkyl and polyfluoroalkyl substances from facilities manufacturing or using perfluoroalkyl and polyfluoroalkyl substances. (b) CONSIDERATIONS; INCLUSIONS.--The interim guidance under subsection (a) shall-- (1) take into consideration-- (A) the potential for releases of perfluoroalkyl and polyfluoroalkyl substances during destruction or disposal, including through volatilization, air dispersion, or leachate; and (B) potentially vulnerable populations living near likely destruction or disposal sites; and (2) provide guidance on testing and monitoring air, effluent, and soil near potential destruction or disposal sites for releases described in paragraph (1)(A). (c) REVISIONS.--The Administrator shall publish revisions to the interim guidance under subsection (a) as the Administrator S. 1790--1093 determines to be appropriate, but not less frequently than once every 3 years. Figure 1-1. FY 2020 NDAA Section 7361. 1.b Scope, significance, and use of interim guidance document This interim guidance presents currently available information on PFAS destruction and disposal. It provides information on the current state of the science and the associated uncertainties for current commercially available disposal or destruction technologies. This interim guidance highlights what major uncertainties, if resolved, would allow for specific recommendations in the future. The present document describes several options to manage PFAS waste that may destroy or control its migration INTERIM GUIDANCE FOR PUBLIC COMMENT Introduction 1 into the environment should destruction or disposal be required at this time. However, there remain several important data gaps, which this document describes. Consistent with the FY 2020 NDAA, it is organized as follows: Section 2: Description of PFAS-Containing Materials Identified in the FY 2020 NDAA Section 3: Technologies for the Destruction and Disposal of PFAS and PFAS-Containing Materials Section 4: Considerations for Potentially Vulnerable Populations Living Near Likely Destruction or Disposal Sites Section 5: Planned Research and Development on Destruction and Disposal Technologies for PFAS and PFAS-Containing Materials 1.b.i PFAS and PFAS-containing materials identified in the FY 2020 NDAA Section 7361 of the FY 2020 NDAA (see Figure 1-1) lists six types of PFAS-containing materials. Although the information included in this guidance would probably be suitable for other types of PFAS and PFAScontaining materials, this guidance addresses destruction and disposal for these six material types, which are described in more detail in Section 2. PFAS are either manufactured in the United States or imported, and then used (as an input or in a formulation) as processing aids or components of commercial and consumer products. Figure 1-2 shows conceptually how these activities could result in material streams that are in the intended scope of this interim guidance. A more global illustration of how PFAS-containing materials may be released to and migrate through the environment is presented in Figure 4-1. Note: The red-outlined portions of this figure show where the FY 2020 NDAA material types occur in the course of manufacture, use, and disposal of PFAS and PFAS-containing materials that are within the scope of this interim guidance. Figure 1-2. Generation of PFAS materials identified in the FY 2020 NDAA. INTERIM GUIDANCE FOR PUBLIC COMMENT Introduction 2 1.b.ii Guidance scope In developing this interim guidance, EPA identified and assessed existing information from published, publicly available sources relevant to destruction and disposal technologies. EPA also considered research and development that is in progress. Consistent with EPA's mission, the intent of this guidance is to identify and describe technologies that may control releases of PFAS waste to protect human health and the environment. This interim guidance generally describes technologies that may be feasible and effective to varying degrees for the destruction or disposal of PFAS and PFAS-containing materials, based on currently available technical information. This document also identifies information gaps and uncertainties with the technologies and identifies ongoing research and development activities related to destruction and disposal technologies, which are designed to address some of these information gaps and uncertainties and may inform more specific guidance in the future (see Section 5). This interim guidance is not a rule and it is not a statement of policy. Any discussion of EPA's regulatory authorities is for the purpose of describing standards and controls relevant to the destruction or disposal of PFAS and should not be considered a description of the applicability of those authorities. This version of the interim guidance takes the following considerations into account: It does not establish what concentrations of PFAS in wastes, spent products, or other materials or media would necessitate destruction or disposal. Regulatory mechanisms, and/or risk-based guidance, are more appropriate for establishing such concentrations. Instead, this guidance provides information and suggested considerations for evaluating destruction and disposal options. It focuses on available technologies that have the potential to destroy PFAS (i.e., break the carbon- fluorine bonds) or control migration of PFAS in the environment. It focuses on destruction and disposal technologies for the materials specified in the FY 2020 NDAA (see Section 1.b.i), including PFAS-containing wastes generated by pollution control technologies at the site of PFAS manufacture and commercial use of PFAS formulations. Such treatment wastes include, for example, spent activated carbon from filtration of air and water waste streams from industrial facilities and water treatment. It is based on currently available information on technology performance and capabilities for destruction and disposal of the PFAS-containing materials specified in the FY 2020 NDAA. Storage of PFAS and PFAS-containing materials is not discussed as a destruction or disposal technology. In some cases, however, interim storage may be an appropriate strategy until identified uncertainties are addressed and appropriate destruction and disposal technologies can be recommended. EPA encourages the safe storage of PFAS and PFAS-containing materials as needed, following manufacturers' recommended best management practices as well as in accordance with any relevant industry, federal, state, or local requirements or guidelines. INTERIM GUIDANCE FOR PUBLIC COMMENT Introduction 3 1.c Destruction and disposal technologies addressed in this interim guidance PFAS are managed in non-hazardous and hazardous waste treatment and disposal systems. As shown in Table 1-1, this interim guidance focuses on three destruction and disposal technologies: thermal treatment, landfilling, and underground injection. Other current PFAS waste management options are not discussed, as they are not in the intended scope of this guidance described in Section 1.b.ii. The land application of biosolids and other wastes (e.g., pulp and paper sludges) containing PFAS, for example, does not meet the Section 1.b.ii goal of PFAS destruction or control of PFAS migration into the environment. Table 1-1. Destruction and Disposal Technologies Discussed in This Guidance, with Examples of PFAS-Containing Materials Destruction and Disposal Technology, by Physical Phase of Materials Solid phase: Landfill disposal Thermal treatment Liquid phase: Underground injection Thermal treatment Gas phase: Thermal treatment Examples of PFAS-Containing Materials (Within the Scope of the FY 2020 NDAA) That Could Be Managed Using These Technologies Drinking water, groundwater, and wastewater treatment residuals o Biosolids o Spent granular activated carbon (GAC) o Ion exchange resins o Filters o High-pressure membranes Air waste stream treatment residuals o Spent GAC o Fly ash Contaminated soil End-of-life products (e.g., textiles) Landfill leachate Aqueous film-forming foam End-of-life products (e.g., spent cleaning solvents) Pollution control residuals (e.g., concentrates) from PFAS production and use Landfill gas Emissions from manufacture, use, or destruction 1.d Summary of destruction and disposal interim guidance The FY 2020 NDAA requires that EPA publish interim guidance on the destruction and disposal of PFAS and PFAS-containing materials. This document contains guidance that is based on currently available research and information and is responsive to the scope of the FY 2020 NDAA. Most significantly, it provides the best up-to-date information on potential releases during the destruction and disposal of PFAS and PFAS-containing materials and identifies data gaps to be filled that can inform future EPA guidance. This interim guidance presents background information on the manufacture and uses of PFAS, as well as solid, liquid, and gas waste streams containing PFAS, including those materials identified in the FY 2020 INTERIM GUIDANCE FOR PUBLIC COMMENT Introduction 4 NDAA: aqueous film-forming foam (AFFF), soils and biosolids, textiles, spent water treatment materials, and landfill leachate. EPA evaluated destruction and disposal technologies that are currently available for the management of PFAS. This interim guidance presents three destruction and disposal technologies that may be effective and are commercially available: thermal treatment (destruction), landfilling (disposal), and underground injection (disposal). Each technology is characterized in terms of the types of PFAS and PFAS-containing materials that typically can be handled, possible design and operating parameters, potentially relevant testing and monitoring methods, and costs, where relevant information is available. While significant uncertainties remain with respect to the potential for migration to the environment associated with the destruction and disposal of PFAS and PFAS-containing materials using the technologies identified, this guidance may enable a manager of PFAS or PFAS-containing materials to make informed decisions in the evaluation of existing destruction and disposal options. EPA recognizes that the relative uncertainty associated with technologies' capabilities to control migration of PFAS to the environment is one of several factors that the public considers in determining how to destroy or dispose of PFAS-containing materials. Other factors would include whether it is imperative to destroy or dispose of the waste immediately versus storing it and waiting for those uncertainties to be reduced, the cost and availability of destruction and disposal options, the type of waste materials, and the concentrations of PFAS in the waste. Managers of PFAS materials could consider the following existing destruction and disposal options in the order of lower uncertainty to higher uncertainty while considering the other factors mentioned above to come up with a decision that is as protective of the environment as possible. 1. Interim storage. While not a destruction or disposal method, interim storage may be an option if the immediate destruction or disposal of PFAS and PFAS-containing materials is not imperative. In general, interim storage (estimated to be anywhere from 2 to 5 years) would be utilized until research reduces the uncertainties associated with other options. 2. Permitted deep well injection (Class I). Underground injection would be limited to liquid-phase waste streams. 3. Permitted hazardous waste landfills (RCRA Subtitle C). These have the most stringent environmental controls in place and higher potential capacity to manage the migration of PFAS into the environment. 4. Solid waste landfills (RCRA Subtitle D) that have composite liners and leachate collection and treatment systems. These landfills receive non-hazardous waste and tend to have environmental controls commensurate with the waste they receive. These controls can vary from state to state. The following options have higher levels of uncertainties regarding theircapacityto manage the migration of PFAS into the environment.In order to reduce the uncertainties, interim storagemaybe consideredforPFAS or PFAS-containing materials before theseoptionsareselected.If entities determine, after considering this guidanceand the uncertainties discussed herein, that certain PFAS waste nonetheless currently needs to be treated in hazardous waste combustors,it is important that the manager of PFAS materials provide the hazardous waste combustion facility with the relative PFAS INTERIM GUIDANCE FOR PUBLIC COMMENT Introduction 5 concentrations for these materials. EPA encourages the manager of PFAS-containing materials, the hazardous waste combustion facility, and the state to work together with EPA to develop and implement protocols for monitoring, emission testing, and data sharing. While developing and implementing these protocols is not a precondition, EPA considers it a key step and requests assistance in obtaining more information to inform research efforts and future guidance. EPA is very interested in collaborating on these protocols. 5. Hazardous waste combustors. These would include commercial incinerators, cement kilns, and lightweight aggregate kilns, subject to the considerations outlined in this guidance. 6. Other thermal treatment. This would include carbon reactivation units, sewage sludge incinerators, municipal waste combustors, and thermal oxidizers, subject to the considerations outlined in this guidance. This document describes a suite of technologies within the three categories noted above: thermal treatment (destruction), landfilling (disposal), and underground injection (disposal). The following have been found to have the greatest potential within each category to control migration of PFAS to the environment if used to destroy or dispose of PFAS-containing materials, based on the available information analyzed for this guidance document: 1. Hazardous waste combustion technologies (commercial incinerators, cement kilns, and lightweight aggregate kilns) can potentially achieve temperatures and residence times sufficient to break apart the PFAS contained in the waste stream being thermally treated. Permitted hazardous waste facilities have stringent regulatory controls on temperatures and other important operating parameters to achieve a 99.99 percent destruction efficiency for other (non-PFAS) organic chemicals. Key uncertainties include the lack of PFAS-specific information on these facilities. EPA currently has no emission characterizations from these sources when they burn PFAS, and is working to develop measurement methodologies as well as gather information to conclude whether potential products of incomplete combustion (PICs) are adequately controlled. EPA recognizes that PICs are formed (even for nonfluorinated compounds); however, based on the unique characteristics of fluorine combustion chemistry, it needs to be determined whether thermal treatment devices and their associated post-combustion control devices are controlling fluorinated PICs. Additional research is needed to minimize or eliminate data gaps or current uncertainties. By the time of the next update to this guidance (within the next 3 years), EPA expects to complete sufficient research to address data gaps. EPA will then make a more informed recommendation on disposal of PFAS compounds and PFAS-containing substances using incineration. 2. Hazardous waste or municipal solid waste landfills are available, feasible, and effective, to varying degrees, disposal options for PFAS and PFAS-containing materials. Permitted hazardous waste landfills employ the most extensive set of environmental controls (e.g., double liner systems with leachate collection and leak detection) and practices (e.g., extensive record keeping) that are currently available for the containment of PFAS waste (see Table 3-4) and as a result would be more effective at minimizing PFAS migration into the environment than other landfill types. Modern municipal solid waste landfills, when constructed with appropriate controls (e.g., liner system and leachate and gas collection and management systems), can also control the migration of PFAS into INTERIM GUIDANCE FOR PUBLIC COMMENT Introduction 6 the environment. Key uncertainties include that, even with these controls in place, the proper management of landfill gaseous and liquid releases needs to be applied for municipal solid waste and hazardous waste landfills to minimize PFAS migration into the environment (as described in Section 3.b.ii). Care must be taken to apply the leachate control technologies that are effective at containing (e.g., through solidification or recirculation) or destroying PFAS (see Table 3-6 for more information). Given the high level of uncertainty associated with PFAS behavior in landfills, research consistent with that described in Section 5--such as research on the effects of PFAS on liner integrity, gaseous emissions from landfills, the effectiveness of leachate treatment for PFAS removal, and the levels and types of PFAS in landfill leachate--will help to further evaluate this disposal method for PFAS and PFAS-containing wastes. 3. Class I deep well injection is another feasible and effective, to varying degrees, disposal option that normally should minimize migration of PFAS into the environment. However, the limited number of wells currently receiving PFAS, as well as location, waste transportation, and associated costs, may significantly limit the practicability of this disposal option. Unlike landfills, underground injection wells are only suited for disposal of liquids. Waste streams disposed of by underground injection will likely need to have low concentrations of suspended solids. This restriction may limit both the type and quantity of PFAS-related liquid waste streams. Performance and testing data--including data on destruction and removal of PFAS in hazardous waste combustors and associated pollution controls, and long-term performance data for landfills and deep well injection--are insufficient to support more specific guidance at this time. See Section 3 for further information about these destruction and disposal methods and their uncertainties. As discussed below, EPA intends to fill gaps in knowledge associated with potential releases from these destruction and disposal methods before issuing further guidance. The FY 2020 NDAA states that releases through volatilization, air dispersion, or leachate may impact vulnerable populations living near destruction or disposal sites. Accordingly, Section 4 of this document advises how to assess the impacts of potential releases and exposure on communities, including the identification of vulnerable populations, incorporation of vulnerability into risk assessment, and community engagement. As described in Section 5, ongoing research is being conducted to address the gaps in the current state of knowledge about PFAS destruction and disposal technologies and PFAS monitoring methods. EPA's own research currently centers on better characterizing PFAS-containing materials targeted for destruction and disposal, assessing the effectiveness of existing and new methods of PFAS destruction and disposal, and developing PFAS monitoring methods. Status and updates on EPA's PFAS research are available at https://www.epa.gov/chemical-research/status-epa-research-and-development-pfas. EPA recognizes that additional information, which may be available from external stakeholders, may help EPA refine and update this guidance as appropriate. This interim guidance serves as a baseline of destruction and disposal capabilities and uncertainties. As required by the FY 2020 NDAA, it will be reviewed and, if appropriate, updated within the next 3 years to reflect EPA's and other organizations' research on improving our understanding of current PFAS destruction and disposal technologies and developing new approaches. EPA will consider revising the INTERIM GUIDANCE FOR PUBLIC COMMENT Introduction 7 guidance in less than 3 years if research results become available that would allow the Agency to issue more specific guidance on PFAS destruction and disposal. INTERIM GUIDANCE FOR PUBLIC COMMENT Introduction 8 2. Description of PFAS-Containing Materials Identified in the FY 2020 NDAA The FY 2020 NDAA identifies six waste streams that commonly contain PFAS (see Figure 1-1 and Section 1.a). This section discusses each FY 2020 NDAA waste stream, its origins, potential sources of PFAS, current disposal and treatment methods, and potential releases to the environment. Data on FY 2020 NDAA-relevant waste streams may come from a variety of sources, and more PFAS data will be available from EPA-managed datasets in the near future. For example, EPA's Chemical Data Reporting (CDR) dataset includes production volumes for manufactured and imported amounts and conveys certain industrial processing and use activities. One data element distinguishes amounts that are recycled instead of discharged or released to a waste stream. In the 2020 CDR reporting cycle, submitters will begin to use Organization for Economic Cooperation and Development (OECD)-based industrial processing and use codes to better harmonize those data (U.S. EPA, 2020a). Additionally, EPA's Toxics Release Inventory (TRI) program collects data related to industrial releases and waste management of certain chemicals. The TRI dataset includes, among other information, quantities of environmental releases to all media (including on-site disposals and land application), as well as quantities transferred to off-site waste management facilities. Under Section 7321 of the FY 2020 NDAA, a total of 172 PFAS were added to the TRI list for reporting year 2020 (U.S. EPA, 2020b). The 2020 TRI data must be submitted by TRI-covered facilities by July 1, 2021; these data will be published shortly thereafter. 2.a Solid, liquid, or gas waste streams containing PFAS from facilities manufacturing or using PFAS PFAS do not occur naturally. They are synthesized for use in a diverse array of industrial and commercial applications. Industrial waste streams containing PFAS stem from two main sources: (1) primary manufacturing facilities of PFAS and (2) secondary industries that use PFAS or manufacture finished products that contain PFAS. A 2009 survey by OECD identified 27 primary manufacturers and processors of PFAS globally (OECD, 2011). At the time of that survey, more than 90 percent of the global annual production of PFAS was generated by eight manufacturers (Posner et al., 2009), all of which participated in EPA's 2010/2015 Perfluorooctanoic Acid (PFOA) Stewardship Program (U.S. EPA, 2006). PFOA is a perfluoroalkyl acid (PFAA) and long-chain PFAS. The goal of the PFOA Stewardship Program was to reduce PFOA facility emissions and PFOA use in products by 95 percent by 2010, compared with 2006 baseline levels, and to eliminate PFOA from all facility emissions and products by 2015 (U.S. EPA, 2006). All eight of the participating manufacturers reported to EPA that they met these goals (U.S. EPA, 2014). Manufacturers achieved these goals by substituting the production and import of long-chain PFAS and their precursors with short-chain PFAS INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials IdFeYnt2i0fi2e0d NinDtAhAe 9 replacements and alternative chemistries. However, uses of these chemical substances continue by companies that did not participate in the PFOA Stewardship Program. Long-chain PFAS and their precursors may still be produced as unintentional byproducts and may persist in facility emissions and as product impurities in small quantities (3M Company, 1999; Boucher et al., 2019; Lehmler, 2009; Kissa, 2001). Furthermore, information on the toxicity and environmental fate and transport of alternative PFAS chemistries is limited (Sun et al., 2016; Wang et al., 2014). In the 2016 CDR full dataset, primary manufacturers reported manufacturing (including importing) about 25,600 metric tons of PFAS at 38 sites in 2015. This represents the aggregate production volume for PFAS produced and imported into the United States, across all industries. Although the aggregate production volume might not include all PFAS sources (for instance, a specific chemical or site may not meet reporting obligations), it provides a proxy quantity of all PFAS domestically produced and imported. PFAS might be released into the environment at every step in the production process, including synthesis, polymerization, application, transport, usage, and waste stream management and disposal (3M Company, 2000b). Table 2-1 lists important PFAS uses and the resulting solid, liquid, and gas waste streams for primary and secondary manufacturers of PFAS-containing materials and certain service sectors as indicated by industry, national and global inventories, and research. However, this list is not exhaustive or representative of all current uses, applications, recovery and recycling practices, or treatment technologies that could affect the volume and characteristics of the resulting waste streams. EPA recognizes the need for continued research to better characterize the multi-media PFAS-containing materials targeted for destruction or disposal, as discussed in Section 5.a. 2.a.i Solid phase wastes Primary manufacturing and secondary industrial use of PFAS can generate solid waste streams with PFAS-containing materials (OECD, 2011, 2015). For example, some PFAS synthesis processes can produce tars consisting of high-molecular-weight byproducts that are either fully or partially fluorinated. These byproducts may be recycled back into the process, disposed of in a hazardous waste landfill, or incinerated (3M Company, 2000a, 2000b). Solid wastes may also be produced as fly ash or spent GAC resulting from PFAS incineration and other treatment processes. Other important solid-phase wastes include sludges and biosolids (see Section 2.c) that result from stabilizing or treating process waters and wastewaters, either on-site or at a municipal wastewater treatment plant (WWTP) that receives influent from industrial sources (Venkatesan & Halden, 2013). In addition to solids produced via treatment, spent water treatment media (such as ion exchange resins) are part of this waste stream (see Section 2.e). Other direct industrial sources of solid wastes containing PFAS include intentional residuals, such as cuttings and fibers from textile manufacturing (see Section 2.d), and materials unintentionally produced outside of product specification. The concentrations and composition of PFAS in solid wastes generated from primary and secondary industrial sources vary by facility and depend on factors such as facility- or industry-specific production processes and the types and quantities of PFAS produced or used (ITRC, 2020). INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials IdFeYnt2i0fi2e0d NinDtAhAe 10 2.a.ii Liquid phase wastes Primary manufacturers and secondary industrial users of PFAS can generate liquid phase wastes in the form of (1) liquid byproducts of PFAS synthesis to be recycled or disposed of (e.g., to a landfill) following stabilization, solidification, or another management method; (2) process wastewater resulting from activities using PFAS as a processing aid (e.g., surfactant, emulsifier, mist suppressant, sizing agent) and production of finished products containing PFAS; (3) spills or unintentional releases of liquid wastes and products containing PFAS; and (4) AFFF/water/foam mixtures from the use of fire-extinguishing agents (see Section 2.b) for emergency response activities and emergency response trainings at industrial facilities. Table 2-1 provides examples of liquid wastes containing PFAS generated by industrial sources and their uses. Another liquid phase waste stream is wastewater effluent discharged directly from a primary manufacturer or secondary industrial PFAS user. Effluent from wastewater treatment facilities that receive wastewater from industrial PFAS sources may also contain PFAS. According to several studies, conventional wastewater treatment technologies are generally ineffective at destroying or controlling PFAS (Schultz et al., 2006) and may result in higher measurable PFAAs (e.g., PFOA, perfluorooctane sulfonate [PFOS], and their homologues) when precursor compounds (e.g., fluorotelomers) are degraded during the treatment process (Buck et al., 2011; Dauchy et al., 2017a; Schultz et al., 2006; Sinclair & Kannan, 2006). Less often, primary industrial PFAS manufacturers have opted to transport liquid wastes off-site for incineration (North Carolina Department of Environmental Quality, 2017). 2.a.iii Gas phase wastes Studies suggest that PFAS in air emissions from manufacturing facilities are a source of both localized (i.e., within a short radius of the facility) and long-distance (i.e., global) transport of PFAS within the environment (Davis et al., 2007; Dreyer et al., 2009). Non-volatile forms of PFAS, such as the anionic PFAAs (e.g., PFOA, PFOS, and their homologues), are associated with airborne particulates when emitted as aerosols from stack emissions at primary manufacturing facilities (Barton et al., 2006; Dreyer et al., 2015). Gas phase emissions of volatile and semivolatile PFAS, and the subsequent transformation of precursor compounds into persistent PFAAs, are a potential mechanism for the atmospheric transport of PFAS. For example, volatile fluorotelomer alcohols (FTOHs) and perfluoroalkyl sulfonamides can transform into perfluoroalkyl carboxylic acids (e.g., PFOA and homologues) and perfluoroalkyl sulfonates (e.g., PFOS and homologues); these can be deposited at significant distances from their origin, which may result in soil and groundwater contamination (Dreyer et al., 2009; Ellis et al., 2004; Martin et al., 2006; Schenker et al., 2008). INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials IdFeYnt2i0fi2e0d NinDtAhAe 11 Table 2-1. Examples of PFAS Waste Streams by Industry Type Industry Type Uses Primary chemical PFAS synthesis, feedstocks for primary products, manufacturing feedstocks for secondary users, processing aids (fluoropolymers) Solid Process byproducts (tars), sludges/ biosolids, off-spec materials,b treatment residuals (GAC/anion exchange resins), spill residues (replacement and legacy), particulate emissions Examples of Waste Streamsa Liquid Degraded/stabilized process wastes, wastewater effluent, stack emissions condensate Secondary Manufacturing (Industry Users of PFAS-Containing Materials)c Adhesives manufacturing Component of solvent- and water-based adhesives, rubber to allow bonding to steel, and urea-formaldehyde adhesive resins for wood particleboard bonding Used filter media and filter residues, residues of cured adhesives, empty containers, used shop rags (from cleaning), contaminated soil (from spill cleanup residues) Residues of liquid adhesives, off-spec products,b contaminated wastewater (from spill cleanup residues) For cleaning: equipment startup, cleaning, and flushing wastes; spent cleaning solvents; and contaminated wastewater Gas Stack emissions, fugitive volatiles Stack emissions, fugitive volatiles Notes 3M Company (1999, 2000b) ASC (n.d.), RadTech International North America (2010) INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials Identified in the FY 2020 NDAA 12 Industry Type Uses Cleaning product manufacturing Component of household cleaners; car wash products; automobile waxes; wiper fluid; strongly acidic or basic cleaners for concrete, masonry, airplanes Used for removal of adhesives, dry cleaning of textiles or metal surfaces, machine parts cleaning after nickel plating, and removal of calcium sulfate from reverse osmosis membranes Component of sealant for electric circuits, zinc battery electrolyte, wetting agents in solders, polar solvents used before welding Solid Examples of Waste Streamsa Liquid Off-spec products,b liquid residues from empty containers, and spills Computers/ electronics manufacturing Film/ lithography manufacturing Used for removal of cured epoxy resins from integrated circuit modules, treatment of insulated wire, alkaline manganese battery MnO2 cathode treatment, production of polymer electrolyte membrane for fuel cells, cleaning of electronic components, and coating of the surface of magnetic recording devices Used in coatings for surface tension, static discharge, and adhesion control for films, papers, and printing plates, and as a surfactant in mixtures used to process imaging films Collected airborne particulates for cleaning/surface preparation Rags and wipes discarded by applicator; solids coated with PFAS from processing, sampling, quality assurance; off-spec productsb Spent acid solution for cleaning/surface preparation, liquid residues from empty containers, and spills Solvent waste, liquid residues from empty containers, spills, and unused application mix Gas Stack emissions, fugitive volatiles Stack emissions, fugitive volatiles Coating application exhaust Notes 3M Company (1999) U.S. EPA (1990) 3M Company (1999), Bowden et al. (2002) INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials Identified in the FY 2020 NDAA 13 Industry Type Metal plating/ fabrication Uses Used as a surfactant, wetting agent, and mist suppressing agent; as a wetting agent fume suppressant for chromium plating and chromium anodizing; as a dispersion product used to coat metals; as a blocking agent for aluminum foil; in plating baths; and to treat metal surfaces Component of chemical barrier used for containing oil spills Solid Off-spec productsb Examples of Waste Streamsa Liquid Spent plating or etching baths, rinse water effluent, liquid residues from empty containers, and spills Gas Stack emissions, fugitive volatiles Notes 3M Company (1999), U.S. EPA (2009b) Oil and gas drilling/ extraction/ refinery/ support Used as a surfactant for recovery in oil/gas recovery wells, a jet fuel/hydrocarbon solvent, and in hydraulic oils Used as a gasoline/petroleum product evaporation inhibitor in storage tanks in the following forms: a floating layer of cereal grains treated with PFAS, an aqueous layer containing PFAS Paint/coating manufacturing Component of coatings, paints, varnishes, dyes, ink Pigment dust jet printer inks, and ski waxes Paper products/ packaging manufacturing Pesticide/ fertilizer/ other agriculture chemical manufacturing Waterproofing/greaseproofing for products including food contact paper (plates, popcorn bags, pizza boxes, food containers, wraps), non-food contact applications (folding cartons, carbonless forms, masking papers) Pesticide and herbicide additive Dusts; solids coated with PFAS from processing, sampling, quality assurance; off-spec productsb Particulate emissions Applied productd (oil spills, oil and gas recovery wells), liquid residues from empty containers, and spills UNEP (2011), Kissa (2001) Unused paint products, off-spec products,b liquid residues from empty containers, and spills Fugitive volatiles, atomized paint Waste Management and Research Center (1992) Spillage, cleanup, and releases during opening, rinsing, and cleaning of PFAS totes Fugitive volatiles U.S. EPA (2009a) Liquid residues from empty containers, spills, off-spec products,b cleaning of equipment, and process wastewaters Fugitive volatiles World Bank Group (1998) INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials Identified in the FY 2020 NDAA 14 Industry Type Plastic materials/ resins/ rubber product manufacturing Textiles/ apparel/ leather/ carpets/ fiber manufacturing Aerospace component manufacturing Automotive component manufacturing Uses Used to make membranes used in fuel cells; chloralkali cells; water, caustic soda, and caustic potash electrolyzers; silicone rubber sealants; composite resins; PTFE (polytetrafluoroethylene, or Teflon); and polyvinylidene fluoride or polyvinylidene difluoride (PVDF) Processing aid for PVDF manufacture, mold-release agent in foam molding, and antiblocking agent for rubbers Dispersion products that coat fabrics: jackets, shoes, umbrellas, carpets, upholstery, leather, tents, sails Mechanical components such as tubing, hoses, and seals; brake and hydraulic fluid additive; wire and cable insulation; used in coating/paint Mechanical components such as tubing, hoses, and seals; brake and hydraulic fluid additive; anti-mist film on windshields; used in coating/paint; used in coatings or surface treatments of textiles and upholstery Solid Examples of Waste Streamsa Liquid Dusts, spillage (micropowders and resins), cuttings, scrap, debris, and off-spec products;b particulate emissions Liquid residues from empty containers, spills, and unused application mix Solids coated with PFAS from cutting, shearing, packaging, lab and color sampling, quality assurance; flakes or dust containing PFAS; off-spec productsb Spills, wastewater effluent from product adhering to inside of drum, unused application mix, etc. Wastewater effluent Wastewater effluent Gas Notes Fumes from PTFE heating (volatile) Ebnesajjad (2015) Releases of vapors and aerosols during application of surface treatment and mechanical finishing U.S. EPA (2009a) FluoroCouncil (2019) FluoroCouncil (2019), ITRC (2020) INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials Identified in the FY 2020 NDAA 15 Industry Type Semiconductor manufacturing Building and construction materials manufacturing Mining industry Medical uses Cosmetics and personal care product manufacturing Uses Etching solutions for photolithography, glass etching, plastics etching, fused silica, aluminum; liquid etchant in photo mask rendering Component of cement and primers used to coat cement mortar; used in wire and cable insulation and coatings for wood particleboards Surfactant for recovery of metals from ores; used in ore flotation to separate metal salts from soil, electrowinning of metals, and nitrogen flotation to recover uranium Video endoscopes; catheters; saline solutions for in vitro diagnostics; treatment/coatings for textiles such as hospital gowns, curtains, drapes; dialysis machines Used in cosmetics, hair conditioning formulations, hair creams, and toothpaste Solid Examples of Waste Streamsa Liquid Spent plating or etching baths, PFOA residues from photoresist developers associated with semiconductor liquid waste streams, liquid residues from empty containers, and spills Photoresists and antireflective coatings stripped off from semiconductor devices before shipment are present in waste solvent streams Cuttings and debris, off-spec materialsb Wastewater effluent Contaminated rock from applied productd Applied productd Laboratory/medical solid wastes (tubing, filters, films, etc.) Off-spec materialsb Wastewater effluent Gas Photoresists and antireflective coatings stripped off from semiconductor devices before shipment are present in waste gas streams Notes Bowden et al. (2002), Tremblay (2015) Buck et al. (2012), FluoroCouncil (2019), U.S. EPA (2009a) ITRC (2020) FluoroCouncil (2019), Posner (2012) Danish EPA (2018), FluoroCouncil (2019), Schultes et al. (2018) INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials Identified in the FY 2020 NDAA 16 Industry Type Uses Fire suppression systemse AFFF and dry fire-extinguishing agents Solid Contaminated soil and debris from applied productd Examples of Waste Streamsa Liquid Applied productd Gas Notes See Section 2.b for more information a The italicized waste streams may contain PFAS, given what wastes the relevant industry sectors are known to generate and given applications of PFAS. The presence and concentration of PFAS have not been quantified. b "Off-spec materials" or "off-spec products" are materials or products that do not meet specified standards or requirements and are discarded rather than sold or used. c Some industries listed under "Secondary Manufacturing" may also include primary manufacturing of PFAS. The waste streams resulting from manufacture of PFAS chemicals in these industry sectors are addressed in the first row, "Primary chemical manufacturing." d "Applied product" refers to the intentional application of a PFAS-containing product to the environment. e Fire suppression systems, which include AFFF, are commonly found in manufacturing, storage, extraction and refining, and national defense facilities, as well as airports, fire departments, and other federal facilities (e.g., facilities operated by the National Aeronautics and Space Administration [NASA] and the U.S. Department of Energy [DOE]). Although this is an industrial use, not an industrial sector, the prevalence of AFFF in the above primary and secondary PFAS manufacturing industries warrants highlighting these waste streams. INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials Identified in the FY 2020 NDAA 17 2.b Aqueous film-forming foam AFFFs are a group of PFAS-containing fire extinguishing agents for low-flashpoint hydrocarbon fuel fires (Tuve et al., 1964). AFFFs are intended for use where a significant flammable liquid fire hazard exists (FFFC, 2016). AFFFs are based on synthetic fluorosurfactants that provide unique low-surface tension and positive spreading coefficient characteristics. When mixed with water and applied, AFFFs form an aqueous film and a foam solution to coat the liquid fuel, seal fuel vapor, and reduce oxygen availability, extinguishing the fire and preventing burnback (FFFC, 2016; SERDP, 2020; Sheinson et al., 2002). Until application, AFFF is managed as a concentrated product containing less than 2 percent PFAS fluorosurfactants by weight for a typical 3 percent AFFF concentrate (ITRC, 2020) and is stored in either fixed, structural dispensing systems, such as those in hangars and aboard vessels, or in mobile, vehiclebased systems (i.e., aircraft rescue firefighting [ARFF] vehicles) (Field et al., 2017). Reserve AFFF concentrate inventory may be stored in hangars or warehouses. The amount of AFFF concentrate in the finished foam varies by manufacturer and application circumstances, but is usually between 1 and 6 percent, meaning the fluorosurfactants are diluted to less than a fraction of a percent (FFFC, 2016; ITRC, 2020). A 2004 inventory estimated that there were 4.6 million gallons of legacy PFOS-containing AFFF in the United States (Darwin, 2011). Frequency of use for firefighting, training, or testing; transfers between locations; and other factors determine rates of AFFF inventory depletion. However, AFFF's characteristically long shelf life means little disposal due to expiration should occur (FFFC, 2016), increasing the possibility that legacy PFOS-containing AFFF concentrate remains in service or reserve inventories. In the United States, AFFF and associated systems are or have been in service at federal facilities, civil airports, and oil refineries. Civilian fire departments also use or have used AFFF. The U.S. Department of Defense (DoD) is working to identify areas of active and former installations where PFOS- or PFOAcontaining AFFFs have been used (Darwin, 2011; DoD, 2020). As of the end of FY 2019, the scope of this assessment of potential PFAS use or release has grown to comprise a more comprehensive inventory of DoD and National Guard installations, beyond just those with potentially significant historical AFFF use (DoD, 2020). The FY 2020 NDAA prohibits any land-based fluorinated AFFF use effective October 1, 2024, or sooner, if the Secretary of Defense deems it practicable. DoD issued policy in January 2016 to discontinue landbased AFFF training and testing activities. Since then, DoD has managed any mission-critical AFFF use in response to an emergency event as a spill response to mitigate impacts to the environment (DoD, 2019, 2020). DoD, among other entities, is also investing in research and development for fluorine-free AFFF alternatives (SERDP, 2020). Examples of AFFF users and locations in the United States are listed in Table 2-2. Note that the list of sources in the table is non-exhaustive. INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials IdFeYnt2i0fi2e0d NinDtAhAe 18 Table 2-2. Examples of AFFF Users and Locations in the United States AFFF User DoD NASA DOE Airports and supporting facilities Fire departments Locations Hundreds of military installations (active and former) with AFFF use In-service systems installed at an estimated 1,350 locations in aircraft hangars and on an estimated 3,000 ARFF vehicles Three centers with ARFF apparatus Nine hangars, including Wallops Flight Facility Lawrence Berkeley National Laboratory Brookhaven National Laboratory Los Alamos National Laboratory Strategic Petroleum Reserve facilities (Gulf of Mexico) 523 Federal Aviation Administration (FAA)-certified civilian airports in 2018 Since 2006, an annual average of nearly 600 certificated airports Supporting facilities include firefighting training sites, such as the FAA Technical Center's Fire Training Area At civilian fire departments throughout the United States Comments DoD discontinued land-based AFFF for training and testing in 2016 and is investing in fluorinefree alternatives The FY 2020 NDAA requires DoD to end any land-based AFFF use no later than October 1, 2024 Sources: DoD (2017, 2019, 2020); CBO (2019); SERDP (2020) NASA discontinued training with AFFF in late 2018 Sources: SERDP (2020); NASA (2020) Sources: DOE (2016, 2017, 2020a, 2020b); Darwin (2011) FAA regulations required certain AFFF quantities at civil airports starting in 1972; since 2006, FAA regulations require most civil airports to purchase military-specification AFFFa 80 percent of respondents to a 2017 survey of U.S. and Canadian airports reported trainingrelated discharge directly to the ground; twothirds reported testing-related discharge directly to the ground FAA has taken steps to reduce AFFF discharges during testing since 2019 Sources: DOT (2019); FAA (2006, 2019); Thalheimer et al. (2017); U.S. EPA (2020c) Legacy PFOS AFFF may be present at fire departments Some states have begun inventorying and reporting of AFFF (e.g., Michigan, New Hampshire) Some states have take-back programs to help local fire departments identify AFFF in inventory and assisting with removal and disposition (e.g., Vermont) Sources: Michigan Department of Environment, Great Lakes, and Energy (2020); New Hampshire Department of Environmental Services (2020); Vermont Agency of Natural Resources (n.d.) INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials IdFeYnt2i0fi2e0d NinDtAhAe 19 AFFF User Oil refineries and processing facilities Ships and other vessels Locations Oil refineries and related facilities (e.g., storage facilities) Ships and other marine vessels, including the U.S. Coast Guard Comments Little information is available about AFFF in this sector, though published industry guidelines recommend AFFF for pipeline emergencies Survey-based data suggest this sector is the second largest consumer of AFFF after federal agencies Sources: Darwin (2011); Noll & Hildebrand (2016) Little information is available about AFFF quantities on ships There has been a shift towards non-fluorinated AFFF for some uses including testing and training, though the Coast Guard has indicated that certain uses (e.g., required inspections) must continue to use fluorinated AFFF Source: U.S. EPA (2020e) a An exception exists for airports with low departure traffic and serving aircraft less than 90 feet in length. See 14 Code of Federal Regulations (CFR) 139.317 for more information (FAA, 2006). Fate and transport of PFAS in AFFF after use depends on the release circumstances and chemical-specific properties. Though sometimes classified as incidental releases (Thalheimer et al., 2017), equipment failure, accidental releases, or operator error can result in substantial leaks (Anderson et al., 2016; Resolution Consultants, 2016; Leidos, 2016). Engineering controls (such as dikes, barriers, or basins) may be installed at facilities with significant flammable liquid hazards to contain foam solution and runoff for later disposal (FFFC, 2016). Where such hazards do not significantly exist, or installed engineering controls are otherwise not practicable, firefighting personnel may as part of their response block sewer drains or deploy portable dikes as containment measures (FFFC, 2016). Runoff can then be pumped out and impacted environmental media removed for disposal (ITRC, 2020). Construction and demolition (C&D) debris originating from facilities where AFFF was historically released may also be a source of PFAS in landfills and groundwater (Solo-Gabriele et al., 2020). Though subject to site-specific characteristics and conditions, studies demonstrate AFFF use at airports is a source of PFAS in soil and groundwater (Ahrens et al., 2015; Dauchy et al., 2017b; Hister et al., 2019). Further, PFAA precursors from original AFFF concentrate products may transform in the environment to more mobile products over time (Houtz et al., 2013), expanding plumes long after AFFF use is discontinued. 2.c Soils and biosolids As required by Clean Water Act Section 405(d), EPA established requirements for the final use or disposal of sewage sludge when it is (1) applied to land as a fertilizer or soil amendment; (2) placed in a surface disposal site, including sewage sludge-only landfills; or (3) incinerated. The regulation at 40 CFR INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials IdFeYnt2i0fi2e0d NinDtAhAe 20 part 503 defines sewage sludge (commonly referred to as "biosolids") as a solid, semi-solid, or liquid residue generated during the treatment of domestic sewage in a treatment works. Sewage sludge includes scum or solids removed in primary, secondary, or advanced wastewater treatment processes and any material derived from sewage sludge (e.g., a blended sewage sludge/fertilizer product) but does not include grit and screenings or ash generated by the incineration of sewage. Part 503 considers domestic septage as sewage sludge and sets separate requirements for domestic septage applied to agricultural land, forests, or reclamation sites. Influent containing PFAS that enters wastewater treatment facilities may result in the presence of PFAS in biosolids. If the biosolids are applied to land, there is the potential for leaching or runoff. Alternatively, if the biosolids are incinerated, there is potential for PFAS to be emitted as PICs (Navarro et al., 2016; Sepulvado et al., 2011; Washington et al., 2010). Total nationwide biosolids generation and management statistics in 2019 (reported to EPA's biosolids program as of May 5, 2020) and data considerations are presented in Table 2-3. EPA does not have data on the volume of biosolids that contain PFAS. Table 2-3. Biosolids Generation and Management in 2019 National Pollutant Discharge Elimination System (NPDES) permits issued to publicly owned treatment works (POTWs)a Biosolids NPDES permitsb Biosolids annual reporters (2019)c Biosolids generated in 2019 (metric tons)d 16,109 9,834 2,273 4,751,267 Land application (metric tons) 2,439,320 Land disposal (also called surface disposal) (metric tons) 120,125 Incineration (metric tons) 765,464 Landfilling (metric tons) 928,131 Other management (metric tons) 498,227 a An NPDES permit is typically a license for a facility to discharge a specified amount of a pollutant into a receiving water under certain conditions. A POTW is a WWTP that is typically owned, and usually operated, by a local or regional government agency (U.S. EPA, 2020b). b Biosolids permits apply to any person who prepares sewage sludge, applies sewage sludge to the land, or fires sewage sludge in a sewage sludge incinerator and to the owners/operators of surface disposal sites, as well as the exit gas from sewage sludge incinerator stacks (U.S. EPA, 2019). c Annual reports are required for POTWs that have design flow capable of serving populations of 10,000 or more, that are required to have approved pretreatment programs (Class I Sludge Management Facilities), or that are otherwise required to report (U.S. EPA, 2017). d Total amount of biosolids generated is reported by each POTW and may not equal the sum of component amounts reported for each management method. Biosolids totals do not represent PFAS presence in biosolids. In addition to land application of PFAS-containing wastes (e.g., biosolids), there are other scenarios where PFAS migration to soils can occur. Direct migration of PFAS into soils can occur through applications of PFAS-containing products such as AFFF, land application of PFAS-containing wastes (e.g., biosolids), and the discharge or application of treated industrial or municipal wastewater containing PFAS. PFAS can also be in soils due to unintentional contact, such as spills or leaks during the production, handling, transport, or use of PFAS-containing materials (see Table 2-1 for examples of industrial sources INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials IdFeYnt2i0fi2e0d NinDtAhAe 21 of PFAS in soils). Both direct and indirect soil impacts might also occur via the atmospheric deposition of PFAS adsorbed to particulates released from stack emissions and atmospheric transformation products of volatile precursors, respectively (Davis et al., 2007; Dreyer et al., 2009; Schenker et al., 2008). Remediation wastes such as soils excavated during the cleanup of sites or during decommissioning of facilities where PFAS was manufactured, used, or applied may contain diverse mixtures of PFAS in elevated concentrations. 2.d Textiles, other than consumer goods, treated with PFAS Because PFAS can repel oil, water, and stains, the textile industry uses these chemicals in a broad range of textile products other than consumer goods (apparel or household textiles). For example: PFAS can be used to treat outdoor equipment such as tents and sails (UNEP, 2011). Technical or occupational textiles, such as protective clothing for firefighters, can be treated with PFAS or woven from fluoropolymers (OECD, 2013). Medical garments can be treated with fluorinated polymers (OECD, 2013). Fluoropolymers can be spun into fibers and used to make sailcloth and fabric for fire suppression needs (Tokarsky & Uy, 2003). PTFE can be woven to make architectural fabrics such as roofs, and can also be used to coat fiberglass for tensile structures or long-life structures (Fabric Architect, 2020). Textiles made from fiberglass coated with or saturated with PFAS are used for high-temperature or corrosive industrial environments. Kevlar and perfluoroplastic composite textiles are used for similar industrial environments (Robco, 2020). Examples of typical PFAS-containing waste streams generated from textiles include discarded industrial or commercial textiles (such as apparel, carpets, or personal protective equipment), solids coated with PFAS from cuttings and shearings, and fugitive volatiles from spray applications of textile surface treatments. The destruction and disposal technologies used for these waste streams include landfill disposal and thermal treatment. (For examples of industrial waste streams from the textiles/apparel manufacturing industry, see Table 2-1.) 2.e Spent water treatment materials Although novel technologies for removing PFAS from drinking water sources and groundwater are being developed, current processes known to be effective are activated carbon, anion exchange resins, and high-pressure membranes (reverse osmosis [RO] and nanofiltration [NF]) (U.S. EPA, 2016a, 2016b). This section discusses the residual streams of these three processes (see Section 3 for discussions on treatment and disposal considerations and costs, and Section 5 for discussions of research needs for more novel treatments). INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials IdFeYnt2i0fi2e0d NinDtAhAe 22 2.e.i Activated carbon Activated carbon (discussed more extensively in Section 3.a.i) is manufactured from carbon-rich sources such as wood and used to treat water or air by filtering contaminants (U.S. EPA, 2012). Activated carbon can be used in either powdered activated carbon (PAC) or GAC form. In PAC treatments, carbon is powdered and added to the water for treatment, and chemicals in the water then stick to the powdered carbon as the water passes through. In GAC treatments, small pieces of carbon adsorb to chemicals in water as the water passes through. PAC application will remove some PFAS from water, though the amount of PFAS removed depends on many factors. For PAC treatment, the residual stream is the sedimentation sludge or the filter backwash solids that contain the PFAS-laden PAC along with the coagulant, coagulant aids (if used), natural particulates, and enmeshed organic carbon (Dudley et al., 2015). Given the many conditions that affect treatment, the weight percent PFAS in a PAC residual stream varies by many orders of magnitude but will be in the same range as GAC treatment, as discussed below. For GAC, the range of PFAS concentrations on spent media can be estimated in several ways (Crone et al., 2019; U.S. EPA, 2020d). A conservatively high loading of PFAS onto GAC (using a GAC with a high capacity potential, a strongly adsorbing PFAS, few competitive contaminants, low organic levels, and a high concentration in the feed water treated) is on the order of 2 percent by weight (e.g., 0.02 grams PFOS per gram of GAC). For other, more common treatment scenarios or for PFAS that are adsorbed more weakly (like the shorter-chain PFAS), the weight percent of PFAS will be orders of magnitude lower. GAC can be reactivated and reused (see Section 3.a.i.2 for a discussion on GAC reactivation, and Section 3.a.vii for a discussion on the costs of GAC reactivation). If the GAC is landfilled, PFAS can desorb off the carbon into the landfill leachate if the GAC comes into contact with a low-PFAS-containing water stream. Desorption will occur due to the disequilibrium between the liquid and solid phases. The resulting PFAS concentrations in the landfill leachate will vary greatly depending on conditions. 2.e.ii Ion exchange resins Like GAC, ion exchange resins are utilized in fixed bed adsorbers. Similarly, the residual stream from this treatment is the spent media; however, ion exchange resins cannot be thermally reactivated like GAC. Due to several factors, the market is moving toward single-use media for anion exchange resin treatment with incineration as the final disposal point for the spent resin. Also similar to GAC, the final PFAS loadings onto resins vary widely. A conservatively high estimate of loading (calculated using a PFAS-selective resin, few competitive constituents, and a PFAS known to adsorb well) is expected to be in the order of 10 percent by weight for the strongly adsorbing PFAS (e.g., 0.1 gram PFOS per gram of resin). The higher percent weight than GAC is due to the high capacities of PFAS-selective resins. Like GAC, more typical scenarios for PFAS that are more weakly adsorbed (like the shorter-chain PFAS) will yield much lower average weight percent of PFAS. Assuming single-use resin is used, landfilling can be less expensive than incineration (see discussions of treatment costs for the respective waste management options in Section 3). If the resin is landfilled, INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials IdFeYnt2i0fi2e0d NinDtAhAe 23 PFAS can desorb off the resin if the resin comes into contact with a water stream whose counter ions can displace the PFAS. The resulting leachate concentrations will vary tremendously depending on conditions. 2.e.iii High-pressure membranes (reverse osmosis and nanofiltration) High-pressure membranes are extremely effective for removing many PFAS from water to a high degree (Crone et al., 2019; U.S. EPA, 2020d). Because the process is based on a rejection phenomenon, water treatment with high-pressure membranes creates a waste stream with potentially high concentrations of PFAS that needs to be treated and disposed. These waste streams also have high concentrations of salts, other contaminants, and dissolved organic matter. Treatment of the concentrate residual stream can be challenging and the cost is likely high, similar to those for landfill leachates, ion exchange spent regenerates, and waters from highly contaminated sites. Many variables could affect the cost of treating these waste streams. At this time, there is no obvious treatment technology choice, especially given that the concentrated retentate stream is typically 20 percent of flow (Baruth, 2005). This represents a sizeable flow, especially for large membrane treatment systems, such as those used by large municipalities (e.g., treating 20 million gallons per day [4 million gallons per day concentrate flow]). This large-volume flow would prevent the use of batch treatment processes, which have higher efficiencies because they can process the water multiple times before discharge. 2.f Landfill leachate containing PFAS Landfill leachate (discussed in more detail in Section 3.b.iii) is the effluent formed by rainwater percolating through waste in landfills. Leachate generation may continue even after a landfill's closure period, as a result of inherent liquids in the waste or if the cap system fails. There are different types of solid waste landfills characterized by the wastes managed, which also dictate the environmental controls employed. MSW and hazardous waste landfills are typically required to collect the liquid leachate captured within the landfill liner and subsequently manage or treat the leachate. While PFAS concentrations in different landfill leachates have been documented (see Table 3-5 in Section 3.b), there are no monitoring or reporting requirements at the federal level for PFAS in landfill waste or leachate. Thus, existing treatment methods are being used to process leachate irrespective of PFAS concentrations. Landfill leachate can be treated on-site or off-site. The most prevalent off-site management approach is to export leachate to a WWTP where it is mixed with wastewater and treated. However, as noted in Section 2.a.ii, conventional wastewater treatment technologies are generally unable to treat or control PFAS (Schultz et al., 2006). Other off-site treatment methods include incineration and underground injection control (see Sections 3.a and3.c, respectively). The on-site leachate treatment technologies employed at landfills are explored in Table 3-4 in Section 3.b.i. Some management approaches and treatment technologies represent significant pathways for PFAS release. Unlined impoundments, release to constructed wetlands, and land applications can release PFAS and potentially contaminate groundwater. Additional research is needed to determine the efficacy of landfill leachate treatments for PFAS (see Section 5). INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials IdFeYnt2i0fi2e0d NinDtAhAe 24 2.g Summary PFAS are synthetic chemicals that are used in a diverse array of industrial and commercial applications. Industrial waste streams containing PFAS stem from two main sources: (1) primary manufacturing facilities of PFAS chemistry, and (2) secondary industries that use PFAS-containing products and/or manufacture finished products containing PFAS. Ultimately, PFAS end up in solid, liquid, or gas waste streams from industrial facilities that manufacture or use PFAS and PFAS-containing products. Other common PFAS-containing waste streams include AFFF, biosolids, textiles, spent water treatment materials, and landfill leachate. Any of these waste streams can contribute to PFAS entering environmental media, including soil and groundwater. The potential disposal and treatment technologies for processing these streams are discussed in Section 3. 2.h References 3M Company. (1999). Fluorochemical use, distribution and release overview (EPA-HQ-OPPT-2002-00430008). https://beta.regulations.gov/document/EPA-HQ-OPPT-2002-0043-0008 3M Company. (2000a). Phase-out plan for POSF-based products (letter from William Weppner, 3M, to Charles Auer, U.S. EPA). https://www.regulations.gov/document?D=EPA-HQ-OPPT-2002-0051-0006 3M Company. (2000b). Sulfonated perfluorochemicals in the environment: Sources, dispersion, fate and effects (EPA-HQ-OPPT-2002-0043-0005). https://beta.regulations.gov/document/EPA-HQ-OPPT2002-0043-0005 Ahrens, L., Norstrom, K., Viktor, T., Cousins, A.P., & Josefsson, S. 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Fluorotechnology: Critical to modern life. https://fluorocouncil.com/wpcontent/uploads/2017/03/Consolidated-application-page-1.pdf (accessed May 2020) Hister, ., Pfaff, A., & Breedveld, G. D. (2019). Leaching and transport of PFAS from aqueous filmforming foam (AFFF) in the unsaturated soil at a firefighting training facility under cold climatic conditions. Journal of Contaminant Hydrology, 222, 112-122. Houtz, E. F., Higgins, C. P., Field, J. A., & Sedlak, D.L. (2013). Persistence of perfluoroalkyl acid precursors in AFFF-impacted groundwater and soil. Environmental Science and Technology, 47(15), 8187-8195. ITRC (Interstate Technology & Regulatory Council). (2020). PFAS technical and regulatory guidance document and fact sheets PFAS-1. https://pfas-1.itrcweb.org/ Kissa, E. (2001). Fluorinated surfactants and repellants (2nd ed.). Marcel Dekker, Inc. Lehmler, H. J. (2009). Production of fluorinated surfactants by electrochemical fluorination. In U. Zoller (Ed.). Handbook of detergents: Part F: Production (pp. 301-322). CRC Press. Leidos. (2016). Timeline for usage of fire-fighting foam (AFFF) containing PFOS/PFOA at the Horsham Air Guard Station. https://www.111attackwing.ang.af.mil/Portals/11/documents/Home/AFD-160525015.pdf Martin, J. W., Ellis, D. A., Mabury, S. A., Hurley, M. D., & Wallington, T. J. (2006). Atmospheric chemistry of perfluoroalkanesulfonamides: Kinetic and product studies of the OH radical and Cl atom initiated oxidation of n-ethyl perfluorobutanesulfonamide. Environmental Science and Technology, 40, 864- 872. https://pubs.acs.org/doi/10.1021/es051362f Michigan Department of Environment, Great Lakes, and Energy. (2020). Foam and PFAS. https://www.michigan.gov/pfasresponse/0,9038,7-365-86514-496805--,00.html NASA (National Aeronautics and Space Administration). (2020). Background, latest information on PFAS at NASA Wallops (as of March 31, 2020). https://www.nasa.gov/feature/background-latestinformation-on-pfas-at-nasa-wallops/ Navarro, I., de la Torre, A., Sanz, P., Pro, J., Carbonell, G., & Martnez, M. (2016). Bioaccumulation of emerging organic compounds (perfluoroalkyl substances and halogenated flame retardants) by earth worm in biosolid amended soils. Environmental Research, 149, 32-39. New Hampshire Department of Environmental Services. (2020). Class A and B firefighting foam. https://www4.des.state.nh.us/nh-pfas-investigation/?page_id=148 INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials IdFeYnt2i0fi2e0d NinDtAhAe 28 Noll, G. S., & Hildebrand, M. S. (2016). Liquid petroleum pipeline emergencies on-scene commander field guide. Fire Protection Research Foundation. North Carolina Department of Environmental Quality. (2017). DEQ verifies Chemours has stopped discharging GenX wastewater. https://deq.nc.gov/news/press-releases/2017/06/27/deq-verifieschemours-has-stopped-discharging-genx-wastewater OECD (Organization for Economic Cooperation and Development). (2011). PFCs: Outcome of the 2009 survey: Survey on the production, use and release of PFOS, PFAS, PFOA PFCA, their related substances and products/mixtures containing these substances (ENV/JM/MONO(2011)1). http://www.oecd.org/officialdocuments/publicdisplaydocumentpdf/?cote=env/jm/mono(2011)1&do clanguage=en OECD (Organization for Economic Cooperation and Development). (2013). Synthesis paper on per- and polyfluorinated chemicals (PFCs). https://www.oecd.org/env/ehs/risk-management/PFC_FINALWeb.pdf OECD (Organization for Economic Cooperation and Development). (2015). Working towards a global emission inventory of PFASs: Focus on PFCAs--status quo and the way forward. https://www.oecd.org/chemicalsafety/risk-management/ Working%20Towards%20a%20Global%20Emission%20Inventory%20of%20PFASS.pdf Posner, S., Roos, S., & Olsson, E. (2009). Survey of the extent of use and occurrence of PFNA (perfluorononanoic acid) in Norway (Swerea IVF Project Report 09/41). https://www.miljodirektoratet.no/globalassets/publikasjoner/klif2/publikasjoner/2562/ta2562.pdf Posner, S. (2012). Perfluorinated compounds: Occurrence and uses in products. In T. P. Knepper & F. T. Lange (Eds.). Polyfluorinated chemicals and transformation products (pp. 25-39). Springer. https://link.springer.com/content/pdf/10.1007%2F978-3-642-21872-9.pdf RadTech International North America. (2010). Guidance on cleanup and disposal of UV/EB-curing waste materials. https://www.radtech.org/images/sustainability_pdfs/GuidanceCleanupDisposal.pdf Resolution Consultants. (2016). Evaluation of potential sources of perfluorinated compounds at the former Naval Air Station Joint Reserve Base Willow Grove, Pennsylvania. https://www.navfac.navy.mil/niris/MID_ATLANTIC/WILLOW_GROVE_NAS/N00158_000774.pdf Robco. (2020). High temperature products. https://robco.com/en/products/hightemperature#robcoperfluoro Schenker, U., Scheringer, M., Macleod, M., Cousins, I. T., & Hungerbhler, K. (2008). Contribution of volatile precursor substances to the flux of perfluorooctanoate to the Arctic. Environmental Science and Technology, 42(10), 3710-3716. https://doi.org/10.1021/es703165m INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials IdFeYnt2i0fi2e0d NinDtAhAe 29 Schultes, L., Vestergren, R., Volkova, K., Westberg, E., Jacobson, T., & Benskin, J. P. (2018). Per- and polyfluoroalkyl substances and fluorine mass balance in cosmetic products from the Swedish market: Implications for environmental emissions and human exposure. Environmental Science: Processes and Impacts, 20(12), 1680-1690. https://doi.org/10.1039/C8EM00368H Schultz, M. M., Higgins, C. P., Huset, C. A., Luthy, R. G., Barofsky, D. F., & Field, J. A. (2006). Fluorochemical mass flows in a municipal wastewater treatment facility. Environmental Science and Technology, 40(23), 7350-7357. https://pubs.acs.org/doi/10.1021/es061025m Sepulvado, J. G., Blaine, A. C., Hundal, L. S., & Higgins, C. P. (2011). Occurrence and fate of perfluorochemicals in soil following the land application of municipal biosolids. Environmental Science and Technology, 45, 8106-8112. SERDP (Strategic Environmental Research and Development Program). (2020). AFFF alternatives: Art of the possible. Sheinson, R. S., Williams, B. A., Green, C., Fleming, J. W., Anleitner, R., Ayers, S., Maranghides, A., & Barylski, D. (2002). Future of aqueous film-forming foam (AFFF): Performance parameters and requirements. In: R. G. Gann & P. A. Reneke (Eds.). Proceedings of the 12th Halon Options Technical Working Conference (pp. 1-6). Sinclair, E., & Kannan, K. (2006). Mass loading and fate of perfluoroalkyl surfactants in wastewater treatment plants. Environmental Science and Technology, 40(5), 1408-1414. https://pubs.acs.org/doi/10.1021/es051798v Solo-Gabriele, H. M., Jones, A. S., Lindstrom, A. B., & Lang, J. R. (2020). Waste type, incineration, and aeration are associated with per- and polyfluoroalkyl levels in landfill leachates. Waste Management, 107, 191-200. https://doi.org/10.1016/j.wasman.2020.03.034 Sun, M., Arevalo, E., Strynar, M., Lindstrom, A., Richardson, M., Kearns, B., Pickett, A., Smith, C., & Knappe, D. R. U. (2016). Legacy and emerging perfluoroalkyl substances are important drinking water contaminants in the Cape Fear River watershed of North Carolina. Environmental Science and Technology Letters, 3(12), 415-419. https://pubs.acs.org/doi/abs/10.1021/acs.estlett.6b00398 Thalheimer, A. H., McConney, L. B., Kalinovich, I. K., Pigott, A. V., Franz, J. D., Holbert, H. T., Mericas, D., & Puchacz, Z. J. (2017). Use and potential impacts of AFFF containing PFASs at airports. National Academies of Sciences, Engineering, and Medicine. Tokarsky, E., & Uy, W. (2003). High speed melt spinning of fluoropolymer fibers. U.S. Patent Office: US 2003/0175513 A1. Tremblay, J. F. (2015). Electronics: Loss of fluorinated compounds narrows options for chipmakers. Chemical and Engineering News, 93(28), 27-29. https://cen.acs.org/articles/93/i28/ELECTRONICS.html Tuve, R. L., Peterson, H. B., Jablonski, E. J., & Neill, R. R. (1964). A new vapor-securing agent for flammable-liquid fire extinguishment (NRL Report 6057). Naval Research Laboratory. INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials IdFeYnt2i0fi2e0d NinDtAhAe 30 UNEP (United Nations Environment Programme). (2011). Guidance on alternatives to perfluorooctane sulfonic acid and its derivatives. U.S. EPA (Environmental Protection Agency). (1990). Guides to pollution prevention: The printed circuit board manufacturing industry. https://archive.epa.gov/sectors/web/pdf/01050.pdf U.S. EPA (Environmental Protection Agency). (2006). 2010/15 PFOA stewardship program guidance on reporting emissions and product content. https://www.epa.gov/sites/production/files/201510/documents/pfoaguidance.pdf U.S. EPA (Environmental Protection Agency). (2009a). Perfluorocarboxylic acid content in 116 articles of commerce (EPA/600/R-09/033). https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NRMRL&dirEntryId=206124 U.S. EPA (Environmental Protection Agency). (2009b). PFOS chromium electroplater study. U.S. EPA (Environmental Protection Agency). (2012). A citizen's guide to activated carbon treatment. https://www.epa.gov/sites/production/files/2015-04/documents/ a_citizens_guide_to_activated_carbon_treatment.pdf U.S. EPA (Environmental Protection Agency). (2014). 2010/2015 PFOA Stewardship Program--2014 annual progress reports. https://www.epa.gov/assessing-and-managing-chemicals-undertsca/20102015-pfoa-stewardship-program-2014-annual-progress U.S. EPA (Environmental Protection Agency). (2016a). Drinking water health advisory for perfluorooctane sulfonate (PFOS). https://www.epa.gov/sites/production/files/201605/documents/pfos_health_advisory_final_508.pdf U.S. EPA (Environmental Protection Agency). (2016b). Drinking water health advisory for perfluorooctanoic acid (PFOA). https://www.epa.gov/sites/production/files/201605/documents/pfoa_health_advisory_final-plain.pdf U.S. EPA (Environmental Protection Agency). (2017). Compliance and annual reporting guidance about Clean Water Act laws. https://19january2017snapshot.epa.gov/biosolids/compliance-and-annualreporting-guidance-about-clean-water-act-laws_.html U.S. EPA (Environmental Protection Agency). (2019). Biosolids laws and regulations. https://www.epa.gov/biosolids/biosolids-laws-and-regulations U.S. EPA (Environmental Protection Agency). (2020a). TSCA 8(a) chemical data reporting revisions: Final rule. https://www.regulations.gov/docket?D=EPA-HQ-OPPT-2018-0321 U.S. EPA (Environmental Protection Agency). (2020b). National Pollutant Discharge Elimination System (NPDES). https://www.epa.gov/npdes U.S. EPA (Environmental Protection Agency). (2020c). Federal Aviation Administration Technical Center (USDOT), Atlantic County, NJ: Cleanup activities. https://cumulis.epa.gov/supercpad/SiteProfiles/index.cfm?fuseaction=second.cleanup&id=0201178 INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials IdFeYnt2i0fi2e0d NinDtAhAe 31 U.S. EPA (Environmental Protection Agency). (2020d). Drinking Water Treatability Database (TDB). https://www.epa.gov/water-research/drinking-water-treatability-database-tdb U.S. EPA (Environmental Protection Agency). (2020e). Vessel Incidental Discharge National Standards of Performance: Proposed rule. https://www.federalregister.gov/documents/2020/10/26/202022385/vessel-incidental-discharge-national-standards-of-performance Venkatesan, A. K., & Halden, R. U. (2013). National inventory of perfluoroalkyl substances in archived U.S. biosolids from the 2001 EPA National Sewage Sludge Survey. Journal of Hazardous Materials, 252-253, 413-418. https://doi.org/10.1016/j.jhazmat.2013.03.016 Vermont Agency of Natural Resources. (n.d.). State partners with local fire departments to safely get rid of toxic fire-fighting foam. https://anr.vermont.gov/node/1276 Wang, Z., Cousins, I. T., Scheringer, M., Buck, R. C., & Hungerbhler, K. (2014). Global emission inventories for C4-C14 perfluoroalkyl carboxylic acid (PFCA) homologues from 1951 to 2030, Part I: production and emissions from quantifiable sources. Environment International, 70, 62-75. https://doi.org/10.1016/j.envint.2014.04.013 Washington, J. W., Yoo, H., Ellington, J. J., Jenkins, T. M., & Libelo, L. (2010). Concentrations, distribution, and persistence of perfluoroalkylates in sludge-applied soils near Decatur, Alabama, USA. Environmental Science and Technology, 44, 8390-8396. Waste Management and Research Center. (1992). Paint waste reduction and disposal options: Executive summary. https://www.ideals.illinois.edu/bitstream/handle/2142/2052/tr07.pdf?sequence=1&isAllowed=y World Bank Group. (1998). Pollution prevention and abatement handbook: Pesticides formulation. https://www.ifc.org/wps/wcm/connect/115011ba-26ca-4166-8cc4a0655d355d08/PPAH.pdf?MOD=AJPERES&CACHEID=ROOTWORKSPACE-115011ba-26ca-4166-8cc4a0655d355d08-jqeAFFh INTERIM GUIDANCE FOR PUBLIC COMMENT Description of PFAS-Containing Materials IdFeYnt2i0fi2e0d NinDtAhAe 32 3. Technologies for the Destruction and Disposal of PFAS and PFAS-Containing Materials EPA has identified three technological solutions that are commercially available and potentially have the capability to destroy PFAS or manage the migration of PFAS in PFAS-containing materials. These technologies are thermal treatment (Section 3.a), landfilling (Section 3.b), and underground injection control (Section 3.c). Each subsection describes various considerations of these technological solutions, including types of treatment, control devices and corresponding emissions, testing and monitoring, and uncertainties. References appear at the end of each subsection. 3.a Thermal treatment Hazardous waste combustion technologies (commercial incinerators, cement kilns, and lightweight aggregate kilns [LWAKs]) can potentially achieve temperatures and residence times sufficient to break apart the PFAS contained in the waste stream being thermally treated. Permitted hazardous waste facilities have stringent regulatory controls on temperatures and other important operating parameters to achieve a 99.99 percent destruction efficiency for other (non-PFAS) organic chemicals, but information on the efficacy of PFAS destruction in these facilities is currently lacking. EPA currently has no emission characterizations from these sources when they burn PFAS, and is working to develop measurement methodologies and gather information to conclude whether potential PICs are adequately controlled. EPA recognizes that PICs are inevitable (even for nonfluorinated compounds); however, based on the unique characteristics of fluorine combustion chemistry, it needs to be determined whether thermal treatment devices and their associated post-combustion control devices are adequately controlling fluorinated PICs. Given all these factors, there is a current need to continue research activities investigating incineration of PFAS. After sufficient research has been completed to address the related knowledge and data gaps, EPA can make a more informed recommendation on disposal of PFAS compounds and PFAS-containing substances using incineration. Thermal treatment units use high-temperature chemical breakdown or incineration to control pollutants. Incineration is an effective and approved method for destroying certain halogenated organic chemicals including chlorinated solvents, polychlorinated biphenyls (PCBs), dioxin-laden wastes, brominated flame retardants, refrigerants, and ozone-depleting substances (ODSs). Fluorine, like chlorine and bromine, is a halogen; thus, PFAS fall into the category of halogenated chemicals. PFAS are difficult to destroy due to the strength of the carbon-fluorine bond--a result of fluorine's electronegativity and the chemical stability of fluorinated compounds. Incomplete destruction or recombination of reactive intermediates can potentially result in the formation of new PFAS or other PICs of concern. Halogenated organic compounds generate the corresponding halogen acid when sufficiently high temperatures and long residence times break the carbon-halogen bond as the INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 33 compounds thermally decompose and the resulting halogen atoms recombine with available hydrogen. For this interim guidance, PFAS destruction is defined as the complete severing of all carbon-fluorine bonds in a PFAS molecule. Severing all carbon-fluorine bonds results in conversion to carbon dioxide, hydrogen fluoride (HF), and other compounds. HF and some of the other products of combustion can be removed in pollution control devices. This section focuses on the viability of thermal treatment of PFAS, discussing: The types of thermal treatment units that manage PFAS-containing waste and their ability to effectively destroy PFAS. The potential for environmental releases during these thermal treatment operations. PFAS monitoring methods relevant to these thermal treatment operations. Uncertainties and unknowns associated with thermally treating PFAS-containing waste, including the ability to effectively measure and monitor thermal treatment performance. Operating costs and commercial availability for the thermal treatment operations known to handle PFAS-containing waste. 3.a.i Types of thermal treatment The following subsections describe the types of thermal treatment devices potentially capable of treating PFAS-containing waste streams identified in Section 2.a, with a focus on design and operation parameters that are important for destroying PFAS. These include hazardous waste combustors (HWCs), non-hazardous waste combustors, carbon reactivation units, and thermal oxidizers. Waste incinerators are typically classified by the type of waste that they combust. 3.a.i.1 Hazardous waste combustors HWCs are hazardous waste incinerators (HWIs), cement kilns, LWAKs, boilers, and hydrochloric acid production furnaces that burn hazardous waste.1,2 Two types of HWCs that have treated PFAS waste in the United States are commercial3 incinerators and LWAKs. Initial studies suggest that cement kilns may be effective at treating PFAS waste (see Section 3.a.ii). All HWIs, LWAKs, and cement kilns are subject to Resource Conservation and Recovery Act (RCRA) and Clean Air Act (CAA) permitting requirements that provide additional regulatory oversight and include operating requirements and emission limitations to safely and effectively treat regulated hazardous contaminants that may not be required for non-permitted facilities. These types of HWCs are subject to CAA Title V permitting requirements, and to maximum achievable control technology standards pursuant to Section 112 of the CAA that include emission limitations for metals, dioxin/furans, 1 Hazardous waste is regulated pursuant to Resource Conservation and Recovery Act authority. See 42 U.S.C. 6903. The regulatory definition is found in 40 CFR 261.3. PFAS is currently not a listed or characteristic hazardous waste, but a PFAScontaining waste may meet the regulatory definition of hazardous waste if PFAS is mixed with a listed hazardous waste or if a PFAS-containing mixture exhibits a hazardous characteristic (e.g., corrosivity or another characteristic stemming from the material that is mixed with PFAS). 2 Hazardous-waste-burning cement kilns and LWAKs are a small subset of the total cement kiln and LWAK universe--i.e., most kilns do not burn hazardous waste. 3 Commercial thermal treatment units primarily treat waste received from other facilities. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 34 particulate matter, hydrogen chloride and chlorine gas, and carbon monoxide or hydrocarbons, as well as limits on minimum organic destruction and removal efficiency (DRE). Also, under the authority of RCRA's "omnibus" clause (Section 3005(c)(3); see 40 CFR 270.32(b)(2)), RCRA permit writers may impose additional terms and conditions on a site-specific basis as may be necessary to protect human health and the environment. Due to these additional safeguards, permitted HWCs may operate under conditions more conducive to destroying PFAS and controlling related PICs relative to thermal treatment units that do not have both RCRA and CAA permits. The following sections generally describe design and operational parameters of commercial HWIs, LWAKs, and cement kilns, focusing on parameters that are important for destroying PFAS. Design and operation information summarized for HWCs is generally based on previous rulemaking background support documents (U.S. EPA, 2005b) and numbers of HWC facilities are based on a 2019 national hazardous waste capacity assessment report (U.S. EPA, 2019). The capacity assurance report also provides a list of these facilities. 3.a.i.1.1 Commercial hazardous waste incinerators There are 10 commercial HWI facilities operating in the United States. HWIs are designed to optimize temperatures, residence times, turbulence, and other parameters to ensure compliance with organic DRE requirements.4 Most commercial HWIs use rotary kilns as primary combustion chambers to facilitate the thermal treatment of containerized wastes (e.g., in drums) and solid wastes such as contaminated soils. Low-heating-value aqueous wastes may also be pumped into the rotary kiln. The kiln maintains a continuous standing flame fueled by high-heating-value wastes and auxiliary fuels that maintain high temperatures. Typically, solids retention time in the kiln is 0.5 to 1.5 hours, while gas residence time through the kiln is usually around two seconds. Kiln flame/solids temperatures range from 650C to 1,650C (1,200F to 3,000F). The rotary kiln is followed by an afterburner where additional high-heating-value gaseous and liquid wastes, and auxiliary fuels are added. The afterburner is typically operated at about 1,100C to 1,370C (2,000F to 2,500F) with a gas residence time from 1 to 3 seconds to maximize organic destruction and minimize the formation of PICs. Depending on the fuels used and waste streams introduced, combustion products include carbon dioxide, water, nitric oxide, a variety of acid gases (sulfur dioxide, hydrochloric acid, HF, etc.), organic PICs, fly ash, and bottom ash constituents. Bottom ash is removed at the end of the kiln and from the bottom of the afterburner and is typically disposed of in hazardous waste landfills (see Section 3.b). Fly ash entrained in the gas is removed downstream by fabric filters (FFs) or electrostatic precipitators, and acid gases are removed by gas scrubbers. Some HWIs use activated carbon injection systems to control dioxin/furan and other emissions. 3.a.i.1.2 Hazardous-waste-burning cement kilns Currently, there are 11 hazardous-waste-burning cement kiln facilities in the United States. A cement kiln is a long, cylindrical, slightly inclined rotating furnace designed to calcine a blend of raw materials such as limestone, shale, clay, or sand to produce a key ingredient of Portland cement. These cement kilns burn hazardous-waste-derived fuels to replace some or all of the fossil fuels. Most of them burn liquid waste; some may also burn solids and small containers containing viscous or solid hazardous waste fuels. Extreme combustion conditions (e.g., temperatures above 1,650C [3,000F]), turbulent mixing, and long gas phase residence time (from 4 to as high as 16 seconds in long kilns) can effectively 4 DRE = [1 - (Wout / Win)] 100%, where: Win = mass feedrate of an organic compound into the combustion device and Wout = mass emission rate of the same organic compound in exhaust emissions. HWCs are required to achieve at least 99.99% DRE. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 35 treat hazardous waste. Cement kilns use either electrostatic precipitators or baghouses to collect particulate and metal emissions, referred to as cement kiln dust (CKD). Portions of the CKD can be fed back into the kiln as a raw material feed or be used in other industries as neutralizers or additives, but usually the excess CKD is land-disposed. Add-on acid gas air pollution control devices, such as wet or dry scrubbers, are typically not used: the high alkaline content of the raw material feeds already prevents or minimizes the formation and release of acid gases by providing for "in situ" absorption of chlorine and other halogens and sulfur. 3.a.i.1.3 Hazardous-waste-burning lightweight aggregate kilns There is one LWAK facility operating in the United States that burns hazardous waste. LWAKs thermally process raw material (clay, shale, and slate) in slightly inclined, rotating furnaces to produce a coarse aggregate used in lightweight concrete products. In hazardous-waste-burning LWAKs, liquid wastes are either blended directly with conventional fuels burned in the hot end of the kiln or pumped separately into the hot end flame. High combustion gas flame temperatures (above 1,650C [3,000F]) and kiln gas residence times (over 2 seconds) are used to destroy hazardous organics. Kiln exhaust gases leave the cold upper end of the kiln at a temperature from 205C to 540C (400F to 1,000F). LWAKs use FFs to control dust contained in the exhaust gas. The collected dust can be recycled back into the kiln (at the hot or cold end) or mixed into the lightweight aggregate product. Some LWAKs also use wet or dry scrubbing for acid gas emissions control. 3.a.i.2 Carbon reactivation units Carbon reactivation units or "furnaces" use high temperatures to thermally desorb contaminants from GAC, which allows for the carbon to be used again. Over a dozen large-scale companies and utilities in the United States reactivate sizeable quantities of GAC. In all, these entities operate about 17 commercial furnaces (Roskill Information Services Ltd., 2017). Four of these commercial furnaces operate under RCRA permits and applicable air permits. RCRA permits provide additional regulatory oversight and include operating requirements and emission limitations to safely and effectively treat the hazardous contaminants, which may not be required for non-RCRA-permitted carbon reactivation furnaces. Due to these additional safeguards, RCRA-permitted furnaces may operate under conditions more conducive to destroying PFAS and controlling related PICs. This discussion focusses on RCRApermitted furnaces because EPA has more design and operational information on these devices as a result of the RCRA permitting process. Reactivation5 of spent carbon is generally carried out in multiplehearth (or "multi-hearth") or rotary kiln furnaces, although fluidized bed and infrared furnaces are also options. While the furnace designs vary, they all use high temperatures and residence times designed to eliminate the adsorbed contaminants and return the carbon to a virgin state for reuse. During reactivation, spent GAC is typically exposed to drying, desorption, pyrolysis, and oxidation as it moves through the furnace. The drying stage eliminates moisture via evaporation and occurs when hot combustion gases ranging from 100C to 110C (212F to 230F) contact the carbon. 5 "Reactivation" refers to a regeneration process that requires high temperatures. Regeneration also includes low-temperature processes, including those using brines, solvents, oxidants, biological treatment, etc. These processes may not be as effective as reactivation for GAC (AWWA, 2018); therefore, they are not considered for this discussion. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 36  During the desorption stage, hydrocarbons, hydrogen, and water vapor escape the pores of the granular carbon at temperatures of 315C to 400C (600F to 750F). The pyrolysis stage eliminates any volatile compounds adsorbed within the carbon porosity, including residual moisture, and thermally decomposes other less-volatile compounds. Pyrolysis occurs when the carbon is exposed to temperatures up to 800C (1,472F) under inert conditions (i.e., low oxygen). A residue of carbonized char is formed from the adsorbed compounds during pyrolysis, which occupies some of the carbon porosity and must be removed in the next stage. The oxidative stage involves the controlled gasification of the pyrolyzed carbon at temperatures usually around 800C (1,472F) in the presence of a mildly oxidizing atmosphere, usually steam or carbon dioxide or a mixture of both. This results in the elimination of most of the charred residue and exposes the original carbon-pore structure (Miguel et al., 2001). The residence times required for carbon reactivation vary by unit design and the contaminant loads and concentrations. For example, two different facilities using multi-hearth furnaces have residence times of at least 38 minutes at one facility and between 90 and 120 minutes at the second facility (Kentucky Energy and Environment Cabinet, 2019; U.S. EPA, 2018).6 To ensure adequate destruction and removal of any remaining contaminants, reactivation furnaces are typically equipped with afterburners/thermal oxidizers. To meet regulatory requirements, afterburners are designed to achieve 99.99 percent DRE via thermal oxidation. The temperature required to achieve 99.99 percent DRE depends on residence time as well as the concentration of contaminants, but minimum temperatures are around 885C (1,625F) and maximum temperatures are as high as 1,316C (2,400F), with a minimum residence above 1 second (U.S. EPA, 2018). Depending on the process or waste streams treated, a reactivation furnace can be equipped with add-on air pollution control equipment to ensure environmental standards are met. These can include venturi scrubbers for particulate matter control, packed-bed scrubbers for acid gas and particulate matter control, and wet electrostatic precipitators or baghouses for additional particulate matter control. 3.a.i.3 Non-hazardous-waste combustion sources Non-hazardous-waste incineration in the United States includes sewage sludge incinerators (SSIs) at wastewater treatment facilities and municipal waste combustors (MWCs). Under Section 129 of the CAA, these units are regulated for emissions of particulate matter, carbon monoxide, dioxins/furans, sulfur dioxide, nitrogen oxides, hydrogen chloride, lead, mercury, and cadmium. The following sections generally describe these incinerator types and their design and operational parameters that may influence the treatment of PFAS-containing waste (U.S. EPA, n.d.). 3.a.i.3.1 Sewage sludge incinerators An SSI unit is a combustion device that is used to burn dewatered sewage sludge. There are currently 170 SSI units operating in the United States (U.S. EPA, 2016). The main types of SSIs are multi-hearth furnaces and fluidized bed combustors (FBCs). 6 These two references are RCRA permits for Evoqua Water Technologies LLC and Calgon Carbon Corporation, two companies that accept spent activated carbon from off-site sources. They each hold RCRA permits, which allow them to treat spent carbon that meets the definition of hazardous waste. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 37 The basic multi-hearth furnace is a vertical cylinder divided into zones. The sludge is dried at temperatures from 425C to 760C (800-1,400F). Sludge combustion occurs as the temperature is increased to about 925C (1,700F) in successive zones. The gas residence times are typically 4 or 5 seconds. Emission controls on multiple hearths can include wet scrubbers, wet electrostatic precipitators, afterburners, and regenerative thermal oxidizers. An FBC consists of a vertically oriented outer steel shell with nozzles designed to deliver fluidizing air at the base of the furnace within a refractory-lined grid. Air is injected into the furnace to fluidize the sludge and the sand. The combustion of the sludge occurs at temperatures between 750C and 925C (1,400-1,700F). The gas residence times are typically 2 to 5 seconds. Emission controls on FBCs can include venturi scrubbers, multicyclones, FFs, activated carbon injection, and carbon bed absorbers. 3.a.i.3.2 Municipal waste combustors There are 193 MWC units operating in the United States (Michaels & Krishnan, 2018). Three main classes of technologies are used to combust MSW: mass burn, refuse-derived fuel (RDF), and modular combustors. Mass burn and RDF combustors are the predominant designs. With mass burn units, the MSW is combusted without any preprocessing other than removal of items too large to go through the feed system or hazardous materials, such as pressurized containers. In a typical mass burn combustor, refuse is placed on a grate that moves the waste through the combustor. The grates typically have three sections. On the initial grate section, referred to as the drying grate, the moisture content of the waste is reduced before ignition. The second grate section, referred to as the burning grate, is where most of the active burning takes place. The third grate section, referred to as the burnout or finishing grate, is where remaining combustibles in the waste are burned. Typical combustion temperatures for mass burn units can range from 800C to 1,100C (1,500F to 2,012F) (Reddy, 2016). RDF combustors burn waste that has been processed to varying degrees to raise its heating value and provide a more uniform fuel. Most boilers designed to burn RDF use spreader stokers and typically operate at around 680C (1,250F). RDF-fired FBCs typically operate at bed temperatures around 815C (1,500F). Residence times of gases within MSW combustors vary from unit to unit, depending on design and operational factors such as furnace volume, excess combustion air percentage, whether flue gas recirculation is employed, and combustor operating load parameters (Scavuzzo et al., 1990; Themelis & Reshadi, 2009). Overall combustion air residence times have been calculated in the 7-10 second range for a small sampling of MWC design loads (Themelis & Reshadi, 2009), with an approximate residence time at temperature above 980C (1,800F) of about 2 seconds at full combustor load (Scavuzzo et al., 1990). Emission controls on MWCs can include spray dryer or dry sorbent injection, electrostatic precipitator or FF, selective or non-selective catalytic reductions, and activated carbon injection. 3.a.i.4 Thermal oxidizers Thermal oxidizers are used to destroy volatile organic compounds (VOCs) and organic hazardous air pollutants (HAPs) from liquid and gaseous process streams at a manufacturing or production facility. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 38 These devices are designed to optimize temperatures, residence times, and turbulence to address the composition of the feedstream and meet the requirements of a regulation or permit. Depending on the type of thermal oxidizer (direct-fired, regenerative, recuperative, or flameless), the operating temperature ranges from 760C to 1,200C (1,400F to 2,190F). The residence time of thermal oxidizers ranges from 0.5 to 2 seconds, depending on site-specific criteria. Catalytic thermal oxidizers operate at lower temperatures than other types of thermal oxidizers--typically about 400C (800F) with similar residence times to non-catalytic thermal oxidizers--while achieving the same efficiency. Emission controls for thermal oxidizers vary widely depending on the facility and the composition of the feedstreams. Existing thermal oxidizers may have no additional pollution controls or may use prefiltration (to prevent fouling of the oxidizer) and/or wet or dry scrubbers or FFs. 3.a.ii Ability of thermal treatment technologies to destroy PFAS Combustion involves burning a fuel in the presence of excess atmospheric oxygen. Combustion progresses through a complex series of physical and chemical processes involving reactant interaction, mixing, and many elementary free radical reactions. The complete combustion of hydrocarbon fuels results in carbon dioxide and water; for PFAS, the final products also include HF. In practice, kinetic (temperature) and transport (mixing) limitations prevent complete combustion of fuels. This is related to the three Ts (time, temperature, and turbulence) used to guide the design and operation of incinerators and thermal oxidizers to maximize complete waste destruction. In real world systems, incomplete combustion leads to emissions of carbon monoxide, soot, and other PICs. The carbon-fluorine bond is much stronger than the carbon-chlorine bond. Breaking the carbon- fluorine bond requires 1.5 times more energy and therefore higher temperatures and reaction times. Based on calculated bond energies, the most difficult fluorinated organic compound to decompose is carbon tetrafluoride (CF4), requiring temperatures over 1,400C (2,550F) (Tsang et al., 1998). This is due to the compound's four carbon-fluorine bonds and symmetrical structure. The presence of carbon- carbon or carbon-hydrogen bonds (as in hexafluoroethane [C2F6] or fluoroform [CHF3]) provides a weak point in the structure and thus significantly lowers temperatures needed for decomposition. Due to their thermal stabilities, short-chain fluorinated carbons such as CF4, CHF3, C2F6, and C3F8 may be good indicators of broader PFAS defluorination. In addition, these compounds may be relatively easy to monitor by Fourier transform infrared spectrometry (FTIR), making them potential low-risk candidate surrogates for thermal destructibility trials. Further, fluorinated organic compounds can be destroyed in flames by free radical initiation, propagation, and branching mechanisms. To increase the efficiency of these processes, it is important to provide high concentrations of hydrogen radicals (as in flames) to promote HF formation, reducing the strong flame inhibition effects of fluorine radicals. There is concern that carbon-carbon bonds can be broken at moderate temperatures, leaving carbon-fluorine fragments. The fate of these carbon-fluorine radicals depends on the local temperatures and concentrations of other free radicals. If the local energies and free radical concentrations are low, these carbon-fluorine fragments may recombine to form fluorinated PICs. However, if the local temperatures and concentrations of free radicals (particularly hydrogen radical) are high, as in flames, the carbon-fluorine species is more likely to degrade further to CO2 and HF. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 39 The stability of perfluorinated radicals and their propensity to recombine present the potential for the creation of PFAS PICs distinctive from the original fluorinated compounds. These reactions are promoted by partial combustion caused by insufficient temperatures, time, and turbulence. Many PFAS are composed of very stable fluorinated carbon chains and relatively weak non-fluorinated functional groups. Often, the functional group is easily removed, allowing the fluorinated chain to react with other radicals and create a variety of compounds, which complicates the determination of DREs and the identification of PICs (Wang et al., 2015). In addition, the presence of catalytic surfaces, often metals, may promote further reaction and PIC formation in post-combustion regions. PFAS PICs may be smaller in molecular weight than the original species or larger in molecular weight when formed via the recombination of two large radicals. Incinerator designs vary, resulting in differing operational and waste feed approaches (see Section 3.a.i). HWIs typically operate at very high average temperatures and employ auxiliary primary and secondary flames. MWCs typically operate at lower temperatures, and often do not employ auxiliary primary or secondary flames. SSIs vary in design, often operating as dryers with very low temperatures. Even within the same incinerator, wastes can be introduced at different locations and experience different time, temperature, and mixing histories. PFAS introduced into a hazardous waste rotary kiln incinerator's main burner, along with auxiliary fuel, may experience very different conditions than the same waste introduced to the kiln as contained charges with solid wastes. These factors are expected to affect PFAS destruction and PIC formation. Limited studies have investigated the influence of various factors on PFAS destruction and PIC formation (see Section 3.a.viii). Carbon reactivation systems can degrade PFAS even at the lower temperatures (150C-700C) (302F- 1,292F) seen in bench-scale research studies. Experimental data suggest that thermal destruction of PFAS will occur in two stages: during reactivation of the GAC, then when the offgas is introduced into a high-temperature zone as high as 1,000C (Forrester, 2018; Watanabe et al., 2016, 2018; Xiao et al., 2020). Carbon reactivation systems, with the concomitant use of offgas incineration (i.e., afterburners) and gas scrubbing units, can destroy PFAS without significant environmental releases, or without PFAS remaining on the reactivated carbon. However, as discussed elsewhere in this interim guidance, more work is needed for confirmation particularly with regard to reactor conditions, differing carbons, and PICs. Thermal oxidizers have historically not been designed with destruction of PFAS as the primary focus, so most currently installed thermal and catalytic oxidizers may not be optimized for PFAS destruction. Thermal oxidizers are being employed to destroy PFAS-containing liquid and gaseous streams, but the data are insufficient to allow conclusions on the overall efficiency of thermal oxidizers in PFAS destruction. EPA is currently unaware of any catalytic oxidizers being used specifically for the destruction of PFAS, particularly in light of their site-specific design and optimization. Though the efficacy of thermal and catalytic oxidizers in destruction of PFAS is currently unknown, a properly optimized thermal oxidizer can readily achieve a DRE of 99.99 percent of VOCs. In addition to incinerators and thermal oxidizers, cement kilns are also used for the destruction of hazardous wastes. Cement kilns operate at very high temperatures (exceeding 1,800C [3,270F]), exhibit very large gas and solid residence times, and have the added advantage of providing a caustic environment for halogen reaction and acid neutralization. A cement kiln in Australia has received an INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 40 operating permit from the government of Queensland to burn PFAS wastes. The permit requires annual monitoring for 21 PFAS (Department of Environment and Heritage Protection, 2018). Processes involving calcium and alumina may have catalytic benefits and require lower energies to destroy PFAS. Recent research (Wang et al., 2011, 2013, 2015) has investigated PFAS interactions with calcium oxide (CaO) and calcium hydroxide (Ca(OH)2) at moderate temperatures 200C to 900C (390F to 1,650F), and found that these calcium species exhibit a pseudo-catalytic effect promoting PFAS destruction and fluorine capture at relatively low temperatures. Similar studies by the electronics industry indicate that alumina catalysts can effectively convert residual CF4 and related species (generated by plasma arc techniques for etching purposes) to carbon dioxide and HF at comparable temperatures. It is not well understood how effective high-temperature combustion is in completely destroying PFAS or whether the process can form fluorinated or mixed halogenated organic byproducts. Few experiments have been conducted under oxidative and temperature conditions representative of different field-scale incineration devices used for PFAS destruction. Limited studies on the thermal destructibility of fluorotelomer-based polymers found no detectable levels of PFOA after 2 seconds of residence time at 1,000C (1,830F) (Yamada et al., 2005; Taylor et al., 2014). One recent field study examining the performance of a specially designed thermal oxidizer to destroy PFAS in process gases at a Chemours production facility near Fayetteville, North Carolina, indicated >99.999 percent destruction of five PFAS (Chemours, 2020). This implies the destruction of the original PFAS, but does not provide certainty that all carbon-fluorine bonds were severed. As discussed previously, emission studies, particularly for potential PICs, are largely incomplete due to lack of validated sampling and measurement methods for the potentially large number of fluorinated and mixed halogenated organic compounds that might be formed. EPA continues to seek information on PFAS that may be present in air pollution control device media (scrubber water, particulate matter control device media) and the presumed effectiveness of these air emission controls (see Section 5 for more information about ongoing research and research needs). 3.a.iii Other thermal treatment byproducts of concern Thermal treatment systems including HWIs, MWCs, and SSIs are configured such that gas phase effluent from the combustion chambers passes through a series of pollution control devices to remove acid gases, particulate matter, and sometimes mercury and other specific HAPs. The behavior of PFAS and PFAS-related PICs in these unit operations is largely unknown (see Section 5 for more information about research on this topic and others). Additionally, these control devices produce secondary waste streams in the form of fly ash and scrubber blowdown solutions, and PFAS PICs may be present in these solid and liquid effluents depending on their vapor pressure and solubility. Thermal oxidation processes used for treating PFAS-containing waste, such as incineration, generate HF as the most stable product from combustion of fluorocarbon compounds. HF is a CAA-listed HAP. Highly corrosive, HF creates significant operation and maintenance issues by damaging thermal system materials such as furnace refractory and metal ductwork. Both wet scrubbing and semi-dry scrubbing processes have been applied to control HF emissions from thermal treatment sources. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 41 A thermal oxidizer with a potential for HF emissions typically uses a wet scrubber integrated with the oxidizer to control HF emissions. Hot flue gas exiting from the oxidizer is cooled rapidly in a quenching unit, and HF (which has high water solubility) is removed by the quenching water. The cooled flue gas then flows up through a multistep wet scrubbing tower for further HF removal by scrubbing water. Flue gas is scrubbed by a sodium hydroxide solution to neutralize the residual HF as the final scrubbing step. After exiting the tower, flue gas is emitted through a stack. All effluents, including those from the quenching unit and scrubber tower, are mixed with a Ca(OH)2 solution in a reactor where calcium is combined with fluorine and precipitation of water-insoluble calcium fluoride (CaF2) occurs. After dewatering, dry CaF2 is sent to a landfill for disposal (see Section 3.b) or used to produce fluorine gas for new PFAS production, and wastewater is discharged from the plant after it is treated by activated carbon to remove trace fluorinated contaminants. Rapid cooling of hot flue gas is known to be effective in reducing catalytic reformation of chlorinated PICs such as dioxins during cooling of incineration flue gas. A thermal oxidizer equipped with a quenching unit to treat PFAS-containing wastes may also limit catalytic reformation of fluorinated PICs if they are actually formed in the oxidizer. Those PICs may be subsequently transferred into the liquid phase in the wet scrubber, which could then be partitioning between solid CaF2 and water in the precipitator, with most of the PICs retained in water then removed by activated carbon adsorption. EPA is not aware of peer-reviewed studies for measuring levels of fluorinated contaminants remaining in both the treated scrubber water stream and the dry CaF2 stream. Such measurements could be useful for evaluating the potential environmental impacts of byproducts and residuals generated from thermal oxidation of PFAS-containing wastes. Spray dryer absorber (SDA) technology has been applied to control emissions of halogen acids including HCl and HF from both MWCs and HWIs. This semi-dry scrubbing process is designed to inject an alkaline slurry, typically lime, to control acid and fly ash. Water in the fine slurry droplets is vaporized by heat carried by the flue gas, and drying lime in droplets neutralizes the halogen acids simultaneously in this two-phase reaction process. The cooled flue gas carries the dried acid neutralization product downstream to a particle collection device, typically an FF. PAC may also be injected into flue gas upstream of the FF to control emissions of mercury and chlorinated dioxins/furans from both MWCs and HWIs. Fly ash, dried acid neutralization product, and PAC are captured by the FF. The SDA/FF with PAC injection flue gas cleaning train produces no scrubber water. The addition of lime (a calcium compound) into the flue gas is known to be effective for forming CaF2 through hydro-defluorination of PFOS at a moderate temperature of about 350C (660F) (Wang et al., 2015); this suggests the SDA may provide a potential co-benefit of controlling fluorinated PICs. The injection of PAC upstream of the FF subsequently may create another potential co-benefit for capturing fluorinated PICs. Studies evaluating PFAS mitigation via SDA/FF with PAC injection (e.g., see research activities in Section 5) will help develop data on this potentially viable technology option. 3.a.iv Potential for releases for thermal treatment technologies Thermal treatment devices used to treat PFAS-containing waste (see Section 3.a.i for descriptions of these devices) are located in both rural and populated areas throughout the United States. Two possible sources of potential PFAS emissions from thermal treatment are the stack emissions and subsequent management of scrubber water and bottom ash/fly ash. As previously discussed, emissions from INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 42 thermal treatment activities may contain PFAS if adequate combustion conditions are not achieved or if adequate acid gas scrubbers or other pollution control devices are not used. EPA is aware of limited peer-reviewed studies that have investigated the extent to which emitted PFAS are transported and deposited to surrounding areas (see Section 2.a.iii). EPA plans to conduct research in this area to better characterize the extent to which PFAS deposition may occur near thermal treatment devices (see Section 5 for more information about these types of research activities). Volatile PFAS releases from thermal treatment device equipment (e.g., fugitive emissions) and waste storage activities are another potential source of PFAS releases, if they are not adequately controlled.7 There is also the potential for releases from management of thermal treatment process residuals such as liquid discharges from acid gas scrubbers, air pollution control device media, and incinerator bottom ash. For example, incinerator bottom ash disposed of in a landfill would be a possible source of release if it contains PFAS and the landfill lacks adequate controls (see Section 3.b for more information on landfill types and controls, and Section 4 for more information about environmental releases and vulnerable populations). HWIs, however, typically dispose of incinerator bottom ash in hazardous waste landfills, minimizing the potential for the release of PFAS to the environment. Again, information on partitioning of PFAS in control technology residuals is lacking at present. 3.a.v Testing and monitoring Validated measurement methods are limited and under development for reliably identifying and quantifying if PFAS are released into the air from stationary sources. The current lack of standardized methods to measure PFAS emissions and the limited availability of data on the performance of methods to measure PFAS introduce uncertainty in the understanding of the efficacy of thermal treatment approaches for destroying PFAS. Ongoing method development has a broad focus that will address PFAS in various waste streams, stack and fugitive emissions, and ambient air. Method development also includes identification of PFAS that are potential PICs, not targeted in current established water methods such as Method 537.1. With the number and complexity of PFAS presently known, a simpler class-specific measurement is also being investigated to determine if a single compound or a small group of compounds is adequate to characterize the completeness of thermal treatment for both targeted PFAS and potential PICs. 3.a.v.1 Semivolatile PFAS sampling and analysis Development of methods to measure PFAS in air has focused on compounds whose physical state is liquid or solid at room temperature. Method development to measure PFAS compounds from air or air sources involves evaluating and then modifying existing sampling and analysis methods for semivolatile organic compounds. Filtered particulate, solid sorbent, and aqueous impinger media sampling procedures have been used to collect and recover a wider range of PFAS and associated byproducts in ambient air and source emissions (Barber et al., 2007; Martin et al., 2002). However, these sampling methods have some limits, 7 For example, CAA and RCRA regulations applicable to HWCs require controls to prevent/minimize combustion system leaks (e.g., due to positive pressure events in the combustion chamber), as well as controls to minimize releases from equipment and tanks that store or manage hazardous waste. See 40 CFR 63.1206(c)(5) and 264.1050-1090. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 43 including poor retention or chemical conversion of the PFAS during sampling and poor recovery during sample preparation prior to chemical analysis (Arp & Goss, 2008). Ambient sampling for semivolatile PFAS roughly follows the high-volume air sampling protocol described in EPA compendium method TO-13a (U.S. EPA, 1999) or National Atmospheric Deposition Program (NADP) approaches for wet and dry deposition sampling (NADP, 2020). High-volume air samples collect both water-soluble PFAS acids and salts and water-insoluble telomer alcohols. NADP sampling has focused on condensable and particulate-bound targeted PFAS captured in polypropylene buckets to evaluate deposition due to rain. Current method development and evaluation for stationary source air emissions is based on EPA SW846 Method 0010--modified to include collection of both targeted and nontargeted PFAS in a single sampling system. Sampling includes heated or stack temperature probe extraction of emission gases followed by collection on filters, XAD sorbent media, and aqueous impingers. EPA plans to release Other Test Method 45 (OTM-45), Measurement of Selected Poly- and Perfluorinated Alkyl Substances from Stationary Sources, based on this method development. These field procedures collect samples that are subsequently transported to a laboratory for extraction and analysis. Analysis procedures include established water methods for targeted compounds and/or non-targeted analysis (NTA) for unknown PFAS. High-resolution mass spectrometry can be used for both targeted analysis and NTA. Qualitative identification of PFAS by NTA reveals PICs/degradants formed during the thermal treatment of PFAS-contaminated media (Aleksandrov et al., 2019; McCord & Strynar, 2019; Newton et al., 2020). NTA, used to identify unknown PFAS, currently relies on high-resolution mass spectrometry, which generates qualitative information about the molecular formula of unknown PFAS. NTA is a critical component of thermal treatment emissions characterizations because it provides the only definitive approach for identifying unknown PFAS or PICs. 3.a.v.2 Gaseous volatile PFAS sampling and analysis Volatile PFAS targets and thermal treatment byproducts from ducted emissions or in ambient air have been sampled using a variety of whole gas sample collection approaches, such as Tedlar bags and SUMMA canisters, as well as sorbent traps and cryogenic solvents. Issues such as sample reactivity, breakthrough volumes, and quantitative transfer to the analysis instrument complicate these approaches. Direct instrumental methods to measure volatile PFAS can suffer from lack of sensitivity compared with extractive methods that allow concentration prior to analysis. To develop more sensitive methods to measure volatile fluorocarbon compounds, EPA has investigated the use of SUMMA canisters for targeted and nontargeted volatile PFAS as well as PICs at multiple-source emissions tests, including a thermal treatment facility for AFFF-contaminated soil (U.S. EPA, 2020b). SUMMA canisters have been used to sample source emissions and perform targeted measurements for PFAS including TFE, HFP, E1, E2, 4:2 FTOH, and 6:2 FTOH. NTA has also been performed on the same samples. EPA and private sector investigators have used specialized commercial sorbent traps and Tedlar bags in laboratory-scale thermal destruction and ambient volatile PFAS measurement of targeted and nontargeted PFAS (Wang et al., 2013, 2015; Yamada et al., 2005). INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 44 In ambient air, EPA also investigated chemical ionization mass spectrometry (CI/MS) to monitor individual PFAS in real time (Riedel et al., 2019). EPA found the technique sufficiently sensitive for fugitive emissions measurements or leak detection. EPA is evaluating FTIR as a suitable measurement technique for CF4 and C2F6 in stationary source emissions. In addition, EPA is exploring the use of SUMMA canister sampling and sorbent traps for offline measurements of CF4 and C2F6. The need to measure volatile PFAS at trace concentrations is based on the desire to introduce a known concentration of a hard-to-destroy fluorocarbon and evaluate the behavior of this compound when exposed to thermal treatment. This approach is consistent with the EPA approach to determine the DRE of fluorinated greenhouse gas abatement equipment in electronics manufacturing (U.S. EPA, 2010). The quantitative measurement of total organic fluorine (TOF) is also being evaluated to represent all, or most, of the PFAS class of compounds as a simpler and more comprehensive measurement alternative to target list approaches that focus on a limited number of PFAS. Several potential techniques warrant consideration and additional evaluation, including (but not limited to) combustion-ion chromatography (CIC), particle-induced gamma emission spectrometry (PIGE), and X-ray photo-electron spectroscopy (XPS) (see Section 5.c). For air and thermal treatment emissions, TOF must measure highly volatile as well as semivolatile PFAS. TOF analysis is an ongoing research area: data users must recognize the benefits of receiving general screening data for a wide array of potentially present PFAS, while also recognizing the limitations and uncertainties associated with potential health risk of not knowing which PFAS or class of PFAS is present in the sample. In addition, to minimize the risk of PFAS false positives, techniques within a validated method or methods must be developed that demonstrate effective separation and removal of inorganic fluorine from organic fluorine (Koch et al., 2020). TOF is not specific to PFAS, and any fluorine-containing compounds (e.g., pesticides, pharmaceuticals) that are retained during extraction would be included in the organic fluorine measurement. HF measurement is included in stationary source measurements to evaluate control efficiency of HF as a HAP at emission outlets. Multiple studies of PFAS thermal decomposition and HF monitoring have demonstrated EPA compliance methods for HF measurement are adequate to meet this need. However, HF is difficult to transport through treatment and control equipment and is therefore not a candidate for mass balance to evaluate PFAS destruction efficiency. 3.a.vi Uncertainties/unknowns EPA is planning to collect additional information and conduct additional research to better understand PFAS destruction and evaluate emission control efficiency (see Section 5). The current lack of a standardized validated methodology for measuring PFAS gaseous emissions (see Section 3.a.v.2) makes consistent direct measurement of PFAS and potential PIC emissions not possible and limits understanding of combustion conditions under which relatively complete destruction of PFAS can occur. EPA also lacks detailed information on the amounts and concentrations of PFAS-containing materials that are generated and managed in thermal treatment devices. Sampling and analytical methodologies must continue to be developed (see Section 5 research activities) so that emissions and other media from thermal treatment devices burning PFAS-containing materials INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 45 can be adequately characterized. EPA recognizes that PICs are inevitable (even for nonfluorinated compounds); however, based on the unique characteristics of fluorine combustion chemistry, it needs to be determined whether thermal treatment devices are adequately controlling fluorinated PICs. Research efforts will address several issues. For example, are the operating temperatures at these various thermal treatment devices adequate to completely destroy PFAS? Can surrogate DRE or TOF indicators be used as reliable indicators to ensure potential PICs are being controlled? Can catalysts be used to enhance PFAS destruction efficiency? EPA and others continue to research these complex and important issues. See Section 5 for a summary of planned research activities specific to thermal treatment of PFAS. 3.a.vii Treatment costs and commercial availability Section 3.a.i describes the commercial availability of thermal treatment devices. The United States has about 22 commercial hazardous waste combustion facilities8 in operation; over a dozen large-scale, commercial carbon reactivation companies with about 17 furnaces; 193 MSW incineration units; and 170 SSIs. Costs associated with treating contaminated media using thermal treatment include operation and maintenance costs of the treatment technology, capital costs, waste transport costs (if applicable), and costs associated with regulatory compliance. Breakdowns of these costs for the thermal treatment units described in this guidance were not readily available. However, operating costs for commercial treatment units are reflected in the amounts these facilities charge to thermally treat the waste streams they receive. This cost can be characterized by a cost charged per ton to treat specific types of waste. Waste transport costs are also important to consider, because some commercial treatment options could involve transporting large volumes of waste over large distances. Treatment of contaminated media in hazardous waste combustion devices, such as incinerators, involves costs associated with the high energy consumption needed to maintain elevated temperatures, as well as the regulatory and permitting costs associated with treating, handling, and storing these waste streams. Table 3-1 summarizes estimated costs to incinerate different types of hazardous waste, and Table 3-2 summarizes the costs to incinerate different types of non-hazardous waste. These estimates in Table 3-1 were used to assess costs and impacts of CAA regulations issued in 2005 (U.S. EPA, 2005a), acknowledging these costs likely have changed over the years. Halogenated waste streams are generally more expensive to treat, and costs are also influenced by whether the waste is a liquid, sludge, or gas. 8 This includes commercial incinerators, cement kilns, and LWAKs that are permitted to burn hazardous waste. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 46 Table 3-1. Estimated Costs to Incinerate Different Types of Hazardous Waste (U.S. EPA, 2005a) Hazardous Waste Type Liquids, sludges, solids (halogenated) Liquids, sludges, solids (non-halogenated) Lab packs Containerized gases Estimated Thermal Treatment Cost per Tona $1,218-1,770 $357-975 $6,042 $2,924 a Cost per ton is assumed to be in 2002 dollars, the same year basis of the regulation from which these costs were obtained. Costs were normalized to 2019 dollars using the Bureau of Economic Analysis (BEA) gross domestic product (GDP) deflator (BEA, 2020) for waste management and remediation services using a base year of 2002. Note that applying the BEA GDP deflator for this industry sector is a top-down approach. For regulatory purposes, a bottom-up approach is typically used, accounting for capital costs based on the Chemical Engineering Plant Cost Index (CEPCI), energy prices typically based on Energy Information Administration (EIA) data, and labor costs based on industry segment indices using Bureau of Labor Statistics (BLS) data. Table 3-2. Estimated Costs to Incinerate Different Types of Non-Hazardous Waste Incinerator Type SSI Multiple hearth Fluidized bed MWCs Estimated Cost per Ton of Waste $114a $80a $60b a Per dry ton, data provided by SSI owners/operators for 2006-2008. Assumed 2008 dollars. Costs were normalized to 2019 dollars using the BEA GDP deflator (BEA, 2020) for waste management and remediation services using a base year of 2002. Note that applying the BEA GDP deflator for this industry sector is a topdown approach. For regulatory purposes, a bottom-up approach is typically used, accounting for capital costs based on the CEPCI, energy prices typically based on EIA data, and labor costs based on industry segment indices using BLS data. b Average tipping fee per ton (2019 dollars) in states with operating MWCs. MWCs charge tipping fees for waste disposal, often through long-term contracts with various municipalities. As such, whether a combustor accepts an additional waste stream may depend on its capacity and how much waste needs to be combusted under its current operations and contractual obligations. Similarly, to reduce sludge transportation costs, SSI units are typically located at, owned by, and operated by the POTWs generating the sludge they incinerate. As a result, an SSI may be sized to handle the sludge generation needs of the treatment works: it may not be capable of accepting more sludge or wastes from outside sources. For MWCs, the costs represent the 2019 average tipping fee charged in states with waste-to-energy facilities (EREF, 2019). Compiled tipping fee rates for waste-to-energy facilities are not available, but this average price is expected to reflect the market price of tipping fees being charged by landfills and wasteto-energy facilities. SSI operating costs, not being typically marketed to the public, reflect facilityreported operating cost estimates provided during SSI regulatory development (U.S. EPA, 2016). Costs associated with incinerating remediation waste such as contaminated soil can be estimated by assuming the contaminated soil will be treated in a commercial HWI. Some sites may treat contaminated soil either on-site or in nearby incinerators that are not required to obtain hazardous INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 47 waste treatment permits. These incinerators may have lower operating costs due to fewer permitting requirements. Several factors affect costs for thermal treatment of contaminated soils, including soil type (e.g., clay content, particle size, moisture content, pH), type and concentration of contaminants that affect the necessary operating temperature, type of emission treatment needed, and type and frequency of maintenance needs such as changeout of filters or carbon (U.S. EPA, 2001). As a result of all these factors, the cost associated with incineration of remediation wastes vary and are site-specific. Ex situ incineration costs ranging from $168 to $3,256 per metric ton (normalized to 2019 dollars from 2016 dollars using the BEA GDP deflator [BEA, 2020]) have been reported (Ding et al., 2019; Vidonish et al., 2016). With respect to carbon reactivation units, financial considerations favor the reactivation of spent GAC as opposed to disposal of the spent media and replacement with virgin media. The analysis is complex and a number of issues need to be considered at the site level, such as those that affect costs (cost of energy, shipping, labor, construction, operation, sampling, etc.) and those that affect other matters (practicality, public versus private ownership, contract availability, regional reactivation availability, offgas permitting, public opinion, etc.). Table 3-3 contains example costs per weight of media for various disposal options. These data are derived from unit costs developed for EPA's work breakdown structure drinking water treatment cost models (Khera et al., 2013; U.S. EPA, 2020a). They are intended to reflect typical conditions and are based on estimates from multiple vendors. However, they do not account for site- or project-specific factors that could affect the cost of media replacement and disposal. Therefore, these unit costs are presented as examples only, to illustrate the tradeoffs between disposal options. As seen in Table 3-3, thermal reactivation of GAC costs less, at $1.41 per pound, than disposing of spent GAC and replacing it with virgin carbon. This is due to the higher cost of virgin media ($1.88/pound versus $1.21/pound for reactivated) (normalized to 2019 dollars from 2018 dollars using the BEA GDP deflator [BEA, 2020]). Although the reactivation procedure results in the loss of a certain percentage of carbon, incorporating this factor does not change the general conclusion that reactivation is a lowercost option. For example, the reactivation costs in the table incorporate a conservative estimate of 30 percent loss and remain lower than the replacement and disposal costs. Therefore, it is expected that entities treating PFAS-contaminated waters with GAC, as well as GAC manufacturers, will desire to reactivate their media. Table 3-3. Example Disposal/Reactivation Costs for Spent GAC for Drinking Water Treatment (Derived from U.S. EPA, 2020a) Method Reactivated GAC--off-site Disposal via landfill Disposal via incineration Cost of Disposal ($/Pound of Media) $0 $0.04 $0.36 Cost of Disposal Plus Replacement Media ($/Pound of Media)a $1.41 $1.92 $2.24 a Cost per pound is in 2018 dollars. Costs were normalized to 2019 dollars using the BEA GDP deflator for waste management and remediation services using a base year of 2002 (BEA, 2020). For GAC, on-site reactivation is possible. However, the utility or site would have to have ample workforce, managerial, and financial (both capital and operating) resources to justify this choice. It is likely to be cost-effective only for very large facilities and would require consideration of other factors including availability of land and public opinion. Due to the complex analysis needed, a full comparison of off-site versus on-site is beyond the scope of this document. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 48 3.a.viii Summary PFAS-containing waste can potentially be treated in several types of thermal treatment devices, including HWCs, MWCs and SSIs, and carbon reactivation furnaces, but further research is planned to gain a better understanding of what may be possible in practice. These treatment devices operate differently and handle different types of PFAS-containing media with varying concentrations. Even within the same category of thermal treatment device, designs and operating conditions may vary across sources in a way that could affect PFAS treatment efficiency. There are limited characterizations of potential PFAS emissions from thermal treatment devices that burn PFAS-containing media, and EPA is not aware of any emission characterizations that have been conducted at HWCs, MWCs, SSIs, or carbon reactivation furnaces. EPA is also not aware of any studies that have been conducted on the extent to which PFAS contaminants partition to air pollution control device residuals or bottom ash, which may also be a concern. This is likely (in part) because PFAS emission measurement methods continue to be developed. Given the unique characteristics of fluorine combustion chemistry (particularly the strength of the carbon-fluorine bond), complete thermal destruction of PFAS requires high temperatures and long residence times and likely benefits from direct flame contact. Studies suggest that combustion temperatures necessary to completely destroy PFAS may be reduced if certain catalysts are present in the thermal treatment system. However, available information on catalyst-aided PFAS destruction is limited. Hazardous waste combustion technologies (commercial incinerators, cement kilns, and LWAKs) can potentially achieve temperatures and residence times sufficient to break apart the PFAS contained in the waste stream being thermally treated. Permitted hazardous waste facilities have stringent regulatory controls on temperatures and other important operating parameters to achieve a 99.99 percent destruction efficiency for other (non-PFAS) organic chemicals, as well as air pollution control devices to prevent certain gaseous and particulate pollutants from entering the atmosphere. However, information on the efficacy of PFAS destruction in these facilities is currently lacking. EPA currently has no emission characterizations from these sources when they burn PFAS, and is working to develop measurement methodologies as well as gather information to conclude whether PICs are adequately controlled. EPA recognizes that PICs are inevitable (even for nonfluorinated compounds); however, based on the unique characteristics of fluorine combustion chemistry, EPA believes it is important to determine whether thermal treatment devices and their associated post-combustion control devices are adequately controlling PICs, especially fluorinated PICs. Given all these factors, there is a current need to continue research activities investigating incineration of PFAS. After sufficient research has been completed to address the related knowledge and data gaps, EPA can make a more informed recommendation on disposal of PFAS compounds and PFAS containing substances using incineration. Similar conclusions can be drawn for carbon reactivation furnaces as for HWCs. Experimental data suggest that thermal destruction of PFAS will occur in two stages: during reactivation of the GAC, then when the offgas is introduced into a high-temperature zone as high as 1,000C. As referenced in Section 3.a.i, a carbon reactivation furnace can be equipped with an afterburner to treat offgases at high temperatures to achieve 99.99 percent DRE. In addition, scrubbers can be installed to remove acid gases. This is a promising treatment method, but more information is needed, including confirmation that PICs are controlled based on actual operations, establishment of standard operating conditions for INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 49 carbon reactivation furnaces of various designs to ensure optimal destruction of PFAS, and an understanding of how thermal treatment influences the physical and chemical properties of GAC (in ways that can affect GAC's adsorption behavior and sorption capacity for PFAS). Research and testing of PFAS destruction performance within MWCs is extremely limited, primarily comprising laboratory and pilot-scale studies (Aleksandrov et al., 2019; Taylor et al., 2014). For example, the Aleksandrov et al. study uses a pilot-scale rotary MWC with afterburner chamber combusting PTFE granules added to wood pellets (also firing natural gas) to assess whether the PTFE is destroyed or reformed as PFAS. This study looked at a half-load scenario of 870C (1,600F) with a 4-second residence time and a full-load scenario of 1,020C (1,870F) for a 2.7-second residence time. There were 31 PFAS compounds analyzed for within the flue gas samples collected, assumed to represent a broad range of PFAS. While the laboratory and pilot-scale studies conclude that MSW incineration of PTFE is not a significant source of PFAS, the laboratory thermal reactor and the pilot incinerator used in these studies may not be representative of the design of MWC units operating in the United States presently. For example, the pilot-scale unit in the Aleksandrov et al. study is a rotary combustion chamber followed by an upflow afterburner. No MWC units operating in the United States have a similar configuration. In addition, while several PFAS species were analyzed for in these studies, it is important to note that there are far more PIC species possible, and no studies have thoroughly evaluated the types and quantities of PICs. As noted earlier in this section, research (Wang et al., 2013) has investigated PFAS interactions with CaO and Ca(OH)2 at moderate temperatures (200C-900C [390F-1,650F]) both with and without sewage sludge. These experiments were conducted in a laboratory (i.e., combustion in a crucible within a muffle furnace) and found that these calcium species exhibit a pseudo-catalytic effect promoting PFAS destruction and fluorine capture at relatively low temperatures. The study did not investigate the evolution of PICs during the thermal treatment process. While this study shows promising results for the use of catalysts resulting in PFAS destruction and fluorine capture at low temperatures, along with the potential for full-scale application (since lime is occasionally added to sewage sludge to control odor at SSIs), it is important to note that, as with the MWC studies described above, there are caveats for applying these results to real-world design and operation of SSI and the lack of robust information on PIC formation. More research is needed to address these issues and develop reliable measurement techniques. Section 5 summarizes EPA's continuing PFAS research, as well as a general proposal to collaborate with stakeholders to address these uncertainties promptly. 3.a.ix References for Section 3.a Aleksandrov, K., Gehrmann, H.-J., Hauser, M., Mtzing, H., Pigeon, P., Stapf, D., & Wexler, M. (2019). Waste incineration of polytetrafluoroethylene (PTFE) to evaluate potential formation of per- and poly-fluorinated alkyl substances (PFAS) in flue gas. Chemosphere, 226, 898-906. https://doi.org/10.1016/j.chemosphere.2019.03.191 INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 50 Arp, H. P. H., & Goss, K.-U. (2008). Irreversible sorption of trace concentrations of perfluorocarboxulic acids to fiber filters used for air sampling. Atmospheric Environment, 42(28), 6869-6872. https://doi.org/10.1016/j.atmosenv.2008.05.012 AWWA (American Water Works Association). (2018). Reactivation of granular activated carbon (ANSI/AWWA B605-18). Barber, J. L., Berger, U., Chaemfa, C., Huber, S., Jahnke, A., Temme, C., & Jones, K. C. (2007). Analysis of per- and polyfluorinated alkyl substances in air samples from Northwest Europe. Journal of Environmental Monitoring, 9(6), 530-541. https://doi.org/10.1039/B701417A BEA (Bureau of Economic Analysis). (2020, April 6). Chain-type quantity indexes for value added by industry. https://apps.bea.gov/iTable/iTable.cfm?reqid=150&step=2&isuri=1&categories=gdpxind Chemours. (2020). Thermal oxidizer performance test report: Chemours Company Fayetteville Works (Focus Project P-001393). https://www.chemours.com/en/-/media/files/corporate/fayettevilleworks/2020-03-thermal-oxidizer-test-report.pdf Department of Environment and Heritage Protection. (2018). Permit: Environmental Protection Act 1994, environmental authority EPPR00846713. https://apps.des.qld.gov.au/envauthorities/pdf/eppr00846713.pdf Ding, D., Song, X., Wei, C., & LaChance, J. (2019). A review on the sustainability of thermal treatment for contaminated soils. Environmental Pollution, 253, 449-463. https://doi.org/10.1016/j.envpol.2019.06.118 EREF (Environmental Research and Education Foundation). (2019). Analysis of MSW landfill tipping fees--April 2019 (rev. 10/31/19). https://erefdn.org/product/analysis-msw-landfill-tipping-fees-2/ Forrester, E. (2018). Removal of short chain PFAS via GAC adsorption. PA AWWA 70th Annual Conference. Kentucky Energy and Environment Cabinet. (2019). Hazardous waste management facility permit, Calgon Carbon Corporation, Catlettsburg, Kentucky. Khera, R., Ransom, P., & Speth, T. F. (2013). Using work breakdown structure models to develop unit treatment costs. Journal AWWA, 105(11), E628. Koch, A., Aro, R., Wang, T., Yeung, L. W. Y. (2020). Towards a comprehensive analytical workflow for the chemical characterisation of organofluorine in consumer products and environmental samples. Trends in Analytical Chemistry, 123, 115423. https://pubag.nal.usda.gov/catalog/6333446 Martin, J. W., Muir, D. C. G., Moody, C. A., Ellis, D. A., Kwan, W. C., Solomon, K. R., & Mabury, S. A. (2002). Collection of airborne fluorinated organics and analysis by gas chromatography/chemical ionization mass spectrometry. Analytical Chemistry, 74(3), 584-590. https://doi.org/10.1021/ac015630d INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 51 McCord, J., & Strynar, M. (2019). Identifying per- and polyfluorinated chemical species with a combined targeted and non-targeted-screening high-resolution mass spectrometry workflow. Journal of Visualized Experiments (146), e59142. https://doi.org/10.3791/59142 Michaels, T., & Krishnan, K. (2018). 2018 directory of waste-to-energy facilities. Energy Recovery Council. http://energyrecoverycouncil.org/wp-content/uploads/2019/10/ERC-2018-directory.pdf Miguel, G. S., Lambert, S. D., & Graham, N. J. D. (2001). The regeneration of field-spent granularactivated carbons. Water Research, 35(11), 2740-2748. https://doi.org/10.1016/S00431354(00)00549-2 NADP (National Atmospheric Deposition Program). (2020). Wet and dry deposition sampling. http://nadp.slh.wisc.edu/siteops/collectors.aspx Newton, S. R., Sobus, J. R., Ulrich, E. M., Singh, R. R., Chao, A., McCord, J., Laughlin-Toth, S., & Strynar, M. (2020). Examining NTA performance and potential using fortified and reference house dust as part of EPA's Non-Targeted Analysis Collaborative Trial (ENTACT). Analytical and Bioanalytical Chemistry. https://doi.org/10.1007/s00216-020-02658-w Reddy, J. P. (2016). Energy recovery from municipal solid waste by thermal conversion technologies. CRC Press. Riedel, T. P., Lang, J. R., Strynar, M. J., Lindstrom, A. B., & Offenberg, J. H. (2019). Gas-phase detection of fluorotelomer alcohols and other oxygenated per- and polyfluoroalkyl substances by chemical ionization mass spectrometry. Environmental Science and Technology Letters, 6(3), 289-293. https://doi.org/10.1021/acs.estlett.9b00196 Roskill Information Services Ltd. (2017). Activated carbon: Global industry, markets and outlook. Scavuzzo, S. A., Strempek, J. R., & Strach, L. (1990). The determination of the thermal operating characteristics in the furnace of a refuse-fired power boiler. In American Society of Mechanical Engineers (Ed.). Proceedings of the 1990 National Waste Processing Conference (pp. 297-404). http://www.seas.columbia.edu/earth/wtert/newwtert/Research/sofos/nawtec/1990-NationalWaste-Processing-Conference/1990-National-Waste-Processing-Conference-40.pdf Taylor, P. H., Yamada, T., Striebich, R. C., Graham, J. L., & Giraud, R. J. (2014). Investigation of waste incineration of fluorotelomer-based polymers as a potential source of PFOA in the environment. Chemosphere, 110, 17-22. https://doi.org/10.1016/j.chemosphere.2014.02.037 Themelis, N. J., & Reshadi, S. (2009). Potential for reducing the capital costs of WTE facilities. In American Society of Mechanical Engineers (Ed.) Proceedings of the 17th Annual North American Waste-to-Energy Conference (NAWTEC17). Tsang, W., Burgess, D. R., Jr., & Babushok, V. (1998). On the incinerability of highly fluorinated organic compounds. Combustion Science and Technology, 139(1), 385-402. https://doi.org/10.1080/00102209808952095 INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 52 U.S. EPA (Environmental Protection Agency). (1999). Compendium of methods for the determination of toxic organic compounds in ambient air--second edition (EPA/625/R-96/010b). https://www3.epa.gov/ttnamti1/files/ambient/airtox/tocomp99.pdf U.S. EPA (Environmental Protection Agency). (2001). Remediation technology cost compendium--year 2000 (EPA-542-R-01-009). https://www.epa.gov/sites/production/files/201508/documents/542r01009.pdf U.S. EPA (Environmental Protection Agency). (2005a). Addendum to the assessment of the potential costs, benefits, & other impacts of the hazardous waste combustion MACT Final Rule standards. https://www.regulations.gov/document?D=EPA-HQ-OAR-2004-0022-0463 U.S. EPA (Environmental Protection Agency). (2005b). Technical support document for HWC MACT standards (Vol. I). https://www.regulations.gov/document?D=EPA-HQ-OAR-2004-0022-0434 U.S. EPA (Environmental Protection Agency). (2010). Protocol for measuring destruction or removal efficiency (DRE) of fluorinated greenhouse gas abatement equipment in electronics manufacturing (EPA 430-R-10-003). https://www.epa.gov/sites/production/files/201602/documents/dre_protocol.pdf U.S. EPA (Environmental Protection Agency). (2016). Final emissions and unit inventory for federal plan requirements for sewage sludge incineration units constructed on or before October 14, 2010. https://www.regulations.gov/document?D=EPA-HQ-OAR-2012-0319-0020 U.S. EPA (Environmental Protection Agency). (2018). Final RCRA permit for Colorado River Indian Tribes and Evoqua Water Technologies LLC for carbon regeneration facility located at: 2523 Mutahar Street, Parker, Arizona 85344. https://www.epa.gov/sites/production/files/201809/documents/evoqua_final_rcra_permit_modules_i-vi.pdf U.S. EPA (Environmental Protection Agency). (2019). National capacity assessment report pursuant to CERCLA Section 104(c)(9). https://www.epa.gov/sites/production/files/201912/documents/final_2019_capacity_assessment_report_20191217v1.pdf U.S. EPA (Environmental Protection Agency). (2020a). Drinking water treatment technology unit cost models and overview of technologies. https://www.epa.gov/sdwa/drinking-water-treatmenttechnology-unit-cost-models-and-overview-technologies U.S. EPA (Environmental Protection Agency). (2020b). PFAS emissions measurement methods development and emissions characterization study at National Response Corporation Alaska, LLC AFFF contaminated soil thermal treatment facility. Report in preparation. U.S. EPA (Environmental Protection Agency). (n.d.). Solid waste disposal. In Compilation of air pollutant emission factors (Vol. 1). https://www3.epa.gov/ttn/chief/ap42/ch02/index.html Vidonish, J. E., Zygourakis, K., Masiello, C. A., Sabadell, G., & Alvarez, P. J. J. (2016). Thermal treatment of hydrocarbon-impacted soils: A review of technology innovation for sustainable remediation. Engineering, 2(4), 426-437. https://doi.org/10.1016/J.ENG.2016.04.005 INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 53 Wang, F., Lu, X., Li, X.-Y., & Shih, K. (2015). Effectiveness and mechanisms of defluorination of perfluorinated alkyl substances by calcium compounds during waste thermal treatment. Environmental Science and Technology, 49(9), 5672-5680. https://doi.org/10.1021/es506234b Wang, F., Lu, X., Shih, K., & Liu, C. (2011). Influence of calcium hydroxide on the fate of perfluorooctanesulfonate under thermal conditions. Journal of Hazardous Materials, 192(3), 1067- 1071. https://doi.org/10.1016/j.jhazmat.2011.06.009 Wang, F., Shih, K., Lu, X., & Liu, C. (2013). Mineralization behavior of fluorine in perfluorooctanesulfonate (PFOS) during thermal treatment of lime-conditioned sludge. Environmental Science and Technology, 47(6), 2621-2627. https://doi.org/10.1021/es305352p Watanabe, N., Takemine, S., Yamamoto, K., Haga, Y., & Takata, M. (2016). Residual organic fluorinated compounds form thermal treatment of PFOA, PFHxA and PFOS adsorbed onto granular activated carbon (GAC). Journal of Material Cycles and Waste Management, 18, 625-630. https://doi.org/10.1007/s10163-016-0532-x Watanabe, N., Takata, M., Takemine, S., & Yamamoto, K. (2018). Thermal mineralization behavior of PFOA, PFHxA, and PFOS during reactivation of granular activated carbon (GAC) in nitrogen atmosphere. Environmental Science and Pollution Research, 25, 7200-7205. https://doi.org/10.1007/s11356-015-5353-2 Xiao, F., Challa Sasi, P., Yao, B., Kubtov, A., Golovko, S. A., Golovko, M. Y., & Soli, D. (2020). Thermal stability and decomposition of perfluoroalkyl substances on spent granular activated carbon. Environmental Science and Technology Letters, 7(5), 343-350. https://doi.org/10.1021/acs.estlett.0c00114 Yamada, T., Taylor, P. H., Buck, R. C., Kaiser, M. A., & Giraud, R. J. (2005). Thermal degradation of fluorotelomer treated articles and related materials. Chemosphere, 61(7), 974-984. https://doi.org/10.1016/j.chemosphere.2005.03.025 INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 54 3.b Landfills Landfills control waste and corresponding pollutants through containment. Because of their many and varied uses, PFAS enter landfills as part of the general municipal waste stream, with some industrial waste, or in other PFAS-containing wastes, with a range of concentrations. Hazardous waste or MSW landfills are available disposal options for PFAS and PFAS-containing materials. Permitted hazardous waste landfills employ the most extensive set of environmental controls (e.g., double liner systems with leachate collection and leak detection) and practices (e.g., extensive record keeping) that are currently available for the containment of PFAS waste (see Table 3-4) and as a result would be more effective at minimizing PFAS migration into the environment than other landfill types. Modern MSW landfills, when constructed with appropriate controls (e.g., liner system and leachate and gas collection and management systems), can also control the migration of PFAS into the environment. EPA plans to conduct research to understand the effects of PFAS on liner integrity, gaseous emissions from landfills, the effectiveness of leachate treatment for PFAS removal, and the levels and types of PFAS in landfill leachate (see Section 5). While landfills might serve as long-term containment sites for PFAS, they have not been designed explicitly for PFAS containment. For example, some hazardous waste landfills are designed to control specific chemicals (e.g., dioxins and other specific hazardous wastes), but it is unclear how effective they are at containing PFAS. Because landfills are a containment method and do not destroy PFAS, PFAS are expected to persist in landfills for the life of the compounds, which could be many years or until they are released. Landfill liners and cover systems are designed to contain leachate and control emissions, but even the best-designed systems will fail at some point unless they are replaced or the waste is removed. Thus, PFAS-containing wastes remain in the landfill until the liner or cap fails or until the waste is removed per future management action. RCRA regulations define a landfill as "an area of land or an excavation in which wastes are placed for permanent disposal, and that is not a land application unit, surface impoundment, injection well, or waste pile" (40 CFR 257.2). The goal of solid waste landfills is to contain waste, and thereby restrict the release of contaminants that may be present within the landfill from entering the environment. Landfills are commonly classified by the types of wastes they accept and/or by their ownership status. Section 3.b focuses on the viability of landfilling as a means of containing PFAS and PFAS-containing material, discussing: The types of landfills that receive PFAS-containing waste. The types of environmental controls and their ability to effectively contain PFAS. The potential for environmental releases of PFAS associated with landfilling. Methods to monitor PFAS at landfills (and corresponding waste streams). Uncertainties and unknowns associated with landfilling PFAS-containing waste. Operating costs for landfill controls that address PFAS. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 55 3.b.i Types of landfills Landfills are typically classified by ownership status and by the type of solid waste they are permitted to receive, which determines the types of environmental controls they must employ. Depending on the type of waste disposed of, a landfill could be subject to regulation and permitting under RCRA, the CAA, and/or the Toxic Substances Control Act (TSCA). RCRA regulates two types of landfills: Subtitle C facilities receive hazardous waste, while Subtitle D landfills are primarily intended for the management of nonhazardous waste and can include MSW landfills, industrial non-hazardous waste landfills, C&D waste landfills, and coal combustion residual landfills. The requirements determine how the landfill must be constructed, operated, maintained, monitored, and closed when it reaches its final capacity. Although categories and environmental controls vary from state to state, the following categories of landfills exist in most states and tend to have similar environmental controls within each category: Hazardous waste. MSW. Ash monofill. Industrial. C&D debris. Table 3-4 compares some of the environmental controls required by landfill types as defined under RCRA Subtitles C and D. The landfill categories differ in how they are constructed, operated, monitored, and closed, reflecting the different types of waste they are allowed to receive. Subtitle C hazardous waste landfills are permitted to receive hazardous wastes, which has been evaluated and determined to pose potential risk to humans and the environment and therefore has the most stringent environmental controls in place; Subtitle D landfills that receive non-hazardous and non-putrescible waste tend to have environmental controls commensurate with the waste they receive. These controls can vary from state to state; for example, certain small MSW landfills in arid or remote locations are exempt from both design and groundwater monitoring requirements. Table 3-4. Required Environmental Controls by Landfill Type Landfill Type Hazardous waste MSW Ash monofills Industrial C&D debris Federally Regulated Under RCRA Subtitle C RCRA Subtitle D 40 CFR part 258 CAA 40 CFR parts 60 and 63 RCRA Subtitle D 40 CFR part 257 RCRA Subtitle D 40 CFR part 257 RCRA Subtitle D 40 CFR part 257 Bottom Liner and Leachate Collection System Yes (double liner or better) Yes (composite liner or better) Yes (composite liner or better) Varies by state, from no liner requirement to composite liner Varies by state, from no liner requirement to composite liner Gas Collection System No Yes No No No Final Cover Flexible membrane liner (FML) cap FML cap Clay cap Varies by state, from no requirements to FML cap Varies by state, from no requirements to FML cap INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 56 PFAS concentrations have been detected in landfill leachates from various types of landfills, as shown in Table 3-5. The following subsections describe the types of landfills that are expected to contain PFAS or PFAS-containing materials, with a focus on design and operation aspects that EPA considers important from a PFAS-treatment perspective. 3.b.i.1 Hazardous waste landfills Hazardous waste landfills are permitted to receive waste that is defined as "hazardous" under EPA's RCRA regulations. This waste either is explicitly listed as hazardous in the regulations or demonstrates at least one of certain characteristics (i.e., toxicity, corrosivity, reactivity, or ignitability). Any Subtitle C landfill is required to have a double liner system. Because most hazardous wastes are not biologically active, hazardous waste landfills typically do not have gas collection systems, although gas collection systems could be installed if a problem arises related to gas migration or gas emissions. Any hazardous waste landfill must have a final cover consisting of an FML covered by soil. 3.b.i.2 Municipal solid waste landfills MSW landfills receive most of the waste generated by households and commercial facilities. An MSW landfill typically has at least a bottom liner and extensive gas collection and control system (GCCS) to collect the landfill gas (LFG) generated when the putrescible waste, such as food scraps and office paper, degrades over time. Some MSW landfills that receive less than 20 tons of waste per day are exempt from installing a liner under RCRA, while others might be exempt from installing a gas collection system under the CAA. Unlined MSW landfills are ineffective at managing the migration of mobile PFAS to groundwater (see Section 4.a). Additionally, those lacking gas collection systems could release fugitive PFAS associated with LFG emissions. 3.b.i.3 Ash monofills Ash monofills are a subtype of MSW landfill that mainly receive ash from MSW incinerators but could also receive other waste streams such as biosolids from WWTPs. Ash monofills typically have a bottom liner and final cover requirements similar to other MSW landfills but typically do not require GCCSs due to the incineration removing putrescible waste. Solo-Gabriele et al. (2020) found ash monofills have lower PFAS concentrations than other landfill types, as shown in Table 3-5. While some landfill wastes, such as MSW ash, may be low in PFAS concentrations, the inclusion of higher-PFAS waste types may increase PFAS releases. With limited data on the presence of PFAS in ash monofill leachate, more research is needed to determine the PFAS and precursor content of ash from different incineration technologies and air pollution control systems. Table 3-5. Average PFAS Concentrations in Different Types of Landfill Leachate Reported in Published Studies Landfill type MSW landfill MSW landfill MSW landfill MSW landfill MSW landfill MSW landfill Country USA Germany Spain Canada Australia China Mean PFAS Range (ng/L) BDL-17,710 BDL-2,968 BDL-840.5 BDL-8,700 BDL-1,700 BDL-41,600 References Solo-Gabriele et al., 2020; Lang et al., 2017; Huset et al., 2011 Busch et al., 2010 Fuertes et al., 2017 Benskin et al., 2012 Gallen et al., 2017 Yan et al., 2015 INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 57 Landfill type Ash monofill C&D debris landfill Country USA USA Mean PFAS Range (ng/L) BDL-742 BDL-4,630 BDL = below detection limit; ng/L = nanograms per liter References Solo-Gabriele et al., 2020 Solo-Gabriele et al., 2020 3.b.i.4 Industrial landfills Industrial landfills receive solid wastes from industrial operations (non-municipal). Industrial landfills are often designed to manage specific waste streams (e.g., furnace slag, fly ash, and plastics). The designs of industrial landfills vary widely, based on the characteristics of the waste they receive. Requirements for environmental controls at these landfills also vary state to state. Depending on the waste types and size of the landfill, some states do not require a liner. If a liner is required, a membrane cap is often also required. Due to the variability in control technologies, industrial landfills may not be an effective disposal option for managing uncontrolled releases of PFAS. Some waste types received at industrial landfills, including plastics and materials with polishes or coatings, are associated with high concentrations of PFAS (OECD, 2013). 3.b.i.5 Construction and demolition landfills C&D landfills receive waste from construction, renovation, and demolition projects, and other material that may be considered inert. The exact list of materials for these types of landfills varies by state, but the wastes are generated in high volumes. The requirements for environmental controls at these landfills vary widely from state to state, ranging from no liner to a required composite liner. If a liner is required, a membrane cap could also be required. GCCSs are not required in C&D landfills due to low levels of putrescible waste received compared to MSW landfills. A GCCS may sometimes be necessary to remediate a specific issue, typically related to gases generated from the decay of drywall. Due to variability in control technologies and the potential lack of monitoring, C&D landfills are unlikely to manage the uncontrolled release of mobile PFAS; however, it is likely that C&D landfills receive some PFAS-containing wastes (e.g., building materials and carpeting with fluoropolymer coatings) (OECD, 2013; Solo-Gabriele et al., 2020). 3.b.ii Ability of engineered landfill components to contain PFAS PFAS are emitted from landfills via two possible routes: landfill leachate and LFG. Landfill leachate is the liquid that has passed through or emerged from solid waste and contains soluble, suspended, or miscible materials removed from such waste. LFG is the result of the natural decomposition of organic material in landfills. LFG is composed of roughly 50 percent methane, 50 percent carbon dioxide, and a small amount of nonmethane organic compounds (NMOCs). Existing efforts to manage contaminants in landfills focus on controlling leachate and gaseous emissions. As shown in Figure 3-1, landfills constructed with environmental controls (bottom liner, leachate collection system, gas collection system, and final cover system, among other controls) manage the release of contaminants into the environment. The uses of the engineered landfill controls shown in Figure 3-1 vary by landfill type due to the variation in types of waste accepted, operating practices, site conditions, and federal and state regulations. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 58 Figure 3-1. Engineered landfill components and potential PFAS release pathways. 3.b.ii.1 Bottom liner and leachate collection system Under RCRA, any new landfill, replacement of an existing landfill, or lateral expansions of an existing landfill must have a double liner and leachate collection system if it receives hazardous waste, in order to limit leachate and gas migration through the bottom of the landfill. Most landfills that are regulated under RCRA to receive non-hazardous waste are subject to design criteria with either a composite liner and leachate collections system or a state-approved design that satisfies performance standards to ensure that regulated chemicals do not migrate beyond a specified distance from the landfill. The variation of landfill types among states poses a challenge for the long-term containment of existing PFAS in landfills: state requirements for landfill liners vary and some landfills are not required to have liners because of waste type or quantities received. Additionally, RCRA-exempt sites may not require liners (40 CFR 258.1). Because PFAS are not a RCRA-regulated hazardous waste, existing unlined landfills could contain PFAS that are easily emitted into the environment. Depending on their mobility, PFAS compounds could impact groundwater if disposed of in an unlined landfill. A liner is built of layers of clay and/or polymers (i.e., FMLs) designed to withstand the weight of waste and soil. Leachate will collect on top of the liner, so its design must include a leachate collection system contoured to collect leachate through a network of pipes leading to a low point called a sump. The collected leachate is pumped from the landfill and managed as liquid wastes (see Section 2.f and Section 3.b.iii on leachate management). Uncontrolled leachate could result in migration of PFAS into the environment. Even if liners successfully prevent leachate from reaching groundwater, very few data exist on whether concentrated PFAS waste interacts with the different types of geotextiles used for landfill liners, thus affecting the performance of the liner. Li (2011) investigated the effect of PFAS on sodium bentonite, a INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 59 type of clay used in liners, and found PFAS did not significantly compromise the performance of bentonite liners (Li, 2011). While the performance of clay liners may not be affected drastically, there is currently no research on the long-term stability of FML in the presence of PFAS. 3.b.ii.2 Landfill gas collection system Landfills use GCCSs to manage gas from decomposing organic waste. A GCCS consists of a network of perforated pipes sunken into the waste. These "gas wells" are connected to a central blower that pulls gas from the wells. Despite collection technologies, gas can still migrate both through the surface of the landfill and underground through the bottom of the landfill. The gas produced by MSW landfills contains a high level of methane that is usually burned off at the site via flares or for energy recovery. As noted in Section 3.b.iv.1, research has found that soluble PFAS with relatively high vapor pressures can be emitted into the atmosphere via the gas generated at landfills (Ahrens et al., 2011; Hamid et al., 2018; Wang et al., 2020; Weinberg et al., 2011). Direct LFG sample evaluation for PFAS concentrations is currently being researched by EPA. The effects of flaring on gaseous PFAS have not been demonstrated. See Section 5 for potential research needs. 3.b.ii.3 Final cover system After a regulated landfill has reached its expected capacity, it must be capped with a cover system. This system consists of some combination of soil and membrane liners and is primarily intended to reduce infiltration of rainwater into the landfill to minimize leachate generation. It also helps increase the efficiency of the GCCS and reduce uncontrolled gas emissions. Synthetic liners and caps are more effective at controlling migration of PFAS than earthen covers. Earthen covers are more subject to wet/dry cycles and cracking and are more likely to result in uncontrolled LFG emissions, which could contain PFAS (Ahrens et al., 2011; Tian et al., 2018; Wang et al., 2020; Weinberg et al., 2011). 3.b.ii.4 Other environmental controls and monitoring systems Landfills control solid waste and corresponding pollutants through containment. Because of their many and varied uses, PFAS enter solid waste landfills as part of the general municipal waste stream, with industrial waste, or in other PFAS-containing solid wastes (e.g., solidification waste). In addition to the major infrastructure discussed above, solid waste landfills implement other practices and systems. In active landfill cells, daily application of a cover material like soil or other inert waste covers exposed solid waste. Daily cover reduces leachate generation, gas emissions, and direct exposure to humans and wildlife. Access control for a landfill site, such as a fence, is typically also required, to reduce the chance of direct human and ecological exposure to waste. Extensive monitoring networks are generally required to measure the landfills impact on surface water, groundwater, and air. RCRA Subtitle C requires all hazardous waste landfills to install groundwater monitoring wells. See Section 3.b.iii for landfill controls. 3.b.iii Leachate discharge controls 3.b.iii.1 Leachate characteristics Landfill leachate is the liquid effluent primarily generated through the percolation or infiltration of rainwater through waste. Leachates often contain high concentrations of biodegradable and non- INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 60 biodegradable organic matter, dissolved and suspended solids, heavy metals, ammonia, and sulfur compounds (Mukherjee et al., 2015; Renou et al., 2008). The waste type, age, climate at the landfill site, and methods of landfill operation dictate the characteristics of leachate. These factors result in highly variable leachate characteristics across landfill types and on a site-by-site basis within the different landfill types. Subtitle C hazardous waste landfills are required to use a leachate collection system during their active and post-closure care periods to mitigate adverse impact to human health and the environment. Since the use of leachate collection systems at Subtitle D landfills varies by landfill type and state requirements, the efficacy of leachate management and PFAS emissions depends on the controls implemented. PFAS containment in landfills is expected to be indefinite, so the generation of PFAS-containing leachates remains a probability during the post-closure care period and beyond. Ideally, the leachate collected at the bottom of the landfill is removed and managed to minimize impacts to human health and the environment. See Section 2 for more a more detailed discussion on the types of leachate and associated PFAS. 3.b.iii.2 Off- and on-site management of leachate The most common method for leachate disposal is off-site treatment at municipal WWTPs, where leachate is mixed with wastewater and treated. The dynamic nature of leachate characteristics, the presence of nonbiodegradable compounds and ammonia, and the presence of emerging contaminants (like PFAS) in the leachate may make it difficult for WWTPs to effectively treat the influent water. In some cases, a landfill with elevated PFAS in its leachate may burden a WWTP's ability to treat, remove, or destroy these compounds before discharge to the environment (Masoner et al., 2020). As mentioned in Section 2.a.ii, wastewater treatment technologies used at most municipal WWTPs are generally ineffective at destroying or controlling PFAS (Schultz et al., 2006) and as a result may also be ineffective at treating PFAS-containing landfill leachate. Furthermore, in WWTPs, PFAS may bind to and accumulate in biosolids, which can lead to PFAS entering the environment if biosolids are applied to land. Some WWTPs have requested that landfill operators pretreat leachate on-site and some WWTPs are implementing surcharges based on the leachate quality. Deep well injection is another form of off-site leachate management (see Section 3.c). Table 3-6 presents leachate management or treatment methods used for the on-site management of leachate. The technologies it reviews may be subject to current research, and the table will be updated as new information is published. Multiple technologies in the table are marked for further research-- technologies for which, at the time of publishing, data do not exist to support or reject application for PFAS treatment. "Secondary treatment required" refers to the remaining concentrated or captured PFAS, which must be disposed of after treatment. "Potential secondary release" refers to the potential for PFAS release or breakthrough during the treatment process. Leachate characteristics are sitespecific; therefore, the effectiveness of leachate technology should be evaluated on a site-by-site basis. (Table 3-5 lists average PFAS concentrations observed in different types of landfill leachate.) Landfill operators should identify management or treatment methods that (1) are suitable for the leachate at their specific sites and (2) meet the leachate discharge standards for chemicals and characteristics of leachate that are regulated. The geography of the landfill site and cost-effectiveness of the methods play a crucial role in the identification of viable approaches to leachate management or treatment. In some cases, leachate treatment strategies may depend on treating a specific chemical(s) INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 61 (e.g., ammonia). The use and effectiveness of leachate management strategies in removing or destroying PFAS during treatment varies (and, as noted in Section 3.b.vii, methods to quantify effectiveness are still under development). Leachate treatment technologies can be largely categorized into physiochemical processes, physical processes, biological processes, natural processes, and other management methods, as grouped in Table 3-6. Considering that leachate contains a variety of chemicals, a combination of physiochemical treatment processes can be used to narrowly target specific parameters for pre-treatment, or as part of a multi-step treatment strategy. Table 3-6. Existing Landfill Leachate Treatment Technologies for PFAS Removal or Destruction Treatment Treatment Technology Mechanism Physiochemical Processes GAC Adsorption PAC with coagulation Adsorption Polymeric adsorption Adsorption Ion exchange resin Ion exchange adsorption Zeolite Ion exchange adsorption Pros for PFAS Treatment Familiar technology Effective for long- chain PFAS Effective for longchain PFAS Tailor for specific compounds Specified for certain compounds More effective than GAC for long-chain compounds Inexpensive Cons for PFAS Treatment References Secondary treatment required Short-chain PFAS breakthrough Potential secondary release Cost Secondary treatment required Costly for high- volume leachate Potential secondary release Secondary treatment required Potential secondary release Secondary treatment required Less effective for short-chain PFAS Potential secondary release Secondary treatment required Low surface area compared to GAC Unknown reaction with short-chain PFAS McCleaf et al. (2017), Pan et al. (2016), Ross et al. (2018) Bao (2014), Pan et al. (2016) Liu (2017) Dickenson & Higgins (2016), McCleaf et al. (2017), Ross et al. (2018) Chiang et al. (2017), Ochoa-Herrera & Sierra-Alvarez (2008) INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 62 Treatment Technology Ozonation/ ozofractionation Fenton oxidation Photocatalytic advance oxidation process Treatment Mechanism Oxidation Oxidation Oxidation Pros for PFAS Treatment Potentially effective multi-contaminant removal Limited data available Permanent degradation Coagulationflocculation Precipitation Limited data available Chemical precipitation Precipitation Limited data available Air stripping Volatilization More research needed Physical Processes Reverse osmosis (RO) Physical separation Commonly used Effective for short and long-chain PFAS Uses less energy Nanofiltration Physical than RO (NF) separation Effective for short- and long-chain PFAS Ultrafiltration (UF); Physical N/A microfiltration separation (MF) Climatic evaporation; thermal evaporation; Volume reduction Limited data available mist evaporation Other On-Site Management Methods Recirculation Containment Co-location with landfill Cons for PFAS Treatment Potential sideproduct formation Secondary treatment required Limited data available References Franke et al. (2019), Lin et al. (2012), Rahman et al. (2014), Ross et al. (2018) None identified Potential sideproduct formation Cost Limited data available Limited data available Potential secondary emissions Lockwood (2018), Ross et al. (2018) Bao (2014), Dickenson & Higgins (2016), ITRC (2018), Rahman et al. (2014) None identified None identified Secondary treatment required for highvolume concentrate Membrane fouling Secondary treatment required Dickenson & Higgins (2016), Ross et al. (2018) Boo et al. (2018), Dickenson & Higgins (2016) Not effective for PFAS U.S. EPA (2020a) Potential secondary emissions None identified Oversaturation Potential surface water contamination Dependent on climate None identified INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 63 Treatment Technology Deep well injection Incineration Treatment Mechanism Containment Thermal destruction Solidification Containment Biological Processes Activated sludge process sequencing; batch reactor; Biological anaerobic; processes digestor; membrane bioreactor Natural Processes Constructed wetlands; aerated ponds; Environmental phyto- release remediation; land application Pros for PFAS Treatment Potential solution for PFAS concentrate PFAS destruction Co-location with landfill Reduces PFAS mobility Limited data available N/A Cons for PFAS Treatment Dependent on site geology Regulatory approval Potential secondary emissions Regulatory approval Consumes air space in landfill Unrealistic for large leachate volume Limited by high concentrations of non-biodegradable organic matter Direct release of PFAS References ITRC (2018) ITRC (2017), Yamada et al. (2005) None identified Ross et al. (2018), Saez et al. (2008), U.S. EPA (2020a) U.S. EPA (2020a) 3.b.iii.3 Leachate management and treatment technologies Membrane treatments separate compounds from the leachate using mechanical filtration and pressure. Leachate passes through selective membranes (such as RO, NF, UF, and MF membranes) that divide it into two parts: permeate (which has passed through the membrane) and concentrate (which has not). The permeate and concentrate can then be treated as independent streams. The primary difference between these membranes is the pore size, which in turn affects the operating pressure and removal efficiency for different types of contaminants. RO is the most commonly used type of membrane for leachate treatment, while NF, UF, and MF are generally used in combination with other treatment technologies including RO. RO and NF are known to be effective in concentrating some PFAS, but UF and MF have pores that are too large to limit the migration of most water-bound PFAS across the filtration membrane. Membrane fouling and a large amount of concentrate generation are two of the major drawbacks observed in implementing the membrane treatment system for landfill leachate and may be further complicated by high concentrations of PFAS (Dickenson & Higgins, 2016; ITRC, 2018; Ross et al., 2018). INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 64 An adsorption process with activated carbon is used for targeted removal of organic matter at some landfill sites. Activated carbon is known to be effective at trapping some PFAS, but it may need to be combined with other treatment methods to manage the range of PFAS found in landfill leachate. Activated carbon is a non-selective treatment method, expected to be less effective in nutrient-laden effluents like landfill leachate. Once saturated, activated carbon needs to be reactivated through a pyrolysis process (see Section 3.a), collected as solid waste, or otherwise treated, with consideration of the PFAS concentration (ITRC, 2017). Leachate also may need to be pretreated before activated carbon treatment to avoid rapidly saturating the carbon. Methods using ozone, Fenton's reagent, or advanced photocatalytic technologies are used to oxidize organic matter in the leachate. Ozone and hydrogen peroxide (H2O2) in combination with other oxidizing agents have been observed to remove up to 99 percent of chemical oxygen demand from leachate at different operating conditions (Renou et al., 2008) and may be effective at reducing or modifying certain PFAS in leachate (Ross et al., 2018). Ultraviolet photocatalytic advanced oxidation is known to be capable of destroying PFAS, but additional studies are needed to understand the subsequent products associated with this method (Lockwood, 2018; Ross et al., 2018). Ion exchange processes using zeolite and magnetic ion exchange resin remove ammonia and organic matter, respectively. Ion exchange can be flexibly designed to address different compounds and may be effective at reducing PFAS in leachate; however, performance data are not currently available. As with activated carbon, the leachate may require pretreatment and the spent media would need to be handled as solid waste or otherwise treated. Air stripping of landfill leachate is used for ammonia removal. While air stripping could be effective in the treatment pathway of leachate if it is used before the removal of PFAS, it would likely lead to emissions of more volatile PFAS to air. Recirculation of leachate within a landfill--a management strategy unique to MSW landfills--keeps the leachate within the landfill. Although recirculation can filter heavy metals and improve leachate quality, it is primarily used as a management option that may also help accelerate biodegradable waste decomposition. The recirculation of leachate in the landfill would return any PFAS to containment within the landfill. Underground injection control, specifically Class I deep well injection, has also been used to manage landfill leachate in the United States (see Section 3.c). Natural processes (such as constructed wetlands and phytoremediation) and biological processes (degradation, nitrification, and denitrification) are expected to be ineffective at treating and preventing release of many PFAS into the environment. Current biological treatment processes such as the activated sludge process and sequencing batch reactor have not been shown to be effective at treating many PFAS, but future research may show biological treatment can play a role in controlling some PFAS or converting them into other types of PFAS. Note that biological treatment does not necessarily result in PFAS releases directly into the environment, because the outputs can be further treated. Leachate treatment through evaporation results in reducing the volume of leachate. Open-air evaporation methods may be effective at concentrating leachate but could be a pathway for secondary INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 65 PFAS releases to air. Commercial evaporators operated through the heat generated by the LFG combustion or other fuel sources are sometimes used at landfills. Exhaust gases emitted from the evaporators may be exposed to high temperatures, but those temperatures may not be high enough or last long enough to destroy PFAS (see Section 3.a). 3.b.iv Landfill gas emission controls 3.b.iv.1 Landfill gas characteristics Under the anaerobic conditions that dominate landfill environments, organic waste (e.g., food waste, paper, cardboard) decomposes and generates LFG. LFG in MSW landfills consists mostly of methane and carbon dioxide. In most landfills where gas is collected, it is burned for energy or to destroy the methane and other organic chemicals it contains. Even at sites that actively collect LFG, a fraction of the LFG is emitted directly to the environment through the landfill surface and other routes. These uncontrolled emissions are referred to as fugitive losses. Research has found that soluble PFAS with relatively high vapor pressures can be emitted into the atmosphere via the gas generated at landfills (Ahrens et al., 2011; Hamid et al., 2018; Wang et al., 2020; Weinberg et al., 2011), but direct LFG sample evaluation for PFAS concentrations is currently being researched by EPA. See Section 5 for details. Unlike waste in MSW landfills, the C&D landfill waste that contributes most to LFG production is generally dominated by gypsum drywall (Yang et al., 2006). Gypsum drywall results in C&D LFG largely consisting of hydrogen sulfide, a highly pungent gas, with a smaller fraction of methane. Because C&D landfills generate a lower volume of gas than MSW landfills, LFG from C&D landfills is not collected and is often emitted to the environment without treatment. 3.b.iv.2 On- and off-site management of landfill gas LFG collection and management are regulated under the CAA through National Emission Standards for Hazardous Air Pollutants (NESHAP) and the New Source Performance Standards (NSPS) programs. After collection, LFG can be managed on-site and burned using a flare. There are two basic types of flares common at MSW sites: open (candlestick) and enclosed flares. LFG can also be managed off-site, where it is usually piped from the landfill site to a nearby gas-fired system to generate heat or power. On-site open flares must operate in accordance with key parameters for exit velocity and flare diameter for non-assisted flares (in 40 CFR 60.18). Additionally, a heat-sensing device must be installed to indicate continuous flame presence (but no specific temperature level). A landfill with an enclosed flare must demonstrate a maximum 20 parts per million by volume (ppmv) NMOC outlet or 98 percent reduction in NMOC with a one-time performance test and operating parameters set during the test for the requisite flare temperature and flow rate. Combustion temperatures and duration may prove to be critical factors for destruction of PFAS in LFG. While on-site flare systems average 850C (1,550F) (U.S. EPA, 2008), engine and boiler systems may run cooler and have a lower destructive potential for PFAS (as indicated in the EPA boiler database). See Section 3.a for a more complete discussion on conditions required for PFAS destruction. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 66 Under the CAA regulations, if LFG is treated for sale or use in a beneficial energy recovery device, it must be treated according to a site-specific treatment plan before being utilized on-site or piped out of the facility. Like liners, active gas collection systems are not required at all landfills, depending on the landfill size and level of NMOCs, which will affect the release of PFAS via fugitive emissions. LFG condensate is a liquid that has condensed in the LFG collection system during the extraction of gas from the landfill. Gases with high concentrations of water vapor condense in traps staged throughout the network. Condensate contains volatile compounds and accounts for a relatively small percentage of flow from a landfill. Gas condensate is commonly collected and managed with the landfill leachate as liquid wastes. PFAS has been detected in LFG condensate, with perfluorobutanesulfonic acid (PFBS) being the dominant species at a concentration of 1,000 ng/L (Li, 2011). 3.b.v Potential for releases during landfilling Over time, the potential increases for certain pollutants to move into the environment beyond the footprint of the landfill. As water passes through the landfill, it may leach pollutants from the waste-- including PFAS from PFAS-containing waste--and move them deeper. Controlled landfill leachate is collected and either reinjected, treated on-site, or sent to a POTW for off-site treatment. In the absence of leachate management systems, uncontrolled leachate releases occur when water travels through the waste, out of the landfill, and into groundwater or surface water (see Section 4). LFG can also contain heavy metals, organic chemicals, and greenhouse gases and can produce explosive mixtures of gas in the vicinity of the landfill if not properly controlled (ATSDR, 2001). LFG capture technologies are widely used to control gaseous emissions from landfills. However, despite the active capture of LFG, a fraction of LFG is emitted directly to the environment through the landfill surface and other routes as fugitive losses (see Section 4). Even years after landfill closure, direct human and ecological exposure is possible if PFAS are emitted through the air, groundwater, or surface water, or if remaining waste is disturbed. Because landfills contain PFAS but are not designed to destroy these compounds, they represent a potential source of PFAS release well beyond the period in which landfills receive waste and the post-closure care period. Ideally, landfill areas could be used for other beneficial purposes after closure; this requires that potential risks from landfill contents be adequately managed. Direct exposure to PFAS from landfilled waste is possible for people living or working near landfills as a result of gaseous or water releases from the site. Additionally, if PFAS-containing wastes are present on trucks and moved to active cells, landfill employees are directly exposed on the job. Research has shown elevated concentrations of PFAS in landfill ambient air (Hamid et al., 2018). 3.b.vi Testing and monitoring Currently, there are no federal requirements for the monitoring of PFAS in landfill waste, leachate, condensate, or LFG. EPA and others are conducting studies to evaluate the effectiveness of landfills in containing or managing PFAS (see Section 5.b). However, the lack of standardized testing may pose a challenge for comparison across destruction/control technologies and types of landfills (see Section 5.a for research needs). INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 67 3.b.vii Uncertainties/unknowns EPA plans to conduct further research on PFAS within landfills, including the potential for PFAS to migrate to leachate or LFG without adequate controls. As with thermal treatment, EPA lacks detailed information on the amounts and concentrations of PFAS and precursor compounds in wastes that are landfilled. There has not been enough research to determine what percent of PFAS can be expected to remain within the confines of landfills, with the many combinations of technology and operating parameters that exist across the thousands of landfills in the United States. Sampling and analytical methodologies must continue to be developed to quantify potential PFAS flows out of landfills, an effort that may be complicated by the long lifespan of some PFAS. Additionally, as detailed above, the efficacy of treatment options for PFAS captured by leachate and LFG systems is not well understood and is in some cases intrinsically entwined with WWTP and thermal treatment options. EPA continues to research these complex and important issues. Refer to Section 5 for a summary of EPA and DoD's planned research activities specific to landfill containment, wastewater treatment, and thermal treatment of PFAS. 3.b.viii Treatment costs The United States has more than 2,600 MSW, around 1,000 stand-alone C&D debris, and at least 169 industrial (reporting to the Greenhouse Gas Reporting Program [GHGRP]) landfills in operation (U.S. EPA, 2020b, n.d.; DHS, 2017). Costs associated with containing PFAS in landfills are associated with tipping fees (gate rates) at landfills, which help pay for operation and maintenance, capital investment, and costs associated with regulatory compliance. The costs associated with sending PFAS wastes to landfills are difficult to assess because the available data are largely associated with general tipping fees for MSW on a per-ton basis. Table 3-7, on the next page, presents the average tipping fees for one short ton of waste at an MSW landfill. The range of costs varies widely by state and region, with a lowest average state-level rate at $29.82 in Kentucky and the highest in the contiguous United States at $110 in Rhode Island; Alaska and Hawaii both have even higher rates. All regions have seen these rates increase over the 4-year period from 2016 to 2019. The national average 2019 tipping fee for MSW was $55.36, while C&D debris disposed of in MSW landfills was slightly lower at $54.04 (EREF, 2019). These costs are not reflective of any additional surcharges leveled for wastes associated with high PFAS concentrations. Hazardous waste, ash monofill, and industrial landfills are often explicitly designed and built for specific waste streams, and their costs vary widely from site to site. Associated with the tipping fees is the cost burden associated with treating the leachate, which can also contain PFAS. The 2000 EPA rulemaking that led to the Landfill Effluent Guidelines identified 1,989 landfills, generating a median daily flow of 5,620 gallons of leachate (U.S. EPA, 2000). Lang et al. (2017) estimated 16.1 billion gallons of leachate generated in 2013, not including leachate recirculated in landfills. Similar to the cost of landfilling PFAS waste, the associated treatment of PFAS-laden leachate is difficult to assess because the available data are associated with typical industrial wastewater generators or typical landfill leachate. These data currently do not include specific information on extra treatment considerations that may be required by an NPDES permit or by an industrial user permit for a discharge into a POTW to control the release of PFAS. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 68 Table 3-7. Average MSW Tipping Fees per Ton for States and Regions (EREF, 2019) Region/State Pacific Alaska Hawaii Washington Nevada Oregon Idaho California Arizona Northeast Rhode Island Delaware New Jersey Maine New Hampshire Maryland New York Pennsylvania Virginia West Virginia Connecticut Massachusetts Vermont Average Tipping Fee $73.03 $154.92 $112.33 $89.08 $74.20 $71.28 $68.71 $55.56 $43.39 $66.53 $110.00 $85.00 $81.91 $78.50 $74.34 $68.57 $68.40 $68.07 $52.22 $51.50 N.A. N.R. N.R. Region/State Midwest Wisconsin Minnesota Missouri Illinois Iowa Indiana Ohio Michigan Kansas Nebraska Average Tipping Fee $48.87 $65.00 $63.52 $62.42 $51.78 $48.47 $47.91 $44.35 $41.97 $39.32 $39.21 Southeast Florida Tennessee Georgia South Carolina North Carolina Mississippi Alabama Kentucky $45.25 $55.08 $50.24 $48.77 $44.03 $43.87 $38.70 $33.41 $29.82 Mountains/Plains Wyoming Colorado Montana South Dakota North Dakota Utah $50.71 $74.45 $62.04 $49.36 $49.14 $46.98 $32.08 South Central Oklahoma Arkansas Texas New Mexico Louisiana $40.92 $50.22 $40.23 $40.18 $38.28 $33.28 Table 3-8 presents the average state-level metered rates for 1,000 gallons of industrial wastewater. The rates vary from $1.63 in Arkansas to $18.45--more than 10 times as much--in Washington. Though they show the variability in regional costs for industrial wastewater treatment, these figures are not commensurate with the rates explicitly reported for leachate treatment. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 69 Table 3-8. Average State-Level Wastewater Treatment Prices for Large Industrial Consumers with an 8-Inch Wastewater Meter (DOE, 2017) State 2016 Volume Charge per kGala Alabama $7.51 Alaska $7.49 Arizona $2.88 Arkansas $1.63 California $3.61 Florida $5.57 Georgia $5.11 Illinois $2.64 Kansas $4.77 Louisiana $6.04 New Mexico $2.39 North Carolina $4.00 Pennsylvania $4.00 South Carolina $2.12 Tennessee $8.39 Texas $4.79 Utah $4.57 Virginia $2.88 Washington $18.45 Wisconsin $3.53 Average $5.05 a Cost per thousand gallons (kGal) is assumed to be in 2016 dollars. Costs were normalized to 2019 dollars using the BEA GDP deflator (BEA, 2020) for utilities using a base year of 2016. Leachate treatment at POTWs has been reported between $33 and $125 per gallon depending on treatment method (Kremen, 2020). This cost does not represent any additional burdens associated specifically with PFAS treatment. Cost estimates were also identified for two on-site leachate treatments that were previously indicated as potential treatment options for leachate containing PFAS: RO and activated carbon. A membrane bioreactor with RO is expected to provide treatment at $64 to $95 per 1,000 gallons for typical landfill leachate, while activated carbon may possibly provide treatment as low as $5.40 per 1,000 gallons using activated carbon with a sequencing batch reactor (Kremen, 2020). Again, though, neither of these ranges accounts for the additional burdens that may be associated with a PFAS-laden leachate (Cunningham, 2019). See Section 3.a (specifically Table 3-3) on thermal treatment for costs specifically associated with the regeneration or disposal of GAC. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 70 3.b.ix Summary Due to widespread use and disposal through typical waste management pathways, PFAS-containing wastes are currently managed through containment in landfills. Though landfills are designed for permanent waste containment and management of liquid and gas production, it is currently unclear if all landfills used for PFAS disposal have controls that are effective for managing PFAS discharges and emissions from waste streams. Given the chemical makeup of PFAS, some compounds are expected to persist in landfills for years. To varying degrees, hazardous waste or MSW landfills are feasible and effective disposal options for PFAS and PFAS-containing materials. Permitted hazardous waste landfills employ the most extensive set of environmental controls (e.g., double liner systems with leachate collection and leak detection) and practices (e.g., extensive record keeping) that are currently available for the containment of PFAS waste (see Table 3-4) and as a result would be more effective at minimizing PFAS migration into the environment than other landfill types. Modern MSW landfills, when constructed with appropriate controls (e.g., liner system and leachate and gas collection and management systems), can also control the migration of PFAS into the environment. Even with these controls in place, the proper management of landfill gaseous and liquid releases needs to be applied for MSW and hazardous waste landfills to minimize PFAS migration into the environment (as described in Section 3.b.ii). Care must be taken to apply the leachate control technologies that are effective at containing (e.g., solidification or recirculation) or destroying PFAS (see Table 3-6 for more information). Given the high level of uncertainty associated with PFAS behavior in landfills, research consistent with that described in Section 5--such as research on the effects of PFAS on liner integrity, gaseous emissions from landfills, the effectiveness of leachate treatment for PFAS removal, and the levels and types of PFAS in landfill leachate--will help to further evaluate this disposal method for PFAS and PFAS-containing wastes. As leachate passes through landfills, PFAS are released from degrading wastes. PFAS have been detected in the leachate for all types of landfills and improper management of landfill leachate would result in PFAS releases. To date, research on the efficacy of wastewater treatment technologies in capturing or destroying PFAS in leachate is limited, as landfills are not currently required to treat leachate for PFAS. The existing data suggest that adsorption and separation treatment mechanisms have been shown to concentrate or capture PFAS from landfill leachate (see Table 3-6). Furthermore, oxidation mechanisms show potential in destroying PFAS during treatment but are still in development and not widely used at this time. Other leachate management options can control the migration of PFAS into the environment, including recirculation and solidification, which return PFAS to the landfill. Leachate treatment through natural processes such as constructed wetlands, land application, or ponds is ineffective for preventing the release of PFAS into the environment. More data are needed on the volatilization of PFAS during leachate handling and treatment. Additionally, PFAS can be emitted with LFG that is generated as waste decomposes over time. On-site and off-site LFG management commonly use flares or boilers to combust LFG. Combustion temperature and duration could be critical factors for the destruction of PFAS in LFG, as discussed in Section 3.a. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 71 3.b.x References for Section 3.b Ahrens, L., Shoeib, M., Harner, T., Lee, S. C., Guo, R., & Reiner, E. J. (2011). Wastewater treatment plant and landfills as sources of polyfluoroalkyl compounds to the atmosphere. Environmental Science and Technology, 45(19), 8098-8105. https://doi.org/10.1021/es1036173 ATSDR (Agency for Toxic Substances and Disease Registry). (2001). Landfill gas primer--an overview for environmental health professionals. Bao, Y. (2014). Removal of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) from water by coagulation: Mechanisms and influencing factors. Journal of Colloid and Interface Science, 6. BEA (Bureau of Economic Analysis). (2020, April 6). Chain-type quantity indexes for value added by industry. https://apps.bea.gov/iTable/iTable.cfm?reqid=150&step=2&isuri=1&categories=gdpxind Benskin, J. P., Li, B., Ikonomou, M. G., Grace, J. R., & Li, L. Y. (2012). Per- and polyfluoroalkyl substances in landfill leachate: Patterns, time trends, and sources. Environmental Science and Technology, 46(21), 11532-11540. https://doi.org/10.1021/es302471n Boo, C., Wang, Y. Zucker, I., Choo, Y., Osuji, C. O., & Elimelech, M. (2018). High performance nanofiltration membrane for effective removal of perfluoroalkyl substances at high water recovery. Environmental Science and Technology, 52(13), 7279-7288. https://doi.org/10.1021/acs.est.8b01040 Busch, J., Ahrens, L., Sturm, R., & Ebinghaus, R. (2010). 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Water and wastewater annual price escalation rates for selected cities across the United States. https://www.energy.gov/sites/prod/files/2017/10/f38/water_wastewater_escalation_rate_study.p df EREF (Environmental Research and Education Foundation). (2019). Analysis of MSW landfill tipping fees--April 2019 (Rev. 10/31/19). https://erefdn.org/product/analysis-msw-landfill-tipping-fees-2/ INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 72 Franke, V., Schafers, M. D., Lindberg, J. J., & Ahrens, L. (2019). Removal of per- and polyfluoroalkyl substances (PFASs) from tap water using heterogeneously catalyzed ozonation paper. Environmental Science: Water Research & Technology, 5, 1887-1896. https://doi.org/10.1039/C9EW00339H Fuertes, I., Gmez-Lavn, S., Elizalde, M. P., & Urtiaga, A. (2017). Perfluorinated alkyl substances (PFASs) in northern Spain municipal solid waste landfill leachates. Chemosphere, 168, 399-407. https://doi.org/10.1016/j.chemosphere.2016.10.072 Gallen, C., Drage, D., Eaglesham, G., Grant, S., Bowman, M, & Mueller, J. F. (2017). Australia-wide assessment of perfluoroalkyl substances (PFASs) in landfill leachates. Journal of Hazardous Materials, 331, 132-141. https://doi.org/10.1016/j.jhazmat.2017.02.006 Hamid, H., Li, L. Y., & Grace, J. R. (2018). Review of the fate and transformation of per- and polyfluoroalkyl substances (PFASs) in landfills. Environmental Pollution, 235, 74-84. https://doi.org/10.1016/j.envpol.2017.12.030 Huset, C. A., Barlaz, M. A., Barofsky, D. F., & Field, J. A. (2011). Quantitative determination of fluorochemicals in municipal landfill leachates. Chemosphere, 82(10), 1380-1386. https://doi.org/10.1016/j.chemosphere.2010.11.072 ITRC (Interstate Technology Regulatory Council). (2017). Naming conventions and physical and chemical properties of per- and polyfluoroalkyl substances (PFAS). ITRC (Interstate Technology Regulatory Council). (2018). Remediation technologies and methods for perand polyfluoroalkyl substances (PFAS). Kremen, A. (2020, February 1). Getting a handle on landfill leachate. Tetra Tech Newsroom. https://www.tetratech.com/en/blog/getting-a-handle-on-landfill-leachate Lang, J. R., Allred, B. M., Field, J. A., Levis, J. W., & Barlaz, M. A. (2017). National estimate of per- and polyfluoroalkyl substance (PFAS) release to U.S. municipal landfill leachate. Environmental Science and Technology, 51(4), 2197-2205. https://doi.org/10.1021/acs.est.6b05005 Li, B. (2011). Perfluorinated compounds in landfill leachate and their effect on the performance of sodium bentonite landfill liners. Master's thesis, University of British Columbia. https://doi.org/10.14288/1.0063208 Lin, H., Niu, J., Ding, S., & Zhang, L. (2012). Electrochemical degradation of perfluorooctanoic acid (PFOA) by Ti/SnO2-Sb, Ti/SnO2-Sb/PbO2 and Ti/SnO2-Sb/MnO2 anodes. Water Research, 46(7), 2281-2289. https://doi.org/10.1016/j.watres.2012.01.053 Liu, C. (2017). Removal of perfluorinated compounds in drinking water treatment: A study of ion exchange resins and magnetic nanoparticles. Ph.D. thesis, University of Waterloo. Lockwood, D. (2018). Photocatalyst shreds PFOA. Chemical and Engineering News, 96(36), 7. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 73 Masoner, J., Kolpin, D., Cozzarelli, I., Smalling, K., Bolyard, S., Field, J., Furlong, E., Gray, J., Lozinski, D., Reinhart, D., Rodowa, A., & Bradley, P. (2020). Landfill leachate contributes per-/poly-fluoroalkyl substances (PFAS) and pharmaceuticals to municipal wastewater. Environmental Science: Water Research & Technology, 6, 1300-1311. https://pubs.rsc.org/en/content/articlehtml/2020/ew/d0ew00045k McCleaf, P., Englund, S., Ostlund, A., Lindegren, K., Wiberg, K., & Ahrens, L. (2017). Removal efficiency of multiple poly- and perfluoroalkyl substances (PFASs) in drinking water using granular activated carbon (GAC) and anion exchange (AE) column tests. Water Research, 120, 77-87. https://doi.org/10.1016/j.watres.2017.04.057 Mukherjee, S., Mukhopadhyay, S., Hashim, M. A., & Gupta, B. S. (2015). Contemporary environmental issues of landfill leachate: Assessment and remedies. Critical Reviews in Environmental Science and Technology, 45(5), 472-590. Ochoa-Herrera, V., & Sierra-Alvarez, R. (2008). Removal of perfluorinated surfactants by sorption onto granular activated carbon, zeolite and sludge. Chemosphere, 72(10), 1588-1593. https://doi.org/10.1016/j.chemosphere.2008.04.029 OECD (Organization for Economic Cooperation and Development). (2013). Synthesis paper on per- and polyfluorinated chemicals (PFCs). https://www.oecd.org/env/ehs/risk-management/PFC_FINALWeb.pdf Pan, G.-C., Liu, Y.-S., & Ying, G.-G. (2016). Perfluoroalkyl substances (PFASs) in wastewater treatment plants and drinking water treatment plants: Removal efficiency and exposure risk. Water Research, 106, 562-570. Rahman, M. F., Peldszus, S., & Anderson, W. B. (2014). Behaviour and fate of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in drinking water treatment: A review. Water Research, 50, 318- 340. https://doi.org/10.1016/j.watres.2013.10.045 Renou, S., Givaudan, J. G., Poulain, S., Dirassouyan, F., & Moulin, P. (2008). Landfill leachate treatment: Review and opportunity. Journal of Hazardous Materials, 150, 468-493. Ross, I., McDonough, J., Miles J., Storch, P., Kochunarayanan, P. T., Kalve, E., Hurst, J., Dasgupta, S. S., & Burdick, J. (2018). A review of emerging technologies for remediation of PFASs. Remediation, 28, 101-126. https://doi.org/10.1002/rem.21553 Saez, M., de Voogt, P., & Parsons, J. R. (2008). Persistence of perfluoroalkylated substances in closed bottle tests with municipal sewage sludge. Environmental Science and Pollution Research, 15: 472- 477. Schultz, M. M., Higgins, C. P., Huset, C. A., Luthy, R. G., Barofsky, D. F., & Field, J. A. (2006). Fluorochemical mass flows in a municipal wastewater treatment facility. Environmental Science and Technology, 40(23), 7350-7357. https://pubs.acs.org/doi/10.1021/es061025m INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 74 Solo-Gabriele, H. M., Jones, A. S., Lindstrom, A. B., & Lang, J. R. (2020). Waste type, incineration, and aeration are associated with per- and polyfluoroalkyl levels in landfill leachates. Waste Management, 107, 191-200. https://doi.org/10.1016/j.wasman.2020.03.034 Tian, Y., Yao, Y., Chang, S., Zhao, Z., Zhao, Y., Yuan, X., Wu, F., & Sun, H. (2018). Occurrence and phase distribution of neutral and ionizable per- and polyfluoroalkyl substances (PFASs) in the atmosphere and plant leaves around landfills: A case study in Tianjin, China. Environmental Science and Technology, 52(3), 1301-1310. https://doi.org/10.1021/acs.est.7b05385 U.S. EPA (Environmental Protection Agency). (2000). Development document for final effluent limitations guidelines and standards for the landfills point source category (EPA-821-R-99-019). https://www.epa.gov/sites/production/files/2015-11/documents/landfills-eg_dd_2000.pdf U.S. EPA (Environmental Protection Agency). (2008). Background information document for updating AP42 Section 2.4 for estimating emissions from municipal solid waste landfills (EPA/600/R-08-116). https://www3.epa.gov/ttn/chief/ap42/ch02/draft/db02s04.pdf U.S. EPA (Environmental Protection Agency). (2020a). Drinking Water Treatability Database (TDB). https://oaspub.epa.gov/tdb/pages/general/home.do U.S. EPA (Environmental Protection Agency). (2020b). Landfill technical data. https://www.epa.gov/lmop/landfill-technical-data U.S. EPA (Environmental Protection Agency). (n.d.). Facility Level Information on GreenHouse gases Tool (FLIGHT). https://ghgdata.epa.gov/ghgp/main.do Wang, B., Yao, Y., Chen, H., Chang, S., Tian, Y., & Sun, H. (2020). Per- and polyfluoroalkyl substances and the contribution of unknown precursors and short-chain (C2-C3) perfluoroalkyl carboxylic acids at solid waste disposal facilities. Science of the Total Environment, 135832. https://doi.org/10.1016/j.scitotenv.2019.135832 Weinberg, I., Dreyer, A., & Ebinghaus, R. (2011). Landfills as sources of polyfluorinated compounds, polybrominated diphenyl ethers and musk fragrances to ambient air. Atmospheric Environment, 45(4), 935-941. https://doi.org/10.1016/j.atmosenv.2010.11.011 Yamada, T., Taylor, P. H., Buck, R. C., Kaiser, M. A., & Giraud, R. J. (2005). Thermal degradation of fluorotelomer treated articles and related materials. Chemosphere, 61(7), 974-984. https://doi.org/10.1016/j.chemosphere.2005.03.025 Yan, H., Cousins, I. T., Zhang, C., & Zhou, Q. (2015). Perfluoroalkyl acids in municipal landfill leachates from China: Occurrence, fate during leachate treatment and potential impact on groundwater. Science of the Total Environment, 524-525, 23-31. https://doi.org/10.1016/j.scitotenv.2015.03.111 Yang, K., Xu, Q., Townsend, T. G., Chadik, P., Bitton G., & Booth, M. (2006). Hydrogen sulfide generation in simulated construction and demolition debris landfills: Impact of waste composition. Journal of the Air and Waste Management Association, 56(8), 1130-1138. https://doi.org/10.1080/10473289.2006.10464544 INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 75 3.c Underground injection Like landfills, underground injection wells are a feasible and effective, to varying degrees, disposal option that normally should minimize migration of PFAS into the environment. Unlike landfills, underground injection wells are only suited for disposal of liquids. A waste stream in the form of PFAScontaining fluids would currently be handled similarly to non-hazardous industrial and hazardous wastes that are injected deep into geologic formations. The limited number of wells currently receiving PFAS, as well as location, waste transportation, and associated costs, may significantly limit the type and quantity of PFAS-related liquid waste streams appropriate for underground injection. 3.c.i Types of wells Underground injection is generally defined as the subsurface emplacement of fluids through a well. Under the Safe Drinking Water Act (SDWA), EPA is authorized to regulate the permitting of injection wells--including construction, operation, monitoring, and proper closure--for the purpose of protecting underground sources of drinking water (USDWs). Underground injection control (UIC) regulations are found in 40 CFR parts 144 to 148. EPA's UIC program shares information for owners and operators of injection wells, regulators, and the public about safe injection well operations to prevent the contamination of USDWs. Under the UIC program, EPA regulates the permitting of the following well types: Class I wells are deep injection wells injecting into geologic formations below the lowermost USDW and are further subdivided into four categories: municipal wastewater, radioactive waste, hazardous waste, and non-hazardous industrial waste disposal wells (see Figure 3-2). Class II wells are used for injection activities associated with oil and gas production and hydrocarbon storage. Class III wells are solution mining wells used to inject fluids for the purposes of dissolving and extracting minerals. Class IV wells, with limited exceptions, have been banned by EPA since 1984 and were used to inject hazardous or radioactive waste into or above geologic formations containing USDWs. Class V wells include injection wells that are not included in Classes I, II, III, IV, or VI. EPA has identified multiple subtypes including stormwater drainage wells, septic system leach fields, and agricultural drainage wells. Class VI wells are used to inject and geologically sequester carbon dioxide. Figure 3-2. Class I well. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 76 Class I wells in the non-hazardous industrial or hazardous waste categories are well suited for the management of PFAS-containing waste material. Class I underground injection wells are designed to dispose of and isolate liquid wastes below the land surface and beneath USDWs. The standards associated with the construction, operation, and monitoring of Class I wells are designed to ensure protection of USDWs. These standards include at least one confining layer between the zone in which the fluid will be emplaced and the lowest USDW. While Class I wells are an option for managing fluids that contain PFAS, this technology may not be appropriate everywhere. The suitability of a site for injection is dependent on the geologic formation in the area. Sites need to be evaluated to ensure that there is an appropriate confining zone and geologic formations that are able to receive fluids. Class I wells for non-hazardous industrial and hazardous waste are currently being used for disposal of PFAS-containing fluid wastes and are the focus of this section. PFAS-containing fluids that may be disposed of via Class I underground injection wells may originate from industrial activities such as chemical production (e.g., products and byproducts) and waste management operation (e.g., landfill leachate). The standards associated with the permitting, construction, operation, and monitoring of Class I hazardous waste wells, which are regulated under RCRA and SDWA, are more stringent than for nonhazardous industrial waste disposal wells. 3.c.ii Siting, engineering, and operational controls 3.c.ii.1 Overview of the regulatory framework Underground injection through Class I non-hazardous industrial and hazardous waste wells is a longstanding, well-regulated disposal technology. Underground injection has been used as a waste disposal practice in the United States since the 1930s, beginning with disposal of brines from oil production activities. Underground injection of wastewaters from industrial facilities has been in practice since the 1950s. In response to concerns around underground injection activities and incidents of well failure, in 1974 (the same year the SDWA was enacted), "EPA issued a policy statement in which it opposed underground injection without strict control and clear demonstration that the wastes will not adversely affect groundwater supplies" (U.S. EPA, 2001). Final UIC regulations were published 6 years later, and federal and state regulation and oversight has been informed by extensive reviews of injection practices and associated risks over time (U.S. EPA, 2001). The requirements for Class I wells under 40 CFR part 146 and 40 CFR part 148 (which applies to hazardous waste wells only) are designed to ensure that injected fluids cannot migrate into USDWs through either of two potential pathways: loss of waste confinement or "improperly plugged or completed wells or other pathways near the well" (U.S. EPA, 2001). These requirements include, but are not limited to: Proper siting. Conducting geologic and hydrogeologic studies that demonstrate that injected fluids will not endanger USDWs. Specific design, construction, and operation requirements. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 77  Continuous monitoring and periodic monitoring and testing requirements. Appropriate well closure and plugging. Specific components of these requirements are discussed further below. 3.c.ii.2 Class I non-hazardous industrial and hazardous waste wells Underground injection to Class I non-hazardous industrial and hazardous waste wells reduces the potential risks of human exposure to injected materials, avoiding discharge to surface and shallow groundwater and generating little or no air emissions. When injected into non-hazardous industrial or hazardous waste Class I wells, fluids are placed below the lowermost USDW. The area into which wastes are injected is referred to as the injection zone. Injection zones of Class I wells typically range from 1,700 to over 10,000 feet in depth (U.S. EPA, 2001). Injection zones are porous and permeable geologic formations. They are separated from USDWs by one or more confining layers of impermeable rock. The confining layer(s) prevent injected fluids from migrating vertically into a USDW. Class I wells are sited in geological areas that are conducive to injection operations. Siting considerations include ensuring that injected fluids will not migrate through natural fractures and faults from the injection zone into USDWs. Likewise, well operators are required to demonstrate the absence of nonnatural pathways (e.g., abandoned wells) or other nearby active wells that could allow for movement of injected fluids into USDWs, within a prescribed area surrounding the well (known as the area of review). In addition to the safeguards offered by siting, engineering, and operating requirements, well design and construction requirements incorporate redundant safety features, and construction materials are "corrosion-resistant and compatible with the wastewater and the formation rocks and fluids into which they come in contact" (U.S. EPA, 2001). Class I wells might also use multiple strings of well casing, inject through tubing set on a packer, and be constructed with adequate cement alongside the entire well string to ensure appropriate protection of any USDWs. Permitted underground injection of fluids through Class I non-hazardous industrial and hazardous waste wells ensures that injected fluids are confined and cannot enter USDWs--the pathway of concern for this waste disposal technology. In its 2001 study of risks associated with Class I wells, EPA stated that the "probability of Class I well failures, both non-hazardous and hazardous, has been demonstrated to be low. In the unlikely event that a well would fail, the geology of the injection and confining zones serves as a final safety net against movement of wastewaters to USDWs" (U.S. EPA, 2001). Injection well operators invest millions of dollars in the permitting, construction, and operation of wells. Development of Class I non-hazardous industrial and hazardous waste wells is a resource-intensive process, with the geologic limitations noted previously. In addition, siting requirements limit the areas in the country where Class I wells can be located (see Section 3.c.iv). The typical construction cost to develop a Class I well has been estimated at $4 million to $6 million (deSilva, 2019). Routine operation and maintenance costs include those to address requirements for extensive mechanical integrity testing, monitoring, and periodic submission of permit/no-migration petitions. 3.c.ii.3 Additional requirements for Class I hazardous waste wells Class I hazardous waste wells are highly protective of USDWs and avoid active seismic areas. The 1984 Hazardous and Solid Waste Amendments to RCRA prohibited land disposal of hazardous waste, INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 78 including via underground injection, with limited exceptions. Hazardous waste disposal via Class I injection well is permitted if the operator can demonstrate that the waste will remain where it has been injected for as long as it remains hazardous (defined under regulation as a period of up to 10,000 years). To demonstrate this, Class I hazardous waste well operators must receive approvals of "no-migration petitions" from EPA. No-migration petitions present information and modeling results using data on local and regional geology, waste characteristics, geochemical conditions of the well site, injection history, and many other factors, which EPA reviews to determine whether the petitioner has adequately demonstrated that the waste will not migrate from the disposal site for as long as it remains hazardous. Furthermore, Class I hazardous waste well facilities are subject to inspections and well operators must conduct annual testing and analysis (including mechanical integrity tests--both mechanical pressure tests and geophysical logging tests used to assess well integrity both internally and externally to ensure injected fluids are being emplaced and remaining within the injection zone) to demonstrate they are meeting the conditions of the permit and that all assumptions, projections, and modeling are still appropriate and valid. 3.c.iii Availability and costs The United States currently has 823 Class I wells. Slightly more than half (53 percent) are permitted for non-hazardous industrial waste injection. Approximately 18 percent are permitted for hazardous waste disposal. The remainder are permitted for municipal wastewater disposal. Currently, EPA is aware of two Class I sites that manage PFAScontaining fluids. One is in Michigan, where a non-hazardous industrial waste well facility is injecting PFAS-containing leachate from a landfill (Usher, 2019). In Texas, more than 50 million gallons of PFAS-containing waters have been injected into Class I hazardous waste wells (Marine, 2020). Figure 3-3 shows all states that currently have at least one permitted Class I injection well of any type (nonhazardous or hazardous waste). Table 3-9 provides a more detailed breakdown of the number of permitted Class I wells by state. Figure 3-3. States with Class I non-hazardous or hazardous waste injection wells. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 79 Table 3-9. Inventory of Permitted Class I Non-Hazardous and Hazardous Waste Wells in the United States (FY 2018; Source: EPA)9 Location of Wells EPA Region State/Tribe 4 Florida 4 Kentucky 4 Seminole Tribe 4 Mississippi 5 Illinois 5 Indiana 5 Michigan 5 Ohio 6 Arkansas 6 Louisiana 6 New Mexico 6 Oklahoma 6 Osage Nation 6 Texas 7 Kansas 7 Nebraska 8 Colorado 8 North Dakota 8 Wyoming 10 Alaska Number of Wells Class I Non-Hazardous Class I Hazardous 251 1 1 0 3 0 8 5 9 2 0 4 31 7 5 12 8 3 17 19 6 0 6 0 1 0 92 77 56 8 10 0 16 0 8 0 85 0 23 0 Class I well capacity is limited, which may affect the costs associated with deep well injection. A presentation in 2019 placed the cost for deep well injection at approximately $0.18 to $0.25 per gallon (deSilva, 2019). As mentioned above, the typical construction cost to develop a Class I well has been estimated at $4 million to $6 million (deSilva, 2019). 3.c.iii.1 Class I non-hazardous industrial waste wells Non-hazardous industrial waste wells are located across 19 states, though the majority are in five states--Texas, California, Louisiana, Kansas, and Wyoming. Disposal to this type of well requires well operators to apply and receive permit modifications and assess long-term consequences of accepting new waste streams. Although current Class I injection wells may have limited capacity for PFAScontaining fluids, many of them are used for specific purposes and disposal of waste generated on-site. To accept PFAS-containing fluids, well permits would have to be modified to recognize that the facility is accepting waste from other entities and authorize the facility to inject modified waste streams. Well operators must also weigh considerations around capacity to accept additional volumes of waste and compatibility of PFAS-containing waste streams with the well material, the geochemistry of the injection formation and formation fluids, and the properties of other injected wastes. 9 EPA's inventory of Class I non-hazardous waste wells consists of all non-hazardous waste wells, including municipal and industrial waste wells. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 80 3.c.iii.2 Class I hazardous waste wwells Most Class I hazardous waste wells in the United States are in Texas and Louisiana and are sited at industrial facilities and dispose of waste generated on-site (U.S. EPA, 2016). There are no Class I hazardous waste wells in EPA Regions 1, 2, 3, 8, 9, or 10 (see Figure 3-3 and Table 3-9). Because of this geographic concentration of Class I hazardous waste wells, waste producers may face transportation and logistical challenges. Estimates of trucking costs associated with transportation of waste fluid ranges from $0.01 to $0.19 per gallon (McCurdy, 2011). There is currently no national information on the number and location of Class I hazardous waste wells that could accept PFAS-containing wastes, or that are willing to accept wastes not generated on-site. However, EPA anticipates the number of current Class I hazardous waste wells that would accept PFAScontaining waste to be very limited due to the necessary modifications of Class I hazardous waste well permits (e.g., increased injection volumes, changes to waste streams, and no-migration petitions) that would involve engineering and scientific evaluations, modeling, and public hearings. 3.c.iv Testing and monitoring Class I non-hazardous industrial waste and hazardous waste disposal wells are subject to extensive testing and monitoring requirements established under federal regulations. Requirements for hazardous waste wells are more stringent than for non-hazardous industrial waste wells. Additionally, by law, states with primary enforcement authority for Class I wells may have more stringent testing and monitoring requirements. Class I monitoring and testing requirements are designed to ensure that there are no leaks within or out of the well and that all injected fluid is contained in the injection zone. Broadly, Class I well operators must: Analyze characteristics of injected fluids at a frequency that results in representative data. Continuously monitor and record injection pressure, annulus pressure, flow rate, and volume. Conduct internal and external mechanical integrity testing. Monitor for fluid migration into the USDW within the area of review. Class I hazardous waste wells operators must conduct mechanical integrity testing more often than Class I non-hazardous industrial waste operators, and also must establish and follow procedures for reporting and correcting mechanical integrity problems. Class I hazardous waste well operators must also develop and follow a waste analysis plan and conduct annual tests of cement at the base of the well (U.S. EPA, 2015). Additional information on testing and monitoring requirements, including mechanical integrity testing, is included in EPA's summary document Requirements for All Class I Wells and Class I Hazardous Waste Wells and EPA Region 5's guidance on Determination of the Mechanical Integrity of Injection Wells. 3.c.v Uncertainties/unknowns The fate and transport of PFAS in the subsurface depends on: The chemical and physical properties of specific PFAS. INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 81  The geochemical properties of the injection zone. Understanding of the long-term fate and transport properties of PFAS (including precursors) in the injection zone is currently limited. Studies have shown wide ranges in PFAS chemical properties, and these can be altered by mixture effects and interactions with co-contaminants. This creates uncertainty in predictions of PFAS contaminant migration and longevity in the injection zone. For disposal of PFAS in Class I hazardous waste wells, these uncertainties need to be considered in the development of the required no-migration petition. 3.c.vi Summary As noted above, Class I (non-hazardous industrial or hazardous waste) wells are well suited for the management of PFAS waste material. Permitted underground injection of fluids through Class I nonhazardous industrial and hazardous waste wells ensures that injected fluids are confined and cannot enter USDWs--the pathway of concern for this waste disposal technology. Research on the long-term fate and transport of PFAS (including precursors) to predict migration potential in the injection zone could support future permits. 3.c.vii References for Section 3.c deSilva, V. (2019). PFAS in landfill leachate. http://www.mowastecoalition.org/resources/Documents/2019%20conference/MWCC2019%20deSilva%20(SCS)%20-PFAS-July%2016,%202019.pdf Marine, F. (2020). Class I UIC wells to manage PFAS in wastewaters. http://www.gwpc.org/sites/default/files/event-sessions/Marine%20-%20Class%20I%20PFAS.pdf McCurdy, R. (2011). Underground injection wells for produced water disposal. https://www.epa.gov/sites/production/files/documents/21_McCurdy_-_UIC_Disposal_508.pdf U.S. EPA (Environmental Protection Agency). (2001). Class I Underground Injection Control Program: Study of risks associated with Class I underground injection wells (EPA 816-R-01-007). https://www.epa.gov/sites/production/files/2015-07/documents/study_uicclass1_study_risks_class1.pdf U.S. EPA (Environmental Protection Agency). (2015). Requirements for all Class I wells and class I hazardous waste wells. https://www.epa.gov/sites/production/files/2015-10/documents/page_uicclass1_summary_class1_reqs_508c.pdf U.S. EPA (Environmental Protection Agency). (2016). Class I industrial and municipal waste disposal wells. https://www.epa.gov/uic/class-i-industrial-and-municipal-waste-disposal-wells Usher, K. H. (2019, July 26). Landfill was responsible for PFAS in Cadillac wastewater. Cadillac News. https://www.cadillacnews.com/news/landfill-was-responsible-for-pfas-in-cadillacwastewater/article_2ae7a3c8-3193-5b8a-8ddf-6d695c3438c5.html INTERIM GUIDANCE FOR PUBLIC COMMENT Technologies for the DestructionPFaAnSd-CDoisnptoasinailnogf MPFaAtSeraianlds 82 4. Considerations for Potentially Vulnerable Populations Living Near Likely Destruction or Disposal Sites The FY 2020 NDAA specifies that the interim guidance consider: The potential for releases of PFAS during destruction or disposal, including through volatilization, air dispersion, or leachate. Potentially vulnerable populations living near likely destruction or disposal sites. This section describes potential releases and exposure pathways associated with destruction or disposal sites, defines potentially vulnerable populations, and provides guidance on considering vulnerable populations when assessing the potential impact of releases. It is intended to be useful to a diverse group of users: risk assessors, permit writers, risk managers, and community relations personnel, as well as the public. In some cases, regulators may be required to consider vulnerable populations during the permitting process or when making decisions about where to send waste or whether to accept waste. But it may also be appropriate to consider vulnerabilities in adjacent communities even when not required. The public may find this section useful to understand potential vulnerabilities in their communities. This section is not a comprehensive primer on risk assessment and risk communication; rather it contains pointers and references to existing information. 4.a Potential releases from destruction and disposal facilities EPA develops regulations, guidance, and policies that ensure the safe management and cleanup of waste. Nonetheless, it is possible for destruction or disposal activities to release PFAS. Figure 4-1 illustrates some of these releases and how they could possibly reach vulnerable populations through multiple environmental media. For example, as described in Section 3.a.iv, thermal treatment activities could potentially release PFAS to the environment via stack emissions. Releases can also occur from the management of thermal treatment process residuals such as liquid discharges from acid gas scrubbers, air pollution control device media, and incinerator bottom ash. In addition, if uncontrolled, leachate can travel out of landfills (see Section 3.b.i) and into groundwater or surface water. Even with active LFG capture, a fraction of LFG remains that is emitted directly to the environment through the landfill surface and other routes. Disposal of PFAS could also result in potential releases from increased transport, management, and handling of waste associated with all of the available technologies. INTERIM GUIDANCE FOR PUBLIC COMMENT Considerations for PNoeteanr tLiiaklelylyVDuelnsetrruacbtlieonPoopruDlaistpioonssalLSivitinegs 83 Figure 4-1. Conceptual model providing examples of potential releases from destruction and disposal of PFAS-containing materials, which the technologies covered in this guidance could help to control.10 Risk assessment and communication are important tools to protect communities and the environment from potential releases of harmful substances. Risk assessments are performed when a facility is being sited, or when there is a change in permit status (U.S. EPA, 2015a). Tools from the risk assessment process may also be useful when considering whether a facility is an appropriate option for receiving PFAS-containing waste. Risk communication and community engagement are important for building trust and addressing concerns about potential releases. EPA has developed resources for assessing, managing, and communicating environmental risks, including guidance and tools available to stakeholders and the public. These resources are summarized in Section 4.c. 4.b Potentially vulnerable populations Considering vulnerability and susceptibility in risk assessment can help protect populations at greatest risk. "Susceptibility" refers to the likelihood of being affected by a chemical or pollutant. Intrinsic (biological) and extrinsic (exposure-related) factors can influence a person's susceptibility to pollutants, or a population's. That is, different individuals and populations might have different susceptibilities. 10 Figure 4-1 provides examples of possible releases and exposures that could be associated with destruction and disposal of PFAS-containing materials, but it is not intended to be exhaustive. INTERIM GUIDANCE FOR PUBLIC COMMENT Considerations for PNoeteanr tLiiaklelylyVDuelnsetrruacbtlieonPoopruDlaistpioonssalLSivitinegs 84  "Vulnerability" refers to differences in risk resulting from the combination of both intrinsic differences in susceptibility and extrinsic (or acquired) factors (U.S. EPA, 2020a). These intrinsic and extrinsic factors may influence the health outcomes of people exposed to harmful substances. Intrinsic, or biological, factors are differences in risk resulting from variations in both a person's response (sensitivity) to a harmful substance and their exposure (U.S. EPA, 2020a). Intrinsic factors include age, gender, race/ethnicity, life stage (e.g., infancy, adolescence, adulthood, pregnancy/lactation), and genetic polymorphisms. These biological factors cannot be changed. Toxicokinetic differences among individuals that affect how easily a chemical is absorbed, metabolized, and excreted are also important factors. A person's susceptibility to an environmental stressor is an important determinant of both the occurrence and severity of an adverse effect. Infants, children, adults of reproductive age, and the elderly are examples of populations that may be more vulnerable due to intrinsic factors. Extrinsic factors are external influences that may be important to consider when assessing human exposure and risk. Extrinsic factors include socioeconomic status, disease status, nutrition status, geographic proximity to sources of exposure, and various lifestyle choices. In many cases, these factors can be changed. Individuals with pre-existing diseases, geographic proximity to sources of contaminants, and lifestyle factors (e.g., exercise, smoking, alcohol consumption) are examples of populations that may be more vulnerable due to extrinsic factors. Vulnerability may also result from disproportionately high exposures to a chemical substance or mixtures of chemical substances. Due to a range of existing physical, chemical, biological, social, and cultural factors, certain populations are more exposed to environmental chemicals or experience greater adverse effects from exposures of similar magnitude due to preexisting health stressors (U.S. EPA, 2003). Examples of vulnerability due to disproportionately high exposures include workers in industries that manufacture, handle, or dispose of PFAS-containing materials; communities living next to facilities that may be releasing chemicals to the environment; children, who may be more highly exposed based on body size, intake rates of food and environmental media, and activity patterns; and hunters, gatherers, and fishers, who may be consuming foods that contain higher concentrations of contaminants. Socioeconomic status is a potential risk modifier for some communities (e.g., low-income, minority, indigenous groups). Socioeconomic status can influence factors such as diet, nutrition, housing quality, and access to health care--and consequently health status. Some studies have found that the presence of pollution sources in a given area (e.g., high-traffic roadways, industrial sites, hazardous waste sites) correlates with the proportion of minority, low-income, or indigenous populations (U.S. EPA, 2013a, 2019), which can, in turn, lead to higher exposure and disease burdens. In some cases, these factors are cross-cutting (i.e., are both intrinsic and extrinsic) and the combination of high exposures (extrinsic) and increased individual susceptibility to environmental stressors (intrinsic) may lead to a predisposition to higher health risks. INTERIM GUIDANCE FOR PUBLIC COMMENT Considerations for PNoeteanr tLiiaklelylyVDuelnsetrruacbtlieonPoopruDlaistpioonssalLSivitinegs 85 Many of these cross-cutting issues are related to environmental justice (EJ) concerns, which encompass the disproportionate exposure and impacts associated with environmental releases. EPA has defined "potential EJ concerns" as "the actual or potential lack of fair treatment or meaningful involvement of minority populations, low-income populations, tribes, and indigenous peoples" (U.S. EPA, 2015b, 2016c). In practice, vulnerability in this context can be considered as "disproportionate impacts on minority populations, low-income populations, and/or indigenous peoples" (U.S. EPA, 2015b, 2016c). The following sections provide examples of different factors that may contribute to vulnerability to PFAS. 4.c PFAS and vulnerability There is evidence that exposure to certain PFAS can lead to adverse health outcomes in humans. If humans, or animals, ingest certain PFAS (by eating or drinking food or water than contains PFAS), the PFAS are absorbed, and can accumulate in the body. PFAS stay in the human body for long periods of time. As a result, as people get exposed to PFAS from different sources over time, the level of PFAS in their bodies may increase to the point where they suffer from adverse health effects (U.S. EPA, 2020b). Research on the two most well-studied PFAS (PFOA and PFOS) demonstrates that they can cause reproductive and developmental, liver and kidney, and immunological effects in laboratory animals (U.S. EPA, 2020b). Both chemicals have caused tumors in animal studies. The most consistent findings from human epidemiology studies are increased cholesterol levels among exposed populations, with more limited findings (U.S. EPA, 2020b) related to: Infant birth weights. Effects on the immune system. Cancer (for PFOA). Thyroid hormone disruption (for PFOS). People with pre-existing conditions, such as liver or kidney disease or immunocompromised status, may be more susceptible to certain PFAS that may target these systems. Children may be particularly vulnerable to certain PFAS exposures, as they can be both more exposed and more sensitive to health effects. Children drink more water, eat more food, and breathe more air per pound of body weight than adults, which can increase their exposure to PFAS in food and the environment. Breast milk from mothers with PFAS in their blood and formula made with water containing PFAS can expose infants to PFAS, and it may also be possible for children to be exposed in utero during pregnancy. Young children who crawl on floors and put objects or hands in their mouths may have a higher risk of exposure to PFAS in household dust or cleaning products (U.S. EPA, 2018, 2019a). Because of these cross-cutting biological, physiological, and exposure factors, children may be more sensitive to the effects of chemicals such as certain PFAS. EPA developed drinking water health advisories for PFOA and PFOS to be protective of adverse developmental effects to fetuses during pregnancy or to breastfed infants, which are the groups most sensitive to the potential harmful effects of PFOA and PFOS (U.S. EPA, 2016a, 2016b). INTERIM GUIDANCE FOR PUBLIC COMMENT Considerations for PNoeteanr tLiiaklelylyVDuelnsetrruacbtlieonPoopruDlaistpioonssalLSivitinegs 86 Certain populations may be highly exposed to environmental contaminants because they live or work near the sources of release or presence in the environment (U.S. EPA, 2003). They may also be disproportionately impacted, due to a variety of cross-cutting factors, including EJ concerns, low socioeconomic status, etc. In the case of PFAS, these groups could include people living near a facility that manufactures PFAS, or those living near and using PFAS-contaminated environments (e.g., drinking water, fishing, hunting, and recreation). Site-specific data on PFAS releases and exposures may be needed to understand such complex interactions and co-exposures. Tribal and indigenous populations may also be more exposed to environmental hazards than the general population due to subsistence lifeways and diets, outdoor activities, or cultural practices. For example, unique tribal practices, such as increased consumption of locally harvested fish and shellfish, might expose tribal and indigenous populations to higher concentrations of contaminants such as PFAS that accumulate in these organisms (U.S. EPA, 2019c). Workers involved in the manufacture, use, transport, transfer, handling, and storage of PFAS-containing waste also may be subject to higher exposures relative to the general population. The National Institute for Occupational Safety and Health (NIOSH) defines a hierarchy of controls to mitigate occupational hazards (https://www.cdc.gov/niosh/topics/hierarchy/default.html) based on the most effective to least effective measures, as follows: (1) eliminate the hazard, (2) substitute the hazard, (3) apply engineering controls, (4) use administrative controls, and (5) use personal protective equipment. In some situations, a combination of controls may be most effective at minimizing worker exposures. 4.d Considering vulnerability Under Executive Order 12898, "Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations" (https://www.epa.gov/laws-regulations/summary-executiveorder-12898-federal-actions-address-environmental-justice), federal agencies are directed to identify and address the disproportionately high and adverse human health or environmental effects of their actions on minority and low-income populations to the greatest extent practicable and permitted by law. In response to these mandates, EPA has developed tools, methods, and approaches to identify and assess the risks of potentially vulnerable populations. 4.d.i Identifying potentially vulnerable populations The consideration of potentially vulnerable populations living near likely PFAS destruction or disposal sites starts with the identification and characterization of adjacent and potentially exposed populations. EPA provides the following tools to assist with this task: EPA EnviroMapper: https://geopub.epa.gov/myem/efmap/index.html EPA Environmental Justice Screening and Mapping Tool (EJScreen): https://www.epa.gov/ejscreen 4.d.ii Incorporating vulnerability into risk assessment EPA provides many tools to assist with the development of risk assessments (https://www.epa.gov/risk). Highlighted here is specific guidance that may be helpful to addressing key aspects of vulnerability. INTERIM GUIDANCE FOR PUBLIC COMMENT Considerations for PNoeteanr tLiiaklelylyVDuelnsetrruacbtlieonPoopruDlaistpioonssalLSivitinegs 87 A particularly useful document that presents technical approaches and methods to help analysts (including economists, risk assessors, and others) analyze potential EJ concerns is the Technical Guidance for Assessing Environmental Justice in Regulatory Analysis (U.S. EPA, 2016c). Although it is designed for regulators, it is broadly useful to external analysts and stakeholders. https://www.epa.gov/environmentaljustice/technical-guidance-assessing-environmental-justiceregulatory-analysis For considerations in assessing risks to children, refer to the EPA Framework for Assessing Risks of Environmental Exposure to Children: https://cfpub.epa.gov/ncea/risk/hhra/recordisplay.cfm?deid=22521 For information on exposure considerations for identified potentially vulnerable and highly exposed populations in the quantitative and/or qualitative assessment of risk, refer to EPA's ExpoBox: https://www.epa.gov/expobox/exposure-assessment-tools-lifestages-and-populations-highlyexposed-or-other-susceptible#fac For considerations of tribal and indigenous lifeways, refer to these tools: EPA memo on traditional ecological knowledge: https://semspub.epa.gov/src/document/11/500024668 Amendments to Superfund Hazard Ranking System guidance incorporating Native American traditional lifeways: http://semspub.epa.gov/src/document/11/175862 For PFAS, which can reside in the human body for months to years, it is particularly important to consider toxicokinetics in the risk assessment using physiologically based pharmacokinetic (PBPK) modeling. For information on available PBPK models for PFAS, refer to the health effects support documents for PFOA and PFOS and EPA's guidance on the use of PBPK modeling in risk assessment: https://www.epa.gov/ground-water-and-drinking-water/supporting-documents-drinking-waterhealth-advisories-pfoa-and-pfos https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=157668 4.d.iii Considerations for community engagement In certain cases, community engagement is required under law. For example, facilities must hold public meetings before submitting part B RCRA permit applications (U.S. EPA, 2013a), and in some cases EPA's policy is to consult and coordinate with tribes (U.S. EPA, 2013b). Community engagement is not merely a matter of meeting requirements, though. It can also have the following benefits under this guidance: reaching out to the community before accepting PFAS-containing waste for destruction or disposal will help build trust and support for operations and can reduce the likelihood of negative reactions stemming from unresolved concerns. Meaningful community engagement typically includes two key elements: INTERIM GUIDANCE FOR PUBLIC COMMENT Considerations for PNoeteanr tLiiaklelylyVDuelnsetrruacbtlieonPoopruDlaistpioonssalLSivitinegs 88  Public outreach to disseminate relevant information to the community. Public participation, which generally entails a dialog with the community to ascertain information and viewpoints. This dialogue is particularly important because the community can provide local knowledge of health and existing conditions, identify concerns and issues that may not be readily apparent outside the community, and offer contextual/cultural perceptions and experience (U.S. EPA, 2016c). Although presenting highly technical information is always a challenge, involving vulnerable populations in a meaningful way may present different challenges and opportunities from those in a general public involvement effort. To foster meaningful participation of all community members, it may be important to address issues that could hinder a community's participation in the decision-making process. These may include time and resource constraints, language barriers, and lack of trust (U.S. EPA, 2016c). Examples of effective practices to engage diverse and vulnerable populations include: Conveying issues in ways that are tailored (for example, translation, timing, location) to each specific population. Bridging cultural and economic differences that affect participation. Developing trust between government and potentially affected populations. Working closely with state and local partners, as well as other federal agencies, to present a unified, consistent message to communities. Developing stakeholder capacity to effectively participate in future decision-making processes (U.S. EPA, 2015b). EPA has developed tools to assist the federal government, states, and private entities with community engagement and outreach. For example, the Superfund Community Involvement Toolkit ("CI toolkit," available at https://www.epa.gov/superfund/superfund-community-involvement-tools-and-resources) provides practical information to design and enhance community involvement activities. While the CI toolkit is designed to enable users to quickly review and adapt a variety of community involvement tools to engage the community during all stages of the Superfund processes, the same tools can be adapted to engage communities adjacent to destruction and disposal facilities. 4.e References U.S. EPA (Environmental Protection Agency). (2003). Framework for cumulative risk assessment (EPA/630/P-02/001F). https://www.epa.gov/risk/framework-cumulative-risk-assessment U.S. EPA (Environmental Protection Agency). (2013a). Compendium of key community engagement practices at RCRA sites. https://www.epa.gov/sites/production/files/2016-11/documents/ceicomp.pdf U.S. EPA (Environmental Protection Agency). (2013b). EPA policy on consultation and coordination with tribes. https://www.epa.gov/sites/production/files/2013-08/documents/cons-and-coord-withindian-tribes-policy.pdf INTERIM GUIDANCE FOR PUBLIC COMMENT Considerations for PNoeteanr tLiiaklelylyVDuelnsetrruacbtlieonPoopruDlaistpioonssalLSivitinegs 89 U.S. EPA (Environmental Protection Agency). (2015a). RCRA's critical mission & the path forward. https://www.epa.gov/sites/production/files/201509/documents/rcras_critical_mission_and_the_path_forward.pdf U.S. EPA (Environmental Protection Agency). (2015b). Guidance on considering environmental justice during the development of regulatory actions. https://www.epa.gov/environmentaljustice/guidanceconsidering-environmental-justice-during-development-action U.S. EPA (Environmental Protection Agency). (2016a). Drinking water health advisory for perfluorooctane sulfonate (PFOS) (EPA 822-R-16-004). https://www.epa.gov/sites/production/files/201605/documents/pfos_health_advisory_final_508.pdf U.S. EPA (Environmental Protection Agency). (2016b). Drinking water health advisory for perfluorooctanoic acid (PFOA) (EPA 822-R-16-005). https://www.epa.gov/sites/production/files/2016-05/documents/ pfoa_health_advisory_final_508.pdf U.S. EPA (Environmental Protection Agency). (2016c). Technical guidance for assessing environmental justice in regulatory analysis. https://www.epa.gov/environmentaljustice/technical-guidanceassessing-environmental-justice-regulatory-analysis U.S. EPA (Environmental Protection Agency). (2018). Children are not little adults! https://www.epa.gov/children/children-are-not-little-adults U.S. EPA (Environmental Protection Agency). (2019a). About the Office of Children's Health Protection (OCHP). https://www.epa.gov/aboutepa/about-office-childrens-health-protection-ochp U.S. EPA (Environmental Protection Agency). (2019b). Guidelines for human exposure assessment (EPA/100/B-1/001). https://www.epa.gov/risk/guidelines-human-exposure-assessment U.S. EPA (Environmental Protection Agency). (2020a). Exposure assessment tools by lifestages and populations--highly exposed or other susceptible population groups. https://www.epa.gov/expobox/exposure-assessment-tools-lifestages-and-populations-highlyexposed-or-other-susceptible U.S. EPA (Environmental Protection Agency). (2020b). Basic information on PFAS. https://www.epa.gov/pfas/basic-information-pfas#main-content INTERIM GUIDANCE FOR PUBLIC COMMENT Considerations for PNoeteanr tLiiaklelylyVDuelnsetrruacbtlieonPoopruDlaistpioonssalLSivitinegs 90 5. Planned Research and Development on Destruction and Disposal Technologies for PFAS and PFAS-Containing Materials 5.a Research needs EPA's PFAS action plan identifies key gaps in the current state of the science to support decision-makers, including gaps in the science of PFAS destruction and disposal. These gaps represent opportunities to increase the effectiveness and decrease the cost of PFAS destruction and disposal by refining existing approaches and developing new technologies (U.S. EPA, 2019). EPA is leading a robust research and development program to address these gaps by leveraging in-house expertise and external partnerships. EPA will incorporate this increased knowledge into future versions of this guidance to help decisionmakers choose the most effective PFAS disposal options for their circumstances. Research is needed in three broad areas: 1. Research to better characterize the multi-media PFAS-containing materials targeted for destruction or disposal (referenced in Section 3.b.vi), including methods to sample and analyze materials and to characterize the efficacy of remediation and treatment technologies. This includes a fuller understanding of which PFAS occur in which materials at what concentrations, as well as a better understanding of the basic chemical-physical properties that relate to those PFAS' persistence or recalcitrance under different destruction or disposal conditions. This information will help managers of PFAS materials decide which management alternatives are most appropriate for given material streams. 2. Research to measure and assess the effectiveness of existing methods for PFAS destruction, improve existing methods, and/or develop new methods for PFAS destruction (referenced in Sections 2.e, 2.f, and 3.a.ii-3.a.viii). This includes a better understanding of the fundamental chemical and physical conditions needed to fully defluorinate PFAS, break the carbon-fluorine bonds, and prevent the formation of potentially environmentally harmful substances associated with incomplete destruction (PICs). Continuing efforts to understand how to optimize incineration and other thermal treatments, including catalytic approaches, will provide the information necessary to design effective PFAS treatment methods. Currently, this research is limited by the ability to measure and quantify PFAS during thermal treatment including potential fluorinated PICs. This research need extends beyond thermal treatments to include multi-media measurement methods suitable for other potential destructive technologies and approaches, such as electron beam, BOHP/UV, and plasma. INTERIM GUIDANCE FOR PUBLIC COMMENT DisposPallaTnencehdnoRleosgeiaerscfhoranPdFADSeavnedloPpFmAeSn-Ct oonntDaiensintrguMctiaotneraianlds 91 3. Research to measure and assess the effectiveness of existing methods for PFAS disposal, improve existing methods, and/or develop new methods for PFAS disposal (referenced in Sections 2.e, 2.f, and 3.b). This includes better understanding of the environmental persistence, mobility, fate, and transport of different PFAS-containing materials, waste streams, and sources (e.g., AFFF, textiles, biosolids, landfill leachate) under different disposal conditions (e.g., landfills, deep well injection, material separation) to ensure that PFAS sequestered or stabilized in material streams have no opportunity to reenter the environment. While EPA's research has been delayed by COVID-19 and by public concerns about EPA collecting data in communities, research is proceeding. Status and updates on EPA's PFAS research are available at https://www.epa.gov/chemical-research/status-epa-research-and-development-pfas. 5.b Current federal research and development activities EPA and DoD are currently the primary federal agencies engaged in research and development of PFAS destruction and disposal; they coordinate efforts and external partnerships to ensure coverage, leverage opportunities and resources, and avoid duplication of effort. They also coordinate with other federal and state agencies doing research in this area. EPA presently supports a research program focused on end-of-life management of PFAS-containing materials, primarily by thermal treatment (as referenced in Section 3.a), advanced oxidation processes, wastewater, and landfills (as referenced in Sections 2.f and 3.b). Thermal treatment research focuses on understanding and modeling the behavior of PFAS under a range of thermal conditions (e.g., temperature, residence time, turbulence, exposure to flame, effect of catalysts) to better understand the conditions required to defluorinate PFAS, thereby informing selection of appropriate thermal treatment for various PFAS-containing materials. EPA is also studying the behavior of PFAS and non-PFAS byproducts that may result from incomplete thermal treatment (e.g., thermal PICs) and subsequently move through different emission control processes. This research informs the consequences of incomplete thermal treatment in terms of these treatment byproducts and the secondary waste streams generated by control processes and will help inform selection of viable control technology options. It includes methods for sampling and analyzing PFAS in air emissions and ambient air to enable monitoring of the environment and testing effectiveness of PFAS control technologies. EPA scientists are also examining the fate of PFAS during wastewater treatment operations and the disposal of wastewater residuals (e.g., sludges and biosolids). This research also examines the benefits of pretreatment technologies to treat PFAS in high-strength waste streams prior to disposal via wastewater, separation, and destruction technologies. Finally, EPA is examining the presence and management of PFAS in different landfill types and controlling emissions and discharges. This research effort includes the evaluation of the effectiveness of leachate treatment technologies to manage PFAS. EPA also supports partnerships through extramural vehicles such as the Science to Achieve Results (STAR) competitive grant program and the Small Business Innovation Research (SBIR) program, both of which have provided funding in recent years to develop and commercialize approaches and technologies to advance the practice of PFAS destruction and disposal. INTERIM GUIDANCE FOR PUBLIC COMMENT DisposPallaTnencehdnoRleosgeiaerscfhoranPdFADSeavnedloPpFmAeSn-Ct oonntDaiensintrguMctiaotneraianlds 92  DoD supports extensive investments in PFAS-related destruction and disposal research via multiple programs. The most significant research has been funded through the Strategic Environmental Research and Development Program (SERDP) and the Environmental Security Technology Certification Program (ESTCP) (DoD, 2020). SERDP focuses on development and application of innovative technologies; ESTCP focuses on promoting the transfer and commercialization of promising innovative technologies. Both focus on technologies to solve DoD environmental challenges, which include remediation of PFAS sites and disposal of PFAS-containing materials. In addition, DoD funds research to characterize sources and other PFAS research specific to PFAS' unique needs or functions as well as the development of fluorine-free AFFF to reduce future inputs of PFAS into the environment. Other federal and state agencies and departments fund limited PFAS research focused on PFAS destruction and disposal. These include programs within the National Institute of Environmental Health Sciences Superfund Research Program, the U.S. Department of Agriculture, the National Science Foundation, NASA, and DOE. These efforts range from fundamental research to characterize physical-chemical behaviors under various conditions to research on specific ways to dispose of unique wastes (e.g., PFAS in agricultural products). Collaboration occurs at the scientist-to-scientist level, and information is exchanged through regular scientific conferences and publications. In addition to EPA, DoD, and other agencies, there are two other significant sources of research and development related to PFAS destruction and disposal: Private industry, the operators of waste disposal operations and technologies, municipal water utilities, professional and trade associations, and relevant research foundations have strong interests in expanding into the area of PFAS material management, disposal, and destruction. These areas offer a growing investment opportunity that provides a valuable service to society, and organizations are actively developing and marketing solutions to address PFAS. EPA is exploring opportunities to partner with industry, municipalities, and associations to leverage occurrence, emission/discharge, and treatment data from sources of PFAS-containing waste. Access to existing industry data could speed the pace at which EPA documents the capabilities of destruction and disposal technologies for different materials and waste streams. Many colleges and universities have engineering and science departments that conduct cutting-edge research on many topics related to PFAS destruction and disposal. These institutions often bring together expertise from many disciplines, enabling the rapid development of innovative approaches for managing the constantly changing set of PFAS-containing materials. 5.c Near-term EPA research and development initiatives The following activities are on a near-term (1-2 years) trajectory, including technologies in late stages of testing and development: PFAS measurement methods. Development of methods for sampling and analyzing PFAS in environmental media, waste streams, and manufactured products is critical to characterize the effectiveness of management approaches and technologies for destruction and disposal of PFAS. These measurements include air (emissions and ambient), wastes, waters, and solids. EPA is using INTERIM GUIDANCE FOR PUBLIC COMMENT DisposPallaTnencehdnoRleosgeiaerscfhoranPdFADSeavnedloPpFmAeSn-Ct oonntDaiensintrguMctiaotneraianlds 93 advanced methods such as high-resolution mass spectrometry for targeted analysis for known PFAS and nontargeted analysis to discover and document unknown PFAS (e.g., thermal PICs). This research builds on existing EPA expertise and methods for aqueous, solid, and air media (e.g., modifying the existing Modified Method 5 sampling trains to characterize air emissions). Characterizing air emissions requires expansion of method applicability to complex mixtures of byproducts and PICs. EPA will publish a draft Other Test Method 45 by the end of 2020, which will include measurement of semivolatile targeted compounds. EPA is also evaluating and developing other sampling and measurement tools to characterize performance of these technologies, such as TOF analysis using CIC and FTIR techniques to measure the broader suite of compounds with carbon-fluorine moieties without identifying specific chemicals. These tools, in combination with more traditional targeted measurements, have a role in characterizing sources, evaluating the fate and transport of PFAS, and monitoring the destruction and disposal approaches used to manage PFAS. Fundamental understanding of PFAS thermal treatment. EPA is researching the incineration conditions (e.g., temperature, residence time, reactor configuration, turbulence) needed to fully defluorinate PFAS. This includes testing different catalysts (e.g., calcium and aluminum) that can be added during incineration or used in separate unit operations to defluorinate more effectively and at lower temperatures. Research is also looking at whether free fluorine can be controlled. Results will be incorporated into databases and models to enable users to make predictions for different PFAS materials under different disposal conditions. This work is being done in bench- and pilot-scale facilities and will enable material managers to determine the thermal conditions needed to dispose of different materials (e.g., hazardous waste, MSW, AFFF). It will include assessing the effectiveness of air pollution control technologies such as afterburners, baghouses, and scrubbers. This information can then be applied to the current universe of incinerators, industrial oxidizers, and other thermal treatment facilities. EPA will use the thermodynamic and kinetic dataset to add fluorine chemistry to existing computational fluid dynamic models for reacting combustion environments to predict potential PFAS destruction and PIC formation in incinerator environments of practical interest. Effectiveness of full-scale PFAS incineration operations. EPA is partnering with real-world facilities to understand the operational effectiveness of commercial PFAS thermal treatment, including HWIs, GAC regeneration facilities, SSIs, municipal waste incinerators, thermal oxidizers, and facilities that thermally treat soils and solid waste contaminated by PFAS. This research involves characterizing the untreated waste inputs, sampling at various stages during treatment, and sampling the stack emissions in order to characterize the efficacy of the treatment process and understand the ultimate fate of the PFAS during treatment. PFAS destruction toolkit. EPA has established a PFAS Innovative Treatment Team (PITT) to expeditiously identify, review, and test novel (as referenced in Section 2.e) but readily available solutions for destroying PFAS in media and wastes. Such solutions may include traditional destruction methods (e.g., common incineration processes) and novel technologies that might, involve non-traditional thermal treatment, photolysis, hydrolysis, catalysis, or bioremediation. For example, EPA recently announced the Innovative Ways to Destroy PFAS Challenge (U.S. EPA, 2020), which challenges problem-solvers to identify a non-thermal way of destroying PFAS in concentrated INTERIM GUIDANCE FOR PUBLIC COMMENT DisposPallaTnencehdnoRleosgeiaerscfhoranPdFADSeavnedloPpFmAeSn-Ct oonntDaiensintrguMctiaotneraianlds 94 AFFF, while creating the least amount of potentially harmful byproducts. Such different approaches will be assembled as a "toolkit" for use by EPA programs and regions, states and tribes, federal agencies, and industry. Management of PFAS-containing treatment media. Research is focused on evaluating PFAS destruction efficiency during the reactivation, regeneration, or disposal of PFAS-containing sorbent media, such as GAC and ion exchange resins. Sorbent media are used in many applications including managing industrial emissions and discharges, in various water treatment operations including drinking water production, and for stabilizing wastes. GAC reactivation is economically favored over replacement with virgin carbon. Therefore, if the PFAS in spent media can be completely removed and destroyed during reactivation, GAC adsorption and subsequent reactivation could be economical and sustainable for certain PFAS treatment scenarios. EPA is researching the efficacy of regeneration, including reactivation processes for spent media and to manage emissions and wastes generated during these processes. Where the risk, liability, or costs are too high for reusing these sorbents, disposal will be required. Researchers are evaluating the benefits, efficacy, and costs of destructive approaches (e.g., incineration) compared to disposal (e.g., landfilling). PFAS management in landfills. Researchers are investigating the composition of PFAS in landfilled materials (e.g., MSW, C&D debris), characterizing air and waste emissions, and characterizing the concentrations and treatment of PFAS in leachate. The research will also investigate the efficacy of existing treatment technology for the management of PFAS in landfill leachate and consider innovative technologies. Finally, researchers will examine potential impacts to and suitability of landfill liners and leachate collection system from PFAS. Research grants have also been awarded to leverage academic, state, and other research organizations to address the waste characterization of source materials and leachates, fate and transport of PFAS, and destruction of PFAS. PFAS treatment methods leading to destruction and disposal. Because PFAS are a complex mixture of chemicals and often occur with other contaminants or in complex matrices, treatment approaches may require a combination of treatment technologies, commonly referred to as treatment trains, to remove non-PFAS contaminants or background matrix components (e.g., dissolved organic carbon) before the PFAS can be effectively treated. As a result, PFAS may be sequestered or concentrated during certain unit operations. These operations do not themselves result in PFAS destruction or disposal; however, they may help increase the efficiency of treatment and destruction/disposal operations. For example, they can concentrate PFAS, reduce the bulk mass of material requiring treatment, or immobilize PFAS to allow time for ultimate destruction/disposal. EPA is exploring technologies for treatment trains to treat PFAS-containing wastes, including composting, solidification/stabilization involving sorbents and chemical stabilizers, novel energyintensive technologies for point dischargers, and installation of membranes to slow or halt PFAS movement. PFAS hazard, exposure, risk assessment, and prioritization. In addition to research that directly supports PFAS destruction and disposal, EPA is conducting a broader program of research and development that encompasses the entire risk paradigm. Research on human and ecological hazards, toxicity, and exposure will help inform which PFAS or groups of PFAS pose the highest risk and therefore should be prioritized for destruction or disposal. Research on PFAS exposure includes INTERIM GUIDANCE FOR PUBLIC COMMENT DisposPallaTnencehdnoRleosgeiaerscfhoranPdFADSeavnedloPpFmAeSn-Ct oonntDaiensintrguMctiaotneraianlds 95 measuring and modeling PFAS fate and transport to better understand the potential for exposures and opportunities for management interventions to break exposure pathways. Better understanding of risk is also critical to setting benchmarks and thresholds for deciding when destruction or disposal efforts are needed, and when the results can be deemed to be successful. A better understanding of risk will enable risk managers to make informed decisions about the tradeoffs between different risk management solutions, leading to better environmental outcomes. 5.d Longer-term EPA research and development initiatives The following activities are on a longer-term (3+ years) trajectory, including technologies in pioneering stages of early development: Continuous monitoring technology for PFAS in source and ambient air. This will include mobile/portable measurement and sensor devices to enable fenceline monitoring and discovery of any fugitive emissions in PFAS destruction and disposal operations. Atmospheric fate, transport, and deposition of PFAS. It is known that many PFAS are emitted to the atmosphere either by design or by accident, but little is known about the chemical transformations that occur, or about the distribution, dispersion, deposition, and potential for remobilization into the atmosphere. EPA is applying proven atmospheric pollution models to enable predictions about fate, transport, and deposition of PFAS in the air (as referenced in Section 3.a). New and innovative technologies for destroying and disposing of PFAS. Technology development from proof of concept to full-scale demonstration and validation requires significant time and resources and is most effectively achieved by partnering across government, academia, and industry. These ongoing partnerships are coordinating research to accelerate the most promising new technologies and approaches for the end-of-life disposal of PFAS. EPA and its partners are developing and evaluating innovative technologies such as electron beam treatment for aqueous and solid wastes, cold vapor plasma technologies for liquid wastes, oxidative and reductive catalysts, higher-efficiency and reactive sorbents, mechanochemical ball milling, supercritical water oxidation, pyrolysis/gasification, electrochemical oxidation, stabilizing agents, and thermal catalysts. In addition, EPA is developing cost and performance models for existing and innovative technologies to compare technologies on a cost and efficacy basis. These models will also allow for the optimization of treatment operations and treatment trains for PFAS. Continued development of the most promising innovative technologies also requires industry partners that have the experience and resources to commercialize these technologies and provide the capacity and the costing to make these viable solutions to this complex problem. 5.e Data and information needs to inform future guidance updates There are many stakeholders with interests in destruction and disposal of PFAS, and many of these stakeholders have generated data and other information that, if made available, could greatly enhance the speed at which EPA can refine and extend this guidance. EPA is always seeking to partner with entities that have information to share. The following discussion identifies the most critical information gaps where information from outside entities might help to strengthen future guidance. INTERIM GUIDANCE FOR PUBLIC COMMENT DisposPallaTnencehdnoRleosgeiaerscfhoranPdFADSeavnedloPpFmAeSn-Ct oonntDaiensintrguMctiaotneraianlds 96 The highest-priority data and information needs to inform future guidance updates include: Data and other information generated through pilot tests of sampling and analysis methods for PFAS in stack emissions. EPA would like to know what sampling approaches have been tried, which ones have worked or not worked, and what data were generated during the tests regarding the presence of PFAS, including PICs (as referenced in Section 3.a.iv). Data and other information generated through thermal treatment tests of different PFAS and PFAScontaining materials under different thermal conditions including temperatures, holding times, measures of turbulence, and presence or absence of flames. EPA would like to increase the database of basic information about thermal conditions required to destroy different PFAS, as well as what specific PICs are produced under what conditions (as referenced in Sections 3.a.ii-3.a.vi). Data and information about approaches for efficiently controlling the emission of PICs, and about PFAS that may be present in air pollution control device media (scrubber water, particulate matter control device media) and bottom ash (as referenced in Section 3.a.ii). Data and other information regarding (1) the presence of different PFAS in landfill leachate samples, (2) the effectiveness of different treatment systems that have been tested for removing PFAS from landfill leachate, and (3) the rate of PFAS migration and transformation from unlined landfill cells and the concomitant impacts on groundwater (as referenced in Sections 2.f and 3.b). Information about PFAS destruction and disposal operators that might be willing to work with EPA and its partners to grant access to facilities and operations, so as to enable EPA to generate additional data to address the information gaps listed above. Additional information that would better inform future guidance includes: Data and information about surrogates that have been tested in incineration and can serve as reference materials for further testing of PFAS destruction. Data and information about facility operator's information needs from EPA or from other sources to better manage the safe destruction and disposal of PFAS-containing materials. Data and information about PFAS disposal or destruction approaches or technologies other than those discussed in Section 2, with particular emphasis on quantitative data regarding the transformations and mass balance (for destructive technologies) or fate and transport (for disposal technologies) for PFAS subjected to such approaches (as referenced in Section 2.e). 5.f References DoD (Department of Defense). (2020). DoD-funded research on PFAS. https://www.serdpestcp.org/Featured-Initiatives/Per-and-Polyfluoroalkyl-Substances-PFASs/DoD-PFAS-Page/DoDPFAS-Page/(language)/eng-US U.S. EPA (Environmental Protection Agency). (2019). EPA's per- and polyfluoroalkyl substances (PFAS) action plan (EPA 823R18004). https://www.epa.gov/pfas/epas-pfas-action-plan INTERIM GUIDANCE FOR PUBLIC COMMENT DisposPallaTnencehdnoRleosgeiearscfhoranPdFADSeavnedloPpFmAeSn-Ct oonntDaiensintrguMctiaotneraianlds 97 U.S. EPA (Environmental Protection Agency). (2020). Innovative Ways to Destroy PFAS Challenge. https://www.epa.gov/innovation/innovative-ways-destroy-pfas-challenge INTERIM GUIDANCE FOR PUBLIC COMMENT DisposPallaTnencehdnoRleosgeiaerscfhoranPdFADSeavnedloPpFmAeSn-Ct oonntDaiensintrguMctiaotneraianlds 98 58 HIGH-PERFORMANCE PLASTICS Fluoropolymers [VEHICLE ENGINEERING] [MEDICAL TECHNOLOGY] [PACKAGING] [ELECTRICAL & ELECTRONICS] [CONSTRUCTION] [CONSUMER GOODS] [LEISURE & SPORTS] [OPTICS] Closing the Recycling Loop Up-Cycling of End-of-Life Fluoroplastics End-of-life fluoropolymers for different applications up to now required incineration. From today they can be decomposed into their monomers with a special method through chemical recycling. The new field of technology in this process is that virgin material is generated rather than recyclates. It's almost impossible to imagine life without fluoropolymers, the high performance polymers used in sophisticated, everyday applications. They are essential to industrial applications and as part of a variety of consumer goods. Their manufacture requires significant amounts of energy and of raw materials, which is reflected in high material prices. An established recycling industry ensures that waste is collected throughout the value chain and, after reprocessing, is made available for a variety of other applications. But what happens to fluoropolymer products when they have reached the end of their life cycle? To answer this question Dyneon GmbH in Burgkirchen, Germany, a 3M Company, has collaborated with the University of Bayreuth and InVerTec, Osburg, Germany, on a project sponsored by the environmental foundation, Deutsche Bundesstiftung Umwelt. The aim of the project is to develop a method for recycling these end-of-life products into new products, with a high conversion rate and no loss of quality. Existing Recycling Methods Polytetrafluoroethylene (PTFE) is not processed using traditional thermoplastic methods such as injection molding or extrusion, but predominantly using a complex pressure sintering method followed by a machining process to produce the final part geometry. Owing to the large amounts of waste generated during production, and also as a result of the relatively high polymer price, a recycling industry sprang up in this sector at an early stage. Specialized companies recycle ma- The Up-Cycling plant will initially process clean fluoropolymer materials, i.e., wet waste, off-specification materials of unfilled PTFE from manufacturers, and unfilled PTFE scrap chining waste and off-cuts from PTFE processing using one of two different methods. In the first, remnants are cleaned, ground and then fed back into the product cycle as pre-sintered reprocessed PTFE for processing using ram extrusion, a special pressure sintering method. Alternatively, after preparatory steps such as sorting, cleaning and grinding, the PTFE polymer is degraded to approximately 1 % of the original degree of polymerisation by using electron beams, gamma rays or thermo-mechanical degradation. There is also a recycling strategy for waste such as sprues, typically produced in the injection molding of PFA (Perfluoroalkoxy alkanes) or FEP (Fluorinated ethylene propylene), the two completely fluorinated members of the fluorothermoplastic product group. Waste materials are ground, cleaned and then, following granulation, fed back to be processed via injection molding or extrusion. This waste processing, however, is not the main focal point of the new 3M Up-Cycling concept, as there are already reprocessing and recycling systems in place. There are also existing markets for these recycled materials. Previously, however, there were no opportunities to recycle products manufactured from PTFE, PFA or FEP when they reached the end of their life cycle. Such products include, for example, PTFE pipe liners in chemical plants, as well as other plant components like pumps, tank liners, seals, hoses, compensators and many other fluoroplastic components and systems. The new Dyneon Up-Cycling method enables components to be recycled that were previously unable to be recycled. So, how does it work? Carl Hanser Verlag, Munich Kunststoffe international 6/2014 Internet-PDF-Datei. Diese PDF Datei enthlt das Recht zur elektronischen Verbreitung. Fluoropolymers HIGH-PERFORMANCE PLASTICS 59 Process for New Materials In contrast to existing recycling methods for fluoropolymers, this innovative process generates new materials rather than recycled materials. In the fluoropolymer sector, these new materials, which have not undergone any processing, are also referred to as `virgin' PTFE, PFA or FEP. To bring the new Up-Cycling approach into operation, Dyneon collaborated with several institutions: Deutsche Bundesstiftung Umwelt (Federal Ministry for the Environment, Nature Conservation and Nuclear Safety), the University of Bayreuth and InVerTec, an institution for innovative process engineering. The laboratory phase of this process development has already been finished. A pilot plant with an annual capacity of 500 t of perfluorinated polymers (PFP) is currently being built and is expected to start operation in the second half of 2014 (Fig. 1). The intention is to increase the operational intake to full capacity by 2015. The new high-temperature recycling process includes a grinding stage, after which the PFPs, which are preferably endof-life products, are decomposed into their monomers at temperatures above 600 C. These monomers are the same chemical components from which the polymers were produced. This process called `pyrolysis', primarily produces tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) with a recovery rate of 90-95 %. The resulting gas mixture is then passed to the Dyneon monomer plant and cleaned by distillation. After this step, TFE with a purity of 99.9999 % is obtained and can be used to manufacture arbitrary new fluoropolymers with no loss in performance. So the derived prod- Production Polymer Monomer Life cycle Chemical recycling PFPs on the end of their life Kunststoffe Fig. 2. Closing the life cycle loop: on reaching the end of their life cycle, components made from perfluorinated polymers (PFPs) are broken down into their monomers and fed back into the polymerization process Fig. 1. Pilot plant of Dyneon for Up-Cycling of end-of-life fluoropolymers with an annual capacity of 500 t (figures: Dyneon) ucts differ in no way from the the source materials, whether it is a PTFE-product, a fluoropolymer or an elastomer. As a result, the description recycling is not considered suitable for this method, so it is now called Up-Cycling, and with good reason; products reaching the end of their life cycle are converted into new high tech products (Fig. 2). Producing TFE/HFP monomers requires vast quantities of energy. The process needs more than 10,000 kWh/t, combined with a massive output of CO during electricity generation. Other raw materials like fluorspar, CaF, chlorine and sulphuric acid are needed, while on the waste side, gypsum and hydrochloric acid are produced. Using the high-temperature pyrolysis method to produce monomers from used PFP products has a massive potential to save resources and to protect the environment at the same time (Fig. 3). Cooperation with Partners for the Overall Concept Previously, end products were predominantly disposed of in landfill or by inciner- ation, with considerable associated Kunststoffe international 6/2014 www.kunststoffe-international.com Internet-PDF-Datei. Diese PDF Datei enthlt das Recht zur elektronischen Verbreitung. 60 HIGH-PERFORMANCE PLASTICS Fluoropolymers costs. Now they need to be collected, if possible at source at the end of their life cycle, pre-processed if necessary, and then transported back to raw materials supplier Dyneon. The structure and organisation of the logistic system is the responsibility of the company and its partners. However, products must be physically collected at source, by the operators of chemical plants, for example. This requires a comprehensive exchange of information to clarify a number of questions: W Which products are suitable? W Is product separation necessary? W Do the products need to be pre- treated? W How is the collection recorded for auditing purposes? These are just a few questions that have to be clarified by intensive communication between the partners of the Up-Cycling process. Often, PFPs are not in pure component form, such as PFA tubing or a PTFE pipe, but in the form of composites. In the context of chemical plant construction, this includes PTFE-lined pipes, tanks, pumps or distillation columns, in particular. Previously, it was only possible to dispose of these problematic parts via landfill, either as a composite, in individual parts or in fractions after a treatment process. Now, after a specialist company has separated steel and PTFE (PFP), there is the option of feeding all components back into the material cycle. As well as components from chemical plants, the new concept also focuses on recycling cables sheathed in fluoropolymers. The Authors Dr. Michael Schlipf is Consultant for Dyneon GmbH, Burgkirchen, Germany. Dr. Thorsten Schwalm is Manufacturing Technology Specialist for Dyneon GmbH. Service Digital Version B A PDF file of the article can be found at www.kunststoffe-international.com/841786 German Version B Read the German version of the article in our magazine Kunststoffe or at www.kunststoffe.de Reduced ecological damage 0 t -2,000 -3,000 -4,000 -5,000 -6,000 -7,000 -8,000 -9,000 -10,000 Chlorine -5,000 CO2 -10,000 Acids -10,000 CaF2 -1,000 H2SO4 Gypsum -2,000 -3,000 Kunststoffe Fig. 3. Reduced environmental impact resulting from the new Dyneon high-temperature pyrolysis process; illustration shows the up-cycling of 1,000 t of PFPs Product type Material Note End-of-life components e.g. tube and pump linnings, cable isolations PTFE, modified PTFE, PFA, FEP Separation from e.g. metal might be required Processing wastes PTFE, PFA and FEP compounds Correct sorting is a precondition, filler has to qualified for Up-Cycling Table 1. Perfluorinated polymer waste materials suitable for Up-Cycling New Possibilities for Processing Companies Although production waste from PTFE, PFA and FEP processing is currently successfully recycled by established companies using tried-and-tested methods, there are problems in this area for which there have been no worthwhile or technically feasible solutions to date. This includes PTFE compounds where basic PFPs contain fillers. Typical fillers include glass fibers, glass beads, coal, graphite and soot. Even in cases where recycling was technically possible, implementation generally failed as, owing to a lack of acceptance among end consumers, there was no opportunity to feed these recycled materials, with known disadvantages, back into the market (Table 1). The global consumption of PFP raw materials in this problem category is currently around 25,000 t per year. Whereas the pressure sintering process for PTFE compounds appears to be waste-intensive, with a waste rate of up to 75 % not uncommon, fluorothermoplastic compounds can be processed with a much lower proportion of waste. Taken together, the annual PFP compound waste disposed of in landfill is estimated at approximately 10,000-12,000 t. A tremendous potential to save landfill is, of course, a key part of the Dyneon Up-Cycling concept. Various correctly sorted compounds of processed waste have already been investigated for their suitability for Up-Cycling in the University of Bayreuth's laboratories. Conclusion The new Up-Cycling process offers the possibility to completely close the material cycle for PFPs and PFP-compounds. For the first time, components at the end of their life cycle and problem waste materials can be fed back into the value chain with a high conversion rate in the form of monomers. There is no loss in quality in the fluoropolymer products newly created by this process. Collecting the recyclables, preprocessing them and Up-Cycling them to produce new primary products requires close cooperation between all the business partners involved. W Carl Hanser Verlag, Munich Kunststoffe international 6/2014 Internet-PDF-Datei. Diese PDF Datei enthlt das Recht zur elektronischen Verbreitung. National Institute for Public Health and the Environment Ministry of Health, Welfare and Sport Per- and polyfluorinated substances in waste incinerator flue gases RIVM report 2021-0143 J. Bakker | B. Bokkers | M. Broekman Per- and polyfluorinated substances in waste incinerator flue gases RIVM report 2021-0143 RIVM report 2021-0143 Colophon RIVM 2021 Parts of this publication may be reproduced, provided acknowledgement is given to the: National Institute for Public Health and the Environment, and the title and year of publication are cited. RIVM attaches a great deal of importance to the accessibility of its products. However, it is at present not yet possible to provide this document in a completely accessible form. If a part is not accessible, it is mentioned as such. Also see www.rivm.nl/accessibility DOI 10.21945/RIVM-2021-0143 J. Bakker (author), RIVM B. Bokkers (author), RIVM M. Broekman (author), RIVM Contact: Joost Bakker Industriele Chennicalien en Milieu-economie @rivnn.nl This investigation was performed by order, and for the account, of Rijkswaterstaat WVL, department LOAC of the ministry of Infrastructure and Water Management DLCE, within the framework of the programme Support for waste and circular economy policy. Published by: National Institute for Public Health and the Environment, RIVM P.O. Box 1 I 3720 BA Bilthoven The Netherlands www.rivnn.nl/en Page 2 of 160 RIVM report 2021-0143 Synopsis Per- and polyfluorinated substances in waste incinerator flue gases By 2050, the Netherlands wants to produce as little waste as possible and to recycle products and materials as much as possible. However, these products and materials must be safe and free of hazardous substances. Some waste incinerators for instance recover carbon dioxide from their flue gases. Carbon dioxide can be used to promote the growth of crops in greenhouses. RIVM has carried out a literature study to investigate whether and, if so, to what degree this carbon dioxide can contain PFASs. This is a first step of a risk assessment process. This study did not consider whether the presence of PFASs presents a risk for the human health or the environment. As many types of PFASs exist, RIVM first described a definition of this group of substances. The next step was to examine whether these substances can be present in the flue gases of waste incinerators. In fact, that appeared to be the case. Based on a literature review, RIVM expects that most of the PFASs will largely degrade during the incineration process and then be removed when the flue gases are cleaned. The remaining PFASs are expected to be removed during the recovery of the carbon dioxide. Some publications about measurements in the chimney of a waste incineration plant do not exclude the possibility that there may still be PFASs in the flue gases. At the same time it appears that a particular group of PFASs is formed during the incineration process and can be present in the cleaned flue gases. This involves strong greenhouse gases that contribute to global warming. To our knowledge, no measurements have been made for PFASs in recovered carbon dioxide and only a few in cleaned flue gases. In view of the application, RIVM considers it desirable that both carbon dioxide and cleaned flue gas are measured for PFASs. Then the risks of the transmission of PFASs can be better understood. It should be technically feasible to measure PFASs in the flue gases and the recovered carbon dioxide. RIVM recommends developing an effective measurement method for that purpose that can be used as a benchmark. Keywords: waste incineration, PFAS, fluoropolymer, thermal degradation, flue gas, CO2 recovery, measurement Page 3 of 160 RIVM report 2021-0143 Page 4 of 160 RIVM report 2021-0143 Publiekssamenvatting PFAS'en in rookgas van afvalverbrandingsinstallaties Nederland wil in 2050 zo min mogelijk afval produceren en producten en materialen zo veel mogelijk hergebruiken. Deze producten en materialen moeten dan wel veilig zijn en geen schadelijke stoffen bevatten. Sommige afvalverbrandingsinstallaties winnen bijvoorbeeld koolstofdioxide uit hun rookgassen. Dat kan gebruikt worden om gewassen in kassen beter te laten groeien. Het RIVM heeft in een literatuurstudie verkend of, en zo ja in welke mate, PFAS'en in gewonnen koolstofdioxide kunnen zitten. Dit is een eerste stap voor een risicobeoordeling. In dit onderzoek is niet gekeken of de aanwezigheid van PFAS'en een risico vormt voor de gezondheid van mensen of het milieu. Omdat er veel soorten PFAS'en bestaan, heeft het RIVM eerst de definitie van deze stofgroep beschreven. Daarna is onderzocht of deze stoffen in de rookgassen van afvalverbrandingsinstallaties kunnen voorkomen. Dat bleek het geval te zijn. Uit literatuuronderzoek blijkt dat de meeste PFAS'en tijdens het verbrandingsproces grotendeels worden afgebroken. Door reiniging van het rookgas worden nog aanwezige PFAS'en er grotendeels uit verwijderd. De PFAS'en die nog overblijven worden naar verwachting tijdens de winning van de koolstofdioxide verwijderd. Enkele publicaties over metingen in de schoorsteen van een afvalverbrandingsinstallatie sluiten niet uit dat er toch nog PFAS'en in de rookgassen kunnen zitten. Ook blijkt uit de literatuurstudie dat een bepaalde groep PFAS'en tijdens de verbranding wordt gevormd en in het gereinigde rookgas zou kunnen voorkomen. Het gaat om sterke broeikasgassen die bijdragen aan de opwarming van de aarde. Voor zover ons bekend zijn er geen metingen gedaan naar PFAS'en in gewonnen koolstofdioxide en maar enkele in gereinigde rookgassen. Gezien de toepassing vindt het RIVM het wenselijk dat zowel in koolstofdioxide als gereinigde rookgas wordt gemeten of er PFAS'en in zitten. Dan kunnen de risico's van de verspreiding van PFAS'en beter in beeld komen. Het zou technisch mogelijk moeten zijn om PFAS'en in de rookgassen en de gewonnen koolstofdioxide te meten. Het RIVM beveelt aan om hiervoor een geschikte meetmethode te ontwikkelen die als standaard kan worden gebruikt. Kernwoorden: afvalverbrandingsinstallatie, PFAS, fluorpolymeer, thermische afbraak, rookgas, CO2-afvang, meting Page 5 of 160 RIVM report 2021-0143 Page 6 of 160 RIVM report 2021-0143 Contents Summary -- 11 Samenvatting -- 17 1 Introduction -- 23 1.1 Background, issue and questioning -- 23 1.2 Objective -- 26 1.3 Literature study -- 26 1.4 Reader's guide -- 26 2 General information on PFASs -- 29 2.1 Terminology and definitions of PFASs -- 29 Non-polymeric PFASs -- 30 Polymeric PFASs -- 32 2.2 Current advices on PFASs to be analysed in soil and water -- 32 Temporary Action Framework -- 33 Knowledge Document and Action Framework of Expertise Centre PFAS -- 36 2.3 Conclusions -- 37 3 Waste incineration -- 39 3.1 Waste incineration processes/installations -- 39 Introduction -- 39 Waste incineration in the Netherlands -- 40 Legal requirements in the EU -- 41 Description of waste incineration installations and the combustion temperatures -- 42 3.2 Residues from waste incineration -- 43 3.3 Flue gas treatment processes -- 43 3.4 Conclusions -- 44 4 Thermal degradation of PFASs and fluoropolymers -- 47 4.1 Introduction -- 47 4.2 The combustion process and experiments -- 47 The combustion process -- 47 Thermal decomposition experiments -- 48 Other combustion related properties -- 50 4.3 Thermal degradation of PFASs -- 51 Experimental studies on the thermal stability of PFASs -- 51 Bond dissociation energy as a relative measure of thermal stability -- 54 Flash point and autoignition temperature as indicators for incinerability -- 57 4.4 Thermal degradation of fluoropolymers -- 58 Decomposition temperatures -- 58 Formation of perfluorocarbons -- 60 Formation of fluorinated dioxins and furans -- 60 Formation of trifluoroacetic acid -- 61 Conclusion -- 62 4.5 Thermal stability of potential by-products -- 62 Perfluoroalkanes -- 62 Page 7 of 160 RIVM report 2021-0143 Perfluoroalkenes -- 63 Cyclic perfluorocarbons -- 64 General findings on the formation of fluorinated by-products -- 64 4.6 Conclusions -- 64 5 Emissions of PFASs from incineration plants -- 67 5.1 PFAS properties -- 67 Introduction -- 67 Information on physical and chemical properties -- 68 Properties of perfluorinated products of incomplete combustion -- 70 5.2 Assessment of collection efficiency -- 71 Binding to fly ash -- 71 Removal of acid components -- 74 Removal of trace organics by activated carbon -- 78 Overall removal of PFASs in flue gas treatment -- 80 5.3 PFAS measurements at incineration plants -- 81 Introduction to the measurement of PFASs in flue gas -- 81 Scientific literature on measurements of PFASs in flue gas -- 82 Discussion and conclusions on PFAS emission measurement methods -- 86 Fly ash and bottom ash: PFAS composition and emission -- 88 Flue gas: PFAS composition and emission -- 93 5.4 Conclusions -- 95 6 Carbon dioxide recovery from incineration plants -- 99 6.1 CO2 recovery process -- 99 6.2 Removal of flue gas components in the carbon capture process -- 101 Measured data on the removal of flue gas components in the CO2 recovery process -- 102 Dissociation of PFASs in scrubber and wash liquids -- 104 Formation of reaction products with monoethanolamine, heat- stable salts -- 104 Flue gas - MEA liquid partitioning of non-dissociating PFASs -- 105 Qualitative assessment of PFAS removal by the wash stages and the MEA absorber -- 105 Removal in the CO2 cooling, compression and drying section -- 108 6.3 Conclusions -- 110 7 Conclusions and recommendations -- 111 8 References -- 117 List of abbreviations -- 135 Annex I. Overview of waste incineration sites in the Netherlands -- 139 Annex II. Description of common waste incineration facilities -- 140 II.1 Fluidised bed furnaces -- 140 II.2 Rotary kilns -- 141 II.3 Moving-grate furnaces -- 142 Annex III: Flue gas treatment techniques -- 144 Page 8 of 160 RIVM report 2021-0143 III.1 Common treatment steps -- 144 III.2 Three examples of flue gas cleaning -- 146 Annex IV. Measured PFASs at the ARV sites at Duiven and Rozenburg -- 148 Annex V. Indication of PFAS removal at flue gas treatment -- 149 Annex VI. PFASs removed and remaining at CO2 recovery -- 155 Page 9 of 160 RIVM report 2021-0143 Page 10 of 160 RIVM report 2021-0143 Summary Background In the Netherlands there are 13 waste incineration plants spread across the country that receive and incinerate different types of waste. In addition to household waste, municipal waste and non-hazardous industrial waste, some plants accept hazardous waste. Waste incineration plants are licensed in accordance with the Dutch Activities Decree and must use the best available techniques. The plants have to comply with the requirements for incineration of non-hazardous waste by maintaining the temperature of the combustion gases at a minimum of 850 C for at least 2 seconds after the last injection of combustion air, in the presence of at least 6% oxygen. For hazardous waste, the minimum temperature of the combustion gases must be 1100 C. Emission limit values have been established for harmful substances in the flue gases in accordance with Article 5.19 of the Activities Decree. There is a knowledge gap regarding whether and to what extent waste incinerators emit per- and polyfluoroalkyl substances (PFASs) via their flue gases and thereby contribute to PFAS contamination. Waste incinerators burn significant amounts of synthetic materials that also contain fluoropolymers and perfluoroalkyl substances. PFASs are known for their persistence, human toxicity and thermal stability. It is unknown whether and to what extent the PFASs present in household and industrial waste are effectively incinerated and converted into other substances in the flue gases. As well as potentially being present in the emitted flue gases, PFASs may occur in solid residues such as slag, and bottom and fly ashes, which are formed during the incineration process. These solid residues are collected at different stages from the incinerator and flue gas treatment system. Depending on the method of storage, as well as on the transport and processing of these incineration residues into useful applications such as building materials, there may be a risk of PFAS spreading. Some waste incinerator companies in the Netherlands recover the carbon dioxide (CO2) in the flue gases and make it suitable for various applications. Whether or not PFASs occur in flue gases largely determines the question of whether PFASs can also be expected in the recovered CO2 and thus whether their presence should be considered for the intended applications. Knowledge about this is important in order to be able to make legal judgments for new applications of the CO2 recovered from waste incinerator flue gases. Against this background, Rijkswaterstaat (RWS) has commissioned RIVM to answer the following research questions on the basis of a literature study: 1) What is the precise definition of a PFAS and what connection is there between the advisory list of individual PFASs in the Temporary Action Framework and that in the Knowledge Document of the Expertise Centre PFAS? Page 11 of 160 RIVM report 2021-0143 2) Can PFASs be present in the flue gases of a waste incinerator as a result of not breaking down (completely)? 3) Can PFASs (not broken down or broken down into smaller molecules) be captured in flue gases after one or more cleaning steps? 4) Can PFASs (partly depending on the answers to questions 2 and 3 above) be present in the carbon dioxide recovered from waste incinerator flue gases? 5) Is the chemical analysis of fluoride sufficiently accurate to reveal the presence of PFASs in flue gases and carbon dioxide? 6) Can RIVM advise on the possible presence of PFASs in the carbon dioxide that is recovered from waste incinerator flue gases for applications such as growth improver in greenhouse horticulture? RIVM study RIVM has searched and studied the relevant literature in different libraries of scientific publications and reports as well as bibliographic literature databases such as Scopus, Pubchem, HSDSB and Google Scholar, and relevant internet pages. The literature study covered a variety of topics, including: the definitions of PFAS; waste incineration processes/installations and the difference between several types of furnaces and flue gas treatment techniques; the different thermal chemical degradation reactions of PFAS components based on theoretical analyses and published experimental studies; the formation and emission pathways of PFAS degradation products resulting from waste incineration processes; PFAS, fluoride and total organic fluorine measurement methods; the effects of the CO2 recovery process on the occurrence of PFASs in the recovered CO2. Conclusions Based on published laboratory experiments and qualitative theoretical assessments, efficient thermal destruction is anticipated for the groups of PFASs considered. Critical is the definition of complete thermal breakdown. Complete breakdown could refer to complete mineralisation of PFASs to hydrogen fluoride and CO2. On the other hand, complete breakdown could mean that the original compounds are completely destroyed but without complete mineralisation. In practice, full mineralisation will hardly ever occur, as thermal degradation is always accompanied by the formation of various gaseous organic fluorine-containing products. If the minimum requirements for waste incineration plants are met, it is concluded that combustion by-products are mainly limited to the smallest members of the PFAS group perfluorinated carbons (PFCs), CF4 and C2F6. Both are potent greenhouse gases, resistant to high temperatures and most likely (a) to be formed and (b) to survive the combustion process. Fluorinated polymers such as polytetrafluoroethylene (PTFE) are also considered PFASs. PTFE is a fully fluorinated polymer that is one of the most thermally stable of all polymers. Based on experimental data found Page 12 of 160 RIVM report 2021-0143 in literature, it is expected that PTFE will thermally degrade completely at the minimum required combustion temperature of 850 C. However, for solid substances like polymers the conditions in the combustion bed are probably even more important than the temperature in the combustion chamber. The residence time and mixing of the incineration bed on the grate should be sufficient to allow for solid materials to burn out, that is to thermally degrade into smaller volatile components that will subsequently be incinerated in the combustion chamber. PTFE as such will not volatilise and then be burned in the combustion chamber. At the expected temperatures in the incineration bed, between 900 and 1100 C, it is expected that PTFE and other fluorinated polymers will fully degrade into small fluorocarbon molecules. For combustion by-products other than those previously mentioned, such as fluorinated dioxins and furans and perfluoroacetic acid, it is judged that their formation from PFASs is unlikely. The formation of fluorinated dioxins and furans, however, cannot be entirely ruled out because of the potential formation of fluorinated benzenes under unfavourable combustion conditions. Fluorinated benzenes could serve as precursors to the formation of fluorinated dioxins and furans. Ultimately, the formation of fluorinated dioxins and furans is not expected because they have not been detected at measurements that were done in order to reveal their occurrence. From the qualitative assessment of the removal efficiencies of the flue gas treatment and CO2 recovery processes it is concluded, for the PFASs considered, that: 1) the types of PFASs with the strongest tendency to pass through the flue gas treatment system are iodine-containing PFASs, fluorotelomer olefins (FTOs), the perfluoroalkanes (PFCs), the fluorotelomer alcohols with a short perfluorinated chain of 3 to 5 fluorinated carbon atoms (3-5:2 FTOH) and the fluorotelomer acrylates (FTACs) - assuming that these compounds survive the combustion process. Iodine-containing perfluoro compounds, for instance, are expected to be the least thermally stable of the perfluoro compounds and most unlikely to survive the incineration process; 2) due to the physical and chemical processes in the CO2 recovery plant it is expected that none or very little of most of the PFASs considered will end up in the extracted CO2. Of the substances considered, the PFASs with the highest tendency to end up in the recovered CO2 stream are non-dissociating substances with a polar character, i.e. mainly fluorotelomer alcohols with a short perfluoro chain and the group of substituted perfluoroalkane sulphonamido ethanols (MeFASEs and EtFASEs). These conclusions are based largely on published laboratory experiments and qualitative theoretical assessments. Published results from field measurements show that various PFASs have been detected in flue gas and incineration residues such as bottom ash and fly ash. The total PFAS concentration measured in flue gas was about 20 ng.m-3. Measurements to detect the presence of PFASs in recovered CO2 have not been conducted as far as we know. Page 13 of 160 RIVM report 2021-0143 The literature study further shows that no standardised methods are yet available for measuring the emission concentration of PFASs in the flue gases of waste incineration plants. However, it should be technically possible to sample different PFAS subgroups, such as gaseous, polar, water-soluble, dust-bound and dust-based (aerosols) PFASs, in the flue gases. In sampling it is common practice to use a train of filters, adsorption columns and impinger absorption liquids connected in series. The collected filters, adsorption columns and impinger fluids can be chemically analysed in an accredited analytical laboratory after sampling. GC-MS and HPLC-MS/MS are particularly suitable for this purpose as analytical techniques. GC-MS lends itself well to the measurement of gaseous and non-polar to mildly polar PFASs, while HPLC-MS/MS is suitable for polar, dissociable and water-soluble PFASs. HPLC-MS/MS has been accepted in available standard requirements for the determination of the content of PFASs in soil, dredge, sediment, and ground and surface water. A feasible limit of quantification (LOQ) for the measurement of PFASs in flue gases is estimated to be within an emission concentration range of 0.1 to 0.5 ng.m-3. A sampling volume of approximately 4 m3 of flue gas is assumed here. The prescribed measurement method for fluoride in flue gas (NEN-ISO 15713) is not to be considered a suitable or replacement method for measuring PFASs. This is because the LOQ of fluoride is a factor of 1000 higher than the LOQ of a measurement method for determining individual PFASs and the fluoride measurement is not selective for the sum of PFASs. The total organic fluorine (TOF) measurement seems to be a better method because the sum of PFASs is part of the TOF. So, if TOF is not being detected there is no PFAS. However, the feasible LOQ is expected be between 50 and 250 ng.m-3, which makes this method less suitable for the detection of the sum of PFASs in flue gases. With regard to the concentration of PFASs in recovered CO2, as an order of magnitude estimate, 10 ng.m-3 could be used for the total concentration of PFASs. The total PFAS concentration measured in flue gas is about 20 ng.m-3. However, the concentration is expected to be reduced substantially during the CO2 recovery process. Recommendations In order to confirm whether PFASs are present in recovered CO2 and to find out in what quantity they are present, measurements should be conducted. For a complete picture is recommended that measurements shall be taken in flue gases as well as in fly ash from incineration plants. Besides the standard set of PFASs according to the advisory list of the Temporary Action Framework, it is recommended in this report to include in the measurements the PFASs that are indicated in this study. It mainly concerns PFASs that are likely to survive or to be formed in the combustion process, to pass through the flue gas treatment system or to end up in the recovered CO2. These include short-chain perfluoro Page 14 of 160 RIVM report 2021-0143 carbons, fluorotelomer alcohols and acrylates, and substituted perfluoroalkane sulphonamido ethanols. It cannot be ruled out that differences in the results of PFAS emission measurements of the flue gases of waste incinerators are due to differences in the methods and laboratory tools used for sampling, sample pre-treatment and measurement. These factors could also explain the differences in the LOQ of up to a factor of 1000. It is therefore essential to standardise the measurement methods, including the sampling and the analytical techniques. Final conclusion Based on a review of the scientific literature and the theory about combustion processes and flue gas cleaning techniques, RIVM concludes that: - PFASs present in household, municipal and industrial waste degrade into other substances when this waste is incinerated in compliance with the legal requirements for waste incineration plants in the Netherlands, - at the same time, a new PFAS group is formed which are strong greenhouse gases such as perfluoromethane and perfluoroethane, - some publications about measurements in the chimney of a waste incineration plant do not exclude the possibility that PFASs may still be present in the flue gases and that they can be emitted as a result. The remaining PFASs are expected to be removed during the recovery of the carbon dioxide. Due to the lack of sufficiently accurate PFAS measurements, it is uncertain what the composition and quantity of PFASs is in the cleaned flue gases and in the recovered carbon dioxide. In view of the application, RIVM considers it desirable to measure both carbon dioxide and cleaned flue gas in order to be able to determine the presence of the PFASs. The risks of the transmission of PFASs can then be better understood. This risk concerns both the flue gas emission from the chimney and the applications of the carbon dioxide extracted from the flue gases, such as the use as a growth improver in greenhouse horticulture. It is also recommended that further research be conducted into the transmission of PFASs via waste streams from waste incineration, such as bottom ash, fly ash and waste water. Page 15 of 160 RIVM report 2021-0143 Page 16 of 160 RIVM report 2021-0143 Samenvatting Achtergrond In Nederland zijn er verspreid over het land dertien afvalverbrandingsinstallaties die verschillende soorten afval in ontvangst nemen en verbranden. Naast huishoudelijk afval, gemeentelijk afval en niet-gevaarlijk bedrijfsafval, accepteren sommige installaties ook gevaarlijk afval. Afvalverbrandingsinstallaties zijn vergunningplichtig conform het Nederlandse Activiteitenbesluit en moeten gebruikmaken van de best beschikbare technieken. De installaties moeten voldoen aan de eisen voor de verbranding van ongevaarlijk afval door de temperatuur van de verbrandingsgassen ten minste twee seconden op 850 C te houden na de laatste injectie van verbrandingslucht in aanwezigheid van ten minste 6% zuurstof. Voor gevaarlijk afval moet de minimumtemperatuur van de verbrandingsgassen worden verhoogd tot 1100 C. Voor schadelijke stoffen in de rookgassen zijn emissiegrenswaarden vastgesteld conform artikel 5.19 van het Activiteitenbesluit. Er is een kennislacune over de vraag of en tot welke hoeveelheden afvalverbrandingsinstallaties via hun rookgassen per- en polyfluoralkylstoffen (PFAS'en) uitstoten en daarmee bijdragen aan de PFAS-verontreiniging. Afvalverbrandingsinstallaties verbranden aanzienlijke hoeveelheden synthetische materialen die ook fluorpolymeren en perfluoralkylstoffen bevatten. PFAS'en staan bekend om hun eigenschappen zoals persistentie, humane toxiciteit en thermische stabiliteit. Het is niet bekend of en in welke mate de PFAS'en die aanwezig zijn in huishoudelijk- en bedrijfsafval effectief worden verbrand en omgezet in andere stoffen in de rookgassen. Naast PFAS-emissies via de rookgassen kunnen PFAS'en ook voorkomen in vaste reststoffen, zoals slakken en bodem- en vliegassen die ontstaan tijdens het verbrandingsproces en gescheiden worden opgevangen in de verbrandingsoven en het rookgasbehandelingssysteem. Afhankelijk van de wijze van opslag, transport en verwerking van deze verbrandingsresten tot nuttige toepassingen zoals bouwstoffen, kan er een risico op verspreiding van PFAS'en bestaan. Enkele afvalverbrandingsinstallaties in Nederland winnen kooldioxide (CO2) uit de rookgassen en maken deze geschikt voor verschillende toepassingen. Het mogelijk voorkomen van PFAS'en in de rookgassen bepaalt grotendeels de vraag of PFAS'en ook in het gewonnen CO2 te verwachten is en of hun aanwezigheid voor de beoogde toepassingen in aanmerking moet worden genomen. Kennis hierover is van belang om rechtsoordelen te kunnen maken voor nieuwe toepassingen van het gewonnen CO2 in de rookgassen van de afvalverbrandingsinstallaties. Tegen deze achtergrond heeft Rijkswaterstaat (RWS) het RIVM opdracht gegeven om op basis van literatuuronderzoek de volgende onderzoeksvragen te beantwoorden: Page 17 of 160 RIVM report 2021-0143 1) Wat is de definitie van een PFAS en welk verband is er met de advieslijst van individuele PFAS'en van het tijdelijk handelingskader en die van het kennisdocument van het Expertisecentrum PFAS? 2) Kunnen PFAS'en in de rookgassen van een afvalverbrandingsoven aanwezig zijn, omdat ze niet (volledig) afbreken? 3) Kunnen PFAS'en die niet afgebroken zijn of afgebroken tot kleinere moleculen na n of meerdere reinigingsstappen in de rookgassen worden afgevangen? 4) Kunnen PFAS'en (mede afhankelijk van de antwoorden op vraag 2 en 3 hierboven) in kooldioxide aanwezig zijn bij de winning van dit gas uit de rookgassen van de afvalverbrandingsinstallaties? 5) Is de chemische analyse van fluoride voldoende nauwkeurig om de aanwezigheid van PFAS'en in de rookgassen en kooldioxide te kunnen aantonen? 6) Kan het RIVM adviseren over de mogelijke aanwezigheid van PFAS'en in de kooldioxide die uit rookgassen van afvalverbrandingsinstallaties worden gewonnen voor toepassingen als groeiverbeteraar in de glastuinbouw? RIVM-onderzoek Het RIVM heeft in verschillende bibliotheken naar relevante wetenschappelijke publicaties en rapporten gezocht en deze bestudeerd. Ook is er gezocht in bibliografische literatuurdatabases zoals Scopus, Pubchem, HSDSB, Google Scholar en relevante internetpagina's. De literatuurstudie omvatte een verscheidenheid aan onderwerpen zoals; de definitie van PFAS; de afvalverbrandingsprocessen/-installaties; het verschil tussen verschillende soorten ovens en de rookgasbehandelingstechnieken; de verschillende thermische chemische afbraakreacties van PFAS- componenten op basis van theoretische analyses en gepubliceerde experimentele studies; de vormings- en emissieroutes van PFAS'en en de afbraakproducten als gevolg van afvalverbrandingsprocessen; de meetmethoden voor PFAS'en, fluoride en totaal organisch fluor; de invloed van het CO2 winningsproces op de aanwezigheid van PFAS'en in het gewonnen CO2. Conclusies Op basis van gepubliceerde laboratoriumexperimenten en kwalitatieve theoretische beoordelingen wordt een efficinte thermische afbraak verwacht voor de beschouwde groepen PFAS. Cruciaal is de definitie van volledige thermische afbraak. Volledige afbraak kan verwijzen naar volledige mineralisatie tot waterstoffluoride (HF) en CO2. Aan de andere kant kan volledige afbraak ook betekenen dat de oorspronkelijke verbindingen geheel worden vernietigd zonder volledige mineralisatie. In de praktijk zal volledige mineralisatie bijna nooit optreden, aangezien thermische afbraak altijd gepaard gaat met de vorming van verschillende gasvormige organische fluorhoudende producten. Page 18 of 160 RIVM report 2021-0143 Als aan de minimumeisen voor afvalverbrandingsinstallaties wordt voldaan, wordt geconcludeerd dat de vorming van bijproducten tijdens de verbranding voornamelijk wordt beperkt tot de kleinste leden van de PFAS groep geperfluoreerde koolstoffen (PFCs), namelijk perfluormethaan (CF4) en perfluorethaan (C2F6). Beide zijn krachtige broeikasgassen, die bestand zijn tegen hoge temperaturen en de meeste kans hebben om gevormd te worden en het verbrandingsproces te overleven. Fluorpolymeren zoals polytetrafluorethyleen (PTFE) zijn eveneens PFAS'en. PTFE is een volledig gefluoreerd polymeer dat een van de meest thermisch stabiele polymeren is. Op basis van de in de literatuur gevonden experimentele gegevens wordt verwacht dat PTFE volledig thermisch zal degraderen bij de minimaal vereiste verbrandingstemperatuur van 850 C. Echter voor vaste stoffen zoals polymeren zijn de omstandigheden in het verbrandingsbed misschien nog wel belangrijker dan de temperatuur in de verbrandingskamer. De verblijftijd en menging van het verbrandingsbed op het rooster moeten voldoende zijn om vaste stoffen te laten uitbranden, dat wil zeggen thermisch af te laten breken tot kleinere vluchtige componenten die vervolgens in de verbrandingskamer worden verbrand. PTFE als zodanig zal niet vervluchtigen en vervolgens worden verbrand in de verbrandingskamer. Bij de heersende temperaturen in het verbrandingsbed van tussen de 900 en 1100 C, wordt verwacht dat PTFE en andere gefluoreerde polymeren volledig zullen afbreken tot kleine fluorkoolstofvebindingen. Voor andere dan de eerder genoemde verbrandingsbijproducten, zoals gefluoreerde dioxinen en furanen en perfluorazijnzuur, wordt de vorming onwaarschijnlijk geacht. De vorming van gefluoreerde dioxinen en furanen kan echter niet volledig worden uitgesloten vanwege de mogelijke vorming van gefluoreerde benzenen onder ongunstige verbrandingsomstandigheden. Gefluoreerde benzenen zouden kunnen dienen als voorlopers voor de vorming van gefluoreerde dioxinen en furanen. Al met al wordt de vorming van gefluoreerde dioxinen en furanen niet verwacht, mede omdat deze bij metingen die verricht zijn naar hun voorkomen niet zijn aangetoond. Uit de kwalitatieve beoordeling van het verwijderingsrendement in de rookgasbehandeling en het CO2-winningsproces wordt voor de beschouwde PFAS'en geconcludeerd dat: 1. de soorten PFAS'en met de grootste kans om ongehinderd door het rookgasbehandelingssysteem te gaan zijn: jodiumhoudende PFAS'en , fluortelomere olefinen (FTO's), de perfluoralkanen (PFC's), de fluortelomeeralcoholen met een korte geperfluoreerde keten van drie tot vijf gefluoreerde koolstofatomen (3-5:2 FTOH) en de fluortelomeeracrylaten (FTAC's). Ten minste, als deze verbindingen het verbrandingsproces zouden overleven. Van jodiumhoudende perfluorverbindingen wordt bijvoorbeeld verwacht dat ze het minst thermisch stabiel zijn van de bekeken perfluorverbindingen. Het is voor deze verbindingen het meest onwaarschijnlijk dat ze het verbrandingsproces zullen overleven; 2. door de fysische en chemische processen in de CO2winningsinstallatie is het de verwachting dat de meeste van de Page 19 of 160 RIVM report 2021-0143 beschouwde PFAS'en niet of nauwelijks in de gewonnen CO2 terecht zullen komen. Van de beschouwde stoffen zijn de PFAS'en met de grootste kans om in de gewonnen CO2-stroom terecht te komen niet-dissocirende stoffen met een polair karakter, zoals fluortelomeeralcoholen met een korte perfluorketen en de groep van gesubstitueerde perfluorsulfonamido-ethanolen (MeFASE's en EtFASE's). Deze conclusies zijn grotendeels gebaseerd op gepubliceerde laboratoriumexperimenten en kwalitatieve theoretische beoordelingen. Uit gepubliceerde gegevens van praktijkmetingen blijkt dat verschillende PFAS'en worden aangetroffen in de rookgassen en verbrandingsresten zoals bodemas en vliegas. De totale PFAS concentratie in het rookgas na de rookgasreiniging is ongeveer 20 ng.m-3. Voor zover bekend zijn er geen metingen gedaan naar de aanwezigheid van PFAS'en in gewonnen CO2. Uit de literatuurstudie blijkt verder dat er nog geen gestandaardiseerde methoden beschikbaar zijn om de emissieconcentratie van PFAS'en in de rookgassen van afvalverbrandingsinstallaties te meten. Het zou echter technisch mogelijk moeten zijn om verschillende PFAS'en zoals gasvormige, polaire, wateroplosbare, aan stof gebonden en stofgebaseerde (aerosolen) PFAS'en in de rookgassen te bemonsteren. Bij het nemen van monsters is het gebruikelijk om een reeks filters, adsorptiekolommen en impinger-absorptievloeistoffen te gebruiken die in serie zijn geschakeld. De opgevangen filters, adsorptiekolommen en impingervloeistoffen kunnen na monstername chemisch worden geanalyseerd in een geaccrediteerd analytisch laboratorium. Als analytische technieken zijn hiervoor in het bijzonder GC-MS en HPLCMS/MS geschikt. De GC-MS leent zich goed voor het meten van gasvormige en niet-polaire tot licht-polaire PFAS'en. De HPLC-MS/MS is daarentegen geschikt voor polaire, dissocieerbare en wateroplosbare PFAS'en. HPLC-MS/MS is geaccepteerd in beschikbare standaardmethoden voor de bepaling van het gehalte aan PFAS'en in bodem, bagger, sediment, grond- en oppervlaktewater. Een haalbare bepalingsgrenswaarde (LOQ) voor het meten van de emissieconcentratie van PFAS'en in de rookgassen wordt geschat te liggen in een concentratiegebied van 0,1 tot 0,5 ng.m-3. Hierbij wordt uitgegaan van een bemonsteringsvolume van circa vier kubieke meter van de rookgassen. De voorgeschreven meetmethode voor fluoride in rookgas (NEN-ISO 15713) mag niet worden beschouwd als een geschikte of vervangende methode voor PFAS'en. De LOQ van het fluoride is een factor duizend hoger dan de LOQ van een meetmethode ter bepaling van individuele PFAS'en. Verder is de fluoridemeting niet selectief voor de som van PFAS'en. De totale organische fluor (TOF) -meting lijkt voor een indicatie een betere meetmethode te zijn, aangezien de som van PFAS'en onderdeel is van de TOF. Met andere woorden als er geen TOF wordt aangetoond dan is er ook geen PFAS. Echter, de haalbare LOQ wordt verwacht te Page 20 of 160 RIVM report 2021-0143 liggen in een concentratiegebied tussen 50 en 250 ng.m-3, waardoor deze methode minder geschikt is om de som van PFAS'en in de rookgassen aan te tonen. Wat betreft de te verwachten concentratie PFAS in de uit rookgassen gewonnen CO2 wordt geschat dat deze in de orde van 10 ng.m-3 ligt. De totale gemeten PFAS concentratie in rookgas is ongeveer 20 ng.m-3. Aan de andere kant wordt verwacht dat de concentratie aanzienlijk zal afnemen tijdens het CO2-winningsproces. Aanbevelingen Om te achterhalen of PFAS'en aanwezig zijn in de gewonnen CO2 en in welke hoeveelheden ze aanwezig zijn, moeten metingen worden uitgevoerd. Voor een compleet beeld is het aan te raden om aanvullend te gaan meten in zowel rookgassen als vliegassen van de verbrandingsinstallatie. Naast de in het Tijdelijk Handelingskader aanbevolen standaardset van PFAS'en die in het milieu worden gemeten, wordt aanbevolen om die PFAS'en op te nemen die in dit onderzoek naar voren zijn gekomen. Het gaat dan vooral om die PFAS'en waarvoor het waarschijnlijk is dat ze het verbrandingsproces zullen overleven of worden gevormd in het verbrandingsproces, niet door de rookgasbehandeling worden afgevangen of waarvoor het waarschijnlijk is dat ze in de gewonnen CO2 terecht kunnen komen. Deze omvatten perfluorkoolstoffen met een korte keten, fluortelomeeralcoholen en acrylaten en gesubstitueerde perfluorsulfonamido-ethanolen. Het valt niet uit te sluiten dat het verschil in de prestaties van de PFASemissiemetingen van de rookgassen van afvalverbrandingsinstallaties wordt veroorzaakt door verschillen in de methoden en laboratoriuminstrumenten die worden gebruikt voor monstername, monstervoorbehandeling en meting. Deze factoren kunnen de verschillen in de bepaalbaarheidsgrens tot een factor van duizend verklaren. Het is daarom essentieel om te komen tot een standaardisatie van de meetmethoden inclusief de bemonstering en de analysetechnieken Slotsom Op basis van een overzicht van de wetenschappelijke literatuur en de theorie over verbrandingsprocessen en rookgasreinigingstechnieken concludeert het RIVM dat: - PFAS'en, aanwezig in het huishoudelijk, stedelijk en industrieel afval, tot andere stoffen afbreken bij de verbranding van dit afval onder verbrandingscondities die voldoen aan de wettelijke eisen voor afvalverbrandingsinstallaties in Nederland. - tegelijkertijd een nieuwe PFAS-groep wordt gevormd die sterke broeikasgassen zijn zoals perfluormethaan en perfluorethaan. - enkele publicaties over metingen in de schoorsteen van een afvalverbrandingsinstallatie niet uitsluiten dat er toch nog PFAS'en in de rookgassen kunnen zitten en ze daardoor kunnen worden gemitteerd. Page 21 of 160 RIVM report 2021-0143 De PFAS'en die nog overblijven worden naar verwachting tijdens de winning van de koolstofdioxide verwijderd. Vanwege het ontbreken van voldoende nauwkeurige PFAS metingen is het onzeker wat de samenstelling en de hoeveelheid van PFAS'en in de gereinigde rookgassen en de daaruit gewonnen koolstofdioxide is. Gezien de toepassing vindt het RIVM het wenselijk dat zowel in koolstofdioxide als gereinigde rookgas wordt gemeten om de aanwezigheid van de PFAS'en te kunnen vaststellen. De risico's van de verspreiding van PFAS'en kunnen dan beter in beeld komen. Dit risico betreft zowel de rookgasemissie uit de schoorsteen als de toepassingen van de uit de rookgassen gewonnen koolstofdioxide zoals de inzet van een groeiverbeteraar in de glastuinbouw. Verder verdient het aanbeveling nader onderzoek te doen naar de verdere verspreiding van PFAS'en via de afvalstromen van de vuilverbranding, zoals bodemas, vliegas en afvalwater. Page 22 of 160 RIVM report 2021-0143 1 Introduction 1.1 Background, issue and questioning In the Netherlands there are 13 waste incineration plants spread across the country that receive and incinerate different types of waste. In addition to household waste, municipal waste and non-hazardous industrial waste, some plants process hazardous waste. According to the latest reported annual figures, a total of approximately 7.5 million tons of waste was incinerated in the Netherlands in 2018 (Rijkswaterstaat, 2020a). In the period 1989 to 1995 the waste incineration plants were negatively reported by the media. The measurements of the National Institute for Public Health and Environment (RIVM) conducted in the context of the monitoring programme for food products revealed that the milk of cows feeding on grassland in the vicinity of the waste incinerators contained high levels of dioxins. It became clear that the waste incinerators were the main source of dioxin contamination. As a result, measures were taken to significantly reduce dioxin emissions by applying improvements in combustion conditions and flue gas cleaning. Outdated waste incinerators were taken out of production (Slob et al., 1993). Waste incineration plants are licensed in accordance with the Dutch Activities Decree and must use the best available techniques (Infomil, 2020). Article 5.19 of the Decree sets emission limit values for various harmful substances in flue gases. The Decree is an implementation of the European Directive 2010/75/EU on industrial emissions (EURLEX, 2010). Despite the successful reduction in emissions of dioxins and related compounds, there is a new gap in knowledge with respect to whether waste incinerators emit per- and polyfluoroalkyl substances (PFASs) via their flue gases and possibly contribute to the PFAS contamination of the environment. Waste incinerators burn significant amounts of synthetic materials that also contain fluoropolymers and non-polymer per- and polyfluoroalkyl substances. In the Netherlands, 33% residual municipal solid waste, excluding paper, consists of synthetic materials, including textiles, plastics, electronics, rubber and carpet (Janmaat, 2020). PFASs are known for their persistence, human toxicity and thermal stability. Until recently little has been known about the extent to which flue gases from waste incinerators contain PFASs. In addition to their possible presence in flue gases, PFASs can occur in slag and in bottom and fly ashes, which remain as residues after the incineration of waste. Depending on the method of storage, as well as of the transport and processing of these incineration by-products into useful applications such as building materials, there may be a risk of PFAS spreading. It is important to know to what extent PFASs can be expected in bottom and fly ashes and whether there is a risk of their spreading to the environment. Page 23 of 160 RIVM report 2021-0143 PFASs can also be expected in the waste water from waste incinerators and therefore to constitute a source of emissions. Waste water is generated, for example, when water is used in flue gas scrubbing to remove acidic components from the flue gases. In the context of the third National Waste Management Plan (LAP3), in which the Dutch policy framework for the prevention and management of waste was established, waste processing companies are encouraged by the national government to implement innovations for waste recycling in their processes (Rijkswaterstaat, 2020b). The recovery of the greenhouse gas carbon dioxide (CO2) from flue gases is an example of this. The Dutch policy for the prevention and management of waste is based on the waste hierarchy, which, from highest to lowest, is: to limit or prevent the production of waste materials to prepare waste for reuse; to recycle materials from waste for their original function or equivalent; to recycle materials from waste for another function; to chemically recycle waste materials into raw materials for making new products; to treat waste for another useful application, including incineration with energy recovery; to remove waste by incineration; to landfill or discharge waste. An important emphasis is placed in the LAP3 on the pursuit of waste management that is part of a transition to a circular economy. At the same time, a specific policy line has been drawn for the handling of waste containing substances of very high concern (SVHC). The transition to a circular economy therefore requires a responsible balance in waste management on the one hand and efforts that are necessary to keep SVHC out of our living environment as much as possible. Some waste incinerator companies in the Netherlands recover the CO2 in flue gases and make it suitable for different applications in the market, e.g. as a growth enhancer in the cultivation of crops for human consumption. A schematic overview of the issue of the circular economy, waste handling and circulation of SVHC such as some individual substances within the group of PFASs is presented in Figure 1. The focus in this scheme is on material circulation and the adjoining circulation of chemicals. The issue that is dealt with in this report is the useful application of the waste treatment side stream to growing crops, resulting in possible human exposure via food consumption (represented by the Waste Management stage in Figure 1). Page 24 of 160 RIVM report 2021-0143 Figure 1 Emissions of and exposure to PFASs during their whole life cycle, including the waste management stage, in a circular economy. Source: EEA-ETC report, Systemic view on fluorinated polymers, forthcoming 2020, as cited in EC (2020). Crucially, the company that produces and supplies the CO2 should provide sufficient evidence that its quality is such that its application will be safe. For this purpose, the company can submit a request to Rijkswaterstaat (RWS), an executive organisation of the Ministry of Infrastructure and Water Management, for a substantiated analysis confirming that the CO2 is safe to use and that the product meets the end-of-waste criteria as set out in Article 6 of the European Waste Framework Directive 2008/98/EG (EURLEX, 2008). Whether or not PFASs can occur in flue gases is of importance to the question of whether PFASs can also be expected to be present as contaminants in the recovered CO2. This knowledge can then be used to judge whether new applications of the recovered CO2 from waste incinerator flue gases fulfil the legally required `end-of-waste-criteria'. Against this background, RWS has commissioned RIVM to answer the following research questions on the basis of a literature study: 1. What is the precise definition of a PFAS and what connection is there between the advice list of individual PFASs in the Temporary Action Framework and that in the Knowledge Document of the Expertise Centre PFAS? Page 25 of 160 RIVM report 2021-0143 2. Can PFASs be present in the flue gases of a waste incinerator as a result of not breaking down (completely)? 3. Can PFASs (not broken down or broken down to smaller molecules) be captured in the flue gases after one or more cleaning steps? 4. Can PFASs (partly depending on the answers to questions 2 and 3 above) be present in the carbon dioxide recovered from the waste incinerator flue gases? 5. Is the chemical analysis of fluoride sufficiently accurate to reveal the presence of PFASs in flue gases and carbon dioxide? 6. Can RIVM advise on the possible presence of PFASs in the carbon dioxide that is recovered from waste incinerator flue gases for applications such as growth improver in greenhouse horticulture? 1.2 Objective RWS is seeking to gain more insight into the behaviour of PFASs and the incineration of waste materials that contain or may contain these substances or their precursors. Attention is focused on the presence of PFASs in flue gases and the extent to which PFASs may be present in the CO2 recovered from the flue gases. With this insight, RWS will be better able to provide legal judgments about the useful application of recovered CO2 from the flue gases of waste incinerators. The literature study should also generate more knowledge about the possible formation of PFASs and their emissions when household, industrial, municipal and hazardous waste are incinerated. This knowledge will provide a scientific basis for advising the national and regional policy and enforcement authorities on topics such SVHC, waste management, licensing, sustainability, risk assessment and circularity. 1.3 Literature study RIVM has searched for information in its own library catalogue of publications and reports, in scientific publications of bibliographic literature databases such as Scopus, Pubchem, HSDSB and Google Scholar and from relevant internet pages. The following keywords have been used in this search: PFAS; incineration plants; air emissions; pyrolysis; thermolysis; combustion; incinerability; emission measurements; flue gas cleaning; fluorinated chemicals, compounds; waste. 1.4 Reader's guide The report starts with an extensive explanation of the definition of PFASs as defined in scientific publications, by different institutes and in various environmental policy contexts (Chapter 2). Characteristic main and subgroups are mentioned and distinguished within the PFAS group. Page 26 of 160 RIVM report 2021-0143 Chapter 3 examines the processes and techniques of burning waste and flue gas cleaning at waste incinerators. The chapter explains, among other things, different types of furnaces and provides information on typical incineration temperatures. Chapter 4 deals with the chemical changes to PFASs that potentially occur in waste during combustion in relation to the incineration conditions. The chapter gives examples of possible PFAS combustion products. Chapter 5 describes the processes and techniques of flue gas cleaning at waste incinerators and the behaviour of PFASs and combustion products during flue gas treatment. The chapter also discusses the availability of measurement methods to identify and quantify the concentrations of PFASs in flue gases and air emissions from those gases. Also presented in this chapter are the results of measurements of PFASs in flue gas and in fly and bottom ashes and estimates of the emissions from waste incinerators to air. Chapter 6 elaborates on the technique of CO2 recovery from flue gases and discusses whether PFASs can be expected to be removed during this production process or may still be present in the CO2 that is recovered. The final chapter concludes with answers to the study questions regarding the presence of PFASs before and after the cleaning of flue gases in a waste incinerator and the presence of PFASs in recovered CO2. Page 27 of 160 RIVM report 2021-0143 Page 28 of 160 RIVM report 2021-0143 2 General information on PFASs In this chapter a general introduction will be provided on the definitions of PFASs that are currently used worldwide by different institutes and in various environmental policy contexts. In addition, two `advice lists' of PFASs to be measured in soil and sediment are discussed. These aim to facilitate the management of PFASs in soil and sediment and are discussed to determine their relevance for assessing the risk of PFASs in incineration gases later in this report. 2.1 Terminology and definitions of PFASs This section describes which substances are considered to be PFASs, followed by a description of the subgroups of PFASs and relevant terminology. In its attempt to build a PFAS list, OECD (2018) encountered several limitations in its PFAS definition and in the terminology recommended by Buck et al. (2011). Recently, OECD published a more inclusive description of the definition and terminology of PFASs (OECD, 2021). In this OECD document PFASs are defined as fluorinated substances that contain at least one fully fluorinated methyl or methylene carbon atom (without any H/Cl/Br/I atom attached to it). In other words, with a few noted exceptions, any chemical with at least a perfluorinated methyl group (-CF3) or a perfluorinated methylene group (-CF2-) is considered a PFAS. As a work in progress relevant to the definition of PFASs the REACH restriction proposal on PFASs should be noted. The Netherlands is working with Denmark, Germany, Norway and Sweden on a proposal for a European restriction on the use of PFASs. In this a clear definition of the PFASs to be restricted will be developed. In this report we will consider a compound with at least one CF2 moiety (i.e. -CnF2n-, n 1) as a PFAS. This broad definition is chosen to ensure inclusion of the recent OECD definitions and the definition under consideration in the ongoing work on the REACH restriction proposal.1 In the sections below, the main non-polymeric and polymeric PFAS groups mentioned by Buck et al. (2011) and OECD (2021) are summarised. Both non-polymeric and polymeric PFAS may be incinerated when discarded as waste, and are therefore relevant for the emission of PFASs from incineration plants. 1 ECHA/NR/20/13, Call for evidence. https://echa.europa.eu/nl/-/five-european-states-call-for-evidence-onbroad-pfas-restriction and https://www.reach-clp-biozidhelpdesk.de/SharedDocs/Downloads/DE/REACH/Verfahren/PFAS_RMOA_Supplementary_document.html Page 29 of 160 RIVM report 2021-0143 Non-polymeric PFASs Within the non-polymeric PFAS group, 10 subgroups are defined by Buck et al. (2011): (aliphatic) perfluorocarbons (PFCs); perfluoroalkyl acids (PFAAs); perfluoroalkane sulphonyl fluorides (PASFs); perfluoroalkane sulphonamides (FASAs); perfluoroalkyl iodides (PFAIs); perfluoroalkyl aldehydes (PFALs) and aldehyde hydrates (PFALH2O); perfluoroalkanoyl fluorides (PAFs); perfluoroalkane sulphonamido derivatives; fluorotelomer (FT)-based compounds, including semifluorinated n-alkanes (SFAs) and alkenes (SFAenes); per- and polyfluoroalkyl ether carboxylic acids (PFECAs).2 In OECD (2021) many more subgroups are added to these (see Figure 2). These subgroups are categorised into four main groups: perfluoroalkyl acids (PFAAs) including perfluoroalkylether acids (PFEAAs or PFAEs); polyfluoroalkyl acids and polyfluoroalkylether acids; PFAA precursors; other PFASs. The per- and polyalkyl acid groups are also considered to cover per- and polyfluoroalkylether acids (Figure 2), i.e. those acids in which the acidic functional group(s) is directly connected to a per- or polyfluoroalkylether chain. Other PFAE- and all PASF- and PFAI-related substances were designated as PFAA precursors, i.e. substances that may be transformed into PFAAs, e.g. by (microbial) degradation, incineration or metabolism (Figure 2). (Linear) PFCs (CnF2n+2), also known as greenhouse gases and notorious for their high global warming potential when gaseous, are considered as PFASs by Buck et al. (2011): `Those PFCs that contain a -CnF2n+1 moiety are, by definition, members of the PFAS family'. However, Buck et al. also state that PFCs are chemically very stable substances, and it is uncertain whether any of them can actually degrade in the environment to give functionalised PFASs. In Figure 2 OECD (2021) included PFCs in the group of `other PFASs' as perfluoroalkanes. 2 Abbreviation not mentioned by Buck (2011), but by OECD (2015). Page 30 of 160 RIVM report 2021-0143 Figure 2 see next page for description of this figure. Figure 2 cont.: A comprehensive overview of PFAS groups, their structural traits, examples and notes on whether corresponding common nomenclatures (including acronyms). Adapted from OECD (2021). Dotted box: Nomenclature Page 31 of 160 RIVM report 2021-0143 including acronyms well covered by Buck et al. (2011). Dash-dot box: Nomenclature including acronyms partially covered by Buck et al. (2011). Dashed box: Common nomenclature including acronyms exist. Arrows () indicate that it is a synthesis pathway, instead of examples. Blue underlined text indicates polymeric PFASs. Note that this figure is intended to be comprehensive, but not exhaustive; in other words, there are other groups of PFASs that are not captured in this figure. * It is recommended that polyfluoroalkyl acids use the acronym PolyFAA to better distinguish from perfluoroalkyl acids. ** Strictly speaking, these substances are not fluorotelomers, as they are not derived from the telomerization process. Despite this, they are termed here "n:1 fluorotelomer-based" substances for readability. *** Depending on the type of linkages between fluorinated side chain(s) and aromatic ring(s), some side-chain fluorinated aromatics may act as precursors to PFAAs or PFEAAs **** Depending on the molecule structure, one may belong to PFAAs, PolyFAAs, PFAA precursors, or other groups that are not described here. Polymeric PFASs According to Buck et al. (2011), the polymers considered as PFASs are: (1) those whose synthesis involves the incorporation of one or more PFASs as monomers; or (2) those whose manufacture requires the use of a PFASs as a production aid (Buck et al., 2011). Within the group of polymeric PFASs, Buck et al. (2011) and OECD (2021) differentiate between (see Figure 2, blue text): Fluoropolymers: fluorinated polymers consisting of carbon-only backbone with fluorine atoms directly attached to this backbone. These fluoropolymers are synthesised from the following monomers or other starting substances e.g.: o polytetrafluoroethylene (PTFE); o polyvinylidene fluoride (PVDF); o fluorinated ethylene propylene (FEP); o perfluoroalkoxyl polymer (PFA); o other fluoroplymers. Side-chain fluorinated polymers: fluorinated polymers consisting of variable compositions of non-fluorinated carbon backbones with polyfluoroalkyl (and possibly perfluoroalkyl) side chains. The fluorinated side chains, including PASF- and fluorotelomer-based derivatives, are potential precursors of PFAAs (Liu and Mejia Avendano 2013). The following three side-chain polymers are mentioned: o fluorinated (meth)acrylate polymers; o fluorinated urethane polymers; o fluorinated oxetane polymers. Perfluoropolyethers (PFPEs): fluorinated polymers consisting of backbones containing carbon and oxygen with fluorines directly attached to carbon. They are not made from PFAAs or their potential precursors; and PFAAs or their potential precursors are not involved in the manufacturing of perfluoropolyethers. 2.2 Current advices on PFASs to be analysed in soil and water In the next two sections (2.2.1 and 2.2.2) two Action Frameworks are discussed. It should be noted that the legal status of these frameworks differs. The Temporary Action Framework (Dutch: Tijdelijk Page 32 of 160 RIVM report 2021-0143 Handelingskader; 2.2.1) is an initiative of the Dutch Ministry of Infrastructure and Water Management and will eventually be incorporated into the existing Soil Quality Regulation. Because of the duty to prevent the spread of polluted soil and sediment, this Temporary Action Framework can already be used in anticipation of the amendment to the Soil Quality Regulation. In contrast, the Knowledge Document and Action Framework of the Expertise Centre PFAS (Dutch: Expertisecentrum PFAS; Section 2.2.2) does not have a legal basis, but is intended as a practical and implementation-oriented framework that can help governments to develop policy, start research, interpret measurement data and determine the next steps in these areas. In addition, it should be noted that the documents discussed in this section date from before the most recent information on background values of PFASs in Dutch soil (Wintersen et al., 2020) became available. Temporary Action Framework (Dutch: Tijdelijk Handelingskader) PFASs are diffusely present in soil and sediments in the Netherlands and Europe and are found in many places at levels above the detection limit. As a result, the re-use of soil and dredged material stagnated. The Temporary Action Framework3 published by the Dutch Ministry of Infrastructure and Water Management aims to eliminate this stagnation where possible, while at the same time applying the basic principle that risks to health and the environment and the spread of PFAS-containing soil and dredged material to areas that are not contaminated or contaminated to a lesser extend are prevented. The Action Framework is deemed temporary because it will eventually be implemented in the Dutch national Soil Quality Regulation (Dutch: Besluit bodemkwaliteit). The Temporary Action Framework considers only the reuse of PFAScontaining soil and dredging sludge and their application on dry land (soil) and in water. In addition, options for storing, cleaning and dumping soil and dredged material containing PFASs, including the acceptance options for the national dredging dumps, are described. When analysing PFASs in soil and dredged material, the Temporary Action Framework recommends using the advisory list4 of PFASs, version 12 (July 2019). If, on the basis of preliminary research, it is expected that PFASs other than those included in this advisory list may also occur in soil or dredged material, for example in the case of a point source, then the list of PFASs must be expanded to include the specific PFAS(s). It has been established that PFOS and PFOA are found diffusely throughout the Netherlands (and Western Europe) (Wintersen et al., 2020). These substances (both linear and branched) must therefore always be analysed. The present advisory list of 30 substances (Table 1) is based on preliminary results showing that these PFASs occur diffusely in (aquatic) soil and sediment in the Netherlands. When determining the definitive 3 https://www.bodemplus.nl/onderwerpen/wet-regelgeving/bbk/grond-bagger/handelingskader-pfas/tijdelijk/ 4 https://www.bodemplus.nl/onderwerpen/wet-regelgeving/bbk/vragen/grond-baggerspecie-pfas-veldwerkanalyse-toetsing/faq/welke-pfas-verbindingen-geanalyseerd/ Page 33 of 160 RIVM report 2021-0143 Action Framework, or as soon as possible on the basis of research results, it will be checked whether the advice list needs to be adjusted. HFPO-DA (a GenX compound, Table 2) has mainly been found in the vicinity of locations where HFPO-DA is produced or discharged. In areas where no direct source or discharge has taken place there is therefore no need to measure HFPO-DA. There are indications that HFPO-DA occurs on more locations in the (aquatic) soil than expected. Some (Dutch) competent authorities therefore make the analysis of HFPO-DA mandatory in certain areas. Page 34 of 160 RIVM report 2021-0143 Table 1 Advisory list of PFASs to be measured in (aquatic) soil (12 July 2019) according to the Temporary Action Framework published by the Dutch Ministry of Infrastructure and Water Management. PFAS categories can be found in Figure 2 # Compound Abbreviation Formula CAS number PFCAs 1 Perfluorobutanoic acid PFBA C4HF7O2 375-22-4 2 Perfluoropentanoic acid PFPeA C5HF9O2 2706-90-3 3 Perfluorohexanoic acid PFHxA C6HF11O2 307-24-4 4 Perfluoroheptanoic acid PFHpA C7HF13O2 375-85-9 5 Perfluorooctanoic acid (linear) PFOA C8HF15O2 335-67-1 6 Perfluorooctanoic acid (branched) PFOA- - NA branched 7 Perfluorononaoic acid PFNA C9HF17O2 375-95-1 8 Perfluorodecanoic acid PFDA C10HF19O2 335-76-2 9 Perfluoroundecanoic acid PFUnDA C11HF21O2 2058-94-8 10 Perfluorododecanoic acid PFDoDA C12HF23O2 307-06-7 11 Perfluorotridecanoic acid PFTrDA C13HF25O2 72629-94-8 12 Perfluorotetranoic acid PFTeDA C14HF27O2 376-06-7 13 Perfluorohexadecanoic acid PFHxDA C6HF31O2 67905-19-5 14 Perfluorooctadecanoic acid PFODA C18HF35O2 16517-11-6 PFSAs 15 Perfluorobutane sulphonic acid PFBS C4HF9O3S 375-73-5 16 Perfluoropentane sulphonic acid PFPeS C5HF11O3S 2706-91-4 17 Perfluorohexane sulphonic acid PFHxS C6HF13O3S 355-46-4 18 Perfluoroheptane sulphonic acid PFHpS C7HF15O3S 375-92-8 19 Perfluorooctane sulphonic acid (linear) PFOS C8HF17O3S 1763-23-1 20 Perfluorooctane sulphonic acid PFOS- - NA (branched) branched 21 Perfluorodecane sulphonic acid PFDS C10HF21O3S 335-77-3 Fluortelomer sulphonic acids 22 4:2 fluorotelomer sulphonic acid 4:2 FTS C6H5F9O3S 757124-72-4 23 6:2 fluorotelomer sulphonic acid 6:2 FTS C8H5F13O3S 27619-97-2 24 8:2 fluorotelomer sulphonic acid 8:2 FTS C10H5F17O3S 39108-34-4 25 10:2 fluorotelomer sulphonic acid 10:2 FTS C12H5F21O3S 120226-60-0 FASA- and PASF-based derivatives 26 N-methylperfluorooctane N-MeFOSAA C11H6F17NO4S 2355-31-9 sulphonamidoacetic acid 27 N-ethylperfluorooctane N-EtFOSAA C12H8F17NO4S 2991-50-6 sulphonamidoacetic acid 28 perfluoro-1-octanesulphonamide PFOSA C8H2F17NO2S 754-91-6 29 N-methylperfluorooctanesulphonamide N-MeFOSA C9H4F17NO2S 31506-32-8 Fluorotelomer phosphates 30 8:2 polyfluoroalkyl phosphate diester 8:2 diPAP C20H9F34O4P 678-41-1 Table 2 PFASs not in advisory list. To be measured when presence is suspected in (aquatic) soil (12 July 2019) # Compound Abbreviation Formula CAS number PFECA and PFAE or PFAA 31 Hexafluoropropyleneoxide dimer acid HFPO-DA or FRD-903 C6HF11O3 13252-13-6 (a GenX compound) Page 35 of 160 RIVM report 2021-0143 Knowledge Document and Action Framework of Expertise Centre PFAS (Dutch: Kennisdocument en handelingskader van Expertisecentrum PFAS) The Expertise Centre PFAS (Dutch: Expertisecentrum PFAS) is a cooperation between the consultancy companies Witteveen + Bos, TTE Consultants and Arcadis. It was established to develop and share knowledge about PFASs.5 In June 2018, the Expertise Centre PFAS published two documents providing (local) governments with guidance on how to deal with PFASs in the soil and water (soil, groundwater, sediment and surface water): the PFAS Knowledge Document (Pancras et al., 2018) and the Action Framework PFAS (Slenders et al., 2018) (not to be confused with the Temporary Action Framework of the Dutch government; Section 2.2.1). The documents are intended as a practical and implementation-oriented framework that can help governments to develop policy, start research, interpret measurement data and determine the next steps in these areas. In addition, the documents provide information about the substance group PFAS and explains why these substances deserve attention. Regarding a list of PFASs to be measured in soil and water, the Expertise Centre PFAS recommends analysing at least the C4-C10 perfluorinated compounds and the precursors 6:2 and 8:2 FTS (Table 3). High concentrations of C11 and C12 PFASs have also been found at some firefighting training sites and fire sites. Supplementing the package of the compounds to be measured can be useful for these sites. Other sources of contamination can also justify the expansion of the analysis package (e.g. GenX substances). Precursors of PFASs may also be present in soil or water. In the environment, these precursors are degraded or transformed into persistent PFAAs such as PFOS and PFOA. According to the Expertise Centre PFAS, two analysis methods are suitable or can be used to measure precursors: total determinations of organically bound fluorine (AOF, PIGE or TOF); TOP analysis, in which almost all precursors are broken down into analysable PFASs (PFOS, PFOA and analogous compounds). 5 https://www.expertisecentrumpfas.nl/ Page 36 of 160 RIVM report 2021-0143 Table 3 Advisory list of PFASs to be measured in soil and water according to the Expertise Centre PFAS. PFAS categories can be found in Figure 2. # Compound Abbreviation Chain length Perfluorocarboxylic acids PFCAs 1 Perfluorobutanoic acid PFBA 4 2 Perfluoropentanoic acid PFPeA 5 3 Perfluorohexanoic acid PFHxA 6 4 Perfluoroheptanoic acid PFHpA 7 5 Perfluorooctanoic acid (linear) PFOA 8 6 Perfluorononaoic acid PFNA 9 7 Perfluorodecanoic acid PFDA 10 Perfluorosulphonic acids PFSAs 8 Perfluorobutane sulphonic acid PFBS 4 9 Perfluoropentane sulphonic acid PFPeS 5 10 Perfluorohexane sulphonic acid PFHxS 6 11 Perfluoroheptane sulphonic acid PFHpS 7 12 Perfluorooctane sulphonic acid (linear) PFOS 8 13 Perfluorodecane sulphonic acid PFDS 10 Precursors 14 6:2 fluorotelomer sulphonic acid 6:2 FTS 8 (1H,1H,2H,2H-Perfluoroctaansulphonzuur) (H4PFOS) 15 8:2 fluorotelomer sulphonic acid 8:2 FTS 10 (1H,1H,2H,2H-Perfluordecaansulphonzuur) 2.3 Conclusions PFASs are divided into two subgroups: non-polymeric and polymeric PFASs. Both of these groups may be present in discarded waste presented for incineration, and are therefore relevant for the emission of PFASs from incineration plants. With regard to the non-polymeric PFAS group, this report focuses on the main PFAS groups as defined by the OECD definition. Ozone-depleting substances matching the broader definition such as chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) and bromine-containing Halons that are used as refrigerants, blowing agents, aerosol propellants, degreasing agents and fire-suppressing agents are not part of this study. These include the hydrofluorocarbons that do not have ozone-depleting properties but are known to act as greenhouse gases. The two Action Frameworks discussed above aim to facilitate the management of PFASs in soil, sediment and water. It should be noted that the legal status of the two frameworks differs (Section 2.2). The PFASs that are to be measured and monitored according to these frameworks have been selected on the basis of their occurrence in soil sediment and (surface) water in The Netherlands. All the substances mentioned in the two action frameworks are generally regarded as PFASs according to all available definitions. (Section 2.1). The listed PFASs are considered relevant when managing contamination in soil and sediment. However, their relevance to assessing the safety of incineration gases may not be sufficient because other PFASs not covered in the lists may be present in flue gases, since the incineration of PFAS-containing waste may produce different PFASs or fluorcontaining gases, as will be discussed in the following chapters. Page 37 of 160 RIVM report 2021-0143 Page 38 of 160 RIVM report 2021-0143 3 Waste incineration This chapter deals with incineration techniques most commonly used in the Western World - and specifically in the Netherlands - for the treatment of hazardous, household and commercial waste. Specialist incineration techniques for the treatment of hospital waste and highly concentrated chemical waste other than that commonly treated in the post-combustion chamber of rotary kilns are not addressed in this chapter. Other waste-handling techniques, such as landfilling and composting, are also not discussed in this section. So far, in the Netherlands, CO2 recovery is carried out only at waste incineration plants that mainly treat biomass and commercial and household waste. Therefore, the most common techniques for incinerating these types of waste are discussed in this chapter. Whether and to what extent PFASs are thermally degraded and end up in recovered CO2 depends on the process conditions at incineration, the subsequent flue gas cleaning and the CO2 recovery process. The latter two subjects will be discussed in the following Chapters 5 and 6. First, an overview is provided of waste incineration techniques in the Netherlands. This is followed by an explanation of the legal requirements relating to operating conditions at waste incineration plants. The most common waste incineration and flue gas treatment techniques will be briefly described in the next section. A more detailed description of the various techniques is included in Annex II. Special attention is paid to process parameters such as temperature, residence time and oxygen content. The physical and chemical techniques used in flue gas treatment, including the process conditions, will be also discussed in this chapter. This information is important in assessing the fate of PFASs at incineration and flue gas treatment, which are described in the following chapters. Finally some information is included on the residues generated at waste incineration, the focus of this report being on the generated flue gas that serves as a source of CO2 but which can also contain PFASs. Besides flue gases being a possible emission source of PFASs, residues such as fly ash and bottom ash might also contain PFASs and thus are also a potential source of emissions into the environment. 3.1 Waste incineration processes/installations Introduction There are various ways of treating waste streams, such as chemical treatment, physicochemical and biological treatment. Residues resulting from these treatment processes must be treated in a subsequent process such as incineration or need to be disposed of through landfilling or can be utilised directly in various applications. Besides landfilling, incineration is one of the most widely used waste treatment steps. There are three main waste incineration processes, used for different types of waste. Household and related commercial waste is usually treated in waste incineration plants using grate kilns. For sewage Page 39 of 160 RIVM report 2021-0143 sludge, fluidised bed firing is usually applied. However, sewage sludge can be combined with household waste for grate firing (ThomKozminesky et al., 2012) and industrial or commercial waste can also be co-incinerated with dewatered sewage sludge in fluidised bed incinerators (Indaver, 2020). In some countries, including Japan and Sweden, fluidised bed furnaces are also used solely for processing municipal solid waste (Thom-Kozminesky et al., 2012). Industrial and hazardous wastes are generally processed in rotary kiln ovens. Cement kilns are a type of rotary kiln in which certain types of waste such as rubber tyres are burned. However, in this document we do not include cement kilns when referring to rotary kilns. The types of waste treated in rotary kilns include solid and liquid residues containing organic matter from industrial production processes that cannot be reclaimed by physicochemical treatment. This group of wastes includes oils, greases, tars, paste-like and liquid residues (Thom-Kozminesky et al., 2012). Organic liquid wastes are usually injected into and burned in the postcombustion chamber of a rotary kiln. If other methods fail or prove to be expensive, waste water can be treated by combustion of the organic constituents. Waste water can either be treated in specialised installations or be injected into the post-combustion chamber of a rotary kiln along with other liquid waste. Wastewater can also be incinerated in fluidised bed furnaces, though it often requires supplementary firing. Waste incineration in the Netherlands An overview of municipal solid waste incineration facilities in the Netherlands, 13 in total, is provided in Annex I, which also lists the facilities used for the combustion of waste water treatment sludges and those used for treating highly contagious hospital waste. All municipal and commercial solid waste incinerators in the Netherlands are moving-grate kilns. Some of them also process a small amount of hazardous waste (Rijkswaterstaat, 2020a; Agentschap NL, 2011). The only rotary kiln incinerator operating in the Netherlands was officially closed in 2005 (VROM-inspectie, 2006). From that year on, hazardous waste was mainly exported to surrounding countries like Belgium and Germany to be treated accordingly, mainly in rotary kilns. Currently, some hazardous waste is treated in moving-grate furnaces in the Netherlands though. To meet the legal obligations for hazardous waste incineration, specific requirements have been set for instance to the caloric value of the waste and deployment of auxiliary burners in order to reach the required minimum combustion temperature of 1100 C in such installations. The facilities where hazardous waste is co-incinerated are EEW in Delfzijl, ARN at Weurt, AEB in Amsterdam and the AVR Rozenburg/Rotterdam-Botlek (Agentschap NL, 2011; STOWA, 2005). Annex I also contains information on the registered average and maximum combustion temperatures of the incineration plants during normal operation, types of ovens, number of incineration lines, types of waste burned, and company name and location. In the Netherlands, there are currently three facilities using fluidised bed incinerators. Two of these are used for the combustion of sludges (Agentschap NL, 2011; STOWA, 2005). The sludges include sewage water treatment sludge and sludge from industrial waste water treatment plants. The fluidised bed incinerator at Duiven processes paper pulp from the paper industry. Part of the generated sludges are Page 40 of 160 RIVM report 2021-0143 also co-fired in power stations, in the cement industry (ENCI) or in municipal solid waste incinerators (Rijkswaterstaat, 2020a; STOWA, 2005). As far as is known, none of the sludge incineration facilities processes solid municipal or commercial waste. The company EEW has advanced plans to build a sludge incineration installation next to their existing municipal solid waste incinerating lines at their site in Delfzijl. Highly contagious hospital waste is thermally converted at the Zavin facility in Dordrecht. Zavin's two-stage incinerator consists of a movingfloor gasification section and a combustion chamber or afterburner (Zavin, 2021). The company AVR-Afvalverwerking B.V. (AVR) at Moerdijk operates Vortex ovens in which industrial aqueous hazardous waste and high caloric petrochemical waste are incinerated. With respect to CO2 recovered from waste incineration flue gases in the Netherlands, there are currently two sites: AVR in Duiven and Twence in Hengelo. AVR is currently conducting a feasibility study to extract CO2 from flue gases at its Rozenburg facility. Legal requirements in the EU According to Article 50 of the Industrial Emissions Directive 2010/75/EU, waste incineration plants must be designed to ensure that flue gases reach a temperature of at least 850 C for at least 2 seconds in order to ensure the proper breakdown of toxic organic substances. The temperature should be measured near the inner wall of the combustion chamber after the last injection of air. In order to comply with this requirement at all times, it is necessary to install back-up auxiliary burners (often fueled by oil), which are fired into the boiler when the heating value of the waste is insufficient to reach this temperature. When hazardous waste containing more than 1% halogenated hydrocarbons is incinerated in a hazardous waste incinerator, the required temperature is at least 1100 C. Incinerators are specifically designed and operated to meet these minimum conditions. By ensuring that the combustion gases are maintained at a minimum temperature for a minimum residence time at a minimum oxygen level, a good burnout of the combustion gases will be achieved. In addition, the Directive requires the installation of measurement systems to monitor the temperature and oxygen level., Also relevant emissions to air and to water must be measured periodically and reported. Achieving the required residence time mainly is a matter of design of the incinerator. The residence time is determined by, among other things, the dimension of the post-combustion chamber, the secondary air flow rate, the number and position of the injection points and the temperature. These should be optimised to ensure the required residence time is achieved (Neuwahl et al., 2019). The residence time usually needs to be demonstrated during plant commissioning or licensing trials (Ellison and Hayes, 1997). Verification of the residence time is usually made indirectly by monitoring the appropriate parameters (Neuwahl et al., 2019). Page 41 of 160 RIVM report 2021-0143 In the following sections, the above-mentioned three main types of waste incineration installation will be described in more detail, with special attention to the typical operating temperatures. Section 3.2 will focus on the residues from waste combustion and the treatment of the exhaust gases. Description of waste incineration installations and the combustion temperatures Fluidised bed furnaces Fluidised bed incinerators are widely applied to the incineration of finely divided waste with a relatively high water or liquid content, such as waste water treatment sludges and industrial sludges. The fluidised bed furnace is a lined combustion chamber in the form of a vertical cylinder. In the combustion chamber, a sand bed on a grate or distribution plate is fluidised with air. The waste is continuously fed into the fluidised sand bed from the top or side. The temperature in the space above the bed is generally between 850 C and 950 C and the bed itself has a lower temperature, e.g. around 650 C. Maximum operation temperatures are about 1200 C. Additional information on fluidised bed furnaces and a schematic representation of a fluidised bed incinerator including flue gas treatment is provided in Annex II.1. Rotary kilns A rotary kiln consists of a cylinder inclined in the transport direction. The interior of the cylinder can be up to 20% filled with waste, which forms a moving bed. Rotation of the furnace turns over the contents and causes them to move toward the lower end. The rotary kiln is very versatile with respect to the type of waste that can be processed in it, ranging from solid materials to paste-like and viscous matter to contaminated liquids that are injected through simple burners in the combustion chamber (Thom-Kozminesky et al., 2012). The mean combustion temperature in the furnace is between 800 and 1400 C, and residence times of the moving bed are ca. 60 min. Afterburning in a post-combustion chamber is provided to ensure complete burning of the combustion gases. The temperature in the postcombustion chamber typically varies between 900 and 1200 C. Additional information and a schematic representation of a rotary kiln incinerator including flue gas treatment is provided in Annex II.2. Grate-fired furnaces The typical incineration plant for municipal solid waste consists of a moving grate. It is the most widely used process for the thermal treatment of waste. In a moving grate-fired incinerator the grate conveys the waste in a horizontal or inclined direction towards the end of the combustion chamber. Secondary air is injected into the combustion space above the grate through nozzles to ensure complete combustion of the gases. Intensive mixing of the combustion gases should prevent the bypassing of unburned gases (Thom-Kozminesky et al., 2012). Page 42 of 160 RIVM report 2021-0143 The maximum temperature in the fuel bed is reached at the end of the ignition zone. Here the temperature in the bed as well as that of the flue gas is about 900 to 1100 C. After the addition of secondary air to the combustion chamber, the temperature of the flue gas lies in the range of 900-1050 C (Gehrmann et al., 2013). Additional information and a schematic representation of grate-fired furnaces including flue gas treatment is provided in Annex II.3. Appendix I contains the recorded average and maximum incineration temperatures of the municipal solid waste incinerator (MSWI) plants in the Netherlands. Average temperatures are higher than the minimum required temperature of 850 C, ranging between 890 and 1195 C. Recorded maximum temperatures range from 974 to 1250 C. In some facilities the average temperature is close to the maximum, but in general, the difference between the average and maximum temperature is between 150 and 250 C. 3.2 Residues from waste incineration Various kinds of residues are generated during the combustion process and the subsequent flue gas treatment. Besides the flue gases that are emitted through the stack, solid residues are formed such as fly and bottom ashes and slags from the kilns. During flue gas treatment, solid residues such as fly ash are collected in bags or by electrostatic filters. Besides these flue gas treatment residues, sludges are formed at the wet treatment when using scrubbers. In case of dry flue gas treatment solid gypsum is formed when using limestone as a desulphurisation agent. From the wet treatment of the flue gases also waste water is generated, from whose treatment waste water sludge is generated. The possible presence of PFASs in these waste incineration residues is not further investigated and analysed. Measured concentrations in residue streams are discussed in Chapter 5 on emissions of PFASs from waste incineration plants. In the remainder of the report the focus is on the assessment of the presences of PFASs in the flue gases and in the CO2 recovered from these flue gases. 3.3 Flue gas treatment processes Typical combustion products from waste incineration are CO, CO2, water vapour, sulphur dioxide and nitrogen oxides. Depending on the composition of the waste, other pollutants are produced, such as hydrogen chloride, hydrogen fluoride, dust, heavy metals, nitrogen oxides, dioxins, and furans. For many of these, such as CO, NOx and dioxins, emission limits are set by regulation (Directive 2010/75/EU). To fulfil these requirements, flue gases must be treated by a combination of cleaning processes, each specifically aimed at removing certain components from the flue gases. The flue gas treatment might vary from installation to installation. There are many components that can be configured in various ways. However, the flue gas treatment system usually consists of one or more of the following operations: dust collection using electrostatic filters, baghouses or cyclones; Page 43 of 160 RIVM report 2021-0143 absorption of acids or acid-forming compounds such as SO2, HCI and HF, usually in several steps through scrubbers or washing towers; sorption of trace organic compounds on activated carbon (AC) powder that is added as to the flue gas, with the optional addition of chalk, in combination with bag filters or the use of an AC filter bed, usually as a final flue gas cleaning step; catalytic and non-catalytic reduction of nitrogen oxides; catalytic oxidation of trace organics such as dioxins and furans. In Annex III.1 the different flue gas treatment operations are discussed in further detail with a focus on the typical process conditions. As a further exemplification, Annex III.2 contains descriptions of the flue gas treatment at three waste incineration sites. 3.4 Conclusions Three common processes for the incineration of hazardous, municipal and commercial wastes have been described. Essential for the assessment of the thermal destruction of PFASs in these installations are the legally required minimum temperature, the residence time and the typical operating temperatures. The typical operating temperatures are presented in Table 4. Three temperature zones can be distinguished: 1) the fuel bed, 2) the flame zone directly above the bed, and 3) the zone where secondary air is added, the afterburning section. The space above the fuel bed is usually referred to as the furnace. Usually, the temperature is measured in the zone after the injection of secondary air. Under normal operating conditions, incineration temperatures are usually somewhat higher than the minimum required temperature of 850 C laid down in the Industrial Emissions Directive 2010/75/EU. The required residence time and oxygen content have not been verified in this research. As well as temperatures, these parameters should be verified by the enforcement authorities to ensure the proper operation of the incineration process. Although it is recognised that all three parameters are essential for full burn-out of the combustion gases, in the further analysis on the incineration of PFASs the focus will be on combustion temperature. Table 4 Typical incineration temperatures in the three most common types of waste incineration installation Type of Temperature (C) installation Typical Maximum Rotary kiln 900-1200 1200 Grate-fired 890-1100 1000-1250 Fluidised-bed Page 44 of 160 RIVM report 2021-0143 Each process in the flue gas treatment process is designed to remove specific flue gas components. The flue gas treatment process usually consist of four steps: dust removal; removal of acid components; removal of trace organic pollutants, particularly dioxins and mercury; reduction of NOx. The cleaning of flue gas from waste incinerators is not specifically aimed at capturing PFASs. Depending on the properties of the different types of PFASs, they can be captured to a greater or lesser extent by the different cleaning steps. The flue gas cleaning efficiency depends not only on the physical and chemical properties of a chemical, but also on the cleaning steps applied (physical or chemical mechanism) and the process conditions at each cleaning step (acidity of the washing liquids, prevailing process temperature, filter efficiency, etc.). The most common unit processes are described together with their typical operating conditions. Page 45 of 160 RIVM report 2021-0143 Page 46 of 160 RIVM report 2021-0143 4 Thermal degradation of PFASs and fluoropolymers 4.1 Introduction One of the research questions addressed in this report is whether PFASs can be present in the flue gases of a waste incinerator because they do not break down (completely)? To answer that question, it was investigated whether and, if so, to what extent and under what conditions PFASs, including fluoropolymers, are thermally degraded and what kind of incineration by-products are formed. To assess this, an overview of available key literature data on the thermal degradation of PFASs and fluoropolymers and the formation of byproducts is presented in this chapter. First, the process of combustion will be discussed, together with the description of various thermal decomposition experiments. This is followed by the description of various properties of chemical substances that could provide an indication of their thermal stability and incinerability. These sections will be followed by a presentation of the available theoretical and experimental information on the thermal degradation of PFASs and fluorinated polymers. 4.2 The combustion process and experiments Before going into more detail on thermal degradation experiments it is useful to describe the terminology used, the combustion process and factors influencing the combustion process. After that, the differences between the various experimental methods and their relevance to the waste incineration process will be discussed. The combustion process Incineration (of waste) is the conversion of (waste) materials into ash, flue gas and heat through combustion. Combustion is a complex sequence of chemical reactions between a substance (fuel) and an oxidising agent that releases heat, and results in a (limited) number of combustion reaction products. Heat is required to activate the chemical reactions and to generate combustible gases in the case of the combustion of solids. Once a combustion process has started, usually enough heat is generated to maintain the process. To support the combustion process and increase its efficiency, external heat can be applied, for instance through gas- or oil-fired burners. Normally, combustion happens with oxygen as the oxidising agent. When single elements are burned, they yield oxides such as CO2, sulphur dioxide and water. When molecules consisting of various elements are burned, other combustion products are generated as well; for instance, in the case of halogens, which react with hydrogen to form the associated acids, HF, HCl and HBr. In reality, combustion is never complete and side products are formed such as carbon monoxide, soot and aromatics in the case of the combustion of hydrocarbons. Page 47 of 160 RIVM report 2021-0143 Combustion and the associated breakdown of organic materials depends on temperature, residence time, oxygen content (fuel/air ratio) and turbulence in the combustion chambers (Moldenhauer and Mischer, 2012). For complete combustion, the various gas streams must be at the same temperature when they are mixed and to achieve a high degree of thermal degradation, the gases must have a sufficiently long residence time (2-5 seconds) at a sufficiently high temperature (850-950 C) (Thom-Kozminesky et al., 2012). The thermal stability and incinerability of a substance also have an impact on breakdown efficiency. Properties such as the flashpoint, the autoignition temperature and the decomposition temperature can possibly be used as indicators for the thermal stability and the incinerability of a chemical. The appropriateness of these properties as indicators for incinerability will be discussed later in this section. Thermal decomposition experiments Thermolysis is the general term for chemical decomposition into at least two fragments by heat. Pyrolysis is the thermal decomposition (thermolysis) of organic materials at elevated temperatures in the absence of oxygen (vacuum) or in an inert atmosphere. Thermolysis and, specifically, pyrolytic reactions are an essential part of the combustion process. Thermolysis experiments are essential to understand combustion reaction pathways. They show the intermittent breakdown products and final combustion products that are formed. Thermal stability and incinerability can be studied by different thermolysis methods. Such studies can be conducted under inert or oxidative atmospheres without applying a flame, so-called non-flame studies. Other experiments can be done by applying combustion in a flame, so-called flame mode studies (Licis, 1984; Dellinger et al., 1986a). Depending on the experimental set-up, thermolysis experiments can provide an indication of thermal stability, reaction rate, possible side products being formed and possible combustion reaction pathways. Both types of non-flame study are useful in investigating the incinerability of chemicals, as both oxygen-rich and oxygen-starved situations can occur during incineration (Taylor and Dellinger, 1987; Licis, 1984; Dellinger et al., 1986a, 2010). Key to understanding the significance of upset conditions is that only a very small fraction of the total volume of the waste needs to experience these less-than-optimum conditions to result in unfavourable destruction efficiencies, and that the post-flame chemistry controls incineration emissions (Dellinger et al., 1986a). In various studies it was shown that pyrolytic methods generated better results than other methods in predicting the (relative) incinerability of chemicals. However, in a later study it was concluded that oxidation kinetics-based ranking of the incinerability of chemicals was slightly superior to the pyrolysis-based ranking (Dellinger et al., 1993). Furthermore, Yamada and Taylor (2003) state that emissions from incineration are controlled by the temperature in the post-flame zones Page 48 of 160 RIVM report 2021-0143 and the residence time. Molecules entering the flame zone can be assumed to be completely destroyed and the small fraction escaping the flame zone can be emitted from the facility. Thus, flame zone failure modes may cause residual constituents to be emitted. The most prominent of these modes are thermal quenching and fuel (waste)/air mixing failure. Poor heat transfer at incinerator surfaces and poor gas phase mixing will thus result in conditions where the rate of destruction is low and the formation of by-products also called products of incomplete combustion (PICs) is favoured. With respect to the relevancy of oxidising and non-oxidising gas-phase thermal stability experiments in determining the incinerability of chemicals, the combustion reactions between the fuel and the oxidizing agent should also be considered. Under non-inert atmospheres, chemicals react with oxidising agents usually oxygen. Abstraction by O or OH radicals dominates over addition reactions, as shown by the lack of oxygen-containing products even under oxidative conditions (Dellinger et al., 1986b). These abstraction reactions are relevant for hydrocarbons but not likely to be significant for halogen-containing compounds. It is most likely that for halogen-containing compounds such as PFASs decomposition appears through a unimolecular process (molecular bond breaking) followed by a reaction with radicals formed from the fuel (H) or with oxygen-containing radicals (Dixon, 2001; Dellinger et al., 2010). According to Dellinger et al., (2010) this means that halogen-containing substances such as halon and CFCs exhibit the same stability under both oxidative and pyrolytic conditions (Dellinger et al., 2010). In conclusion, the oxidising and non-oxidising gas-phase thermal stability methods appear to be equally relevant in determining the incinerability of chemicals. For the potential emission of combustion by-products, often referred to as products of incomplete combustion (PIC), the results of pyrolysis experiments under inert conditions are valuable, although the chemical stability of any PICs formed also has to be taken into account when considering the degree of mineralisation and the possibility of being formed at and emitted from the waste incineration process. Thermolysis experiments indicate at what temperature a chemical starts to decompose, The decomposition temperature provides a good indication of the potential destruction in waste incineration when comparing it with the minimum required and typical operation temperatures for the various waste incineration processes. If the kinetic parameters for the destruction reaction are also measured in these studies, the temperature and time needed to destroy a compound to a certain degree can also be derived (Licis, 1984; Tsang et al., 1998; Dellinger et al., 2010). Gas-phase thermal stability such as the temperature for 99% destruction at 2 seconds' residence time may be used to predict relative incinerability. Thermal stability rankings based on laboratory experiments were published in early nineties (Taylor et al., 1990; Dellinger et al., 1993) for a number of chemicals. However, since then, to our knowledge, such information for other chemicals has not become available. Page 49 of 160 RIVM report 2021-0143 Other combustion related properties If such data are not available, other data could possibly be used for an indication of the thermal stability and incinerability of a chemical. Several properties have been proposed thus far for ranking the relative incinerability of hazardous organic compounds, such as the heat of combustion, the autoignition temperature of the pure compound, flame destruction efficiencies and the previously mentioned thermal decomposition experiments (Licis, 1984; Dellinger et al., 1986a). The heat of combustion and the autoignition temperature are most relevant for destruction efficiencies achieved in the flame zone of an incinerator. As compounds can be assumed to be completely destroyed in the flame zone and relevant emissions appear to be generated in the postflame/combustion stage, these parameters can be considered less relevant in relation to the overall incinerability according to Taylor and Dellinger (1987). As mentioned earlier when comparing the results of various experimental methods for ranking the relative incinerability of chemicals, thermal decomposition results provide the most consistent results. The autoignition temperature is the temperature at which an air-vapour mixture spontaneously ignites without an external source in the presence of air and begins to self-heat at a sufficient rate to produce combustion. The autoignition temperature is actually the temperature required to supply the activation energy needed for combustion. The flash point is the lowest temperature at which there will be enough flammable vapour to induce ignition when an ignition source is applied. Therefore, there is a strong relationship with the vapour pressure. Furthermore, a prerequisite in estimating the flash point is that the chemical compound is flammable. Even if sufficient vapour is generated, a non-flammable compound will not ignite. Therefore, the flash point is thought not to be a good indicator for combustibility or thermal stability. The autoignition temperature, on the other hand, is thought to provide a better indication, although autoignition temperature is considered less relevant with regard to overall incinerability in terms of the rate of destruction (see previous paragraph). Other information that can be used to better understand the thermal stability of substances are the bond dissociation energies of the different bonds between atoms in a molecule. In the combustion process, chemical compounds usually start to decompose at a specific temperature and then react with, for instance, oxygen. Decomposition reactions usually occur by bond scission and continue via a radical chain mechanism. Different bonds have different strengths and thus different dependencies on the temperature, the weakest bond breaking at the lowest temperature (Dixon, 2001). At sufficiently high temperatures several bonds will be broken and a broad range of radicals can be formed. Data on the properties discussed in this section will be presented in the next section. Page 50 of 160 RIVM report 2021-0143 4.3 Thermal degradation of PFASs Experimental studies on the thermal stability of PFASs The thermal degradation of PFASs has been investigated in several studies. Dixon (2001) described the potential degradation pathways for fluorochemicals in the incineration process. The focus of that study was on perfluoroalkyl sulphonates and perfluoroalkyl sulphonamides. Dixon (2001) showed that the carbon-sulphur (C-S) bond is the bond most likely to break first, the carbon-carbon (C-C) and carbon-fluor bonds having higher bond energies in the perfluoro chain of PFASs considered. The decomposition mechanism describe by Dixon (2001) is that, if a C-C or a C-S bond breaks, an oxygen molecule will react with the radical, leading to the formation of carbonyl fluoride and a perfluoroalkyl radical that is one carbon shorter. The chain decomposition will continue until finally a CF3 radical is formed, which reacts with oxygen to finally form HF and carbonyl fluoride (COF2) when abstracting a hydrogen atom from the hydrocarbon fuel. The main products formed from the decomposition of the fluorocarbon chain are therefore COF2 and HF. COF2 is an unstable substance that will react with water and decompose to CO2 and HF (Farlow et al., 1960; Francisco, 1993). RF-CF2SO2OH RF-CF2 + SO2OH RF-CF2 + O2 RF-CF2OO RF-CF2O + O RF-CF2O RF + COF2 CF3 + O2 CF3OO CF3O + O CF3O + H CF3OH COF2 + HF COF2 + H2O CO2 + HF According to Dixon (2001) there is a concern regarding the formation of by-products such as CF4 and C2F6. Fluorinated by-products may be formed from the range of radicals formed, that can be re-joined to newly formed fluorocarbons before complete combustion occurs. As stated by Dixon (2001), this is not a temperature issue but rather a matter of mixing and temperature distribution in the incinerator, as this influences the residence time at sufficiently high temperatures. Yamada and Taylor (2003) investigated the thermal degradation of PFOS and two perfluoroalkyl sulphonamides in a laboratory-scale simulation of a full-scale hazardous waste incinerator. The conditions were chosen to be representative of a full-scale incineration installation. In batchcharged continuous flow reactors, the organic materials are thermally stressed through combustion using methane as a fuel under controlled time, temperature and excess air level. The exit gas stream is analysed by GC-MS. Combustion tests were performed at 600 and 900 C. Based on measurements of the reactor effluent, a high level of conversion of PFOS was observed from the incineration tests, which was concluded from the fact that PFOS was not detected in quantifiable amounts (DL 10 ng.mL-1) at both temperatures. The authors concluded that the findings Page 51 of 160 RIVM report 2021-0143 suggest that the C-S bond was completely destroyed. Furthermore, it was shown that PFOS was already thermally converted at a temperature of 450 C and a high degree of degradation of PFOS and sulphonamides (PFASAs) is established at a temperature of 600 C. Fluorinated organic intermediates were observed in the reactor effluent, such as fluorobenzene C1 and C2 fluoroalkanes with likely products being CHF3, CF4 and C2F6. For C2F6, the concentration at 900 C was much lower than at a combustion test temperature of 600 C. Small amounts of 1,1-difluoroethene and 1,2-difluoroethene (C2H2F2) were also observed at 600 C. Higher molecular weight fluorinated polycyclic aromatic hydrocarbons were not detected (Yamada and Taylor, 2003). It can thus be concluded that mainly short-chained saturated and unsaturated perfluorinated carbons are formed. Yamada and Taylor (2003) also concluded that incineration of PFOS and C8-perfluorosulphonamides is not likely to be a significant source of PFOS at incineration and that, with the exception of stable C1 and C2 fluorocarbons such as CF4 and C2F6, fluorinated organic by-products are unlikely to be emitted from waste incineration facilities during the combustion of these substances. In a paper by Vecitis et al. (2009) it was stated that the required decomposition temperatures of perfluorinated sulphonate salts are 100 to 200 C higher than for the corresponding carboxylate salt. In the same paper it was mentioned that results from gas-phase NMR studies showed that for various PFOA salts the temperature at which more than 99% of the chemical is destroyed is in the range 300-350 C. This temperature is lower than that reported by Stockenhuber et al. (2019), which showed that PFOA started to degrade at temperatures above 450 C under an inert nitrogen atmosphere. The information provided by Vecitis et al. (2009) suggests a degradation temperature for PFSAs of about 450 C, which is in line with the findings of Wang F. et al. (2015), which reported that degradation of PFOS and PFHxS starts at around 450 C. Wang F. et al. (2015) also showed that the decomposition temperature of PFOA was around 100 C, suggesting that PFOA underwent a self-decomposition mechanism, losing the carboxyl functional group under the formation of HF and leaving the fluorinated chain mainly intact. Furthermore, the experimental data from Wang F. et al. (2015) show that the decomposition temperature of FOSA was 150 C and the data suggest that PFOS underwent a self-decomposition mechanism, while FOSA underwent a combustion mechanism, during the thermal treatment. The thermal stability and decomposition mechanisms of seven perfluoroalkyl carboxylic acids, three perflouroalkyl sulphonic acids and one perfluoroalkyl ether carboxylic acid on spent granular activated carbon (GAC) was studied by Xiao et al. (2020) under different atmospheres. The decomposition of the PFCAs started at a temperature of 200 C and PFECAs (such as HFPDO -DA) were even more readily decomposed at the same chain length. PFASs such as PFOS required a higher temperature of 450 C. According to Xiao et al. (2020), this indicates that a perfluoro compound becomes less stable with the inclusion of an ether group. For the PFASs investigated, near complete Page 52 of 160 RIVM report 2021-0143 decomposition (>99.9%) and high mineralisation rates occurred at a temperature of 700 C or higher. On the basis of their data, the authors concluded that effective thermal destruction of PFASs during incineration or combustion is very likely. Volatile organofluorine species were the main decomposition products at temperatures below 600 C. The results of Xiao et al. (2020) show that the carboxylic acid group of PFCAs is less thermally stable than the sulphonate group in PFOS, which is in line with the findings reported by Vecitis et al. (2009). Furthermore, Xiao et al. (2020) found that thermal decomposition decreased with increasing perfluoroalkyl chain length. According to the proposed degradation mechanism for PFOA, the following volatile products are formed: unsaturated compounds like CF2, C2F4 and radicals like CHF2, CF3, C3F3 and fluorine atoms. As indicated by Dixon (2001) and Yamada and Taylor (2003), these compounds are not expected to be formed under normal combustion conditions in the presence of air and moisture though. Radicals will possibly recombine to form fluorinated hydrocarbon compounds or react with oxygen. Unsaturated compounds such as those mentioned above are not expected to occur at temperatures of >600 C (Yamada and Taylor, 2003). Yamada et al. (2005) investigated the thermal decomposition of a telomer alcohol at 200 and 600 C. The experiments showed that decomposition of the telomer alcohol functionality occurred at 200 C. As part of a study on the fate of HFPO-DA (GenX) during the incineration of sewage sludge, Intertek Polychemlab (2018) investigated the thermal stability of HFPO-DA using both flash thermogravimetric analysis (TGA) under oxygen atmosphere and pyrolysis GC-MS (Helium atmosphere). The flash experiments indicated that initial degradation occurred between 323 and 353 C. Analysis of the breakdown products formed showed the molecule breaks down in two major components and most likely breaks at the ether bond while the carboxyl group remains intact. The pyrolysis GC-MS experiments under inert conditions show that at 800 C, besides CO2 and hydrogen fluoride, a multitude of perfluoro radicals (CF3, C2F3, C3F5, etc.) and several fluorinated products such as hexafluoropropylene, tetrafluoroethene and perfluoro-1-butene are formed. At this temperature, HFPO-DA molecule was not detected and was therefore assumed to be fully degraded. The findings from the experiments performed by Intertek Polychemlab (2018) are in line with the findings reported by Xiao et al. (2020). Fully fluorinated perfluoroalkyl (PFC) compounds are the most stable of PFASs and require a high temperature for a high degree of thermal destruction. CF4 is the most thermally stable compound composed of carbon and fluorine. The temperature at which 99.99% of the substance degrades in 1 second 1440 C for CF4 and 961 C for the two-carbon PFC (C2F6). The 99% degradation rate temperatures in 2 seconds are 1380 C and 930 C, respectively (Tsang et al., 1998). However, thermal degradation starts at a lower temperature of about 1100 C for CF4 and 750 C for C2F6. Based on the above information, the following order of thermal stability, in terms of the approximate temperatures at which the compounds start to decompose, can be derived for individuals PFASs: Page 53 of 160 RIVM report 2021-0143 CF4 > C2F6 > PFOS > PFOA HFPO-DA > FOSA In more general terms, in line with Xiao et al. (2020) and the findings of Wang F. et al. (2015), the order of thermal stability for the groups of PFASs is: PFCs> PFSAs > PFCAs > PFECAs > FTOHs > PFASAs Bond dissociation energy as a relative measure of thermal stability As described in the previous section, theoretical and experimental studies on the thermal stability of PFASs have been done for only a limited set of PFAS groups. There is a vast number of different types of PFASs in use, as discussed in Chapter 2, that have not yet been investigated. Following the degradation mechanism proposed by Dixon (2001), the thermal stability of PFASs is to a great extent determined by the bond dissociation energy (BDE) of the bond between the carbon of the perfluoro chain and the relevant atom of the functional group. Dixon (2001) showed, on the basis of structure calculations, that, in the sulphonate group containing PFASs he investigated, the C-S bond has a BDE of 64 kcalmol-1. The bond between the fluorinated carbon directly attached to the sulphonate group and the remaining perfluoroalkyl chain fragment CnF2n+1-CF2SO2OH was calculated to have a BDE of 85 kcalmol-1. The average bond energies of C-C bonds in the perfluoroalkyl chain located further from the functional group are likely to be in the order of 95 kcalmol-1 and the bond energy of the C-F bond in the perfluoroalkyl chain is about 120 kcalmol-1. Based on these bond energies, the C-S bond is the bond most likely to break (Dixon, 2001). For the sulphonamido structures (CF3SO2NH2 and CF3SO2NHCH3) investigated by Dixon (2001), the calculated S-N bond energy for both the alkyl-substituted nitrogen (78 kcalmol-1) and unsubstituted nitrogen (79 kcalmol-1) and the C-N bond (94 kcalmol-1) are higher; thus, these bonds are thus stronger than the C-S bond (68 kcalmol-1) which is most likely to break first in the sulphonamido structures.Dixon (2001) concluded on the basis of bond energy calculations that temperatures in incinerators are high enough (about 1000 C) for most decomposition processes readily to take place. Following the line of reasoning presented by Dixon (2001), BDEs for the bond between the fluorinated chain and the terminal functional group can be used to assess the thermal stability of other PFASs. This is true if the bond breaking mechanism is homolysis, the breaking of a bond yielding two free radicals. Taylor and Dellinger (1987) applied the same reasoning in their analysis of the thermal stability ranking of a range of chemicals. However, they also indicated that other reaction pathways may exist that result in lower (and sometimes higher) energies than those that are required to break the bond with the lowest BDE. If the different compounds are ranked according to their BDEs and the degradation temperatures are added for those substances for which it is known that the mechanism is homolysis, the BDEs could be used to check whether a certain temperature is high enough to break the bond between the perfluoro chain and a functional group. Page 54 of 160 RIVM report 2021-0143 In addition to the data on the BDEs and degradation temperatures for the PFASs previously presented, Table 5 contains two additional fluorine-containing chemicals (CF2CL2 and CCl4), with homolysis as the reaction mechanism including their BDE and the temperature to establish 99% degradation at 2 seconds residence time (T99,2). The degradation temperatures for PFOA and PFOS are also included in Table 5. It should be stressed however it is unclear to which extent these temperatures relate to homolytic bond breaking. Table 5 Homolytic bond dissociation energies for fluorinated compounds Bond BDE (kcalmol-1) Reference Tdeg start* Tdeg 99^ CF3-F 131 1 1100 1380 CF3-OH 115 1 CF3-H 106 1 CF3-CF3 99 1 750 930 CF3-COOH 89 1 FCl2C-F 80 2 790 C8F17-C(O)OH ~79 & 200 ~350 CF3-SO2NHCH3 78 4 CF3-SO2OH; 72.8; 3 C2F5-SO2OH 70.7 Cl3C-Cl 71 2 670 CF3-SO2NH2 68 4 C8F17-SO2OH; 64 4 450 600 C3F7-SO2OH CF3-I 54 1 C4F9-I 49 1 1) Luo (2007); 2) Taylor and Dellinger (1987); 3) Khan et al. (2019); 4) Dixon (2001). * Tdeg,start is the temperature in C at which decomposition starts. Tdeg,99 is the temperature in C at which 99% of the substance is decomposed at 2 seconds residence time. & own assessment. For PFOA (C8F17COOH), the binding energy is estimated to be 10 kcal lower than that for perfluoroacetic acid. This follows from the trend that the binding energy is strongest in the case of a single carbon atom (CF3) `fluorinated chain' and that the bond is weaker when one fluorine atom is replaced by another CF3 group or a longer perfluorinated chain CF3(CF2)n. This can induce a lower bonding energy of 5-10 kcalmol-1. This trend can be derived, for instance, from the available data for the different sulphonic acids provided by Dixon (2001). Looking at the BDEs presented in Table 5, it is interesting to note that the bond strength between the perfluorinated chain and the carboxylate group is higher than that of the sulphonate group, which seems not to be in line with the data reported by Vecitis et al. (2009) and Xiao et al. (2020). Based on their findings it can be concluded that the carboxyl group is less stable than the sulphonate group. The data in Table 5 also show that the BDE associated with 99% decomposition at the minimum residence time required (2 seconds) and a temperature of 850 C, should be somewhere between 99 kcalmol-1 and 80 kcalmol-1, most probably around 90 kcalmol-1. From this we could make the generalisation that, for PFASs with a bond strength Page 55 of 160 RIVM report 2021-0143 between the perfluorinated chain and the functional group of less than roughly 90 kcalmol-1, 99% decomposition would be achieved at 850 C and 2 seconds residence time. Furthermore, the data on incineration temperatures presented in Chapter 3 show that in many facilities the average temperature for grate-fired furnaces in the Netherlands is above the minimum required and around Tdeg,99 for the second-most recalcitrant PFAS. Unfortunately, for other groups of PFASs the required BDEs are not available. However, it is likely that for many PFASs, BDEs will be lower than the BDE for the C-C bond in hexafluoroethane (99 kcalmol-1) and will be efficiently thermally degraded in grate-fire furnaces at average operating temperatures. In several studies, alternative mechanisms to the thermal decomposition by detachment of the terminal functional group via direct bond breaking have been elucidated for both PFOS (Khan et al., 2019) and PFOA (Krusic and Roe, 2004; Stockenhuber et al.; 2019 and Xiao et al., 2020). These studies revealed a rather similar mechanism for both PFSAs and PFCAs involving a transitional state and the release of HF and SO2 and CO2, respectively, in the removal of the functional group. The activation energies for the reactions of the two compounds are 58 kcal.mol-1 (Khan et al., 2019) and 27 kcal.mol-1 (Stockenhuber et al., 2019), respectively. This indicates that PFOA is less recalcitrant than PFOS, which is in line with the results from the experimental studies discussed. This clearly shows that other mechanisms might exist that result in lower temperatures being needed to start thermal decomposition. However, using bond-breaking energies for the terminal groups could still be helpful for PFASs, as these could serve as a kind of worst-case estimate. As stated before, the alternative decomposition mechanisms to direct bond breaking leave the perfluorinated chain nearly intact, producing different perfluoro compounds in the initial decomposition. Depending on the proposed mechanism, these could be 1-H-perfluoroheptane (Krusic and Roe, 2004) and perfluoroalkenes (Stockenhuber et al., 2019) for PFCAs and for PFSAs the initial decomposition products could be perfluoroalkylaldehydes (PFALs) and perfluoroalkenes (Khan et al., 2019). The decomposition proceeding from perfluorooctene-1 from the carboxyl and sulphonate elimination will follow the chain-shortening pathway and lead to the formation of CF2, CF3, C2F6, C2F4 and HF, among these the fluorocarbons compounds expected to transform into COx in the presence of oxidizing media except C2F6. Perfluoroalkyl aldehydes are known to rapidly hydrolyse to PFCAs (Khan et al., 2019). In addition, Wang F. et al. (2015) suggested that PFOSA underwent a combustion mechanism at a relatively low temperature rather than a selfdecomposition mechanism and started to decompose at a much lower temperature than PFOS. Based on the bond energy, however, PFOSA would have been assessed to be thermally more stable than PFOS. The order of thermal stability based on the bond dissociation energies for direct bond breaking (of the terminal group) as presented amongst others by Dixon (2001), Luo (2007) and Khan et al. (2019) is as follows: Page 56 of 160 RIVM report 2021-0143 PFCs > PFCAs > N-alkyl FASAs > PFSAs> PFASAs > PFIs Flash point and autoignition temperature as indicators for incinerability The flashpoint and the autoignition temperature of a chemical could provide information on the thermal stability of a chemical. Not all of these are equally relevant indicators for incinerability, as previously discussed in section 4.2.3. In their assessment of the degree of degradation on waste incineration, Houben and Boerleider (2020) collected information on the flashpoint of several PFASs. The data they collected on flashpoints was retrieved from the CompTox Chemicals Dashboard (US EPA, 2020). In addition to experimental information the database also provides predicted values for the flammability based on similar chemicals (consensus method). Although not all the details of the prediction method are known, it seems as if flammability is mainly or even completely based on the relationship between the rate of formation of vapour and the temperature, regardless of whether a chemical is flammable or not. As indicated in section 4.2, there is a strong relationship between the flash point and the vapour pressure, because the flash point is the temperature at which there is enough vapour to result in combustion when ignited. Results for the predicted flammability of perfluorocarbons provided in the Comptox database suggest that this relationship mainly affects the predictions. This is clearly shown by the predicted flash points for CF4 and C2F6, predicted to be 7 and -13 C, respectively. Perfluorocarbons, however, are thermally stable compounds (sections 4.3.1 and 4.3.2) and many perfluorocarbons are not flammable in air in any proportion (Kopylov, 2020; Wikipedia Contributors, 2021; Stacey et al., 1963), although some higher perfluorocarbons are flammable in pure oxygen. These predictions are therefore considered to be unreliable. Although PFASs are generally known for their low or non-flammability, this does not mean that all fluorine-containing organic chemicals are non-flammable. This is, for instance, not the case for fluorocarbons containing a significant amount of hydrogen or a double bond. For example, C2HF3 has an autoignition temperature in the range of 450-500 C and for C2F4 the autoignition temperature is 180 C (Stacey et al., 1963). The flashpoints and the autoignition temperatures of some familiar PFASs are presented in Table 6. Most of these data came from the ECHA database of REACH-registered substances (ECHA, 2021), but we did not extensively search the ECHA database, our focus was on the familiar PFCAs, PFSAs and FTOHs. For many of these well-known PFASs no information is available on flash point or autoignition temperature because, according to the registration dossiers, they are considered to be not flammable, these studies are not required according to the REACH and CLP regulation or the specific substances are not registered under REACH. Page 57 of 160 RIVM report 2021-0143 Table 6 Flammability characteristics of some PFASs Compound CAS Flashpoint (C) PFBS 6:2 FTOH 375-73-5 647-42-7 6:2 FTS PFHpA PFOSF PFAA 27619-97-2 375-85-9 307-35-7 2043-47-2 6:2 FTAC 17527-29-6 6:2 FTMAC 2144-53-8 HHTVOP 1644-11-7 Propion acid 85631-54-5 perfluoroalkyl ester Perfuoro methyl 756-13-8 pentanone ECHA: ECHA (2021); PubChem: PubChem. 177 > 200 Not flammable Not flammable > 113 > 100 Not flammable > 100 94.5 110 30 Not flammable 49 Autoignition point (C) 649 Reference ECHA ECHA ECHA Pubchem ECHA ECHA 360 ECHA 385 ECHA 650 ECHA ECHA 590 ECHA From the data in Table 6 it is clear that some PFASs are flammable and can autoignite at a certain temperature. The autoignition temperatures are well below the legally required incineration temperature of 850 C. 4.4 Thermal degradation of fluoropolymers In addition to the various perfluorinated compounds, fluorine-containing polymers and elastomers may be present in waste to be incinerated. A distinction must be made between fluoropolymers consisting of a fully or partially fluorinated backbone of carbon atoms and polymers with fluorinated side chains attached to a non-fluorinated carbon backbone, so-called side-chain fluorinated polymers (SFPs), see Chapter 2. The first category is generally used to manufacture articles or fibres, but may also be used as (micro)powder in emulsions or mixtures or to coat, for instance, kitchen ware. The SFPs are usually applied to treat textiles or paper in order to make them water- and grease-repellent. Decomposition temperatures Fluoropolymers such as polytetrafluoroethylene (PTFE) have the reputation of being thermally stable. Indeed, they are one of the most thermally stable plastics. However, they start to generate toxic air contaminants due to thermal decomposition at or just above their recommended processing temperatures (Huber et al., 2009). PTFE, also known as under the brand name Teflon, is a fully fluorinated polymer that is the most thermally stable of all fluoropolymers, including fluorine-containing polymers that are only partially fluoridated such as polyvinylidene fluoride (PVDF) and ethylene-tetrafluorethylene (ETFE), as shown by the results from the research by Giannetti (2005). According to this study, PTFE can be used for a long time at 260 C and for a short time up to a temperature of 450 C without loss of mass due to the formation of fluorine-containing gases. Significant mass loss does, however, occur at temperatures of >550 C. For the other polymers studied, degradation occurred at temperatures of 470 C for EFTE or Page 58 of 160 RIVM report 2021-0143 lower (Giannetti, 2005). As far as weight loss is concerned, the order of relative thermal resistance is: PTFE > PFA> MFA> FEP> ETFE > PVDF PE > ECTFE > PCTFE (Gianetti, 2001, 2005). For PFA, MFA and FEB significant weight loss occurred at temperatures between 550 and 520 C. In addition to Gianetti (2005), several other studies investigated the thermal stability of PTFE. Garcia et al. (2007) found that, in spite of its thermal stability, PTFE decomposition begins slowly at 260 C and noticeable decomposition occurs at temperatures above 400 C. According to Aleksandrov et al. (2019) thermal degradation of PTFE starts at about 500-550 C and is complete at a temperature of about 650 C;. Thermogravic analysis (TGA) performed by Aleksandrov et al. (2019) under a nitrogen and oxygen atmosphere resulted in estimated half-life times at 800 C well below 0.1 s, which would result in complete thermal destruction within 1 second. On the basis of this information, it is expected that PTFE will thermally degrade completely at a minimum required combustion temperature of 850 C (Aleksandrov et al., 2019). To show whether PTFE can be fully transformed into fluorine (F), a fluorine balance was generated including the formation of HF. No clear conclusions were drawn from the fluorine balance on the rate of conversion and mineralisation. It should be noted, however, that the TGA mainly provides insight into mass loss and gasification behaviour rather than the thermal decomposition profile including the formation of combustion by-products. It could be assumed that, for solid polymers like PFTFE, the polymer molecules are destroyed with the gasification of the polymer, but this does not provide information on the kind and degree of by-products formed and the rate of mineralisation. Besides the above-mentioned fluoropolymers with a fluorinated carbon backbone, there is the category of side chain fluorinated polymers. This category of polymers does not have a fully or partially fluorinated backbone but rather a hydrocarbon backbone with (fully) fluorinated side chains attached to it. Yamada et al. (2005) conducted a study on the non-flame thermal degradation of a side-chain fluorinated polymer, a fluorotelomer-based acrylate polymer. The thermal degradation of the fluorotelomer and polyester-treated textile fabric was conducted under conditions (85% excess air, average temperature 1000 C and residence time of 2 seconds). Gasification of the telomer-based polymer started around 100 C and was nearly complete at 600 C. The experiments showed that thermal decomposition of the telomer alcohol functional group occurred at 200 C and a variety of combustion by-products and fluorinated radicals were formed at 600 C. These included fluorobenzene and difluorobenzene, the CF3 radical and a compound containing the CF2CH=CH2 fragment. The amount of formed ions decreased with increasing temperature. The relative amount of the two major radicals formed was less than 0.1% at a temperature of 1000 C. At this temperature it was proven that 99.9% or more of the polymer had been mineralised. This temperature was slightly higher than that measured for other fluorotelomer-based materials in other studies, which may be related to the levels of excess air; previous tests employed considerably higher excess air levels, according to Yamada et al. (2005). Page 59 of 160 RIVM report 2021-0143 Formation of perfluorocarbons Many analyses have been performed of the fumes formed at thermal degradation of PTFE under inert atmospheres, in air or using steam, as summarised by Garcia et al. (2007). In air, carbonyl fluoride (COF2) was found and when using steam, the primary decomposition products were C2F4 and CF2 radicals. It was found that CF4 and CO2 can be formed by secondary reactions such as through the reaction of C2F4 with oxygen. C2F4 can react to generate C3F6 and C4F8 above 600 C under inert conditions. Garcia et al. (2007) themselves determined the compounds generated in the degradation of PTFE at high temperatures (750-1050 C), studying the influence of different atmospheres, going from pyrolysis to nearly total combustion conditions. In pyrolysis runs, only the perfluorocarbons C2F4 and C3F6 were found. Under oxidative conditions, C2F6, C3F6 and CF4 were detected, the shares varying as a function of temperature and oxygen proportion in the atmosphere. At a temperature of 850 C under inert conditions, C2F4 and C3F6 were formed and no other fluorocarbon compounds were detected. At increasing oxygen ratios, C2F4 and C3F6 began to disappear and decrease and fluorocarbons like C2F6 and CF4 began to appear. From this Garcia et al. (2007) concluded that it seems that the presence of oxygen in combination with high temperature favours the combustion reaction of pyrolytic products. This is in line with the considerations on the reaction mechanism by Dixon (2001). Garcia et al. (2007) mentioned a third combustion reaction where C2F6 reacts with oxygen to produce CF4 and CO2 and noted that this reaction seems to become more significant as the oxygen fuel ratio increases. They derived conversion factors for CF4 and C2F6 for different temperatures and oxygen/fuel ratios under fuel-rich conditions. Under typical incineration temperatures of 850-1050 C, between 12.5% and 60.9% of the mass of PTFE incinerated was converted into C2F6 and between 5.5% and 9.3% was converted into CF4. These figures indicate the large potential of the incineration of fluorinated polymers such as PTFE to contribute to emissions of the powerful greenhouse gases CF4 and C2F6. A literature survey on the emissions from incineration of fluoropolymer materials was conducted by Hubert et al. (2009), who listed the main decomposition products formed for a variety of fluoropolymers exposed at different temperatures. For waste incineration temperatures above 800 C are most relevant. Many of these experiments were done under an inert atmosphere, mostly nitrogen. They also considered the result obtained by Garcia et al. (2007) performing thermal degradation experiments using air. For the fluoropolymers considered, at temperatures above 800 C the main products formed under inert atmosphere are tetrafluoromethane (CF4) hexafluoroethane (C2F6, HFE), CHF3, trifluoroethylene (C2F3, TFE), hexfluoropropene (C3F6, HFP) and perfluoro isobutene (C4F8, PFIB). Formation of fluorinated dioxins and furans Although they do not fall under the definition of PFAS, we briefly discuss the possible formation of fluorinated dioxins and furans at waste incineration plants. Page 60 of 160 RIVM report 2021-0143 Huber et al. (2009) report that several fluoro-dioxins and fluorobenzofurans besides other fluorinated aromatic compounds were identified by Herzke (1998) on the thermolysis of PTFE. Weber and Hagenmaier (1997), however, showed that the formation of PFDDs and PFDFs in industrial processes by `de novo synthesis' does not occur. They explain that this is because the formation mechanism of PCDDs/PCDFs, where Cl2 leads to the formation of C-Cl bonds, is impossible for fluorine due to its redox potential. Although formation of the C-F bond from carbon and fluorine ions occurs at 900 C, dioxins are destroyed rather than formed at these temperatures. However, PFDDs/PFDFs can be formed from pre-dioxins such as fluorinated benzenes. The potential for formation of PFDDs/PFDFs at waste incineration thus depends on the formation of fluorinated pre-dioxins. Only in the study conducted by Yamada et al. (2005) on the non-flame thermal degradation of a side chain fluorinated polymer, fluorinated benzenes were found as products of incomplete combustion. Weber and Hagenmaier (1997) reported that in the burning of Teflon (PTFE) and Teflon-containing materials no formation of PFDDs or PFDFs could be detected, and the analysis of a number of fly ash samples from municipal waste incinerators revealed no PFDDs/PFDFs with detection limits of about of 0.01 ng.g-1 for individual compounds. Nakamura et al. (1999) report that PFDDs/PFDFs were not detected at a detection limit of 0.01 ng.Nm-3 in flue gas at thermal destruction of CFCs in municipal solid waste incinerators. Their results confirm the differences in the formation characteristics of PFDD/PFDFs compared with chlorinated compounds. Formation of trifluoroacetic acid In Huber et al. (2009) reference is made to the possible formation of trifluoroacetic acid (TFA) and chlorodifluoroacetic acid (CDFA) and C3C14 perfluorinated carboxylic acids (PFCAs) from fluoropolymer thermolysis at temperatures up to 500 C, as reported by Ellis et al. (2001). However, the formation of these decomposition products as reported by Ellis et al. (2001) relates to the formation during the regular use of the fluorinated polymers at moderate elevated temperatures in a variety of applications such as ovens, cookware, industrial and car engines, and heat exchangers. Ellis et al. (2001) themselves state that incineration processes differ from thermolysis in that a source of fuel is used to induce complete decomposition, which is therefore unlikely to yield TFA due to the high temperatures and oxidising conditions, which will result in the cleavage of most carbon-fluorine bonds. The findings from a study done by Ochi et al. (2008) are in line with those reported by Ellis et al. (2001). From the results of PTFE degradation at a temperature of 550 C in an oxygen-rich atmosphere, many perfluorinated compounds were confirmed from both volatile and less volatile fractions. HFP, HFE and perfluorocyclobutane (PFCB) were identified in volatile fractions including PFIB and several Freon gases. The generation of PFCAs such as PFOA was suspected in less volatile fractions. These results relate to situations where fluoropolymers are exposed to moderate elevated temperatures in air, comparable to the circumstances described in Ellis et al. (2001). These conditions are Page 61 of 160 RIVM report 2021-0143 different from those at incineration; therefore, the compounds formed cannot be considered representative of incineration of PTFE. Conclusion PTFE (Teflon) is the most stable fluorine-containing polymer. For PTFE it can be concluded that complete thermal decomposition is achieved at a temperature of about 800 C. It can therefore be assumed that other fluorine-containing polymers also thermally decompose completely at a temperature of 800 C. At thermal decomposition a variety of gaseous fluorine-containing products are formed. In order to determine the rate of mineralisation, supplementary information is needed on the amount and type of by- and end-products formed and their thermal degradation rates at waste incineration temperatures. To evaluate whether and to what extent fluoropolymers degrade on incineration, the temperature in the combustion bed on the grates of the incinerator should considered rather than the temperature in the combustion chamber. Fluoropolymers are solids that do not evaporate with rising temperatures but rather start to decompose into volatile fluorinated compounds that will undergo combustion and thermal degradation in the flame zone and at secondary combustion. Temperatures at the pyrolysis front and the combustion front in the waste-burning bed range from 900 to 1100 C (Mnard et al., 2006; Asthana et al., 2006), which is well above the temperature of 800 C at which the complete thermal decomposition of PTFE is achieved. During the combustion of PFASs and fluorine-containing polymers, various kinds of fluorine-containing combustion products can be formed. In addition to the aforementioned PFCs, these are in particular unsaturated PFCs (C2F4 and C3F6) and cyclic perfluorocarbon compounds, perfluoroisobutene (C4F8) and perfluorocyclobutane (C4F8). In general, it can be said that the higher the combustion temperature, the fewer byproducts are formed, the smaller the absolute quantities and the smaller their molecular mass. The unsaturated compounds are generally unstable and are not expected to be formed in substantial amounts during waste incineration compared with the saturated PFCs. 4.5 Thermal stability of potential by-products This section provides some information on the thermal stability of the fluorinated by-products that are most likely to be formed on the incineration of PFASs and fluorinated polymers. The thermal stability of most of these substances was not discussed in the previous paragraphs with the exception of the perfluoroalkanes. All of the fluorocarbon by-products are fully fluorinated compounds that contain only carbon and fluorine. Fluorocarbons include perfluoroalkanes, perfluoroalkenes, perfluoroalkynes and perfluoroaromatic compounds. Perfluoroalkanes Kopylov (2002) investigated the flammability of several saturated fluorocarbons in oxygen. He concluded that three of the saturated fluorocarbons (CF4, C2F6, C3F8) and CF3H are non-combustible in the Page 62 of 160 RIVM report 2021-0143 presence of oxygen. Kopylov (2002) found that this is in agreement with available literature data but also mentioned that C4F10 is able to combust in oxygen in contrast with other findings. Fully fluorinated compounds are rather resistant to high temperatures. As indicated in Section 4.3, Tsang et al. (1998) provide estimates of the temperatures needed to decompose 99.9% of a fluorocarbon in 1 second. For CF4 this is about 1440 C and for C2F6 about 930 C. Based on this information, incineration temperatures have to be well above 1000 C to decompose fully fluorinated compounds and prevent byproduct formation Perfluoroalkenes Unsaturated fluorocarbons are far more reactive than perfluoroalkanes and many are highly toxic by inhalation, showing acute as well as chronic toxicity (Timperley, 2000; Tsai, 2009). Perfluoroisobutane and hexafluorocyclobutene, for instance, causing acute lung damage with symptoms that are very similar to those caused by inhalation of phosgene (Timperley, 2004). The toxicity of fluorinated olefins is apparently proportional to their reactivity towards nucleophiles (Siegemund et al., 2016). C2F4 The main hazard associated with TFE is that of explosion, especially if oxygen is present. TFE reacts with oxygen at low temperatures to form an explosive oxide (Gozzo and Camaggi, 1966). Giannetti (2001) notes that TFE is thermodynamically unstable, breaking down into CF4 and C. The autoignition temperature of C2F4 is 180 C (Stacey et al., 1963). C3F6 Although C3F6 is a non-flammable gas (ECHA, 2021), it reacts readily with hydroxyl radicals (Acerbonia et al., 2001), the main degradation product being CF2O. In the combustion process large quantities of radicals are formed such as typical hydrocarbon radical pool and oxygen species (H, O, and OH). The reaction of hexafluoropropene with molecular oxygen was investigated. Measurements were conducted at a total pressure of 450 kPa and over the temperature range 190-220 C, giving three major products, viz. hexafluoropropene oxide, carbonyl fluoride, and trifluoroacetyl fluoride (Lokhat et al., 2012). Although the above information is not based on pyrolytic or combustion experiments, it shows the potential of C3F6 to react with oxygen and hydroxyl radicals. According to Moore and Drobny (2006) hexafluoropropylene is thermally stable up to 400-500 C and decomposes at about 600 C. In several studies on the thermal decomposition of tetrafluoroethylene it has been shown that at medium temperatures (550-700 C), perfluoropropene and perfluorobutene are produced, which are finally converted into perfluoroethane, nonvolatiles and a low yield of perfluoromethane at temperatures above 700 C (Matula, 1968; Atkinson and Trenwith, 1953; Atkinson and Atkinson, 1957). Perfluoroisobutene, C4F8 (PFIB) Perfluoroisobutene is highly reactive towards nucleophiles. It hydrolyses readily to give the relatively innocuous (CF3)2CHCO2H, which readily Page 63 of 160 RIVM report 2021-0143 decarboxylates to give hexafluoropropane (Timperley, 2000). At temperatures above 700 C perfluoroisobutene is shown to disproportionate, giving perfluoroethane and various non-volatile products by a first-order mechanism (Atkinson and Atkinson, 1957). Cyclic perfluorocarbons Perfluorocyclobutane is indicated to be a non-reactive gas under normal atmospheric conditions. According to the REACH registration dossier, the compound is considered to be a non-flammable gas (ECHA, 2021). Perfluorocyclobutane undergoes a reversible decomposition to tetrafluoroehtylene and hexafluoropropene in the temperature range 360-560 C. The formation of C2F4 is enhanced by traces of oxygen (Butler, 1962). General findings on the formation of fluorinated by-products Short-chain fluorinated products are mainly formed under pyrolytic oxygen-starved conditions. With the exception of perfluoroalkanes, most of them seem to be thermally - and some of them chemically - unstable. At normal incineration temperatures and levels of excess air it is unlikely that these compounds will be formed in substantial quantities as incineration by-products. Only in unfavourable conditions in the postflame zone with low-temperature pockets and low oxygen levels these incineration by-products can be formed. As indicated in Section 4.3, according to Dixon (2001) and Yamada and Taylor (2003), fully fluorinated unsaturated compounds and radicals are not expected to be formed under normal combustion conditions in the presence of oxygen and moisture. Radicals may recombine to form fully fluorinated hydrocarbon compounds or react with oxygen. Unsaturated compounds such as those mentioned above are not expected to occur at temperatures of >600 C (Yamada and Taylor, 2003). Garcia et al. (2007) also concluded that the presence of oxygen in combination with high temperature favours the combustion reaction of pyrolytic products. 4.6 Conclusions A literature search was conducted on the thermal stability of PFASs and fluorine-containing polymers and the formation of fluorine-containing combustion products. From the literature studied, it can be concluded that at the minimum combustion temperature of 850 C required by Directive 2010/75/EU for municipal waste incinerators, the studied PFASs thermally degrade. Thermal degradation usually starts at relatively low temperatures and a high degree of degradation is achieved at 600 C, which is well below the minimum required combustion temperature. An exception to this is fully fluorinated saturated short-chain PFCs, which are thermally very stable. Considering their use, it is unlikely that saturated short-chain PFCs will occur in the waste that is to be incinerated. However, they can be formed as by-products during the combustion of PFASs. For a high degree of thermal degradation, temperatures higher than the minimum required temperature are required. This certainly applies to the most stable compound perfluoromethane (CF4), for which a temperature of Page 64 of 160 RIVM report 2021-0143 approximately 1400 C is needed. For C2F6 this is about 950 C, which is close to the typical combustion temperatures. On the basis of experimental thermal degradation data and bond dissociation energies (BDEs) of the functional groups attached to the perfluorinated chain that were found in the literature study, PFASs were ranked according to their thermal stability. The ranking of PFASs based on the BDE between the functional group and the perfluorinated chain shows to be a worst-case approach, since different decomposition mechanisms requiring lower energies have been identified. Based on the BDEs for the direct bond breaking of terminal groups, PFASs can be ranked as follows: PFCs > PFCAs > N-alkyl FASAs > PFSAs > PFASAs > PFIs Based on experimental data PFASs can be ranked according to their thermal stability as follows : PFCs> PFSAs > PFCAs > PFECAs > FTOHs > PFASAs The experimental data show that, with the exception of PFCs, decomposition temperatures are far below the minimum required incineration temperature for non-hazardous waste incinerators. Additional information on autoignition temperatures for some PFASs shows that they are all below the minimum required incineration temperature of 850 C for municipal solid waste incinerators. Polytetrafluoroethylene (PTFE or Teflon) is the most stable fluorinecontaining polymer. For PTFE it can be concluded that complete thermal decomposition is achieved at a temperature of about 800 C. It can therefore be assumed that other fluorine-containing polymers also thermally decompose completely at a temperature of 850 C. To evaluate whether and to what extent fluoropolymers degrade on incineration, the temperature in the combustion bed on the grates of the incinerator should be considered rather than the temperature in the combustion chamber. Temperatures at the pyrolysis front and the combustion front in the waste-burning bed range from 900 to 1100 C, which is well above the temperature of 800 C at which the complete thermal decomposition of PTFE is achieved. During the combustion of PFASs and fluorine-containing polymers, various kinds of fluorine-containing combustion products can be formed. In addition to the aforementioned PFCs, these are in particular unsaturated PFCs (C2F4 and C3F6) and cyclic perfluorocarbon compounds, perfluoroisobutene (C4F8) and perfluorocyclobutane (C4F8). In general, it can be said that the higher the combustion temperature, the fewer byproducts are formed, the smaller the absolute quantities and the smaller their molecular mass. The unsaturated compounds are generally unstable and are not expected to be formed in substantial amounts during waste incineration compared with the saturated PFCs. Page 65 of 160 RIVM report 2021-0143 Other fluorine-containing combustion products such as fluorinecontaining dioxins and furans, and perfluoroacetic acid have also been mentioned as possible combustion products. Closer examination leads to the conclusion that incineration temperatures are unfavourable to the formation of these compounds. Fluorinated dioxins and furans can however be formed from precursors such as fluorobenzenes. In one study fluorobenzenes are reported to be formed. All in all, formation of fluorinated dioxins and furans is judged to be unlikely but cannot be completely ruled out. The literature search shows that a number of PFASs have already been extensively researched. However, much is still unclear about the different reaction mechanisms that lead to degradation and the formation of by-products. The amount of research in this area is increasing, but the picture is not yet complete. In addition, information on the thermal degradation of many types of PFASs is still lacking. Page 66 of 160 RIVM report 2021-0143 5 Emissions of PFASs from incineration plants This chapter deals with the question whether PFASs and their combustion products are captured effectively by the available flue gas cleaning techniques at waste incineration plants. It provides insight into the different physical and chemical PFAS properties to explain the expected behaviour of the PFASs and their combustion products. A theoretical assessment of the removal of PFAS from flue gas is made. This chapter also describes measurement methods to characterize the PFAS emission concentrations. The main question to be answered is whether the chemical analysis of fluoride is sufficiently accurate to detect the presence of PFASs in flue gases. Different techniques and methods of sampling and chemical analysis of flue gas are mentioned. Finally, the chapter covers the different emission pathways from a waste incineration plant. These include the emission of PFASs via flue gas and fly and bottom ashes, and their migration from the source through ambient air and leaching. 5.1 PFAS properties Introduction As indicated in Chapter 2, there are a large number of substances with a perfluoroalkyl moiety, which can be subdivided into a number of groups according to their chemical structure. There is a wide variety of physical and chemical properties among PFASs and their various subgroups. To assess the fate of PFASs in the flue gas treatment process and in the recovery of liquefied CO2 from incineration flue gases (see Chapter 6), information on the physical and chemical properties of the individual PFASs and their combustion by-products is required. For PFASs with a functional group that can be ionised, the pH of the washing solutions is an important factor in assessing the distribution. The degree of ionisation is determined by the acid dissociation constant (pKa) of the compound of concern. In addition to the pKa, the air-water distribution coefficient and the octanol-air distribution coefficient are also required in the assessment. These coefficients will be used in determining the extent to which substances are absorbed from the flue gases into the washing liquids and adsorbed by AC, respectively. The extent of adsorption of PFASs to AC and which properties are important in this respect is still subject to discussion. In this study, the octanol-air partition coefficient is used as an indicator to assess the degree of absorption by AC. Research shows that, in the assessment of possible binding to fly ash and AC, the melting and boiling point are also relevant properties, as will be discussed later in this chapter. Physical and chemical property information for a substantial number of well-known and commonly referenced PFASs has been collected or generated in several studies. Our assessment is based on the information from these data collections. In case essential information Page 67 of 160 RIVM report 2021-0143 was lacking, however, the data were completed with information from additional sources such as publicly available databases and other scientific publications. In addition, the physical and chemical properties of the fluorinated substances generated as by-products of incomplete combustion were needed because these were either not or only partly included in the various data collections consulted. Therefore, an additional literature search was conducted, the results of which are presented in Section 5.1.3. It should be stressed that the PFASs included in our study are obtained from publicly available information sources and cover only a fraction of all the commercially available PFASs known. No effort has been undertaken to review the data obtained from the sources mentioned below. The key properties in relation to the operational conditions for the different processes units will be discussed in Section 5.3. Information on physical and chemical properties The following collections of physical and chemical data on PFASs have been consulted in assessing the removal of PFASs in the flue gas treatment of waste incinerators and in the carbon recovery processes. Concawe (2016) provided a review of published literature on the environmental fate of PFASs, describing the main types of PFASs and their physical and chemical properties, including melting and boiling points, acid dissociation constants (pKa) and sorption coefficients. Another source of information that was consulted is a database composed by ITRC (2020) as part of a guidance document to support stakeholders wishing to gain a working knowledge of the current state of PFAS science and practice. The data cover melting and boiling points, organic carbon partition coefficients and pKa values. Additionally, data gathered and generated by Wang Z. et al. (2011) was consulted. Wang Z. et al. (2011) provided estimates of various physicochemical properties, including air-water portioning coefficients and pKa values, of 134 individual PFASs using a quantum-chemical model. The data provided by Wang Z. et al. (2011) lacked information on the pKa for various groups of PFASs such as FASAs, Me- and EtFASAs, FASEs and Me- and EtFASEs, FASAAs and the group of fluortelomer phosphate esters and fluortelomer sulphonates. pKa values for these groups were obtained from Field and Seow (2017), BarzenHanson et al. (2017), Gao et al. (2017), Wang Z. et al. (2014), Ahrens et al. (2012), Riddell et al. (2011), Rayne and Forest (2009a, 2009b, 2009c) and the 2018 Human Metabolome Database (Wishart et al., 2018). Physical and chemical properties for the perfluoroalkane sulphonamido acetic acids (FASAAs) have been generated from EPI Suite version 4.11 (US EPA, 2012). For FTCAs and FTUCAs no pKa values were found in literature. Not accounting for dissociation can be considered as a worst case when assessing the removal. In addition to the physical and chemical properties of the 134 PFASs provided by Wang Z. et al. (2011), Gomis et al. (2015) provided physicochemical properties of an additional 22 emerging and novel perand polyfluoroalkyl substances, some of which are used as alternatives Page 68 of 160 RIVM report 2021-0143 to PFOA, PFOS and 8:2 FTOH. Finally, the set of substances was completed with 6:2 fluortelomer acrylate and 6:2 fluortelomer methacrylate, for which most of the information was obtained from the registration dossiers (ECHA, 2020). pKa values for many PFAs have been published by Wang Z. et al. (2011), Gomis et al. (2015) and ITRC (2020). However, there was little information on the pKa values of some specific PFASs such as perfluoroalkyl phosphinic acids and the perfluoroalkyl phosphate esters. Additional information was found in literature and public internet sources for perfluoroalkyl mono phosphate esters. According to Riddell et al. (2011) and Jackson (2013), perfluoroalkyl monophosphate esters have pKa values of 3. Similar to Lee (2013) we applied read-across for the remaining phosphate-based PFASs using the information on pKa values for alkylphosphate esters (Kirby and Nome, 2015; Vipperla et al., 2017). From this information it is concluded that for these groups of PFASs the pKa is expected to be lower than 2. Overall, it can be concluded that for nearly all PFASs with acid functional groups (PFAAs), including phosphate-based PFASs, the pKa values are lower than 3, in some cases substantially lower. According to Ahrens et al. (2012) and Wang Z. et al. (2014), the estimated pKa for perfluorotelomer acrylates is about -5, as calculated by the SPARC tool. However, the SPARC pKa results for 6:2 FTMAC and 6:2 FTAC appear to have been misinterpreted. Acrylates do not contain an acid group and are weak bases. Most likely the pKa values represent those of the conjugated acid. This becomes clear when looking at the pKa values of some acrylates. For example, the pka of ethyl acrylate is -6.8 (HMDB, 2021). However, it is important to note that the reported pKa in HMDB (2021) is the strongest basic pKa. The strongest basic pKa is that of the protonated molecule. In our assessment we therefore assume that acrylates do not dissociate and are present only in the protonated form at very low pH values (50% at a pH of -6.8) and thus consider them as neutral compounds at positive pH values. For perfluoralkyl sulphonamides (PFASAs) additional estimated pKa values were provided in the papers by Rayne and Forest (2009b) and Ahrens et al. (2012). The reported values for individual compounds differ by about 3 units. This is due to the fact the branching of the perfluoroalkyl chain was expected to have substantial impacts on amide moiety acidity in these PFAS groups, although the results were not conclusive with respect to the branching effect and direction (Rayne and Forest, 2009b). As with the PFSAs and PFCAs, sulphonamides have also been historically produced by the electrochemical fluorination method, which leads to a potentially large, and presently undefined, suite of linear and branched congeners that could be present in the environment. In the light of the above information, in this study we used the pKa value of the linear congener, which has the lowest value. For other perfluoralkyl sulphonamides, such as the methyl- and ethylsubstituted and sulphonamido ethanols, the reported pKa values are higher, in the range 8-14. Estimated pKa values for the carboxylate groups of sulphonamidoacetates (PFASAAs) range from 3.86 to 4.04 (Rayne and Forest, 2009b). The HMDB 2018 (Wishart et al., 2018) gives Page 69 of 160 RIVM report 2021-0143 lower estimates, with pKa values of about 1 for EtFOSAA and MeFOSAA. As a worst case we used the higher pKa values in estimating the degree of ionisation. Not all categories of PFASs might be equally relevant for waste incineration. The set of substances taken from Wang Z. et al. (2011) also includes categories that do not have a commercial application. These categories are mostly substances that are formed during biotic and abiotic degradation in the environment. According to Buck et al. (2011), these include environmental transformation products such as: fluorotelomer aldehydes (FTAL) and unsaturated aldehydes (FTUAL); fluorotelomer carboxylic acids (FTCA) and unsaturated carboxylic acids (FTUCA); perfluoroalkane sulphinic acids (PFSIA); perfluoroalkyl aldehydes (PFAL); perfluoroalkane sulphonamido acetic acids (FASAA). It is expected that these substances are not present (or present only in small quantities) in waste to be incinerated. However, in the case of the combustion of (industrial) waste water treatment sludges, these conversion products may be more relevant. The outcome of the calculation for these PFAS categories is included in the report (see Appendixes V and VI). However, we did not consider them in the further analysis of our findings. Properties of perfluorinated products of incomplete combustion Wang Z. et al. (2011) included in their study information on four perfluoroalkanes with carbon chain lengths ranging from C4 to C10. The lighter perfluoroalkanes and alkenes that may be formed on incineration are not included in their study. In this section, the physical and chemical properties of perfluorinated products of incomplete combustion relevant to this study are presented. Fully fluorinated saturated substances, or perfluorocarbons, are known greenhouse gases with a high global warming potential that do not deplete the ozone layer. Perfluoroalkanes are gases up to C4. Nearly all other fluoroalkanes are liquids or solids (Siegemund et al., 2016; Wikipedia Contributors, 2021). CF4 is a vapour that is slightly soluble in water. CF4 is a greenhouse gas with a Global Warming Potential (GWP) of 6,630 (Myhre et al., 2013). It does not deplete the ozone layer (EEA, 2020). C2F6 has a GWP of 11,100 (Myhre et al., 2013). At ambient temperatures and atmospheric pressure C2F6 is a gas. An overview of the Henry's Law constants and log KOW values is presented in Table 7. The data are based on Mackay et al. (2006) and public information on substances registered under REACH (ECHA, 2020). For perfluoroisobutene the data comes from Chemspider (2021). Page 70 of 160 RIVM report 2021-0143 Table 7 Some environmental properties of perfluorocarbons: Henry's law constant, air-water distribution coefficient (KAW) and octanol-water partition coefficient (KOW). Compound Molecular Henry's Law Log KAW Log KOW formula constant (Pa.m3/mol) Tetrafluoromethane CF4 539,961 2.4 1.18 Hexafluoroethane C2F6 1,715,432 2.9 2.00 Perfluorocyclobutane C4F8 391,925 2.2 1.60* Tetrafluoroethene C2F4 61,981 1.4 1.21* Hexafluoropropene C3F6 349,397 2.2 1.95* Perfluoroisobutene C4F8 179,649^ 1.9 3.03^ Source: ^ Chemspider (2021) reports a Henry's Law constant of 1.773 atm.m3/mol at 25 C. * ECHA (2020); otherwise Mackay et al. (2006). As stated by Mackay et al. (2006), fate calculations show that, when released into the environment, virtually the total mass of volatile fluorinated alkanes and alkenes will partition to the atmospheric compartment. 5.2 Assessment of collection efficiency A qualitative assessment is made of the extent to which PFASs are removed from flue gas before it is emitted or further processed in the CO2 recovery installation. The assessment is based on the materials used in the flue gas cleaning process, the process conditions at the different stages of the cleaning process and the physical-chemical properties of the compounds. The physical-chemical properties are essential in this because they significantly determine how the substances behave under the specified process conditions. The most relevant parameters are the Henry's Law constant, the log KOW the boiling point and the melting point and the acid dissociation constant pKa. The effect of the process conditions and materials used on the removal of PFASs from incineration flue gas will be discussed for each step in the flue gas treatment process, starting with the binding to fly ash, followed by the removal of acid compounds and ending with the removal of trace organics by AC. Binding to fly ash In assessing the adsorption and binding of PFASs to waste incineration fly ash, the chemical composition, as well as the physical form, of the fly ash is important. Adsorption to fly ash is determined by the total available surface area of the particles, which is in turn determined by the concentration of the particles in the gas stream, the specific surface area of the particles and the porosity of the particles. On the substance side, the degree of adsorption is correlated to the boiling point and the vapour pressure. With respect to physical adsorption, Ma et al. (2021) found that the removal by AC exhibited good linear relationships with the boiling point and saturated vapour pressure. They concluded that the boiling point was the key factor affecting the efficiency of the removal of volatile Page 71 of 160 RIVM report 2021-0143 organic chemicals (VOCs). For an explanation of this they referred to Zhang et al. (2017). Zhang et al. (2017) stated that the physical adsorption process of the chemical being adsorbed (adsorbate) on porous adsorbent is similar to vapour-liquid phase transitions, where the adsorbates with higher boiling points would be adsorbed in preference to those with a lower boiling point because of the stronger intermolecular forces. Additionally, liquid-like condensation plays an important role in VOC adsorption onto AC; thus, the boiling point of is a crucial factor in the adsorption process (Zhang et al., 2017). As well as physical adsorption, chemisorption plays a role, depending on the composition of the fly ash particles. Chemisorption involves the formation of chemical bonds between the adsorbate and adsorbent. Here especially, the chemical groups at the surface of the adsorbent are important, as they can form chemical bonds with certain functional groups of the chemical compounds to be adsorbed. This is, for instance, the case for silica and alumina, which are known as polar adsorbents, as they have a high surface polarity. This surface polarity corresponds to affinity with polar substances such as water, alcohols and carboxylic acids. Besides silica (gel) and (porous) alumina, other examples of polar adsorbents are zeolites and silica-alumina (Filho and Do Carmo, 2004). This affinity is also illustrated by the experimental results reported in a paper by Arp et al. (2006). The results show that non-polar perfluorinated compounds bind less to activated alumina, quartz and calcium carbonate than polar perfluorinated compounds. For the nonpolar compounds the binding differentiates little between the substrates, while for the polar compounds the highest binding is achieved by calcium carbonate. With respect to the composition of fly ash, fly ash from waste incinerators contains a high share of soluble salts, in contrast to fly ash from coal combustion, which contains a higher share of minerals such as silica and alumina. Fly ash also contains carbon. As regards its form, fly ash from waste incinerators usually consists of particles with a variety of forms, while fly ash particles from coal combustion are generally spherical and often glass-like with the carbon fraction encapsulated. Based in the limited content of minerals in fly ash, physical adsorption is expected to prevail. On the other hand, polar perfluorinated substances show an equal or slightly higher affinity with carbonate salts like calcium carbonate; thus, chemisorption could also play a significant role in adsorption to fly ash. Because of the good linear relationship with the boiling point and the physical adsorption process, chemicals with higher boiling points will be adsorbed in preference to those with a lower boiling point. To provide a first indication of the degree of adsorption of the various PFASs to fly ash, the boiling points of PFASs in relation to the temperature of the flue gas are discussed next. The temperature of the flue gas that exits the steam boilers is about 200-230 C. As mention in Section 3.3, typical operating temperatures for electrostatic precipitators are 160-260 C. Fabric filters used in large-scale waste incineration plants are operated at temperatures ranging from 170 to 200 C. Page 72 of 160 RIVM report 2021-0143 At these operating temperatures most of PFASs are liquids or gases. Only within some of the PFAS categories the molecules with long perfluoro chains have melting points well above these temperatures. In particular, sulphur-containing PFASs such as perfluorosulphonic acids and phosphorous containing PFASs, even those with shorter perfluorinated chains, have relatively high boiling points, well above 200 C. The more volatile PFASs with boiling points below the temperature in the dust filters, exist in the vapour phase. PFOA for instance has a boiling temperature of 188-192 C and exists in the vapour phase at a temperature of 200C. The same holds for PFCAs with a shorter perfluoro chain. PFCAs with longer perfluorinated chain have boiling points above 218 C. To conclude, PFASs that are in liquid or solid form at typical process temperatures are expected to be most strongly adhered to fly ash particles. For PFASs that are liquid and near their boiling point the binding to fly ash particles is less and it is more likely that they will pass to the next flue gas cleaning stage. The adsorption of a chemical to aerosols in the atmosphere can be calculated using the Junge-equation (Pankow, 1987) The Junge-equation is based solely on the saturated vapour pressure. The Junge-equation is in line with the findings presented by Zhang et al. (2017) and Ma et al. (2021) with respect to the physical adsorption to particles in air or a gas stream. As a measure of the adsorption of PFASs to fly ash we use the Jungeequation (Pankow, 1987) because the same physical principles hold for both aerosols and fly ash. The Junge-equation assumes that partitioning involves mainly physical adsorption, thus not explicitly including chemical adsorption. When the adsorption of reactive chemicals by chemisorption or electrostatic attraction onto mineral surfaces would make a significant contribution to the adsorption, then the adsorption calculated according to the Junge-equation is likely to underpredict the actual adsorption. Although the mineral content of fly ash is limited, by neglecting chemical sorption to minerals with a high surface polarity, the actual adsorption of polar chemicals to fly ash is most likely higher than the Junge-equation will predict. The fraction associated with aerosols according to the Junge-equation is calculated as follows: = + In which: fraction associated with aerosols (-) aerosol surface area (m2.m-3) PL (sub-cooled) liquid phase saturated vapour pressure (Pa) c constant (Pa.m). Page 73 of 160 RIVM report 2021-0143 According to Takaoka et al. (2016) fly ash concentrations range from 1.4 to 3.4 g.m-3. Based on that range we use a typical concentration of 2 g of fly ash per cubic metre of flue gas. Kao et al. (2000) reported that the specific area of fly ash is in the range 5-42 m2.m-3. In our calculations, a value of 20 m2.m-3 is applied. For the constant in the Junge-equation, a value of 0.002 atm.cm is used, which is a relatively high value applicable to polycyclic aromatic hydrocarbons. The constant is substance-dependent; a value of 1.710-4 atm.cm is usually used for organic substances. For chlorinated organic chemicals like dieldrin and DDT the constant has a value of about 1.310-4 atm.cm (Noordijk and de Leeuw, 1991). Because of the elevated temperatures in the flue gas, the vapour pressure should be corrected using the enthalpy of evaporation. For several PFASs the heat of evaporation can be obtained from Zhang M. et al. (2020), their publication contains data on the heat of sublimation (Hsub) and the heat of fusion (Hfus). The difference between the heat of sublimation and the heat of fusion is the heat of evaporation, which is then used to calculate the vapour pressure of the substance at 200 C. Additionally, the heat of evaporation for perfluoroalkanes was obtained from Dias et al. (2005) and Tsai (2009). The vapour pressures at 25 C were taken from Wang Z. et al. (2011) except for perfluorodecaline (PFDF), where we used hte higher (measured) value of 910 Pa (Dias et al., 2005). Using the vapour pressure at 200 C in the Junge-equation shows that high molecular FTOHs and PFCAs with 10 or more carbon atoms could still significantly bind to fly ash at a temperature of 200 C (Table 8). For the non-polar perfluoroalkanes the vapour pressures are higher compared with the polar analogues, resulting in lower binding to fly ash. Table 8 Calculated fraction () of the selected PFASs bound to fly ash at a temperature of 200 C applying the Junge-equation Substance Hvap (kJ.mol-1) Hsub (kJ.mol-1) Hfus (kJ.mol-1) log PL (Pa)1 log PL, 200 C (Pa) 8:2 FTOH 73.6 85 11.4 0.56 5.6 10:2 FTOH 76.9 94.3 17.4 -0.26 5.0 PFHxA 51.4 68.5 17.1 2.66 6.1 PFHpA 59.9 77.9 18.0 2.2 6.3 PFOA1 64.7 88.9 24.2 1.73 6.1 PFNA 64.7 88.7 25.2 1.27 5.7 PFDA PFHxF PFOF PFDF 58.1 32.53 413 41.52 101.5 43.4 0.82 4.8 4.43 3.40 2.962 Hvap = heat of vaporisation; Hsub = heat of sublimation; Hfus = heat of fusion; PL = subcooled liquid vapour pressure. 1 Data from Wang Z. et al. (2011); 2 data from Dias et al., (2005); 3 data from Tsai (2009). (-) 2% 8% <1% <1% <1% 2% 12% <1% <1% 1% Removal of acid components In the first stage of the wet flue gas cleaning process, acid components such as HCl and HF are removed using water as a scrubbing agent. The operating temperature is below 80 C. The temperature is low in order Page 74 of 160 RIVM report 2021-0143 to protect the equipment. The pH of the scrubber water has a typical value of 1. Depending on the acid dissociation constant (pKa) of the chemical and the acidity (pH) of the solution, deprotonating PFASs such as PFCAs (perfluorocarboxylic acids) will dissociate to their anions in an aqueous solution. Ionised forms in aqueous solutions behave differently. For instance, the perfluorooctanoate anion is highly water-soluble and has negligible vapour pressure, whereas the neutral form of PFOA has very low water solubility and a sufficiently high vapour pressure to partition out of water into air (Buck et al., 2011). As a general rule, it can be assumed that the ionised fraction in the solution will not volatilise and therefore the air-water partition coefficient needs to be corrected (Schwarzenbach et al., 1993). PFASs with acid functional groups such as PFSAs and PFCAs are not the only ionising PFASs. Primary and secondary substituted amide protons of perfluoroalkyl sulphonamides (FASAs) and perfluoralkane sulphonamido ethanols (FASEs) are also acidic at near neutral pH values, n-FOSA having a pKa of between 6.2 and 6.5 (Rayne and Forest, 2009c; Buck et al., 2011). PFASs with a pKa lower than 1, such as many PFCAs and PFSAs, exist for more than 50% in the dissociated form at a pH of 1 in the scrubber solution. At the second washing stage, where SO2 is removed, alkaline agents are added to enhance the removal of SO2, the pH of the scrubbing solution being in the range 5-7. At these pH values, all the acid group containing PFASs with a pKa below 3 are expected to be fully (>99%) deprotonated. When the pKa is lower than 4, the fraction dissociated is at least 90%. As shown in Figure 3, a chemical with a pKa of 3 is 99% dissociated at a pH of 5 and 50% at a pH of 3. Only perfluoroalkane sulphonamides having a pKa of between 6 and 7 are 50-90% dissociated at a pH of 3 and only 10% at a pH of 5. Page 75 of 160 RIVM report 2021-0143 Dissociated fractoin 1,0 0,9 0,8 99% dissociated 0,7 0,6 50% dissociated pH range of the sulfurdioxide scrubber 0,5 0,4 50% dissociated 0,3 0,2 0,1 0,0 1 2 3 4 5 6 7 8 pH pKa = 6 pKa = 3 Figure 3 Fraction of the ionising substance dissociated in the SO2 scrubber as a function of the pH and the acid dissociation constant, pKa Most of the PFASs with acid functional groups are fully deprotonated in the SO2 scrubbing solution and therefore do not volatilise but remain dissolved in the scrubber solution once absorbed. Those PFASs can be more effectively removed at the washing stages. For PFASs with non-dissociating groups, the degree to which a substance tends to partition between the flue gas and the scrubber solution is determined only by the Henry's Law constant. The dimensionless form of the Henry's Law constant is the air-water partition coefficient (KAW). PFASs with non-dissociating, non-polar groups such PFIAs, FTIs and PFCs have relatively high KAW values (log KAW 2-5) and are likely to mainly remain in the gas phase and pass the flue gas washing stages. Non-dissociating PFASs with a monopolar group, such as FTOHs, have intermediate KAW values (log KAW -2-1). PFASs such as FASAs and FASEs also have acidic moieties and will be substantially ionised at environmental pH values (Rayne and Forest, 2009b). At lower pH values, however, these PFASs are only partly ionised, as mentioned above. These PFASs, with two polar functional groups have log KAW-values between -2 to -4, thus expected to remain in the scrubber solution once dissolved. It is interesting to note that within the same functional group, the KAW increases with increasing perfluorinated chain length and that the introduction of a CH2 group between a bipolar functional group and the perfluorinated chain, as in the case of telomer compounds, decreases the KAW values (Wang Z. et al., 2011). Page 76 of 160 RIVM report 2021-0143 The potential removal of PFASs by the washing stages is qualitatively assessed from the absorption factor. The absorption factor indicates to what extent PFASs can be absorbed by the applied washing liquids. Key in this assessment are the pH of the solution, the ratio of the washing liquid flow rate to the flue gas flow rate, the G/L ratio, the pKa and the air-water partition coefficient. The air-water partition coefficient needs to be corrected for the fraction of the chemical that is ionised in the washing solution (Schwarzenbach et al., 1993): 1 = 1 + 10- = In which: non-dissociated fraction of the substance (-) pH acidity of the solution (-) pKa acid dissociation constant of the substance (-) KAW air-water partition coefficient (m3air.m3water) DAW air-water distribution coefficient (m3air.m3water). The absorption factor is calculated using the following equation: / = 1 - / + 1/ In which: Fabs the absorption factor (-) G/L flue gas to washing liquid flow rate (m3flue gas.m-3wash liquid) DAW air-water distribution coefficient (m3air.m3water). The volume-based G/L ratios and the pH values for the different washing stages are shown in Table 9. According to Wang Z. et al. (2015), the value of L/G usually ranges from 8 Lm-3 to 25 Lm-3 to ensure desulphurisation efficiency. These values correspond to G/L ratios of 125 and 40, respectively. In the calculations, a conservative value of 250 for the G/L ratio was used. For the quench, a G/L value of 1000, based on the data provided by Jordan (1987), was used. For the Venturi wash the G/L ratio was set equal to that of the quench. Table 9 Volume-based gas to liquid ratios (G/L) for the different washing stages in the flue gas treatment process Stage G/L ratio pH Range Quench SO2 trap Venturi 1000 250 1000 1 0.3-1 5 5-7 4 4-7 The results of the qualitative assessment of the removal of the different PFASs in the flue gas washings are presented in Appendix V. In the qualitative assessment the following gradations are used, which are indicated by colours in Appendix V: red refers to poor removal, orange to average, yellow to good and green to very good. For a more quantitative interpretation, indicative removal efficiencies are provided Page 77 of 160 RIVM report 2021-0143 here for the different classes: green >99%; yellow 90-99%; orange 90-75% and red <75%. These indicative values are an expert judgement based on the measured removal efficiencies achieved for well-known and studied flue gas components such as HCl, HF, SO2 and particulate matter (see Section 6.2). In conclusion, PFASs with non-dissociating, non-polar groups such as PFIAs, FTIs and PFCs, have high KAW values (log KAW 2-5) and are likely to remain mainly in the gas phase and pass through the different flue gas scrubbing stages. PFASs with polar functional groups, PFASs such as the FTOHs, FTMAC, PFPiAs, PFSAs, FASAs and FASEs, including the alkyl-substituted and the novel PFASs Novec 1230 and PFOTSi, also have the tendency to remain in the gas phase and are thus expected to be removed from the flue gas only to a limited extent. Removal of trace organics by activated carbon After the removal of acid pollutants in the preceding washing stages, AC adsorption is applied for the fine cleaning of flue gas. This can be done by leading the flue gas through a fixed bed adsorber or by injecting carbon powder into the gas flow, after which the carbon powder must be filtered out using, for instance, bag filters or cyclones. Different types of AC have different adsorption efficiencies for different types of pollutant. The adsorption efficiency is very much influenced by the AC manufacturing process. Like fly ash particles, the adsorption efficiency of AC is influenced by the particle size, the specific surface area, the pore volume, the pore size distribution and the chemical composition of the AC surfaces (Ma et al., 2021; Zhang et al., 2017). The removal efficiency is enhanced by a smaller AC particle size, longer AC residence time, and greater AC feeding rate (Ma et al., 2021). The adsorption efficiency generally decreases with increasing temperature. Adsorptive capacity often tends to increase with the gas phase concentration, molecular weight, diffusivity, polarity, and boiling point of the pollutant (Ma et al., 2021; Zhang et al., 2017). AC can adsorb a wide range of VOCs; however, there are some limitations. AC is less effective for compounds that are highly polar or volatile or have small diameters. As discussed in Section 5.2.1, removal efficiency exhibits good linear relationships with boiling point and saturated vapour pressure. Ma et al. (2021) concluded that boiling point was the key factor affecting the efficiency of the AC in removing VOCs. Thus, boiling point is a crucial factor in the adsorption process (Zhang et al., 2017). Rao et al. (2002) found that the order of adsorption efficiency from aqueous solution onto GAC for the investigated pharmaceuticals and personal care products correlated well with their log KOW values. Ridder (2012) found that hydrophobic partitioning was an important mechanism, which especially dominated the removal of relatively hydrophobic solutes. For more hydrophilic solutes, hydrogen bond formation between the solute and the AC surface strongly affected solute removal. Aromatic solutes showed slightly better adsorption than Page 78 of 160 RIVM report 2021-0143 aliphatic solutes, due to the potential to form pi-pi bonds with the basal planes of AC. This clearly shows that different types of bonding are relevant for different types of chemicals. Studies comparing the sorption of PFASs from aqueous solution to GAC and powder active carbon (PAC) have shown PAC to be a better sorbent of PFASs than GAC (Schedin, 2013). As mentioned in Concawe (2016), sorption of PFASs increases with increasing perfluorinated chain length, decreasing pH and increasing concentration of Ca2+. Furthermore, it was stated that PFAS sorption to GAC is lower than for organics with similar molecular weights, and other co-contaminants will compete for, and preferentially utilise, the adsorptive potential of the GAC media. Sorption velocity is faster for longer-chained PFAS and smaller-diameter GAC particles and, therefore, GAC that is optimised for the removal of one PFAS will not optimally remove other PFASs. From the above it is clear that a lot of factors influence the adsorption efficiency of AC. This makes it difficult to assess the removal of PFASs by AC. In this study we assume that adsorption to AC correlates with the solubility in octanol and that the saturated vapour pressure is also a key factor. The octanol-air partition coefficient (KOA) - is therefore thought to be a reasonable indicator for the removal of PFASs from flue gas by carbonaceous materials such as AC, lignite or coke. Ren et al. (2020) also indicated that the vapour/particle phase partitioning of organic chemicals in the atmospheric environment is usually described by octanol-air partition coefficients (KOA), which are inversely proportional to the saturated vapour pressure of organic chemicals. They explored the relationship between flue gas-to-fly ash partition coefficient (Kp) values of chlorinated aromatic congeners and their KOA values. The results were not fully conclusive, but they inferred that in the bag filter section, log Kp values of chlorinated aromatics were linearly correlated to their log KOA values. To assess the potential removal by AC, an adsorption factor is defined. The adsorption factor is calculated from the amount of AC added per cubic metre of flue gas and the octanol-air partition coefficient: = - + 1/ In which: Fads-AC DOSEAC KOA the activated carbon adsorption factor (-) dose of activated carbon to flue gas (m3AC.m-3flue gas) octanol-air partition coefficient (m3octanol.m3air). A dosing rate of 100 mg.m-3 is used (Cabot, 2016) and for the bulk density we took an average value of 400 kg.m-3 (Inaqua, 2021), leading to dosing of 2.510-4 m3AC.m-3flue gas. Using these values to calculate the adsorption factor it appears that substances with a log KOA value higher than 2 are significantly bound to Page 79 of 160 RIVM report 2021-0143 AC. Based on the octanol-air partition coefficients derived by Wang Z. et al. (2011), all of the 134 individual PFASs included in their study had calculated log KOA values of 2 or higher, the lower values applying to the smaller molecules. Only perfluoroaldehydes with a fluorinated chain of 4 and 5 carbons had a slightly smaller log KOA of 1.68 and 1.93, respectively, the perfluoroalkanes having the lowest log KOA values, 0.29 and 0.87 for C4F10 and C6F14, respectively. For the PFASs included in the study by Gomis et al. (2015) only Novec 1230, had a log KOA lower than 2; for all the other PFASs the log KOA is at least two orders of magnitude higher. The calculated adsorption factors are presented in Appendix V. From the calculations it is expected that the applied AC, coke or lignite has a strong potential to filter out most of the PFASs from flue gas. For those compounds that tend to pass through the scrubbing stages, it is expected that PFIAs, FTIs, PFCs, FTOHs, Novec 1230 and FTMACs are also not filtered out by treating the flue gas with AC, the smaller molecules with higher saturated vapour pressures having the lowest binding potential. Expected to be adsorbed to a low degree by AC are: FTOs, FTIs, PFIAs, PFCs, FTOHs < 6:2 FTOH, Novec 1230 and FTMACs. The adsorption factor only provides an indication of the potential binding to AC. As discussed, there are many factors that determine the actual removal efficiency that are not taken into account such as temperature, residence time and certain substance-specific properties. This model takes into account only the affinity of the chemical to carbonaceous material, with octanol as a surrogate and the tendency of a molecule in the gas phase to adhere to particulate material by means of the saturated vapour pressure. In this study the adsorption factor is used as a qualitative measure of removal efficiency in order to compare the different PFASs and indicate which PFASs are most likely not to be removed efficiently by AC treatment. Overall removal of PFASs in flue gas treatment The qualitative assessment of the overall removal of PFASs in the flue gas treatment system is presented in Appendix V. The overall removal factor combines the removal efficiency of each three individual flue gas cleaning step. The overall removal factor is calculated as follows: - = 1 - (1 - -) (1 - -2) (1 - -) (1 - -) In which: Frem-overall Fabs-quench Fabs-SO2 Fabs-venturi Fads-AC overall removal factor for the flue gas cleaning (-) absorption factor for the quench (-) absorption factor for the SO2 trap (-) absorption factor for the venturi wash (-) adsorption factor for the AC cleaning (-). From the calculated removal factors it can be concluded that the majority of PFASs are removed effectively from flue gas. Some groups of PFASs are more difficult to remove. Based on the calculated removal Page 80 of 160 RIVM report 2021-0143 factors, the overall removal is expected to be limited for the following groups: FTOHs < 6:2 FTOH; FTOs; FTIs < 8:2 FTI; PFAIs; PFCs; the fluorinated aldehydes; NOVEC 1230 and the fluorotelomer acrylates. 5.3 PFAS measurements at incineration plants To gain sufficient insight into the occurrence and emission routes of PFASs, measurement and monitoring at the different stages of the process at an incineration plant can be helpful. First, attention is given to available methodologies for sampling and chemical analysis of the composition and emission of PFASs via flue gas. In the remainder of this chapter, studies on various PFAS emission pathways are discussed in detail. The focus is on flue gases and bottom and fly ashes. Additional information is provided on PFASs in ambient air at or near incinerators, landfills and transfer stations of PFAS-containing waste and ashes. Also included is information on PFAS leaching and wastewater from these sites. Introduction to the measurement of PFASs in flue gas A perfect, complete combustion of PFASs results, in theory, in the emission of water, CO2, HF and, depending on the functional groups in the PFAS, sulphur dioxide, phosphorus oxide and nitrogen dioxide. These combustion products are not specific to the combustion of PFASs, but are also formed by the combustion of other chemicals that are present in municipal and industrial waste materials. HF, for example, originates from the incineration of various inorganic and organic fluorine compounds that are found in waste, including PFASs. More insight into the presence of PFASs and their relationship with HF in flue gases is obtainable by the availability of validated and standardised measurement methods for the quantification of the emissions of PFASs to the air. This RIVM study looked at the availability and the validity of methods for the determination of air emission of PFASs from the flue gases emitted by waste incineration plants. Currently, there is a lack of standardisation of measurement methods. This has partly to do with the absence of legal standards for the emission of PFASs to the air. There are, however, emission standards for PFOA and PFOS (Risks for Substances, 2020). An overview of these can be found in Table 10, which also includes the emission limit values for hazardous substances in the flue gases from waste incinerators obtained from the Dutch Activities Decree (Infomil, 2020). Unlike PFASs, there are standardised measurement methods for HF and polychlorinated dioxins, furans and dioxin-like PCBs. The substances mentioned present comparably problematic environmental and health issues that made it necessary to regulate these substances. They triggered the development of methods for sampling, sample preparation and chemical analysis in flue gases that could be valid for PFAS as well, e.g. parts of the standardised methods for dioxin, CxHy and HF measurements may also be suitable for PFASs. Page 81 of 160 RIVM report 2021-0143 Table 10 Emission limit values and mass flows of the air emission of PFOA, PFOS, HF and 2,3,7,8-tetrachlorodioxin in the Netherlands and emission limit values for waste incinerators in milligrams per (normalized) cubic metre Substance Emission limit a Mass flow Substanceh value classification milligrams per Nm3 grams per hour PFOA 1 2.5 MVP2 PFOS 0.05 0.15 MVP1 HF 3 15 gA.2 2,3,7,8-TCDD b 0.1 c 20 d ERS Emission limit values for waste incineratorse half-hour and daily average PM 5 CxHy 10 HCl 8 HF 1 SO2 40 NOx 180 CO 30 Hg 0.05 Sum Cd and Tl 0.05 Sum Sb, As, Cr, Co, 0.5 Cu, Pb, Mn, Ni and V Sum dioxins and 0.1 g furans f a) Source: Risk for Substances (2020). b) 2,3,7,8-tetrachlorodibenzodioxine(TCDD). c) 2,3,7,8-TCDD has a toxicity equivalence (TEQ) factor of 1, which means that the given value, which should be expressed in nanogram TEQ per Nm3, can also be expressed in nanogram per Nm3. d) 2,3,7,8-TCDD has a TEQ factor of 1, which means that the given value, which should be expressed in milligram TEQ per year, can be expressed in milligram per year. e) Source: Infomil, 2020 (Dutch Activity Decree, article 5.19, table 5.19) f) The sum of 17 congeners calculated in toxic equivalents to 2,3,7,8-TCDD with the help of the corresponding TEQ per congener. g) The emission limit value expressed in nanograms TEQ per Nm3 h) The emission values of SVHC are classified in order of increasing hazard: MVP2, MVP1 and ERS. MVP (in Dutch: minimalisatieverplichting) is a substance classification meant to take effort to minimise the emission of SVHC. ERS (in Dutch: extreem risicovolle stof) is the most critical hazard category of SVHC. Scientific literature on measurements of PFASs in flue gas There are many applications published about the use of analytical techniques to detect, identify and quantify PFASs. However, the measurement methods mainly concern the chemical analysis of environmental matrices such as soil, groundwater, surface water, sediment and drinking water. Only a few scientific publications on PFAS measurements for the determination of the PFAS concentration in the flue gases were found. On-site measurements of PFASs in ambient air and emission concentration measurements of PFASs in flue gases in particular have hardly been tested, but are now attracting worldwide attention. Page 82 of 160 RIVM report 2021-0143 In 2009, a Norwegian research group published a list of degradation products of different fluoropolymers on the basis of a review of various publications (Huber et al., 2009). The studies included in the review relate mainly experimental research on laboratory scale to the hypothesis about the reaction mechanisms and the identification of products of pyrolysis and combustion of fluoropolymers. They conclude that fluoropolymers such as PTFE-containing waste treated in incinerators cause the formation and emission of greenhouse gases. During combustion PTFE at a temperature between 750 and 1050 C, fluorocarbons such as CF4, CHF3, C2F6, C3F6 and C4F8 are formed. Huber et al. (2009) recommended developing and validating measurement methods to determine of the emission concentrations and emission loads of these substances. Much later, it was established from a presentation by the US EPA that no standardised methods are yet available for measuring emissions of PFASs in the flue gases of waste incinerations (Ryan, 2019). The presentation mentions a series of interesting sampling and analysis techniques to measure polar, non-polar, non-volatile, semi-volatile and volatile PFAS compounds in the flue gases. For the discontinuous timeaveraged measurements of the PFAS emission concentrations, the modified EPA MM5 method was used (EPA, 1986). The flue gases are isokinetically sampled with a (heated) probe placed in the chimney. The flue gases pass through the probe connected to a heated (glass fibre) filter unit, followed by an XAD-2 adsorbent column and three seriesconnected impingers. The first two are filled with deionised water or a 0.1 molar sodium hydroxide, sodium acetate or sodium borate water solution. The third and final impinger contains silica gel to retain the moisture still present before the flue gas leaves the sampling unit and is released into the ambient air. Optional is the placement of a second column of XAD-2 adsorbent between the second and third impinger for the purpose of identifying any breakthrough of PFAS from the first XAD2 column. Ideally, there should be no breakthrough. If there is, the chemical analysis of the second XAD-2 column will help determine the correct final emission concentration PFAS. The sample materials such as filters, XAD-2 adsorbents, impinger fluids and methanol or ammonium sweep liquids are then chemically analysed for PFAS. The various samples can be measured with an HPLC-MS/MS after suitable work-up of extraction, purification and concentration. This analysis technique is now fairly standard in the chemical analysis of non-volatile, semivolatile, non-polar and polar PFAS compounds in modified water measurement solutions. The volatile neutral PFAS compounds having boiling points below 100 C may be sampled in a SUMMA canister. This is a metal vessel that can be brought to underpressure or overpressure and is equipped with connectors, valves, flow controllers and a pressure gauge. For the sampling of the flue gases the canister is connected in an identical manner to the train of XAD and impingers by a probe that is inserted into the chimney and is provided with a heated filter unit. The sampling into the canister, which is set under pressure, starts as soon as the valve is opened. In addition to sampling by underpressure, it is also technically possible to sample the flue gases by overpressure in the canister with the aid of a pump. The metal inner wall of the canister is specially treated to make it inert to PFAS and other substances. After completion of the sampling procedure, the canister is easily Page 83 of 160 RIVM report 2021-0143 disconnected after closing of the valve. Thereafter, the canister is easily connected to a GC-MS to start the chemical analysis. The analysis is in accordance with EPA TO15 method, wherein the composition of the standard substance mixture should be adjusted in line with the choice of target PFAS substances (EPA, 1998). The sampling method illustrated in the EPA presentation makes it possible to determine the emission concentration of both dusty PFASs and gaseous PFASs. Relevant performance characteristics of the measurement methods such as the limit of determination, measurement range and reproducibility are not presented. An overview of the measured values is also not presented. A German research group has largely used the same sampling method for discontinuous HF and PFAS emission measurements (Aleksandrov et al., 2019). A pilot plant was used for this, which was equipped with the best available techniques for combustion and flue gas cleaning in accordance with German legislation. The measurements were performed with a train of serially coupled filter units, impingers filled with absorption liquids and XAD/PU adsorbent columns. The method differs from the EPA method in terms of the sample train configuration, in which the solid adsorbent column is placed after the second impinger instead of before the first impinger. A chemical analysis was performed to determine the emission concentration of 31 individual PFAS compounds. For this purpose, the filters, impinger fluids and XAD/PU adsorbent columns were analysed with HPLC-MS-MS on the content of the individual PFAS compounds. The researchers performed another chemical analysis to determine the total fluorine content in the fuels, the dust-like flue gas particles collected on filters, and the gaseous fluorine in impinger water solutions and the XAD/PU adsorbent columns. The gaseous part of total fluorine was analysed with an ion chromatographical measurement technique to determine the fluoride levels of the aqueous solution that remained after treatment the absorption media. The particulate fluorine fraction in the collected fly ash was chemically analysed after a pyrohydrolytic treatment with a potentiometric (fluoride ion-selective electrode) measurement in the resulting water solution. Based on an analysis of the fluorine balance, it was concluded that the contribution of dust-bound fluorine in flue gases is negligible compared with that of gaseous fluorine. It is not clear whether this means that the fraction of dust-bound/dust-like PFASs in the filter is also negligible, or not above the limit of detection (LOD) of the measurement method. The LOD is equal to three times the value of the standard deviation of a blank measurement. The limit of quantification (LOQ) equals ten times the value of the standard deviation of a blank measurement. Nothing about the experimental fluorine limit values was disclosed in the investigation. The LOQ of the chemical analysis of the 31 individual PFAS compounds amounts 0.3 g.m-3 to the majority of the substances. The limit depends on the sample volume of flue gas emissions. In this study, 100 litres or 0.1 cubic metre was taken by isokinetic sampling at 4 litres per minute for a period of 25 minutes. The measurements show that the PFASs were not detected above their LOQ, so that they cannot be quantified. The LOQ of the gaseous fluorine as fluoride was also not reported. However, this can be derived from other publications and standard regulations (Ministry of the Environment of Japan, 2013; Standard Committee, 2009). Starting from the above- Page 84 of 160 RIVM report 2021-0143 mentioned sampling method, an LOQ of gaseous fluorine of about 0.3 mg.m-3 can be derived. Taking into account the measurement uncertainty, this limit value is more than sufficiently low to be able to test whether the emission limit value of HF is exceeded. On the basis of the published results a relationship between the air emission of dustbound/dust-like and gaseous PFASs on the one hand and dustbound/dust-like and gaseous fluorine on the other hand is not sufficiently clear. A course for environmental professionals on the topic of PFAS sampling presented several methods of air sampling and chemical analysis of PFAS (EPOC, 2019). The air measurements included both emissions of flue gases and ambient air concentrations of PFASs at locations near emission sources. These sources included industries that make and use PFASs and incinerate PFAS-containing waste. As explained, the methods of sampling PFASs in the flue gases of waste incinerators correspond to those of the EPA presentation and the research of Aleksandrov et al. (2019). In Harlingen (the Netherlands) the Residual Energy Plant (REC) burns household waste for the production and supply of energy to companies and households in the region. In 2016, this plant carried out a project in which time-averaged measurements of chlorinated dioxins/furans, dioxin-like PCB, brominated dioxins, brominated diphenyl ethers and the sum parameters of PFOA and PFOS were measured. In January and February, a total volume of 461.7 m3 of flue gases was sampled for 30 days. Afterwards, the collected sample media were chemically analysed for the aforementioned substances by a German laboratory with the aid of high-resolution HRGC-MS. An emission concentration of the sum of PFOA and PFOS of 0.0143 ng.m-3 was reported. This measurement value includes the determination limit value of 0.00108 ng.m-3 (Eurofins GfA Lab Service, 2016). We note that in this study a large volume of the flue gases was sampled compared with the 0.1 m3 in the PFAS emission measurements of the pilot plant (Aleksandrov et al., 2019). This also deviates from the flue gas volume to be sampled according to standard measurement methods for determining dioxin emissions, which is approximately 4 m3. The LOQ of the sum of PFOA and PFOS can be estimated on the basis of a calculation at 0.13 and 0.50 ng.m-3 if 4 or 0.1 m3 of the flue gases, respectively, are sampled. Compared with the previously mentioned 0.3 g.m-3 for individual PFAS compounds, the calculated LOQ is a factor of 600 lower. The large difference is probably due to differences in the methods of extraction, purification and concentration during sample pretreatment in the laboratory. Detailed information on the emission measurements carried out on the sample before treatment was not made available. Intermezzo Half an hour to several hours of isokinetic flue gas sampling is common for discontinuous time-averaged emission measurements from stationary sources. A relevant example is the standardised measurement of dioxins and dioxin-like PCBs according to NEN-EN 1948:2006. Part 1 of the measurement standard describes three variants of the method to detect dioxins and (dioxin-like) PCBs in Page 85 of 160 RIVM report 2021-0143 the flue gases (Standard Committee, 2006a). This is very similar to published methods of PFAS emission measurement such as the EPA MM5 method (EPA, 1986). In order to maintain the performance characteristics of the measurement method for dioxins and PCB described in part 3 of the NEN-EN standard, the sample volume must be at least 4 m3 (Standard Committee, 2006b). This can be achieved with an isokinetic gas flow rate in the range 0.5-5.0 m3 per hour, depending on the sampling method chosen in part 1. In meeting these requirements an LOQ of the individual dioxins can be established in an emission concentration range from 0.1 to 8.8 picograms per (normalised) m3. The international and Dutch measurement standard ISO-NEN 15713: 2011 is suitable for measuring the emission concentration of gaseous fluorine in stationary point sources (Standard Committee, 2011). The sampling method is the same as that of the EPA-MM5 method. The difference from the ISO-NEN method is the fact that it does not contain any columns with solid adsorbent in the sampling train. In accordance with ISO-NEN 15173:2011, the measurement of hydrogen fluoride in the flue gases of incineration plants should determine the emission of HF to the atmosphere for assessing the exceedance of the emission limit value mentioned in table 10 This follows from the measurement obligation of Article 5.29 of the Dutch Activities Decree. The chemical analysis in the laboratory of the collected impinger fluids for fluoride content is carried out according to the measurement standard using a fluorine ion-selective electrode. Fluoride measurement is also possible based on an ion chromatographic analysis of anions and conductivity detection (NEN-EN-ISO 10304-1). The LOQ for fluoride converted to HF in flue gases for both analysis methods is set at 0.1 mg.m-3. This is based on approximately 4 m3 of sampled flue gases. Discussion and conclusions on PFAS emission measurement methods It cannot be ruled out that, due to differences in the methods and laboratory tools used for sampling, sample pre-treatment and measurement, other factors and circumstances may influence the comparability of the performance of the PFAS emission measurements of the flue gases of waste incinerations. At the same time, they can explain the differences in the LOQ up to a factor of 1000. This is therefore a reason to standardise the measurement methods. From the foregoing it is clear that larger sample volumes of flue gases result in a lowering of the LOD and LOQ. A target list of PFASs can be used to screen for the detectability and emission concentration of selected PFAS compounds. The target list includes compounds for PFAS pure standard substances and their corresponding C13 labelled isotopes for laboratory tests. The preparation and chemical analysis of appropriate concentrations of standard mixtures of PFASs make it possible to quantify the emission concentrations of the individual PFASs of the target list in flue gases. Because of the broad spectrum of substance properties within the PFAS group, the target list serves best for statements about (the behaviour of) PFASs as a whole, and therefore all possible properties should be Page 86 of 160 RIVM report 2021-0143 represented. A selection of only about 30 substances, such as in the advisory list of PFASs to be measured in (aquatic) soil (Table 1), implies that uncertainty is accepted because only some of the known PFAS groups are represented. This was extensively discussed in Chapter 2, on the definition and properties of PFASs. The Knowledge Document of the Expertise Centre PFAS (Pancras et al., 2018) refers to a PFAS target list of approximately 30 standard substances that has been compiled on the basis of the latest insights. These substances are routinely offered by contract laboratories for the PFAS analysis. However, the list is mainly used for the accurate measurement of PFASs in liquid and solid environmental matrices. The list is also discussed in Section 2.2.2. The suitability of such a target list for the air emission measurements of stationary sources of waste incineration is open to discussion. As indicated above, short-carbon chain (C6), non-polar and gaseous PFASs are to be expected in the flue gases. These are suitable for measuring with GC-MS, with options for variation in the configuration of the MS instrumental part. The advantage is that these PFASs does not first have to be transformed into a water solution. However, effective adsorption or absorption and preferably a process of concentration of the PFAS must be carried out. This sample treatment must be developed and validated in a measurement method. The previously explained sampling technique with the use of canisters requires hardly any additional treatment before a chemical analysis with GC-MS takes place. It is possible to search for non-target PFAS substances. These are PFAS compounds that do not occur in the standard substance mixtures of the chemical analysis, but can be characterised and identified by applied mass spectrometric detection methods with the help of smart software data processing techniques. A common technique is HPLC-ESI-tandemMS. For the GC-MS analysis, a `hard' ionisation method by electron impact of the MS is suitable for the characterisation of the PFAS compounds. The ionisation method is fairly standard for the detection and identification of organic compounds in environmental samples. The choice for `soft' ionisation methods such as positive or negative chemical ionisation are also applicable. Relationship between measured PFASs versus total fluorine and total organic fluorine (TOF) in flue gases If we compare the LOQ of the HPLC-ESI-tandem-MS or GC-MS analysis of individual PFAS compounds with that of the ion chromatographic or potentiometric analysis of fluoride, it is clear that the LOQ of the fluoride analysis is intrinsically a factor of 1000 higher. This implies that the detection limits are also related in the same way. The LOD is by definition a factor of 3 lower than the LOQ. Due to the lower LOD for the PFAS measurement, we can expect that individual PFAS compounds can still be detected if the fluoride measurement does not exceed its LOD. In addition to the measurement of fluorine, analytical methods have now been developed to determine the total content of the organic fluorine compounds. These are referred to as TOF (total organic fluorine) analyses. The Knowledge Document (Pancras et al., 2018) mentions, Page 87 of 160 RIVM report 2021-0143 among other things, the combustion ion chromatographic TOF analysis method for determining the content of organic bounded fluorine compounds in environmental matrices such as groundwater and surface water, sediment and soil. Variants of the TOF analysis are further explained in various scientific publications (Abercron et al., 2019; Yeung et al., 2013; Miyake et al., 2007). These essentially involve solid phase extraction (SPE) or liquid extraction (LLE) of the organic bounded fluorine compounds from sample matrices. A measured volume of the organic extract of the sample is injected into an oven at a temperature of about 1000 C. The TOF converts to inorganic hydrogen fluoride, which is then absorbed into a water liquid. A partial volume of the absorbing liquid is analysed by ion chromatography in which the anions such as fluoride, chloride, bromide, sulphate are fractionated and detected. The analysis technique largely corresponds to that of the standardised HF measurements in the flue gases. The LOQ of the TOF measurement depends on the maximum reconcentration step during the SPE or LLE. A limit of between 2 and 10 g.L-1 in the impinger fluids is achievable. This corresponds to a range of 50-250 nanogram TOF per m3 in the flue gas, which is still well above that of the achievable LOQ of individual PFAS compounds. Although the TOF is more selective for the detectability of PFAS concentrations and on that basis is a better indicator measurement, the disadvantage remains that the expected LOQ of the TOF measurement still seems inadequate. This means that the TOF measurement is also a less suitable indicator for the detectability of PFAS in flue gases. Fly ash and bottom ash: PFAS composition and emission In addition to their emission via the flue gas from waste incineration plants, PFASs may also be present in bottom ash and fly ash. They can occur in ashes as a result of the incomplete combustion of municipal and industrial waste. Therefore, the ashes can form an additional emission source. Emissions depend on how the ashes are treated and used. Bottom ash and fly ash are used as secondary building materials in many construction applications. Where bottom ash and fly ash do contain PFASs, the storage, transportation, processing (to make the ashes suitable as building materials) and use (especially given their long presence in building and road construction sites) are potential sources of PFAS emissions. Emissions can, for example, result from the blowingaway of dust-bound PFASs and the leaching of water-soluble PFASs after contact with (rain) water. Besides measurements of PFASs in flue gases, a few studies have measured PFASs in bottom ash and fly ash. Particularly interesting is the experimental study on PFASs in bottom ash, fly ash, condensation water and waste water from four waste incineration plants in Sweden (Sandblom, 2014). All four plants were operating in line with the laws and regulations set by the EU and the Swedish government (European Parliament, directive 2000/76/EG; Miljbalken, 1998: 808; Avfalsfrordning, 2011: 927). This means that the waste is incinerated at a minimum temperature of 850 C. Chemical analysis methods have been developed and validated in this experimental study. Table 11 provides an overview of the reported measurement values of a target list of eight Page 88 of 160 RIVM report 2021-0143 PFAS perfluorocarboxylic acids and one perfluorosulphonic acid with chain lengths of 4 to 12 carbon atoms. The best known are PFOA and PFOS. Table 11 Average values of the PFAS acids in bottom and fly ash in g.kg-1 (ng.g-1) and PFAS concentrations in condensation and waste water in ng.L-1 in four incineration plants in Sweden Bottom asha Fly asha Condensate Waste LOD water waterb Solid samples LODc Water samples PFBA PFHxA PFOA PFNA PFDA PFUnDA PFDoDA PFHxS PFOS 1.148 0.384 3.74-6.68 3.74 0.170 0.832 1.772 0.312-5.91 0.614 0.024 0.196 0.395 0.874-1.88 0.874 0.013 1.877 5.909 0.932-8.69 0.932 0.022 0.141 0.318 0.165-9.71 0.165 0.114 0.088 0.085 0.244-1.82 0.244 0.085 0.118 0.118 0.285-2.90 0.285 0.118 0.014 0.027 0.122-0.298 0.158 0.003 0.380 1.778 1.52-2.04 1.52 0.128 Note: The values in italic are concentrations at the LOD. a) Refers to average values of chemical analyses of samples gathered from four waste incineration plants. b) Relates to one sample from one of the four waste incineration plants. c) LOD is 3 times the standard deviation of measurements at blank level and corrected for blank matrix effects. Source: Sandblom (2014). 3.74 0.312 0.874 0.932 0.165 0.244 0.285 0.122 1.52 Particularly striking is the variation in measurement values of the condensation water. The variation might be assumed to be caused by taking samples at different points in the flue-gas cleaning process. The wastewater was sampled and chemically analysed only once at one of the four incineration plants. The research shows that the waste incineration installations do not fully destroy the PFAS. The sum value for the concentration of PFAS carboxylic acids with chain lengths from C4 to C12 are quantified at a level of 10 g.kg-1 in bottom and fly ashes. The condensation water contained a level of 30 ng.L-1 of the sum value. The waste water in this study contained a sum value at the level of the LOQ. The analytical methods developed are found to be valid and fit for the purpose of quantifying the individual target PFAS compounds in the solid and water samples. The methods for sample pre-treatment, such as digestion, extraction, purification and concentration, as well as for chemical analysis with HPLC-MS/MS are similar to other analytical methods. This applies to the chemical analysis of soil, fly ashes, condensation and waste water. The laboratory research was carried out with sufficient quality control and quality assurance. One plant used internal standards, C13 labelled standard PFAS compounds and the determination of a number of performance characteristics such as LOD, recovery, blank analysis procedure, precision and bias. The limitation of this study is that the list of selected PFAS compounds does not fully represent PFASs as a group. As a result, there are Page 89 of 160 RIVM report 2021-0143 uncertainties about the nature and quantity of the categories of PFAS not included in the study. There may thus be an underestimation of the actual PFASs issued, such as non-polar neutral PFASs, short-chain versus long-chain PFASs, volatile versus non-volatile PFASs and precursors of PFASs, the nature and size of whose influence is unknown. The concentrations of PFASs in bottom ash and fly ash, measured at two sites owned by the AVR in the Netherlands, are available from a report by Houben and Boerleider (2020); see Annex IV. Concentrations in the fly ash from the Rotterdam-Botlek site were sampled only once and were all below the LOD of 0.1 g.kg-1. With regard to bottom ash, the highest concentrations were measured at the site in Duiven. At the Rotterdam-Botlek site only 4 of the 34 substances were found to be above the LOD, namely 6:2 FTS, PFBS, PFAS and 8:2 FTS. At Duiven, of the PFASs analysed, 19 were found to be above the LOD, 6:2 FTS having the highest concentration of 36 g.kg-1. The concentrations in the bottom ash varied considerably. Of the three measurements at the site in Duiven at least one was below the LOD of 0.1 g.kg-1 for all 19 PFASs. Using the highest measured concentrations per substance, the total concentration of PFASs in the bottom ash at the site at Duiven is 48.95 g.kg-1. Using the total annual amount of bottom ash generated at this site (125,000 tonnes; Houben and Boerleider, 2020), this results in a total amount of about 6.12 kg PFASs per year in the bottom ashes. This amount should be considered as a high estimate because the highest concentration for each substance was used for calculating the total amount of PFAS. Furthermore, the concentration is mainly determined by just one substance, 6:2 FTS. In many samples the concentrations were below the LOD for the same substance in different samples. Therefore, the numbers should be considered as indicative and additional measurements at other waste incineration sites are needed to obtain a representative picture. A recent study investigated PFAS emissions from bottom and fly ash via leaching at various landfills in Florida (Solo-Gabriele et al., 2020). The landfills studied included sites filled with mixed bottom ash and fly ash, sites filled with bottom ash, fly ash and (unburned) municipal waste and sites filled with bottom ash, fly ash, municipal waste and gas condensate. Landfills with exclusively municipal waste and landfills with construction and demolition materials were also included. A chemical analysis was performed for 11 individual PFAS compounds, including seven perfluorocarboxylic acids, three perfluorosulphonic acids and one precursor 5:3 fluorotelomer carboxylic acid. The findings showed that almost all PFAS compounds were above the LOD in the leachates. The lowest measurement values were found in the leachate from landfills with 100% mixed bottom ash and fly ash in a concentration range from 0.1 g.L-1 to 0.6 g.L-1. For the other two types of landfills the measured concentrations were up to a factor of 10 higher for the majority of PFASs. The relevant PFAS compounds found in the leachates of the sites filled with only bottom ash and fly ash were quantified at 0.25 g.L-1 (PFOA) and 0.12 g.L-1 (PFOS). Solo-Gabriele et al. (2020) also looked at the measured values for the sum of the 11 PFAS compounds and the relationship of the leaching of PFAS from ashes formed with the different Page 90 of 160 RIVM report 2021-0143 combustion temperatures. There appears to be a consistent relationship between the concentration of PFASs in the ashes available for leaching and the combustion temperature at which the ashes are formed. The ashes in landfills originating from the waste incinerations plants with the highest combustion temperatures, namely 930-980 C, contain sum levels of PFAS target compounds in the leachates up to a maximum of 3.4 g.L-1. The sum value increases to 8.4-8.7 g.L-1 for ash originating from incineration plants with combustion temperatures of 815-870 C. The highest values were found for ashes from plants with combustion temperatures of 760-870 C, namely from 12.3 to 13.5 g.L-1 for the sum of 11 PFAS target compounds. The samples of leaching water from the landfills were taken onsite by drilling monitoring wells to a depth of a few centimetres and 10 metres. The water samples were collected in HDPE 0.5-litre bottles. The chemical analysis of the PFASs was performed by the laboratories of the EPA in Triangle Park in Raleigh, USA. Sample preparation consisted of an addition of internal standards and corresponding isotope-labelled substances. The filtration was carried out with a glassfibre filter, followed by solid phase extraction with SPE columns in two batches with Oasis WAX cartridges and Envicarb cartridges. The SPE was eluated with a mixture of ammonium hydroxide and methanol (1: 1000). After evaporation with nitrogen until dry, the residues were added with 2.5 molar ammonium acetate preparing measuring solutions for the chemical analysis of the PFAS. A time-of-flight HLPC/MS was used as the selected analysis technique. The LOQ was 300 ng.L-1 for the majority of the target PFAS compounds. This suggests that the LOD is 100 ng.L-1. It is noticed that the LOD of the analytical method of the Swedish study (Sandblom, 2014; see Table 11) is approximately a factor of 100 lower. Intermezzo In outline, the sample preparation and the technique of chemical analysis of various analytical methods for the determination of PFAS in water matrices such as surface water, drinking water, wastewater and groundwater are rather standard. The methods are available from a number of commercial and institute laboratories located in the Netherlands. Chapter 7.2.2 of the Knowledge Document of the Expertise Centre PFAS contains a description of the standard applied analytical technique of the HPLC-MS-MS for the determination of the PFAS content of water. Detection limits of 0.65 to 1.0 ng.L-1 are achievable for these measurement methods. In wastewater, the detection limits are slightly higher according to the Knowledge Document. The LOD of PFAS in groundwater of 5 ng.L-1 is sufficient low to measure PFAS, while for surface water it should be 0.5 ng.L-1, according to the Knowledge Document. Standards developed worldwide for the determination of PFAS in water matrices include: ISO 25101: 2009. This method is suitable for the analysis of PFOS and PFOA in unfiltered drinking water, groundwater and surface water (fresh and salt water) and can be used in a concentration range of 2.0 to 10,000 ng.L-1 for PFOS and 10 to 10,000 ng.L-1 for PFOA (Technical Committee, 2009). US EPA method 537.1: This modified method contains a target list of 18 PFAS compounds consisting of 11 carboxylic acids, 4 sulphonic acids, 2 Page 91 of 160 RIVM report 2021-0143 precursors of sulphonamide acetic acids and FRD-903 (HFPO-DA or a PFAS in the GenX process). Depending on the PFAS compound, the LOD lies in a concentration range of 0.53 to 6.3 ng.L-1 (EPA, 2020). DIN 38407 -42. This German method is suitable for the determination of the concentration of PFAS in drinking, ground, surface and waste water. The LOD lies between 10 and 25 ng.L-1, depending on the matrix (National Committee, 2011). In their conclusion Solo-Gabriele et al. (2020) recommend further investigation of the contribution of precursor PFASs, which can increase the total of persistent PFASs. This recommendation also applies to research into the composition of ash, condensation and waste water (Sandblom, 2014). The Knowledge Document of the Expertise Centre PFAS (Pancras et al., 2018) contains an explanation of the total oxidisable precursor PFAS (TOP) analysis in chapter 7.2.4. The analytical method was developed to investigate the broad spectrum of PFASs, the principle being that a sample on the target list of PFAS is analysed before and after the oxidation step according to the method for the PFAS analysis of water samples. The difference calculated from the PFAS concentration analysed before and after the oxidation yields the concentration for the PFAS precursors. The oxidation takes place in the sample treatment through a thermolysis of persulphate to the formation of hydroxyl radicals, which, in turn, convert the precursors into stable perfluorocarboxylic acids. In another recently published study the emission of PFASs from municipal waste was measured at three landfills, two temporary storage sites and two industrial waste incineration plants in Tianjin, China (Wang et al., 2020). The measurements were carried out for (1) air emissions due to evaporation of volatile PFAS and/or blowing-up of dust-bound PFAS and (2) leaching through contact of rainwater with the waste containing PFAS. The air measurements were carried out per object at various strategic measurement locations by passive sampling with Sorbent Impregnated Polyurethane (SIP) foam disks. With an air flow rate of 4 m3 per day, a total volume of 120 m3 was sampled over a period of 30 days. The sample handling was carried out in accordance with good laboratory practice by packaging the disks in aluminium foil and preserving the storage conditions (frozen at -20 C) until the start of the chemical analysis in the laboratory. Of the PFAS target list to be screened, 22 ionisable PFAS components were analysed with HPLC-MS/MS and 7 neutral PFAS components with GC-MS. The seven neutral PFAS are 6:2, 8:2 and 10:2 fluorotelomer alcohols; N-methyl and N-ethyl perfluorooctane sulphonamides (N-MeFOSA and N-EtFOSA); N-methyl and N-ethyl perfluorooctane sulphonamide ethanols (N-MeFOSE and NEtFOSE). Of the ionisable PFAS there are 11 perfluorocarboxylic acids (C2-C12), 3 perfluorosulphonic acids (C4, C6 and C8), 6:2 and 8:2 fluorotelomeric unsaturated acids (6:2 and 8:2 FTUCAs), 6:2 and 8:2 Cl-PFAESs and 6:2 and 8:2 diPAPs. Depending on the individual PFAS compounds, the method detection limit is between 0.03 (NMeFOSA) and 0.22 (N-EtFOSE and 6:2 FTOH) pg.m-3. The analytical method for the determination the ambient air concentration of PFASs was developed and validated several years earlier (Tian et al., 2018). Page 92 of 160 RIVM report 2021-0143 Approximately 0.5-litre water samples of the leachates (n = 14) and the effluents (n = 8) were taken in duplicate and collected in polypropylene bottles (Wang et al., 2020). The effluent is the leachate that has undergone a biochemical treatment. Good laboratory practice of packaging, coding, preservation, transport and transfer to the analysis laboratory was performed. All samples of leachates and effluents were also chemically analysed for the concentration contribution due to the presence of precursor PFAS compounds. A previously developed TOP analytical method was used for this. The oxidation step, as explained in the Knowledge Document, was carried out with potassium persulphate at a temperature of 85 C for a period of 6 hours. The water samples were chemically analysed before and after oxidation using solid phase extraction over oasis WAX SPE cartridges. The sample treatment and measurement are largely in accordance with other published analytical methods using HPLC-MS/MS. The performance characteristics of the analytical method used are also in line with those of other analytical methods. Wang et al. (2020) conclude that PFAS emissions occur particularly through the leaching of PFASs from municipal waste dumps, transfer stations and industrial waste incinerators. They found surprisingly high PFAS leaching through the contribution of precursor PFAS compounds. An underestimation of the actual PFAS emissions of approximately 6 to 49% is found if only the target list of PFAS is considered. Flue gas: PFAS composition and emission The study by Wang B. et al. (2020) investigated the air emission of neutral PFASs. Measured air concentrations were in the range 393-19.000 pg.m-3, or 0.393-19 ng.m-3. Of the neutral PFASs, the fluorotelomer alcohols are dominant in the total air emissions. The ambient air concentrations of the proportion of anionic PFASs vary from 0.458 to 13 ng.m-3. The perfluorocarboxylic acids are dominant here. The total air concentration of PFASs at the central measurement locations of the investigated objects was a factor of 2 to 30 higher than the measurement locations upwind per object examined. Figure 4 shows the calculated emissions of the total of neutral and anionic PFASs in kilograms per year per location (landfill site, temporary storage site and industrial site of combustion installation). Page 93 of 160 RIVM report 2021-0143 Figure 4 Mass flows for the different emission routes and waste treatments Source: Wang et al. (2020). PFAS measurements were also performed on flue gas at the AVR site in Rotterdam-Botlek and the results were published by Houben and Boerleider (2020). The data are provided in Annex IV. The flue gas concentrations presented are the average values of single measurements at four different stacks. The measured flue gas concentrations at the AVR site in Rotterdam-Botlek show that the highest concentration of 8.9 ng.Nm-3 was measured for PFOA (linear and branched). The total concentration of detectable PFASs (n = 19) was 20.26 ngNm-3 excluding the concentrations below the detection limit. Most of the 30 PFASs listed in Table 1 were included in the measurements at the site in Rotterdam-Botlek, except PFPeA. From the measured concentrations at the Rotterdam-Botlek site and the amount of flue gas produced by the three MSW incineration lines at the AVR site in Duiven (~107 000 Nm3hour-1 per line; Houben and Boerleider, 2020), a yearly emission to air of 56.8 g PFAS is calculated. The amount of flue gas relates to 394,082 tonnes of waste incinerated. These numbers result in an emission factor of 0.14 mg PFAS per tonne of waste burned. Applying this emission factor to the AVR site at Botlek, with an annual amount of 1,322,937 tonnes of waste burned, would result in emissions to air of ~191 grams PFAS per year. Th RotterdamBotlek site is the second largest MSWI in The Netherlands after the AEB in Amsterdam. The amounts of waste burned include not only municipal and commercial waste, but also non-hazardous and hazardous industrial wastes and filter residues (Rijkswaterstaat, 2020a). Because the information from two different sites is combined, the calculated emissions in this section should be considered with care and should be taken as indicative. Additional measurements at other waste incineration site are needed to obtain a representative picture. Wang B. et al. (2020) estimated the total emissions to the atmosphere of measured neutral and anionic PFASs from waste incineration plants in China to be in the range of 7-10 grams per year per site (Wang et al., Page 94 of 160 RIVM report 2021-0143 2020: Figure 4). Emission factors are calculated from the estimated loads to air and the reported incineration capacity (see Table 12). The emission factors of the incineration plants in China are a factor of 3-5 lower comparted to the estimated emission factor for the site at Rotterdam-Botlek. The difference in the emission factors can mainly be explained by the difference in the set of PFASs included in the measurements. Back calculation of the emissions from surrounding air measurements introduces additional uncertainty, in contrast to direct measurements in the flue gases. Table 12 PFAS release factors from the estimated loads to air and incineration capacity. Air loads are from Wang B. et al. (2020). Incineration plant IP1 IP2 Air load (kg.year-1) Total neutral PFASs 2.510-3 4.310-3 Total ionizing PFASs 4.610-3 7.110-3 Total PFASs 7.110-3 11.510-3 Incineration capacity (tonne.day-1) 600 1200 Release factor (g PFAS/tonne waste) 3.2.10-5 2.6.10-5 As described above, Wang B. et al. (2020) measured 20 PFASs in leachate, and determined air emissions from landfills and stored waste and concentrations in air upwind of and in the central area of two incinerator facilities. The set of PFASs included several PFASs not measured at the AVR sites and also not included in the advisory list of PFASs to be measured in soil and water (Table 1). Those not included are 8:2 FTUCA (environmental transformation product), the 6-10:2 fluortelomer alcohols, N-EtFOSA, N-MeFOSE and N-EtFOSE. The last two were not detected in air upwind and downwind of the incineration plant, but N-MeFOSA and N-EtFOSA were. Of the anionic PFAs, PFPeA and PFHpA were detected in only a few cases (in the leachate of one landfill and in the air and leachate of one of the two incineration plants investigated). All in all, the investigated PFASs were detected at each stage, i.e. landfill site, transfer station and incineration plant, and could therefore be regarded as relevant. It should also be noted that NMeFOSE and N-EtFOSE, PFHpA were not detected in the air samples at the incineration sites. 5.4 Conclusions Removal from flue gas Perfluorinated acids such as perfluoroalkyl sulphonic acids, carboxylic acids are strong acids that are expected to be highly deprotonated in the washing and absorber solutions and thus to be removed from the flue gas. PFASs with a non-dissociating, non-polar terminal groups such PFIAs, FTIs, PFCs and FTACs have relatively high KAW values (log KAW 2-5) and are likely to remain in the gas phase and pass through the flue gas scrubbing stage. FTOHs also have this tendency, especially FTOHs with a perfluorinated chain consisting of eight or more carbon atoms. Page 95 of 160 RIVM report 2021-0143 The octanol-air partition coefficient (KOA) is used as an indicator of binding to AC. It is expected that a number of PFAS groups will not be captured (or captured only to a limited extent) by AC. This is mainly the case for iodine-containing PFASs, fluorotelomer olefins (FTOs), the perfluoroalkanes (PFCs), the fluorotelomer alcohols with a short perfluoro chain of 3 to 5 carbon atoms (3-5:2 FTOH) and the fluorotelomer acrylates (FTACs). With respect to the PFCs, this also includes the main perfluorinated by-products formed during incineration, as indicated in the previous chapter. Overall, if present in the flue gas that comes from the combustion chamber, the substances most likely to pass through the flue gas treatment system are iodine-containing PFASs, FTOs, PFCs, the fluorotelomer alcohols with a short perfluoro chain of 3 to 5 carbon atoms (3-5:2 FTOH) and the FTACs. PFAS emission measurement methods In publications from 2009 and onwards, scientists have emphasised a trajectory of development, validation and standardisation of new measurement methods for determining PFAS emission concentrations, but our literature study shows that no standardised methods are yet available to measure the emission concentration of PFAS compounds in the flue gases of waste incineration plants. It is nevertheless concluded that, among other things, volatile fluorinated gases are most likely to be formed on incineration and to be present in flue gases. Of these gases perfluorocarbons such as tetrafluoromethane (CF4), hexafluoroethane (C2F6), both of which are greenhouse gases, are most likely to be formed. Other perfluorinated carbons like perfluorocyclobutane (C4F8), tetrafluoroethylene (C2F4), hexafluoropropene (C3F6) and perfluoroisobutene (C4F8) are less likely to be present in flue gases. To be mentioned as a relevant part of the measurement method it is technically possible to sample this subgroup of gaseous PFASs, as well as other forms such as polar, water-soluble, dust-bound and dust-based (aerosols) PFASs in flue gases. It is common practice to use a sampling train of filters, adsorption columns and impinger absorption liquids connected in series. The collected filters, adsorption columns and impinger fluids can be chemically analysed in an accredited laboratory after sampling. GC-MS and HPLC-MS/MS are particularly suitable for this purpose as analytical techniques. GC-MS lends itself well to the measurement of gaseous and non-polar to mildly polar PFAS compounds. HPLC-MS/MS, on the other hand, is suitable for polar, dissociable and water-soluble PFAS compounds. HPLC-MS/MS has been accepted as a valid analytical technique for the determination of the content of PFAS compounds in soil, dredge, sediment, groundwater and surface water. An alternative for the use of adsorption columns to the sampling and GC-MS analysis of gaseous PFAS compounds is the use of canisters, as they are much easier to use. Page 96 of 160 RIVM report 2021-0143 Fluoride measurement is an obligation in the Dutch Activities Decree for determining the HF emission concentration in the flue gases of waste incineration plants. The standard prescribed measurement method for HF in flue gas, ISO-NEN 15713:2011, is not considered a suitable method of PFAS measurement or a replacement for measurement by GC-MS or HPLC. Furthermore, fluoride measurement is not selective for the PFAS. The LOQ of the standard fluoride methods is three orders of magnitude higher than the LOQ of the HPLC-ESI-tandem-MS or GC-MS analysis of individual PFAS compounds. A feasible LOQ for the measurement of the emission concentration of PFAS compounds in flue gases is estimated to be in the range 0.1-0.5 ng.m-3. A sampling volume of approximately 4 m3 of flue gases is assumed here. The TOF measurement is another indicator method for the presence of PFAS concentrations in flue gases. It is selective for the sum of PFAS compounds as part of the TOF. However, the limit of quantitation for the TOF measurement is expected between 50 and 250 ng.m-3 flue gas, which is still well above the achievable LOQ of individual PFAS compounds. This means that the TOF measurement is also a less suitable indicator of the detectability of PFAS in flue gases. In view of the expected gaseous PFAS compounds in flue gases, it is recommended to compile a PFAS target list for chemical analysis that includes the gaseous PFAS compounds. It would also be sensible to measure the non-target PFAS compounds, because of the unfamiliarity of the presence of PFASs in the flue gases. This is easily achieved through the use of MS detection techniques. PFAS measurements at waste incinerators Recent scientific studies have shown on the basis of PFAS measurements that PFAS emissions from waste-processing activities take place not only via the flue gases from waste incineration. It appears that PFASs can also be released from the site of a waste incineration plant to the outside air (evaporation and/or emitted flue gases) and can leach into the underlying soil. These emissions also take place in landfills or temporary waste storage sites. Evaporation and leaching of PFASs is also possible from the bottom and fly ashes that arise as residual flows after incineration. In The Netherlands, these residual flows are used as secondary building materials. One of the publications concluded that the emission route via leaching causes significantly higher emission loads than that via ambient air. This applies to total PFASs as well as to the subgroups distinguished therein of neutral and ionic PFAS compounds. From the measurements of PFASs in flue gases and in air, annual emissions from two waste incineration plants located in the Netherlands, as well as emission factors, could be derived. The emission factors based on the flue gas measurements are about a factor of 5 higher than those based on the concentrations in air. As a first indication, emissions of PFASs are expected to be in the range 10-20 g per 100,000 tonnes of waste incinerated. Measured concentrations in bottom ash from the studies in the Netherlands and in Sweden appear to match reasonably Page 97 of 160 RIVM report 2021-0143 well, and are in the same order of magnitude. The amount of PFAS in bottom and fly ashes is about a factor of 100 higher than the amount emitted via flue gases. These numbers should, however, be considered as indicative, as they are based on a limited number of samples at one or two sites. Additional measurements at other waste incineration sites are needed to obtain a representative picture. It has been shown that several PFASs that were not included in the available flue gas measurements are present in waste and emitted from waste incineration sites. The list of PFASs could be extended to include these compounds to improve the insights into the presence of PFASs in MSWI flue gases. The PFASs in question are 6:2, 8:2 and 10:2 FTOH, and N-MeFOSA. N-MeFOSE and N-EtFOSA were detected in emissions from landfills and waste storage sites but were not detected in the air samples at the incinerators. Based on the available information on emission measurements and our analysis of the incinerability of PFASs, the generation of incineration byproducts and the removal of PFASs via flue gas cleaning, it is proposed that all the PFASs on the advisory list should be measured and that the list should be extended to include the following substances: Iodine-containing PFASs, FTOs, PFCs, the whole range of FTOHs and FTACs, N-MeFOSA, N-MeFOSE and N-EtFOSA. Perfluoroalkyl iodides and fluorotelomer iodides are raw material intermediates used to produce additional building blocks that are further reacted to create a family of `fluorotelomer-based' surfactants and polymer products. Fluorotelomer olefins are also used as raw material intermediates and may be formed as an impurity in the synthesis of fluorotelomer alcohols (Buck et al., 2011). It is not expected that these three PFAS categories will be present in municipal and similar commercial or industrial waste and it is therefore probably less relevant to include these PFASs in an extended advisory list for the measurement of PFASs in flue gas, fly ash and bottom ash. Page 98 of 160 RIVM report 2021-0143 6 Carbon dioxide recovery from incineration plants In this chapter the influence of the carbon capture and liquefying process on the composition of the flue gas finally emitted and the liquid CO2 produced at waste incineration plants will be described. The following sections first describe the carbon recovery process. This is followed by a description of what is likely to happen to the PFASs during the carbon capture and liquefaction processes. All the PFASs that were considered in the previous chapter will be taken into consideration, including those that are likely to be formed as incineration by-products. Available information on the removal of some well-known flue gas components will also be discussed to provide some quantitative information on expected removal rates. This will be followed by qualitative assessments of the different kinds of PFASs considered. A qualitative indication will be provided both for the expected removal from the flue gas that is finally emitted from the CO2 capture process and for the final liquid CO2 produced. The information provided in this chapter should give an answer to the main research question whether PFASs can be present in CO2 that is recovered from waste incinerator flue gases. 6.1 CO2 recovery process CO2 in waste incinerator flue gas can be recovered, to be applied, for instance, in greenhouse farming. In the CO2 recovery plant the flue gases are first cooled and washed and then absorbed in an aqueous solution of monoethanolamine (MEA). In the next stage, the captured CO2 is desorbed from the MEA solution and finally liquefied in order to be transported by tank truck. The following description of the CO2 capture and liquefaction process is largely based on the general description of the process at the waste incineration plant in Duiven, the Netherlands, provided by Houben and Boerleider (2020). Additional information obtained by literature searches is provided, e.g. on auxiliary materials (chemicals) used and the processing temperatures and pH of the scrubber water and absorber solution. A process diagram of the CO2 capture installation is provided in Figure 5. The various elements of the installation will be described next. DCC-tower: In a direct contact cooling (DCC) tower, flue gas is simultaneously cooled from about 65 to 45 C and washed to remove residues of sulphur dioxide by adding caustic soda to the scrubbing water. Cooling improves the absorption of CO2 in the subsequent stage and minimises solvent loss due to evaporation. For effective removal of sulphur dioxide the pH should be in the same range as for the flue gas desulphurisation (FGD) unit, with pH values in the range 5-7. The optimum pH for the dissolution of SO2 is about 5 (Houben and Boerleider, 2020). Page 99 of 160 RIVM report 2021-0143 CO2 absorber: CO2 is removed from flue gas by bringing it into contact with an absorption agent, also called a solvent. The solvent is usually a solution of MEA in water. Other amine absorption agents can be used, such as diethanolamine (DEA) or methyldiethanolamine (MDEA). Nonamine based solvents are also available, such as glycol based. In the absorber, CO2 binds to MEA, removing about 80-85% of the CO2 from the flue gas. The inlet temperature of the absorber is about 45 C and the outlet temperature about 60 C. MEA is a weak base with a pKa of 9.51 (Gangarapu, 2014). The pH of the MEA solution decreases with the CO2 loading, starting at a pH of about 13 and finally reaching a pH of about 8 (Lv et al., 2015; Zhang et al., 2015). Usually, the absorber is equipped with an integral recirculating water wash stage for the removal of MEA solution droplets and aerosols. A small fraction of the recirculating wash water is going to the absorber in order to balance the water that is lost from the absorber (Khakharia, 2015; Moser et al., 2014; Knudsen et al., 2009; IEAGHG, 2012; IPPC, 2005). Figure 5 Process diagram of the CO2 capture unit taken from Fernandez (2013) In the acid washer, flue gas from the absorber is treated, usually using sulphuric acid, to maintain the pH below a value of 4-5 Knudsen et al. (2013). According to Khakharia (2015) the pH acid wash solution was maintained at a value of 3 in their pilot plant The maximum temperature in the absorber is about 60 C, which is the outlet temperature of the flue gas leaving the absorber and the temperature of the lean solvent entering at the top of the absorber (Khakharia 2015; Supekar, 2015). At the acid wash stage, water and basic solvent droplets, vapour such as ammonia and decomposition products from the MEA solution are removed from the flue gas (Houben and Boerleider, 2020; Khakharia, 2015; Knudsen et al., 2013). The absorbed CO2 in the enriched solvent is removed in the stripper by heating the saturated MEA solution with steam to a temperature of about 120 C (100-145 C). Steam/water is recovered in the condenser and fed back to the stripper, while the CO2 product gas leaves the stripper (IPPC, 2005). Page 100 of 160 RIVM report 2021-0143 After the absorption and stripping section, the captured CO2 is liquefied by compression and cooling. In the first step the concentrated CO2 stream from the CO2 stripper is cooled from about 120 C when leaving the stripper to about 35-40 C before entering the CO2 compression section (Seo et al., 2015; Supekar, 2015) and washed by direct contact with cold circulating water (Usher and Cerimele, 2012). As the gas stream cools, part of the water that is present is condensed and captured. In the next stages, the gaseous CO2 stream is compressed and cooled to finally produce liquid CO2. The first stage is compressing the CO2 gas to a pressure of about 16 bar. At compression the temperature rises and the CO2 gas is then cooled back to about 35 C (Seo et al., 2015; Supekar, 2015). Again, at the various compression and cooling stages water condenses and is removed from the CO2 gas stream in knock-out drums. In this way a concentration of about 150 ppm of water in the CO2 will be established. Remaining water is removed in the drier section using a desiccant such as activated alumina or silica gel (Topham et al., 2014). Triethylene glycol can also be used as a dehumidifier (IEAGHG, 2012). Water removal is essential, as water accelerates corrosion, especially in the presence of CO2 and other acid substances such as H2S, NO2 and SO2. Furthermore, ice and hydrate formation during gas conditioning can cause damage to or even plugging of process equipment. Therefore, drastic drying is required prior to CO2 transport (Walspurger and van Dijk, 2012). According to information provided by Houben and Boerleider (2020), a drying section is present at the site in Duiven but no information was provided on the type of desiccant used. An inquiry with the company AVR revealed that in Duiven alumina (Al2O3) is used as a drying agent. After drying, the CO2 is liquefied by cooling the pressurised gas (16 bar) to a temperature of -16 C. Condensed water is also removed at this stage. There was no information in the process description provided by Houben and Boerleider (2020) on the presence of an additional AC adsorber. It was therefore assumed that there was no AC bed present for the removal of impurities from the captured CO2 at the AVR site in Duiven. The planned CO2 recovery facility at the Twence site in Hengelo/ Enschede will include an AC filter (Acker et al., 2019). CO2 can be liquefied under various conditions (e.g. pressure and temperature) between the triple point and the critical point. At the site in Duiven low-pressure refrigerated liquid CO2 is produced. Besides this type of liquefied CO2, high-pressure liquid CO2 (at a pressure of about 69 bar and kept at an temperature of around 18 C in steel cylinders) can be produced. Low-pressure liquid CO2 is usually transported in insulated road tankers or trailers at a pressure of around 21 bar and a temperature of around -18 C (Linde, 2021). The Twence CO2 recovery facility, for instance, will produce liquid CO2 at a pressure of about 16-18 bar and a temperature of -26 C (Acker et al., 2019). 6.2 Removal of flue gas components in the carbon capture process As described in Section 3.3, the flue gas from waste incineration is thoroughly treated to remove different kinds of pollutants such as SOx, Page 101 of 160 RIVM report 2021-0143 NOx, CO, dust, and trace impurities such as mercury, dioxins and PAHs. In the carbon capture and liquefying process various treatment and processing steps are applied that also influence the composition of the flue gas and the liquid CO2 produced. The following section describes what is likely to happen in the carbon capture and liquefaction process to the PFASs that have survived the waste incineration stage and to those that are likely to be formed as by-products and might not be captured by the various preceding flue gas treatment steps. As described in Section 5.2, the more volatile PFASs are likely to be only partly captured by the flue gas treatment system of the waste incinerator - especially those that are inert or non-polar or have nonionising functional groups. At the various stages in the carbon capture process, PFASs can be removed from the flue gas and the captured CO2. The carbon capture process scheme presented in Figure 5 shows that CO2-lean flue gas and a CO2-rich stream are the two main streams that are separated in the absorber-stripper section. Besides these, aqueous waste streams also result from the process. The focus in this report is on flue gas and recovered CO2. Before being emitted to the atmosphere, the flue gas entering the carbon capture and liquefying process is washed three times, i.e. in the DCC tower with a caustic solution, in the absorber tower and in the acid wash section. The CO2-rich stream is washed twice before going to the compression and cooling section, where the captured CO2 is liquefied - that is in the wash section of the stripping tower and in the CO2-wash section. At the stages in the liquefying process where water is condensed and removed into the water knock-out drums and in the drying section, possible residual contaminants can also be removed from the CO2 stream. Each of these stages of the carbon capture and liquefying process will be discussed in the following paragraphs with a focus on the removal of PFASs. Measured data on the removal of flue gas components in the CO2 recovery process As far as is known to date information on the removal of PFASs via the CO2 capture process is not available. Therefore, a qualitative assessment will be made on the degree to which PFASs, if present in flue gas, might end up in both the captured and liquefied CO2 and in the flue gas that is emitted from the CO2 recovery process to the atmosphere. The assessment is based on the applied processes and process conditions such as the acidity of the washing solutions in combination with the physical-chemical properties of the different PFASs that might be present in the flue gas from which the CO2 is recovered. There are only a few studies in the scientific literature that address the effects of carbon capture systems on the emissions of air pollutants from combustion facilities. There is some quantitative information on the removal of acid components like HCl and HF and particulate matter at the various wash stages. Koornneef et al. (2010) mentioned that for non-methane volatile organic compounds (NMVOCs) there is a lack of Page 102 of 160 RIVM report 2021-0143 quantitative information on the effect of CO2 capture and still to date there seems to be little or no information. The available information on the well-known flue gas components will be discussed first to provide some quantitative information, which will then be used for the qualitative assessment of the removal of the different kinds of PFASs. The removal and accumulation of dust, SOx, NOx, HCl and HF in a CO2 recovery plant were assessed by Iijima et al. (2007) by measuring these components in both the gas and liquid streams at the inlet and outlet of the different sections in the CO2 recovery plant. The measurements of dust showed that the capture efficiency of dust is about 40-50% in the combined flue gas cooler and DCC tower and about 40-60% in the CO2 absorber. The removal of SOx at the cooler was 98%, while only about 1-3% of the NOx was removed. The tests performed by Iijima et al. (2007) confirmed that no chlorine or fluorine was detected in the flue gas after the DCC and absorber solvent section, and that chlorine and fluorine were already deeply removed upstream of the CO2 recovery plant by the preceding flue gas desulphurisation system and other pretreatment equipment. Acid gases such as SO2, NO2 and HCl react with MEA to form heat-stable salts (Kohl and Nielsen, 1997; Rao and Rubin, 2002; Laribi et al., 2018; Islam et al., 2011). Rao and Rubin (2002) reported the following removal efficiencies by the MEA absorber: for SO2 >99%, NO2 20-30% and for HCl 90-95 %. Koornneef (2008) provided an overview of removal efficiencies for various flue gas components based on various publications (see Table 13). According to Koornneef (2008), mercury and other heavy metals may be partially removed in the CO2 capture process. He reported that mercury is found in the MEA reclaimer bottoms. For indicative purposes he assumed a removal efficiency of 50%. Table 13 Removal efficiencies for some acid flue gas components (Koornneef, 2008) Compound Removal efficiency (%) Comments SO2 90 Depends on type of amine, highest for MEA NOx 1.25 In the range 1-3% HCl 95 Based on Rao and Rubin (2002) HF 90 Lower than for HCl (own assessment) High removal rates are obtained for gas components forming highly soluble salts and those that are strong acids with low pKa values and low air-water partition coefficients. The log KAW for HCl and HF is <-2 with pKa's of -6 and 3, respectively. For non-reactive and nondissociating gaseous components with high partition coefficients such as nitrogen oxides, the removal rate is low. The log KAW for nitrogen oxides is between 0.5 and 1.5. Page 103 of 160 RIVM report 2021-0143 Dissociation of PFASs in scrubber and wash liquids To qualitatively assess the removal of PFASs, the same approach as for the flue gas treatment at the waste incineration plant is used here. Within the group of perfluoralkyl sulphonamides (FASAs)With a pKa values between 6.3-9.7, this means that in the DCC tower FASAs are only slightly dissociated. However, in the MEA scrubber FASAs are completely dissociated at a pH of 8-13. For other perfluoralkyl sulphonamides, such as the methyl- and ethyl-substituted and sulphonamido ethanols, reported pKa values are higher, in the range 8-14. This results in a situation where the degree of dissociation in the MEA absorber is more diverse and uncertain, varying from almost complete to about 10% and not dissociated at all for MeFOSE and EtFOSE with a reported pKa value of 14.4 (Ahrens et al., 2012). Estimated pKa values for the carboxylate groups of sulphonamido acetates (PFASAAs) range from 3.86 to 4.04 (Rayne and Forest, 2009b), resulting in a high degree of ionisation in the DCC tower (pH 5-7) and complete dissociation in the MEA scrubber (pH 8-13). PFASs can be removed in the acid washer as well as in the DCC tower and MEA scrubber. The acid washer treats the flue gas coming from the MEA scrubber. The pH of the feed of the acid washer is about 3 and it is maintained at a value below 4 to 5 in the washer. For near complete dissociation, the pKa should be lower than 2, only PFASs with sulphonate and phosphate groups being largely dissociated (50-90%). Based on the above information, for PFASs that are fully dissociated in the DCC tower and the MEA absorber, the removal efficiency is expected to be in the same order as for SO2, HCl and HF. Thus, near complete removal can be assumed, with a removal efficiency of about the same magnitude (>95%) as for inorganic acid components at each stage. It is, however, important to consider that in the case of absorption, the air-water partition coefficient (KAW) - will determine the extent to which a chemical will dissolve from the gas phase into the acid wash solution. For dissociating substances, the fraction dissociated has to be accounted for by using the effective dimensionless air-water partition coefficient, also known as the air-water distribution coefficient (DAW), as explained in Section 5.2. Formation of reaction products with monoethanolamine, heat-stable salts Of the potentially reactive gas phase impurities that may enter the absorber such as organic acids (formic or acetic acids), HCl, HCN, SO2, NH3 and mercaptans, the acidic compounds form salts with the alkaline amines. If the acids are stronger than CO2 and H2S, their amine salts are not efficiently decomposed under the stripping conditions (which are designed to decompose the amine-CO2 and amine-H2S salts), and they build up in the solution as heat-stable amine salts (Kohl and Nielsen, 1997). According to Rao and Rubin (2002), besides acid gases such as SO2, NO2 may also react with MEA to form heat-stable salts. Heat-stable salts may also be formed through reaction with MEA degradation products that are formed from the oxidation of MEA due to oxygen. Well-known degradation products are carboxylic acids such as Page 104 of 160 RIVM report 2021-0143 formic acid, acetic acid, glycine, glycolic acid and oxalic acid (Scheiman, 1962; Verma et al., 2009; Supap et al., 2011). Carboxylic acids that react with MEA can form the corresponding amide compound by dehydration (Supap et al., 2011; Penttill et al., 2014; Dux and Schallert, 2016). MEA + R-COOH MEA+ + R-COO- Hot spots located in the regenerator section of the scrubbing system might provide a suitable environment for dehydration (Scheiman, 1962), forming the following products: MEA+ + R-COO- MEA-CO-R + H2O The formed product is not a heat-stable salt. The relevance of this reaction was not further assessed. In this report we consider only the formation of heat-stable salts. As with carboxylic acids, other PFASs with an acid group will react with ethanolamine. Thus, for PFASs that are relatively strong acids, that fully dissociate at the prevailing pH in the MEA absorber and that will react with MEA to form heat-stable salts, near complete removal from the CO2 stream can be assumed. Flue gas - MEA liquid partitioning of non-dissociating PFASs Some PFASs without an acid functional group also may react with the scrubber or absorption solutions. Scheiman (1962) suggests that MEA can react with aldehydes and ketones in MEA scrubber solutions to form high-boiling-point amino-alcohol products and points to the possible reaction of acids with alcohols to form a positively charged oxonium ion. Neutral and non-reactive chemicals that are extremely soluble in water and MEA are readily absorbed by amine solutions. They do not, however, react chemically to the amines and are generally expected to be expelled in the stripper, depending on the boiling point of the chemical. On the other hand, neutral non-ionising compounds that are sparingly soluble in water or in MEA remain in the flue gas. Either way, in general the absorption of these compounds is expected to be lower than that of ionising and reactive PFASs, and those that are absorbed are expected to be partially or fully desorbed in the stripper column together with the absorbed CO2. Qualitative assessment of PFAS removal by the wash stages and the MEA absorber An indication of the potential removal via the wash stages and the MEA absorber is obtained in the same way as explained in Section 5.2.2 for flue gas treatment. An absorption factor is calculated for each individual stage. The absorption factor is calculated from the volume-based ratio of the flue gas flow rate (G) and the solvent flow rate (L), the G/L ratio, and the air-water distribution coefficient (DAW). For estimating the absorption in the MEA solution, MEA-based partition coefficients should be used. However, these are available only for those Page 105 of 160 RIVM report 2021-0143 chemicals that are usually removed from gas streams by MEA absorption, such as CO2 and H2S. As no MEA-specific partition coefficients are available, the air-water partition coefficient (KAW) is used instead, as this is the only available alternative and thought to provide a good indication. It should be noted that many neutral organic chemicals are known to have higher solubility in MEA solutions than in water (the salting-in effect). Therefore, the removal in the CO2 absorber based on the KAW is expected to be under estimated. Based on the foregoing, the absorption factors should be considered indicative. They should be seen as a relative measure to compare the removability between substances rather than an absolute measure. Calculating the absorption factors thus requires G/L flow ratios for the DCC tower, the MEA absorber, the acid wash and the CO2 wash stages. Knudsen et al. (2009) reported that for a pilot plant at a coal-fired power station, the optimum absorber liquid (solvent) to flue gas ratio (L/G) lies between 2.0 and 3.0 (kg/kg). An L/G ratio of 2.5 (kg/kg) is chosen that corresponds to a volume-based G/L ratio of about 300. G/L ratios for the DCC tower are calculated from the available data on the flue gas flow rates and DCC water spray flow rates reported in IEAGHG (2012), resulting in an average volume-based ratio of about 650. For the acid wash we used the same G/L ratio as for the DCC tower. For the flue gas emitted from the CO2 recovery plant, the indicative removability for the MEA absorber alone and combined with the DCC tower and acid wash, is presented in Table 14. Dissociation is not accounted for in these calculations. The first column gives the removal efficiency for the MEA absorber alone, showing that little to no absorption is expected for PFASs with a log KAW value of zero or higher. High removal efficiencies are expected for PFASs with a log Kaw of -4 or lower. Assuming equal removal efficiencies for the DCC tower and acid washer, this provides an indication of the total PFAS removal from the flue gas. Overall, for the three washing stages the indicative removal efficiencies are 95% or higher for log KAW values of -3 or lower. Table 14 Indicative absorption factors for the MEA absorber and total PFAS removal including the DCC tower and acid washer log Kaw Removal MEA DCC and MEA DCC, MEA and absorber absorber acid washer -4 97% 100% 100% -3 74% 90% 96% -2.6 53% 71% 82% -2 22% 33% 42% -1 3% 4% 6% 0 0% 0% 1% 1 0% 0% 0% 2 0% 0% 0% 3 0% 0% 0% Page 106 of 160 RIVM report 2021-0143 For the non-polar substances or monopolar substances with log KAW values of about -1, the overall removal in the washing towers and absorber is expected to be low: less than 10% and for the non-polar PFASs with higher air-water partition coefficients even less. Taking into account the dissociation of the compound in the absorber liquids, the absorption factors and the overall removal factor for the flue gas emitted from the CO2 recovery plant is calculated according to the following equations: The absorption factor: / = 1 - / + 1/ - = 1 - (1 - -) (1 - -) (1 - - ) In which: G L DAW Frem-overall Fabs-DCC Fabs-MEA Fabs-acid washi gas flow rate (m3) liquid flow rate (m3) air-to-water distribution constant (-) overall removal factor for the flue gas from the CO2 recovery (-) absorption factor for the DCC tower (-) absorption factor for the MEA absorption stage (-) absorption factor for the flue gas acid wash (-). For the recovered CO2 the calculation needs to be adapted because we are interested in the fraction of PFASs ending up in the CO2 steam. The reason for this is that PFASs that are absorbed by the MEA solution will to some degree be released in the stripper column and end up in the recovered CO2. As a worst-case we assume that the non-dissociated fraction (, see Section 5.2) in the MEA solution will be released completely and end up in the recovered CO2 during the regeneration process in the stripper column. In addition, the removal in the DCC tower has to be taken into account as well as the removal in the CO2 wash. The fraction of PFASs in the recovered CO2 is calculated according to the following equation: 2 = (1 - -) - (1 - -) (1 - -2 ) In which: FCO2 Fabs-DCC Fabs-MEA Fdiss-MEA Fabs-CO2 wash fraction of PFASs ending up in the recovered CO2 (-) absorption factor for the DCC tower (-) absorption factor for the MEA absorption stage (-) fraction of PFASs dissociated in the MEA solution (-) adsorption factor for the CO2 wash stage (-). The results of the qualitative assessment of the removal of the different PFASs from the flue gas in the CO2 recovery process are presented in Appendix VI. The colour coding presented in Section 5.2 is used, red standing for poor removal, orange for average, yellow for good and green for very good. Page 107 of 160 RIVM report 2021-0143 For the presence of PFASs in the recovered CO2 before cooling and liquefying, the following qualitative indication is used: green for a very small amount, yellow for a small amount and red for a considerable amount. Based on the calculations it can be concluded that the substances having the highest tendency to end up in the recovered CO2 stream, are the nondissociating substances with a polar character such as fluorotelomer alcohols with a short perfluoro chain of six carbon atoms or smaller (6:23:2 FTOH) and the group of substituted perfluoroalkane sulphonamido ethanols (MeFASEs and EtFASEs), and also some of the PFCAs such as PFDA and PFUnDA, 12:2 FTS, DONA, and PFOTSi-hydrates. Non-dissociating non-polar PFASs are likely not to end up in the recovered CO2, mainly because according to our assumptions and calculations they are not absorbed by the MEA solution. Removal in the CO2 cooling, compression and drying section Vapour-liquid separator drums are needed to prevent liquid entrainment in the CO2 compressors. Separation by gravity using liquid-vapour separator drums is the simplest and most cost- and energy-effective way to remove the bulk of components with higher density than gaseous CO2. Components with high solubility in water or components with higher boiling points than CO2 will be removed, together with the water in the separator drums (Aspelund and Jordal, 2007). Condensable components, having a boiling point in the same range as CO2, are propane, ethane, H2S, NO2 and SO2, that will condense with CO2 in the final compression-cooling stage (Walspurger and van Dijk, 2012). As the gas is compressed and cooled, most of the remaining water condenses and is removed into the separator drums prior to the compressor stage. With proper design the vapour-liquid separator drums can remove water down to approximately 400-500 ppm (Aspelund and Jordal, 2007). With a CO2 concentration of about 15 mol% in the flue gas entering the CO2 capture process and a content of 95 mol% in the captured CO2 after the regeneration column, the concentration of micro-contaminants, which are in the order of ng.m-3 in the flue gas, would be a factor of 6 higher, assuming that all contaminants remain in the captured CO2 gas stream, but the concentration will still be in the ng.m-3 or part per trillion (ppt) range. At such low concentrations, condensation of microcontaminants at the inter-stage cooling is not likely to occur. To what extent components are removed from the CO2 stream at the interstage cooling steps is difficult to assess. Aspelund and Jordal (2007) indicated that components with a boiling point higher than CO2 and with high solubility in water might be removed to some extent. Boiling points for frequently reported PFASs are reported by ITRC (2020) and Concawe (2015). The lowest boiling points of the PFASs considered are in the same range as the boiling point of water, so some removal with the condensed water might be possible for all PFASs that have boiling points higher than that of water. However, due to the anticipated low concentration, removal is expected to be low. Page 108 of 160 RIVM report 2021-0143 Perfluorinated combustion by-products that are formed from the incineration of PFASs have boiling points comparable to that of CO2. They will therefore probably condense with the liquefied CO2. According to the phase change data, perfluorocyclobutane will be in liquid form and condense with the CO2. CF4, having a boiling point of -128 C, which is much lower than the boiling or sublimation point of CO2 (-78.5 C), will be in the gaseous phase in the conditions where CO2 is liquefied. In conclusion, of the fluorinated combustion by-products that are formed, perfluoroethane and perfluorocyclobutane may be present in the liquid CO2. However, as stated before it is unlikely that these PFCs will end up in the recovered CO2 as they will not be absorbed by the MEA solution. This is especially true of the volatile PFCs. Our assessment also shows this to be true for the higher molecular weight PFCs (C4-C10). Additionally, contaminants may be removed in the drying section depending on the process and type of drying medium used. The AVR site in Duiven for instance uses activated alumina as a drying agent. Activated alumina is a polar adsorbent having a high affinity with polar substances such as water and alcohols and are therefore also called a hydrophilic adsorbent. There are several other polar adsorbents, such as zeolites and silica gel. As discussed before polar compounds such as organic acids in particular bind strongly to alumina and other polar compounds such as those with a hydroxyl group also adsorb well, as indicated by Filho and Do Carmo (2004), see also Section 5.2.1. Thus, PFASs with an acid en group such as PFCAs and PFSAs and those with a hydroxyl group such as FTOHs are also expected to strongly bind to polar adsorbents like alumina. Arp et al. (2006) show that FTOHs bind a factor 1000-10,000 better to activated alumina, quartz and calcium carbonate than FTOs. This shows that fluorinated substances, compounds with a polar group, bind better to alumina than non-polar ones. Furthermore, small PFAS molecules bind less well than larger ones (Arp et al., 2006). Any PFAS with a highly polar functional group (acids and alcohols) still present after compression and cooling will bind to the alumina and will be removed from the CO2 to some extent before the CO2 is liquefied. Neutral and non-polar compounds will not bind (or hardly bind) to alumina. In conclusion, to what extent components are removed from the CO2 stream is difficult to indicate. On the basis of the available information we assume that microcontaminants are not at all, or only to a very limited extent, removed at the inter stage cooling. Any PFAS with a highly polar functional group (acids and alcohols) still present after compression and cooling but before liquefaction, will bind to the alumina and will be removed from the CO2 to some extent at the drying stage. Neutral and non-polar compounds, such as perfluorinated products of incomplete combustion, will not bind (or will hardly bind) to alumina. They might be condensed with the liquid CO2. However, it is unlikely that these compounds will end up in the recovered CO2 because they will not be absorbed in the MEA solution. Page 109 of 160 RIVM report 2021-0143 6.3 Conclusions Compounds with a high air-water partition coefficient are only partially or not at all absorbed in the absorption liquid of the absorption-desorption section and therefore do not end up in the extracted CO2 stream but are emitted via the flue gas from the recovery process. This applies, for example, to the fluorotelomeric olefins, the iodine-containing compounds and perfluorocarbon compounds. Strong acids (PFCA, PFSA, FTS, monoand diPAP, PFECAs, etc.) are completely dissociated at the prevailing pH of the MEA absorption solution and form heat-stable salts. They will therefore also not end up in the recovered CO2 stream. The substances that have the highest tendency to end up in the recovered CO2 stream are non-ionising substances (or those that ionise only to a limited extent) with a polar character. This mainly applies to fluorotelomer alcohols with a short perfluoro chain of six carbon atoms or smaller (6:2-3:2 FTOH) and the group of substituted perfluoroalkane sulphonamido ethanols (MeFASEs and EtFASEs). Finally, contaminants may be removed in the drying section depending on the process and type of drying medium used. Acid compounds such as PFCA and PFSA can bind to alumina, which is a polar adsorbent that for instance is used in the CO2 recovery process at the AVR site in Duiven. Compounds containing a polar group such as fluorotelomer alcohols can also bind to alumina through the formation of hydrogen bridges. Because of this it can be expected that members of the above-mentioned three PFAS groups will bind to some extent to the applied alumina. As an overall conclusion it is expected that most of the PFASs considered will not end up (or will do so only to a very limited extent) in the extracted CO2 due to the physical and chemical processes in the washing section, in the CO2 regeneration section and at the liquefaction stage. Of the substances considered, the ones with the highest tendency to end up in the recovered CO2 stream are substances with a polar character that do not ionise (or do so only to a limited extent). This mainly applies to fluorotelomer alcohols with a short perfluoro chain and the group of substituted perfluoroalkane sulphonamido ethanols (MeFASEs and EtFASEs). Page 110 of 160 RIVM report 2021-0143 7 Conclusions and recommendations 1. What is the precise definition of a PFAS and what connection is there between the advisory list of individual PFASs in the Temporary Action Framework and that in the Knowledge Document of the Expertise Centre PFAS? In this report we consider all compounds with at least one CF2 moiety (i.e. CnF2n-, n 1) as PFASs. This broad definition is chosen to ensure the inclusion of all past definitions and the definitions that are under consideration in the ongoing work of the OECD and the REACH restriction proposal committee. However, the primary focus is on those PFASs with a perfluoroalkyl moiety with three or more carbons, following the OECD definition. Ozone-depleting substances matching the broader definition such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and bromine containing Halons that are used as refrigerants, blowing agents, aerosol propellants, degreasing and fire-suppressing agents (and, in principle, the short-chain hydrofluorocarbons that do not have ozone-depleting properties but are known to act as greenhouse gases), are not part of this study. PFASs are normally divided into two main subgroups: non-polymeric and polymeric PFASs. There are, however, many different groups of PFASs, each with their own physical, chemical and toxicological properties. The two action frameworks discussed in Chapter 2 aim to facilitate the management of PFASs in soil, sediment and water. The PFASs that are to be measured and monitored according to these frameworks have been selected on the basis of their occurrence in soil sediment and (surface) water in The Netherlands. All the substances mentioned in the two action frameworks are generally regarded as PFASs according to all available definitions. The listed PFASs are considered relevant to the management of contamination in soil, sediment and surface water. However, their relevance to assessing the safety of incineration gases can be questioned, since the incineration of PFAS-containing waste may produce other PFASs. 2. Can PFASs be present in the flue gases of a waste incinerator as a result of not breaking down (completely)? Yes, despite efficient thermal degradation in the combustion chamber, the presence of PFASs in the flue gases of waste incinerators cannot be ruled out. To limit the formation of pollutants during waste incineration and their emission into the environment, legal requirements for operating conditions and emission limit values for hazardous pollutants are set for waste incineration facilities. Page 111 of 160 RIVM report 2021-0143 The minimum requirements for non-hazardous waste are a combustion chamber temperature of at least 850 C, for at least 2 seconds, in the presence of at least 6% oxygen. For hazardous waste, the minimum temperature of the combustion gases must be 1100 C. If these conditions are met, waste incineration is expected to result in a high degree of thermal destruction in the combustion chamber for the groups of PFASs considered, with the exception of PFCs. The short-chain PFCs (C1 and C2) are likely to be formed as products of incomplete combustion from the incineration of PFASs. PTFE is a fully fluorinated polymer that is the most thermally stable of all known fluorinated polymers. On the basis of experimental data, it is expected that PTFE will thermally degrade completely at the minimum required combustion temperature of 850 C. However, polymers are solid materials that must evaporate before combustion can occur. Due to their high molecular weight polymers do not evaporate as such but rather first thermally degrade into smaller molecules that evaporate and can be incinerated in the combustion chamber. Key to the combustion of those solid materials are the temperature in the combustion bed, the residence time of the combustion material on the grates of the incinerators and the degree to which the material is mixed. If these factors are insufficient, the material may leave the incinerators incompletely burned via the bottom ashes. The temperature in and at the surface of the bed are well above 1000 C and thus high enough for the complete pyrolysis of PTFE. Like non-polymeric PFASs, short-chain PFCs are products of incomplete combustion formed on the incineration of polymeric PFASs. Most important to note is that 100% thermal destruction at waste incineration is unlikely to occur. The central question is to what extent PFASs can thermally be destroyed; and from the studied literature it is concluded that thermal destruction is efficient and a high degree of thermal degradation is usually achieved. Also critical is the definition of complete combustion. Complete combustion could refer to complete mineralisation to HF and CO2. It could also mean that the original compounds are destroyed without conversion into end products. In practice, full mineralisation will hardly ever occur, as thermal degradation is always accompanied by the formation of various gaseous organic fluorine-containing products. If the minimum requirements are met, the formation of combustion by-products seems to be limited mainly to the smallest members of perfluorinated carbons, CF4 and C2F6. Both are potent greenhouse gases, resistant to high temperatures and most likely to survive the combustion process. These gaseous PFCs have a much stronger global warming potential compared to CO2. Short-chain PFCs are expected to be the main products of the incomplete combustion of PFASs and fluoropolymers. For other combustion products, such as fluorinated dioxins and furans and perfluoro acetic acid, it is judged that formation from PFASs is unlikely. However, the formation of dioxins and furans cannot be completely ruled out because of the potential formation under unfavourable Page 112 of 160 RIVM report 2021-0143 combustion conditions of fluorinated benzenes, which could serve as precursors to fluorinated dioxins and furans. On the other hand, fluorinated dioxins and furans have not been detected in waste incinerator flue gas or fly ash. All things considered, the formation of fluorinated dioxins and furans is not expected. Our conclusions on the expected thermal destruction of PFASs and fluorinated polymers are based largely on laboratory experiments and qualitative theoretical assessments. Field measurements clearly show that various PFASs have been detected in flue gas and incineration products such as bottom ash and fly ash, leading to the conclusion that, despite efficient thermal degradation in the combustion chamber, the presence of PFASs in the flue gases of waste incinerators cannot be ruled out. 3. Can PFASs (not broken down or broken down into smaller molecules) be captured from flue gases after one or more cleaning steps? This depends very much on the physical and chemical properties of the different groups of PFASs considered. Some types of PFASs may be efficiently removed from flue gas while for others removal is expected to be less efficient. From the qualitative assessment of the removal efficiencies of the flue gas treatment and the CO2 recovery processes for the PFASs considered, the types of PFASs with the strongest tendency to pass through the flue gas treatment system are iodine-containing PFASs, fluorotelomer olefins (FTOs), the perfluoroalkanes (PFCs), the fluorotelomer alcohols with a short perfluoro chain of 3 to 5 carbon atoms (3-5:2 FTOH) and the fluorotelomer acrylates (FTACs) - assuming that these compounds survive the combustion process. 4. Can PFASs (partly depending on the answers to questions 2 and 3 above) be present in the carbon dioxide recovered from waste incinerator flue gases? The high degree of thermal degradation in the combustion chamber, the removal of PFASs during flue gas treatment and the subsequent CO2 recovery process mean that the presence of certain PFASs in the recovered CO2 is unlikely. However, it cannot be entirely ruled out. Due to the physical and chemical treatment steps in the CO2 regeneration process it is expected that most of the PFASs considered will not end up in the extracted CO2 - or only to a limited extent. Of the substances considered, the ones with the greatest likelihood of ending up in the recovered CO2 stream are non-dissociating substances with a polar character, which mainly relates to fluorotelomer alcohols with a short perfluoro chain and the group of substituted perfluoroalkane sulphonamido ethanols (MeFASEs and EtFASEs). Results from field measurements show that various PFASs have been detected in flue gas. The total PFAS concentration found in flue gas was about 20 ng.m-3. No measurements of PFASs in recovered CO2 have been conducted, as far as we know. Page 113 of 160 RIVM report 2021-0143 As an order of magnitude estimate, 10 ng.m-3 could be used for the concentration in recovered CO2 based on the total PFAS concentration measured in flue gas. However, the concentration is expected to be reduced significantly during the CO2 recovery process. 5. Is the chemical analysis of fluoride sufficiently accurate to reveal the presence of PFASs in flue gases and carbon dioxide? No. Existing methods such as HF measurement and TOF analysis are not suitable or sufficiently accurate to determine the presence of PFASs. The literature study shows that no standardised method is yet available to measure the emission concentration of PFAS compounds in the flue gases of waste incineration plants. It is technically possible to sample gaseous, dust-bound and dust-based (aerosols) PFAS in flue gases. GC-MS and HPLC-MS/MS are suitable analytical techniques to measure PFASs. HPLC-MS/MS has been accepted in available standard requirements for determining the amount of PFASs in soil, dredge, sediment, groundwater and surface water. The current HF measurement methods (ISO-NEN 15713:2011 and NENEN-ISO 10304-1) are not considered a suitable or replacement method for PFAS measurement, as fluoride measurements are not selective for the PFAS. Furthermore, a feasible LOQ for the measurement of the emission concentration of PFAS compounds in flue gases is estimated to be in the range ng.m-3, whereas the LOQ of the fluoride method is an order of magnitude higher by a factor of 1000. As an alternative, the total organic fluorine (TOF) measurement method can be used to indicate the presence of PFASs in flue gases. It is selective for the sum of PFASs as part of the TOF. However, the LOQ for the TOF measurement is expected be between 50 and 250 ng.m-3 flue gas, which is well above the achievable LOQ of individual PFASs. This means that the TOF measurement is not a suitable indicator of the presence of PFASs in flue gases. In view of the expected presence of gaseous PFAS compounds in flue gases, it is logical to compile a PFAS target list for chemical analysis. It would also be sensible to measure the non-target PFAS compounds, because the nature and extent of PFASs in flue gases is unknown. This can easily be done through the use of MS detection techniques. 6. Can RIVM advise on the possible presence of PFASs in the carbon dioxide that is recovered from waste incinerator flue gases for applications such as growth improver in greenhouse horticulture? The presence of certain PFASs in the recovered CO2 is unlikely but cannot be entirely ruled out. Concentrations of PFASs in the recovered CO2 are expected to be low - a maximum of a few nanograms per cubic metre. As far as we know, no measurements of PFASs in recovered CO2 have been conducted that could confirm our findings and quantify their Page 114 of 160 RIVM report 2021-0143 presence. In order to confirm whether PFASs are present in recovered CO2 and to what extent measurements should be conducted, measurements should be conducted simultaneously in the flue gas from the waste incinerator and CO2 recovery plant and in the recovered CO2. This could provide some insight into how PFAS might enter and leave the CO2 recovery process via (gaseous) streams. In addition to the standard sets of PFASs measured in soil and the aquatic environment, it is recommended to measure the PFASs that this study shows to be most likely to survive the combustion process, pass through the flue gas treatment system or end up in the recovered CO2, if these are not already included in the standard lists. 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Page 133 of 160 RIVM report 2021-0143 Page 134 of 160 RIVM report 2021-0143 List of abbreviations General AOF ADRT BDE BTX CLP DCC EPS FGD GAC GC HPLC LOQ MS MSWI NMVOC PAC PCDDs PCDFs PFCB PFAS PIGE pKa RWS SNCR SCR SVHC TGA TOF TOP VOCs PFASs ADONA DONA diPAP ECTFE EtFASA EtFASE ETFE FASA FASAA FEP FRD-903 FT FTI FTOH adsorbable organic fluorine Avira dioxin reduction technology bond dissociation energy benzene, toluene and xylenes classification, labelling and packaging direct contact cooling electrostatic precipitator flue gas desulphurisation granular activated carbon gas chromatography high-pressure liquid chromatography limit of quantification mass spectrometry municipal solid waste incinerator non-methane volatile organic compound powdered activated carbon polychlorinated dibenzo-p-dioxins polychlorinated dibenzofurans perfluorocyclobutane per- and polyfluorinated alkyl substances particle-induced gamma ray emission negative log of the acid dissociation constant Rijkswaterstaat, executive agency of the Ministry of Infrastructure and Water Management, selective non-catalytic reduction selective catalytic reduction substance of very high concern thermogravimetric analysis total organic fluorine total oxidisable precursor PFAS volatile organic chemicals 3H-perfluoro-3-[(3-methoxy-propoxy)propanoic acid], ammonium salt 3H-perfluoro-3-[(3-methoxy-propoxy)propanoic acid] disubstituted polyfluoroalkyl phosphate (see also PAP) ethylene/chlorotrifluoroethylene copolymer N-Ethyl perfluoroalkane sulphonamide N-Ethyl perfluoroalkane sulphonamido ethanol ethylene/tetrafluoroethylene copolymer perfluoroalkane sulphonamide perfluoroalkane sulphonamido acetic acid fluorinated ethylene propylene polymer, tetrafluoroethylene/hexafluoropropene copolymer 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)-propanoic acid fluorotelomer (substance) fluorotelomer iodide fluorotelomer alcohol Page 135 of 160 RIVM report 2021-0143 FTAC FTMAC FTS FTUCA GenX HFE HFP HFPO-DA MeFASA MeFASE MFA PAF PAP PASF PCTFE PE PFA PFAA PFAE PFAI PFAL PFASA PFASE PFBA PFBS PFC PFCA PFDA PFDoDA PFDS PFECA PFESA PFHpA PFHpS PFHxA PFHxDA PFHxS PFIB PFNA PFOA PFODA PFOS PFOSA PFPA PFPE PFPeA PFPeS PFPIA PFSA PFSiA PFSIA Page 136 of 160 fluorotelomer acrylate fluorotelomer methacrylate fluorotelomer sulphonate fluorotelomer unsaturated carboxylic acid technology used in the production of fluoropolymers hexafluoroethane hexafluoropropylene hexafluoropropylene oxide dimer acid N-Methyl perfluoroalkane sulphonamide N-Methyl perfluoroalkane sulphonamido ethanol tetrafluoroethylene/perfluoro(methylvinyl ether) copolymer perfluoroalkanoyl fluoride per/polyfluoroalkyl phosphoric acid ester, per/polyfluoroalkyl phosphate, fluorotelomer phosphate perfluoroalkane sulphonylfluoride poly(chlorotrifluoroethylene) polyethylene perfluoroalkoxy alkanes or tetrafluoroethylene/perfluoro(propylvinyl ether) copolymer perfluoroalkyl acid per/polyfluoroalkyl ether perfluoroalkyl iodides perfluoroalkyl aldehyde perfluoroalkyl sulphonamide perfluoroalkyl sulphonamido ethanol perfluorobutanoic acid perfluorobutane sulphonic acid perfluorocarbon perfluorocarboxylic acid perfluorodecanoic acid perfluorododecanoic acid perfluorodecane sulphonic acid per/polyfluoroether carboxylic acid per/polyfluoroether sulphonic acid perfluoroheptanoic acid perfluoroheptane sulphonic acid perfluorohexanoic acid perfluorohexadecanoic acid perfluorohexane sulphonic acid perfluoroisobutylene perfluorononanoic acid perfluorooctanoic acid perfluorooctadecanoic acid perfluorooctane sulphonic acid perfluorooctane sulphonamide perfluorophosphonic acid perfluoropolyether perfluoropentanoic acid perfluoropentane sulphonic acid perfluorophosphinate / perfluoroalkyl phosphinic acid perfluoroalkyl sulphonic acid perfluoroalkyl sulphinic acid perfluoroalkyl sulphinic acid RIVM report 2021-0143 PFTeDA PFUnDA PTFE PVDF perfluorotetradecanoic acid perfluoroundecanoic acid polytetrafluoroethylene polyvinylidene fluoride Page 137 of 160 RIVM report 2021-0143 Page 138 of 160 RIVM report 2021-0143 Annex I. Overview of waste incineration sites in the Netherlands Province Location Company Type of kiln Groningen Friesland Drenthe Overijssel Gelderland Delfzijl Harlingen Wijster Hengelo Weurt EEW Delfzijl BV REC Harlingen Attero Noord BV Twence afval en energie, AEC & BEC ARN B.V. Duiven AVR Afvalverwerking NoordHolland Alkmaar HVCafvalcentrale Amsterdam Afval Energie Bedrijf Zuid-Holland Rotterdam- AVR Rozenburg Botlek Dordrecht HVCafvalcentrale Moving grate, 2 lines Moving grate Moving grate, 3 lines Moving grate, 3 lines Moving grate, 1 line Moving grate, 2 lines Moving grate, 3 lines Fluidized bed Moving grate, 4 lines AEC: Moving grate HRC: Moving grate Moving grate, 7 lines Vortex ovens Moving grate, 5 lines Fluidized bed NoordBrabant Dordrecht Moerdijk ZAVIN CV Attero AEC Moerdijk Moving concrete floor Moving grate, 4 lines Moerdijk N.V. Slibverwerking Fluidized bed Noord-Brabant (SNB) Roosendaal SUEZ ReEnergy Moving grate, 2 lines Non-hazardous waste refers to household and commercial waste Combustion chamber Parallel Centre Parallel Centre Centre Type of waste Non-hazardous Non-hazardous waste Non-hazadous waste Non-hazardous waste Biomass Hazardous and non-hazardous waste Non-hazardous waste Paper pulp residue Non-hazardous waste and biomass Temperature (C) Average Max 1195 1200 - - 950 1100 900 1100 980 1050 1050 1100 1100 1250 900 1150 Centre Hazardous and non-hazardous waste 1100 1100 3 Counter 4 Parallel Parallel Hazardous and non-hazardous waste and biomass Aqueous hazardous and high caloric petrochemical waste Non-hazardous waste Sludges (waste water) Centre Specific (contagious) hospital waste Non-hazardous 950 1200 890 920 920 890 1200 950 974 1121 1036 1005 1300 1200 Sludges (waste water) Parallel Non-hazardous 950 1170 Page 139 of 160 RIVM report 2021-0143 Annex II. Description of common waste incineration facilities II.1 Fluidised bed furnaces Fluidised bed incinerators are widely applied to the incineration of finely divided waste. For heterogeneous waste, fluidised bed combustion requires the selection and pre-treatment of the waste so that it meets size specifications. Pre-treatment usually consists of sorting and crushing larger inert particles, and shredding. Removal of ferrous and non-ferrous materials may also be required (Neuwahl et al., 2019). A fluidised bed furnace is a lined combustion chamber in the form of a vertical cylinder (Figure 6). In the lower section, a sand bed on a grate or distribution plate is fluidised with air. The waste that is to be incinerated is continuously fed into the fluidised sand bed from the top or side. A schematic overview of a fluidised bed incinerator including the flue gas treatment process is presented in Figure 6. Figure 6 Schematic representation of a fluidised bed incinerator including flue gas treatment system Source: Indaver (2020a). Approximate temperature indication by colour: red = 1000-1200 C; orange = 850-1000 C; yellow = 700-600 C; green = 250-100 C; blue = <80 C. The colour of the stack does not match; the stack temperature is usually in the range of 80-110 C. According to Thom-Kozminesky et al. (2012), the sand bed has a temperature of about 800-850 C. Neuwahl et al. (2019) report that the temperature in the space above the bed is generally between 850 C and 950 C and that in the bed itself the temperature is lower and may be around 650 C. In the bottom part of the bed the material first undergoes partial or complete degassing. Actual combustion of the waste happens in Page 140 of 160 RIVM report 2021-0143 the upper part of the bed, where the secondary air is added. The main advantage of fluidised bed furnaces is the complete mixing of waste and combustion air, thus establishing an even temperature distribution and heat transfer within the furnace. Complete mixing allows the whole mass of waste, fuel and sand to be fully circulated through the furnace, resulting favourable incineration conditions and fast combustion. Typical operation temperatures for fluidised bed furnaces are between 850 and 950 C (SNB, 2019; Indaver, 2020a), with a maximum of 1200 C (Thom-Kozminesky et al., 2012). II.2 Rotary kilns A rotary kiln consists of a cylinder inclined in the transport direction and lined on the inside with refractory material or a cooled steel shell (Figure 7). Figure 7 Schematic representation of a rotary kiln incinerator including flue gas treatment system Source: Indaver (2020b). Approximate temperature indication by colour: red = 1000-1200 C; orange = 850-1000 C; yellow = 700-600 C; green = 250-100 C; blue = <80 C. The interior of the cylinder can be up to 20% filled with fuel, which forms a moving bed. Rotation of the furnace about its longitudinal axis turns over the contents and, by virtue of the inclination, causes it to move toward the lower end (Thom-Kozminesky et al., 2012). The rotary kiln is very versatile with respect to the type of waste that can be processed, ranging from solid materials to paste-like and viscous matter to contaminated liquids, which are injected through simple burners in the combustion chamber. The mean combustion temperature in the furnace is between 800 and 1400 C, and residence times are c. 60 minutes. As a rule, the residence time of the reaction gases in the furnace is insufficient for complete Page 141 of 160 RIVM report 2021-0143 burning, and afterburning in a post-combustion chamber is carried out to ensure complete burning of the combustion gases. Liquid wastes are injected directly into this chamber through burners (Thom-Kozminesky et al., 2012). The temperature in the post-combustion chamber typically varies between 900 and 1 200 C depending on the installation and the waste feed (Neuwahl et al., 2019). Indaver (2020b) indicates that the combustion temperature is maintained at a minimum of 950 C. Neuwahl et al. (2019) report that the operating temperatures of rotary kilns range from around 500 C (when used as a gasifier) to 1450 C (as a high-temperature ash melting kiln). Higher temperatures are sometimes encountered, but usually in non-waste incineration applications. When the kilns are used for conventional oxidative combustion, the temperature is generally above 850 C. Kiln temperatures in the range of 900-1200 C are typical when incinerating hazardous wastes. II.3 Moving-grate furnaces The most common incineration plant for municipal solid waste is a moving-grate incinerator. The older and simpler kind of grate incinerator was a brick-lined cell with a fixed metal grate over a lower ash pit. It is the most widely used process for thermal treatment of wastes. In a moving-grate incinerator the grate conveys the waste in a horizontal or inclined direction towards the end of the combustion chamber (Figure 8). Primary air is distributed beneath the grate. Combustion takes place in the combustion chamber above the grate. Only a small amount of waste is burned on and immediately above the grate; most of it is turned into volatiles. Most of these volatiles are burned in the combustion space above the solid waste. Grate firing has the disadvantage that the generation of reaction products is largely uncontrollable. In the boundary zone between the drying and combustion steps, degasification processes generate carbon compounds that cannot be completely destroyed in the combustion space. Secondary air is injected into the combustion space through nozzles to ensure complete burning of the combustion gases, and intensive mixing of combustion gases to prevent residual unburned gases (ThomKozminesky et al., 2012). The maximum temperature in the fuel bed is reached at the end of the ignition zone. Here, the temperature in the bed as well as that of the flue gas is about 900 C. At the end of the grate, the temperature of the bed has dropped to about 400 C. At this stage the temperature of the gas is slightly higher: about 450 C. After the addition of secondary air to the combustion chamber, the temperature of the flue gas lies in the range 900-1050 C (Gehrmann et al., 2013). Indaver (2020c) states that combustion temperatures in its moving-grate waste incinerator range from 850 to 1000 C. Page 142 of 160 RIVM report 2021-0143 Figure 8 Schematic overview of a grate incinerator including flue gas treatment system Source: Indaver (2020c). Approximate temperature indication by colour: red = 1000-1200 C; orange = 850-1000 C; yellow = 700-600 C; green = 250-100 C; blue = <80 C. Moving-grate incinerators can be subdivided according to the position of the entrance to the afterburn chamber with respect to the grate. The afterburn chamber, or the post-combustion chamber, can be considered as the first duct of the steam boiler. The entrance can be positioned at the beginning, the middle or the end of the moving grate. This determines the direction of the flow of the flue gases over the combustion bed. Therefore, three different types of combustion chambers can be distinguished: parallel flow, counter flow and centre flow kilns (Van der Linden and Briffaerts, 2005). In order to ensure as complete combustion as possible, secondary air is injected, which also facilitates the mixing of the combustion gases. Typically, secondary air injection takes place in the transition area between the kiln and afterburn chamber. Enhanced burning is achieved by counter flow chambers. The residence time is higher using parallel flow, which also leads to higher temperatures in the post combustion chamber (Van der Linden and Briffaerts, 2005). For the municipal solid waste incinerators in the Netherlands, the type of kiln according to the position of the secondary combustion chamber is provided in Appendix I in this report. Page 143 of 160 RIVM report 2021-0143 Annex III: Flue gas treatment techniques III.1 Common treatment steps Each process unit in the flue gas treatment system is designed to remove specific flue gas components. The most common unit processes are listed below, together with their typical operating conditions. Dust collection The separation of solid particles and liquid droplets in an electrostatic precipitator (ESP) is achieved by the action of electrostatic forces in an electric field. Separation efficiency is very good and reaches up to 99% (Achternbosch and Richers, 2002). Typical operating temperatures for electrostatic precipitators are 160-260 C (Neuwahl et al., 2019). Operation at temperatures of up to 450 C is possible but this is generally avoided, as it can increase the risk of polychlorinated dibenzop-dioxin and dibenzofuran (PCDDs/PCDFs) formation. During the process of NOx reduction the temperature in the electrostatic filter the temperature should not be lower than 180 C to prevent the condensation of injected ammonia, which otherwise affects the quality of the fly ash. Operating temperatures of electrostatic precipitators in modern waste incineration plants are around 200 C (Achternbosch and Richers, 2002). Bag filters, also called baghouse filters or fabric filters, are widely used in waste incineration plants. Filtration efficiencies are very high (99%) across a wide range of particle sizes. Bag filters can also be used after an ESP or wet scrubber process. Operating temperatures depend on the bag filter material used and range from 80 C for cotton up to 260 C for polyamide and fibreglass. According to Achternbosch and Richers (2002), fabric filters used in large-scale waste incineration plants are operated at temperatures ranging from 170 to 200 C. Cyclones and multi-cyclones use centrifugal forces to separate dust from the gas stream. Depending on the particle size, cyclones are generally less efficient than bag and electrostatic filters: about 80% of the dust contained in the flue gas can be removed (Achternbosch and Richers, 2002). A major advantage of cyclones is their wide operational temperature range and robust construction. Cyclones can be used at gas temperatures of up to 1300 C (Achternbosch and Richers, 2002). Removal of acid components Acid gases such as sulphur dioxide and gaseous halogenides such as HF are generally cleaned from flue gases by the injection of alkaline reagents into the flue gas. Depending on the technique, the reaction products are either dissolved or dry salts. Three main types of processes are applied: wet, semi-wet and dry. 1) Wet The wet process usually consist of two parts. The first stage is aimed at the removal of acids such as HCl and HF by a water quench. The scrubber solution is typically strongly acidic, with a typical pH between 0 Page 144 of 160 RIVM report 2021-0143 and -1. The scrubbing water can be recycled many times without much fresh water addition. Removal of SO2 at this stage is low. Removal of sulphur dioxide is achieved in a second washing stage, controlled at a pH of 5-7 (Neuwahl et al., 2019). To maintain scrubbing efficiency and prevent clogging in the wet scrubbing system, a portion of the scrubber liquid must be removed from the circuit as waste water. This waste water must be treated before discharge or re-use. 2) Semi-wet Water and the absorption agent (hydrated lime) are injected separately or as a suspension or solution into the hot flue gas flow via a spray tower. The heat of the flue gas serves to evaporate the solvent (water). The reaction products generated are solid and need to be deposited from the flue gas as dust in a subsequent stage, e.g. bag filter. 3) Dry In a dry sorption process, the absorption agent, an alkaline material such as lime is fed into the reactor as a dry powder. If there is no prededusting stage (e.g. electrostatic precipitator or cyclone), particles are removed with the used reagent and reaction products. Solid particles need to be removed from the flue gas as dust in a subsequent stage, normally a bag filter. Reduction of NOx During combustion, part of the nitrogen in the air is oxidised to nitrogen oxides (NOx). There are two important techniques for reducing emissions of NOx: selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR). In the SNCR process, NOx is removed by injecting ammonia or urea into the hot flue gases. The reactions occur at temperatures of between 850 and 1 000 C. In the SCR process, an ammonia-air mixture is added to the flue gas and passed over a catalyst, where ammonia reacts with NOx to give nitrogen and water vapour. To be effective, the catalyst usually requires a temperature of between 150 and 450 C. The majority of systems used in waste incinerators currently operate in the range 180-250 C. Removal of trace organic contaminants and mercury The flue gas of waste incinerators can contain a variety of trace organic compounds such as polycyclic aromatic compounds, chlorobenzenes and monoaromatic hydrocarbons (BTX). Adsorption on coke, lignite or activated carbon (AC) is often applied for the fine cleaning of flue gas after the removal of acid pollutants. This can be done by leading the flue gas through a fixed bed absorber or by injecting activated carbon powder (PAC) into the gas flow, after which the carbon needs to be filtered using bag filters. Alternatively, the powder can be injected before the scrubber section, where the AC is removed, a so-called ADRT (Avira Dioxin Reduction Technology) system. In this system the AC is collected in the filter cake of the waste water treatment section. AC shows a high adsorption efficiency for mercury as well as for PCDDs/PCDFs. Different types of activated carbon have different Page 145 of 160 RIVM report 2021-0143 adsorption efficiencies, which are very much influenced by the manufacturing process. The adsorptive capacity of the solid carbon for the gas tends to increase with the gas phase concentration, molecular weight, diffusivity, polarity and boiling point. AC can adsorb a wide range of VOCs; however, there are some limitations. First, AC is less effective for compounds that are highly polar or volatile or have small diameters. Typical operating temperatures for activated coal adsorption range from 25 to 40 C, although adsorption can take place at temperatures as low as 0 C and even higher than 40 C (Sorrels, 2018). As volatility plays an important role in adsorption, temperatures should stay within certain limits depending on the type of contaminant to be captured. At high temperatures thermodesorption will occur. Thermodesorption is a process used, for instance, to regenerate spent AC. The operating temperature for carbon adsorption very much depends on where in the flue gas treatment process it is applied. Injection of the carbon into the flue gas can be done upstream, after dust filtering or at a later stage, downstream of the web scrubbing system. For the effective capturing of dioxins by AC Lu et al. (2012) showed that the temperature should not exceed 150 C. Vito (2020) indicates that the typical operating temperature is below 50 C (15-80 C) except for the dioxin removal stage, where higher temperatures may be employed. As a maximum an operating temperature of 150 C can be assumed. In the dry process where injected AC and lime are removed by a bag filter, the temperature is about 80-100 C, as indicated below (SNB, 1993, 2019). In the (semi-)dry process involving application of the CircoClean reactor, the temperature is about 165 C according to SLECO (2018). According to Herden et al. (2002), the operating temperature of the CircoClean reactor at a pilot plant was about 140 C. In the wet process, carbon is injected into the flue gas at a temperature of between 160 and 200 C. In the scrubber section, where the carbon is removed, the temperature is about 75 C. SCR systems used for NOx reduction can also destroy gaseous or nonparticle-bound trace organics such as PCDDs/PCDFs through catalytic oxidation. However, to establish high destruction efficiencies the SCR system must be designed accordingly (Neuwahl et al., 2019). III.2 Three examples of flue gas cleaning Three examples of flue gas cleaning configurations for a fluidised bed furnace are described in the following paragraphs. In the first case (SNB, 1993, 2019) the temperature of the flue gas entering the boiler is about 900 C. In the boiler, the flue gas cools to a temperature of about 200 C. Before entering the scrubber, the flue gas is further cooled to a temperature of 160 C. After the washing stages, the temperature is reduced to 75C and then the gas is reheated to 80-110 C to prevent the condensation of water vapour. To remove mercury and trace organics like dioxins, the flue gas is treated with an adsorbent (mixture of AC and calcium hydroxide) and led through a bag filter. Entering the stack, the flue gas is at about the same temperature as when entering the bag filter: 80-110 C. As a final step, heat can be recovered from Page 146 of 160 RIVM report 2021-0143 the cleaned flue gas by condensers before it enters the stack, and the temperature may then be reduced to about 50 C. The second case is the flue gas treatment system at the Sleco fluidised bed incinerator at Doel in Belgium (SLECO, 2018). Hot primary air at 600 C is blown into the sand bed and, above, secondary air is added to ensure complete combustion. Flue gas with a temperature of at least 850 C exits the incinerator through the flue gas duct, where urea is injected to convert oxides of nitrogen into nitrogen gas. In the boiler, where steam is generated, the gas is cooled from about 900 C to an average temperature of 230 C. The first flue gas treatment step is an electrostatic filter for the removal of solid particles (dust). The next step is a semi-wet scrubbing, where lignite and lime are dosed to capture heavy metals, dioxins, chlorine and sulphur. Here, the flue gas is cooled to 165 C. The lime and lignite added in the previous step are removed in a bag house filtering system. The final step is a caustic scrubbing column for the removal of any remaining chlorine and sulphur. At this stage, the flue gas is cooled to 65 C. The third case is the AVR incineration site at Duiven (Houben and Boerleider, 2020). At this site, CO2 is recovered from the flue gas. The recovered CO2 will be used as a plant fertiliser for greenhouse farming. Starting at a combustion temperature of 1200 C, the flue gas decreases to a temperature of about 1000 C as it moves towards the steam boiler. Before it enters the boiler at a temperature of between 850 and 1000 C, ammonia is injected to reduce the formation of NOx by SNCR. In the upper part of the boiler, the temperature is about 650- 700 C and it is gradually reduced to a temperature of 250 or 280 C depending on the heat recovery system applied in the final stage. In the electrostatic filter, the temperature should not be lower than 180 C to prevent the condensation of ammonia, which affects the quality of the fly ash. The electro filter removes up to 99% of the dust (fly ash). To remove dioxins and other pollutants, AC is injected into the flue gas before it enters the washing stage. The AC is captured during the washing. The washing stage consists of three consecutive sections combined in one system, the ADRT system: quench with wash water to remove salts, ammonia and acids (fly ash that passed the electrofilters is also captured by the wash water); the maximum temperature is 77 C; SO2 trap, where SO2 is removed through an alkaline solution (NaOH) at an optimal pH of 5; Ring-jet (venturi washer) to remove aerosols and mercury. Page 147 of 160 RIVM report 2021-0143 Annex IV. Measured PFASs at the ARV sites at Duiven and Rozenburg PFAS Bottom ash Bottom ash Rozenburg Duiven (n=3) (n=2) Fly ash Filter cake Rozenburg Rozenburg (n=1) (n=1) Emission to air Emission Rozenburg to water (average) Rozenburg (n=4)1 (n=2)2 g/kg g/kg g/kg g/kg ng/Nmo g/l PFPeA < 0.10 0.29 & < 0.1 < 0.1 < 0.1 nb < 0.02 PFHxA < 0.10 1.1 & < 0.1 < 0.1 < 0.1 2 < 0.02 PFHpA < 0.10 < 0.1 & < 1.0 < 0.1 < 0.1 0.4 < 0.02 PFOA (lineair) < 0.10 1.3 & < 0.1 < 0.1 < 0.1 8.2 < 0.01 PFOA (branched) < 0.10 0.16 & < 0.1 < 0.1 < 0.1 0.7 < 0.01 PFNA < 0.10 0.12 & < 0.1 < 0.1 < 0.1 0.2 < 0.02 PFBA < 0.10 1.2 & < 0.1 < 0.1 < 0.1 nb < 0.02 6:2 FTS 9.9 36 & < 0.1 < 0.1 < 0.5 0.3 < 0.05 FRD 903 < 1.0 < 0.1 < 0.1 < 0.1 < 0.01 < 0.02 E1 nb nb nb nb nb nb PTFE nb nb nb nb nb nb PPVE nb nb nb nb nb nb PFDA < 0.10 0.42 & < 0.1 < 0.1 < 0.1 2.9 < 0.02 PFUnDA < 0.10 0.21 & < 0.1 < 0.1 < 0.1 0.1 < 0.02 PFDoDA < 0.10 0.17 & < 0.1 < 0.1 < 0.1 1 < 0.02 PFBS 0.59 & < 0.1 3.6 & < 0.1 < 0.1 < 0.1 0.06 < 0.02 PFHpS < 0.10 < 0.1 < 0.1 < 0.1 < 0.01 < 0.02 PFHxS < 0.10 < 0.1 < 0.1 < 0.1 < 0.01 < 0.02 PFPeS < 0.10 < 0.1 < 0.1 < 0.1 < 0.01 < 0.02 PFOS (linear) 0.15 & < 0.1 0.56 & < 0.1 < 0.1 < 0.1 0.1 < 0.001 PFOS (branched) < 0.10 0.22 & < 0.1 < 0.1 < 0.1 0.05 < 0.001 PFOSA < 0.10 0.53 & < 0.1 < 0.1 < 0.1 0.03 < 0.02 PFTeDA < 0.10 < 0.1 < 0.1 < 0.1 0.6 < 0.02 PFTrDA < 0.10 < 0.1 < 0.1 < 0.1 0.1 < 0.02 PFHxDA < 0.20 < 0.1 < 0.1 < 0.1 0.24 < 0.02 PFODA < 2.0 < 0.1 < 0.1 < 0.1 0.08 < 0.02 PFDS < 0.10 < 0.1 < 0.1 < 0.1 < 0.02 < 0.02 4:2 FTS < 0.10 < 0.1 < 0.1 < 0.1 < 0.01 < 0.05 8:2 FTS 0.66 2.5 & < 0.1 < 0.1 < 0.1 1.1 < 0.1 10:2 FTS < 0.10 0.24 & < 0.1 < 0.1 < 0.1 2.1 < 0.05 N-MeFOSA < 0.10 < 0.1 < 0.1 < 0.1 < 0.04 < 0.02 N-MeFOSAA < 0.10 0.13 & < 0.1 < 0.1 < 0.1 < 0.05 < 0.02 N-EtFOSAA < 0.10 < 0.1 < 0.1 < 0.5 < 0.05 < 0.02 8:2 diPAP < 0.10 < 0.2 & < 0.1 < 0.1 < 0.1 < 0.05 < 0.1 1 average of single measurements at four stacks; 2 average of two effluents. Source: Houben and Boerleider (2020; tables 6.4 and 6.5). Page 148 of 160 RIVM report 2021-0143 Annex V. Indication of PFAS removal at flue gas treatment PFAS Total removal in Quench Fluortelomer alcohols 4:2 FTOH Poor 6:2 FTOH Poor 8:2 FTOH Poor 10:2 FTOH Poor Perfluorinated carboxylate acids (PFCAs) PFBA Average PFPeA Poor PFHxA Poor PFHpA Poor PFOA Poor PFNA Perfluorinated sulfonic acids (PFSAs) Poor PFBS Very Good PFHxS Very Good PFOS Very Good PFDS Perfluoroalkyl sulfinic acids (PFSiAs) Very Good PFBSi Poor PFHxSi Poor PFOSi Poor PFDSi Poor Perfluorinated phosphonic acids (PFPAs) PFBPA Very Good PFHxPA Very Good PFOPA Very Good PFDPA Perfluoroalkyl phosphinic acids (PFPiAs) Very Good C6/C6 PFPiA Poor C8/C8 PFPiA Poor C6/C8 PFPiA Poor Total removal in SO2 trap Poor Poor Poor Poor Very Good Very Good Very Good Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Good Very Good Very Good Very Good Very Good Very Good Good Poor Total removal Removal in venturi by PAC wash Total removal Poor Poor Poor Poor Average Good Good Very Good Average Good Good Very Good Very Good Very Good Good Poor Good Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Good Average Poor Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Average Poor Poor Very Good Very Good Very Good Very Good Very Good Very Good Page 149 of 160 RIVM report 2021-0143 PFAS Total removal in Quench Fluorotelomer olefins (FTOs) 4:2 FTO 6:2 FTO 8:2 FTO 10:2 FTO 12:2 FTO Fluorotelomer sulfonate (FTSs) 4:2 FTS 6:2 FTS 8:2 FTS 10:2 FTS 12:2 FTS Fluorotelomer iodides (FTIs) 4:2 FTI 6:2 FTI 8:2 FTI 10:2 FTI 12:2 FTI Perfluoroalkyl iodides (PFAIs) PFBI PFPeI PFHxI PFHpI PFOI PFNI PFDI PFUnI PFDoI PFTrI PFTeI Perfluoroalkyl sulfonamides (FASAs) FBSA FPESA FHXSA FHpSA FOSA Poor Poor Poor Poor Poor Very Good Very Good Good Average Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Average Poor Poor Poor Poor Total removal in SO2 trap Poor Poor Poor Poor Poor Very Good Very Good Very Good Good Average Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Good Average Average Poor Poor Total removal Removal in venturi by PAC wash Total removal Poor Poor Poor Poor Poor Very Good Very Good Very Good Average Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Average Poor Poor Poor Poor Average Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Poor Average Good Very Good Very Good Poor Average Good Very Good Very Good Poor Poor Poor Poor Poor Poor Poor Average Average Good Good Poor Poor Poor Poor Poor Poor Poor Average Average Good Good Average Poor Poor Poor Poor Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Page 150 of 160 RIVM report 2021-0143 PFAS Total removal in Quench N-Methyl perfluoroalkane sulfonamides (MeFASAs) MeFBSA Poor MeFPeSA Poor MeFHxSA Poor MeFHpSA Poor MeFOSA N-Ethyl perfluoroalkane sulfonamides (EtFASAs) Poor EtFBSA Poor EtFPeSA Poor EtFHxSA Poor EtFHpSA Poor EtFOSA Perfluoroalkyl sulfonamido ethanols (FASEs) Poor FBSE Good FPeSE Good FHxSE Average FHpSE Poor FOSE N-Methyl perfluoroalkane sulfonamido ethanols (MeFASEs) Poor MeFBSE Poor MeFPeSE Poor MeFHxSE Poor MeFHpSE Poor MeFOSE Perfluoroalkane sulfonamido acetic acids (FASAAs) Poor FOSAA Poor MeFOSAA Poor EtFOSAA Poor N-Ethyl perfluoroalkane sulfonamido ethanols (EtFASEs) EtFBSE Average EtFPeSE Poor EtFHxSE Poor EtFHpSE Poor EtFOSE Poor Total removal in SO2 trap Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Good Good Good Average Average Average Average Average Poor Poor Poor Poor Poor Good Average Average Poor Poor Total removal Removal in venturi by PAC wash Total removal Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Good Good Average Poor Poor Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Poor Poor Poor Poor Poor Poor Poor Poor Average Poor Poor Poor Poor Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Page 151 of 160 RIVM report 2021-0143 PFAS Fluorotelomer phosphate monoesters (monoPAPs) 4:2 monoPAP 6:2 monoPAP 8:2 monoPAP 10:2 monoPAP 12:2 monoPAP Fluorotelomer phosphate diesters (diPAPs) 4:2 diPAP 4:2/6:2 diPAP 6:2 diPAP 6:2/8:2 diPAP 8:2 diPAP 8:2/10:2 diPAP 10:2 diPAP 10:2/12:2 diPAP 12:2 diPAP Perfluoroalkanes (PFFs) PFBF PFHxF PFOF PFDF Fluorotelomer carboxylic acids (FTCAs) 2:2 FTCA 4:2 FTCA 6:2 FTCA 8:2 FTCA 10:2 FTCA 12:2 FTCA Fluorotelomer unsaturated carboxylic acids (FTUCAs) 2:2 FTUCA 4:2 FTUCA 6:2 FTUCA 8:2 FTUCA 10:2 FTUCA 12:2 FTUCA Total removal in Quench Very Good Very Good Very Good Very Good Very Good Good Good Good Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Good Poor Poor Poor Poor Poor Average Poor Poor Poor Poor Poor Total removal in SO2 trap Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Good Good Poor Poor Poor Poor Good Good Very Good Poor Poor Poor Good Poor Poor Poor Poor Poor Total removal Removal in venturi by PAC wash Total removal Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Good Good Average Good Poor Poor Poor Poor Poor Poor Good Poor Good Poor Poor Poor Average Poor Poor Poor Poor Poor Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Poor Poor Poor Poor Poor Poor Poor Poor Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Page 152 of 160 RIVM report 2021-0143 PFAS Total removal in Quench Fluorotelomer aldehyde (FTALs) 2:2 FTAL Poor 4:2 FTAL Poor 6:2 FTAL Poor 8:2 FTAL Poor 10:2 FTAL Poor 12:2 FTAL Fluorotelomer unsaturated aldehyde (FTUALs) Poor 4:2 FTUAL Poor 6:2 FTUAL Poor 8:2 FTUAL Poor 10:2 FTUAL Poor 12:2 FTUAL Poor Perfluorinated aldehyde (PFALs) PFBAL Poor PFPAL Poor PFHxAL Poor PFHpAL Poor PFOAL Poor PFNAL Poor PFDAL Poor PFUnAL Poor PFDoAL Poor PFTrAL Poor PFTeAL Poor PFOA replacements Adona Poor GenX Poor PFTECA1 Poor PFTECA2 Poor EEA Poor 6:2 FTCA Poor PFOS replancements F-53 Poor F-53B Poor PFBSaPA Very Good Total removal in SO2 trap Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Total removal Removal in venturi by PAC wash Total removal Poor Poor Poor Poor Poor Poor Poor Poor Poor Average Good Good Poor Poor Poor Average Good Good Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Very Good Very Good Good Good Very Good Average Good Very Good Very Good Poor Poor Poor Good Good Poor Poor Poor Good Good Poor Poor Poor Poor Poor Poor Poor Poor Poor Average Average Poor Poor Poor Poor Poor Poor Poor Poor Poor Average Average Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Page 153 of 160 RIVM report 2021-0143 PFAS Total removal in Quench Total removal in SO2 trap Total removal Removal in venturi by PAC wash 8:2 FTOH replacements 3:1 FTOH Poor Poor Poor Poor 5:1 FTOH Poor Poor Poor Average Other alternatives EF-N441S-30 Very Good Very Good Very Good Good Novec 1230 Poor Poor Poor Poor Forafac 1183 Very Good Very Good Very Good Very Good PFOTSi Poor Poor Poor Good PFOTSi -(OH) Poor Poor Poor Very Good PFOTSi -(OH)2 Poor Good Poor Very Good PFOTSi -(OH)3 Very Good Very Good Very Good Very Good RM720 Poor Average Poor Very Good RM720-(OH) Very Good Very Good Very Good Very Good RM720-(OH)2 Very Good Very Good Very Good Very Good RM720-(OH)3 Very Good Very Good Very Good Very Good Fluorotelomer metacrylates 6:2 FTMAC Poor Poor Poor Poor Fluorotelomer acrylates 6:2 FTAC Fluorinated products of incomplete combustion Poor Poor Poor Poor PFM Poor Poor Poor Poor PFE Poor Poor Poor Poor PFCB Poor Poor Poor Poor TFE Poor Poor Poor Poor HFP Poor Poor Poor Poor PFIB Poor Poor Poor Poor The colours indicate the degree of removal as follows: red = poor, orange = average, yellow = good and green = very good. For a more quantitative interpretation, indicative removal efficiencies are provided here for the different classes: green = >99%; yellow = 90-99%; orange= 90-75% and red = <75%. For the qualitative assessment the calculations are described in Sections 5.2.2-5.2.4. Total removal Average Average Very Good Poor Very Good Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Poor Poor Poor Poor Poor Poor Poor Poor Page 154 of 160 RIVM report 2021-0143 Annex VI. PFASs removed and remaining at CO2 recovery PFAS Removal from Fraction from Removal in flue gas flue gas in CO2 CO2 washer Fluortelomer alcohols 4:2 FTOH 6:2 FTOH 8:2 FTOH 10:2 FTOH Perfluorinated carboxylate acids (PFCAs) PFBA PFPeA PFHxA PFHpA PFOA PFNA Perfluorinated sulfonic acids (PFSAs) PFBS PFHxS PFOS PFDS Perfluoroalkyl sulfinic acids (PFSiAs) PFBSi PFHxSi PFOSi PFDSi Perfluorinated phosphonic acids (PFPAs) PFBPA PFHxPA PFOPA PFDPA Perfluoroalkyl phosphinic acids (PFPiAs) C6/C6 PFPiA C8/C8 PFPiA C6/C8 PFPiA Poor Poor Poor Poor Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Considerable Small Very small Very small Poor Poor Poor Poor Very small Very small Very small Very small Very small Very small Very Good Very Good Very Good Average Very Good Very Good Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very Good Very Good Very Good Very Good Very Good Very Good Good Average Very Good Very Good Very Good Very Good Good Average Poor Fraction left in CO2 before liquefaction Considerable Small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Page 155 of 160 RIVM report 2021-0143 PFAS Removal from Fraction from Removal in flue gas flue gas in CO2 CO2 washer Fluorotelomer 4:2 FTO 6:2 FTO 8:2 FTO 10:2 FTO 12:2 FTO Fluorotelomer (FTSs) 4:2 FTS 6:2 FTS 8:2 FTS 10:2 FTS 12:2 FTS olefins (FTOs) sulfonate Poor Poor Poor Poor Poor Very Good Very Good Very Good Very Good Good Fluorotelomer iodides (FTIs) 4:2 FTI 6:2 FTI 8:2 FTI 10:2 FTI 12:2 FTI Perfluoroalkyl iodides (PFAIs) PFBI PFPeI PFHxI PFHpI PFOI PFNI PFDI PFUnI PFDoI PFTrI PFTeI Perfluoroalkyl sulfonamides (FASAs) FBSA FPESA FHXSA FHpSA FOSA Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Very Good Very Good Very Good Very Good Very Good Very small Very small Very small Very small Very small Poor Poor Poor Poor Poor Very small Very small Very small Small Considerable Very small Very small Very small Very small Very small Very Good Very Good Very Good Good Poor Poor Poor Poor Poor Poor Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Very small Very small Very small Very small Very small Average Poor Poor Poor Poor Fraction left in CO2 before liquefaction Very small Very small Very small Very small Very small Very small Very small Very small Very small Considerable Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Page 156 of 160 RIVM report 2021-0143 PFAS Removal from Fraction from Removal in flue gas flue gas in CO2 CO2 washer N-Methyl perfluoroalkane sulfonamides (MeFASAs) MeFBSA MeFPeSA MeFHxSA MeFHpSA MeFOSA N-Ethyl perfluoroalkane sulfonamides (EtFASAs) EtFBSA EtFPeSA EtFHxSA EtFHpSA EtFOSA Perfluoroalkyl sulfonamido ethanols (FASEs) FBSE FPeSE FHxSE FHpSE FOSE N-Methyl perfluoroalkane sulfonamido ethanols (MeFASEs) MeFBSE MeFPeSE MeFHxSE MeFHpSE MeFOSE Perfluoroalkane sulfonamido acetic acids (FASAAs) FOSAA MeFOSAA EtFOSAA N-Ethyl perfluoroalkane sulfonamido ethanols (EtFASEs) EtFBSE EtFPeSE EtFHxSE EtFHpSE Good Good Good Average Poor Good Average Average Poor Poor Very Good Very Good Very Good Very Good Very Good Very Good Good Good Average Poor Very Good Very Good Very Good Very Good Good Good Average Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Good Good Average Average Poor Considerable Considerable Considerable Considerable Considerable Average Poor Poor Poor Poor Very small Very small Very small Poor Poor Poor Considerable Considerable Considerable Considerable Average Poor Poor Poor Fraction left in CO2 before liquefaction Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Small Small Considerable Considerable Considerable Very small Very small Very small Small Small Considerable Considerable Page 157 of 160 RIVM report 2021-0143 PFAS EtFOSE Fluorotelomer phosphate monoesters (monoPAPs) 4:2 monoPAP 6:2 monoPAP 8:2 monoPAP 10:2 monoPAP 12:2 monoPAP Fluorotelomer phosphate diesters (diPAPs) 4:2 diPAP 4:2/6:2 diPAP 6:2 diPAP 6:2/8:2 diPAP 8:2 diPAP 8:2/10:2 diPAP 10:2 diPAP 10:2/12:2 diPAP 12:2 diPAP Perfluoroalkanes (PFFs) PFBF PFHxF PFOF PFDF Fluorotelomer carboxylic acids (FTCAs) 2:2 FTCA 4:2 FTCA 6:2 FTCA 8:2 FTCA 10:2 FTCA 12:2 FTCA Fluorotelomer unsaturated carboxylic acids (FTUCAs) 2:2 FTUCA 4:2 FTUCA 6:2 FTUCA 8:2 FTUCA 10:2 FTUCA 12:2 FTUCA Page 158 of 160 Removal from Fraction from Removal in flue gas flue gas in CO2 CO2 washer Poor Considerable Poor Very Good Very Good Very Good Very Good Very Good Very small Very small Very small Very small Very small Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Poor Poor Poor Poor Small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Good Very Good Very Good Very Good Very Good Good Very Good Average Good Poor Poor Poor Poor Very Good Very small Very Good Very Good Average Poor Poor Poor Poor Considerable Considerable Considerable Small Small Very small Average Poor Poor Poor Poor Poor Fraction left in CO2 before liquefaction Considerable Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Small Considerable Considerable Small Small Very small RIVM report 2021-0143 PFAS Fluorotelomer aldehyde (FTALs) 2:2 FTAL 4:2 FTAL 6:2 FTAL 8:2 FTAL 10:2 FTAL 12:2 FTAL Fluorotelomer unsaturated aldehyde (FTUALs) 4:2 FTUAL 6:2 FTUAL 8:2 FTUAL 10:2 FTUAL 12:2 FTUAL Perfluorinated aldehyde (PFALs) PFBAL PFPAL PFHxAL PFHpAL PFOAL PFNAL PFDAL PFUnAL PFDoAL PFTrAL PFTeAL PFOA replacements Adona GenX PFTECA1 PFTECA2 EEA 6:2 FTCA PFOS replacements F-53 F-53B PFBSaPA Removal from Fraction from Removal in flue gas flue gas in CO2 CO2 washer Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Very Good Small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Very Good Very Good Very Good Very Good Very Good Good Very Good Very Good Very Good Fraction left in CO2 before liquefaction Small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Very small Page 159 of 160 RIVM report 2021-0143 PFAS Removal from Fraction from Removal in flue gas flue gas in CO2 CO2 washer Fraction left in CO2 before liquefaction 8:2 FTOH replacement 3:1 FTOH 5:1 FTOH Poor Poor Considerable Small Poor Poor Considerable Small Other alternatives EF-N441S-30 Novec 1230 Forafac 1183 PFOTSi PFOTSi -(OH) PFOTSi -(OH)2 PFOTSi -(OH)3 RM720 RM720-(OH) RM720-(OH)2 RM720-(OH)3 Very Good Poor Very Good Poor Poor Very Good Very Good Very Good Very Good Very Good Very Good Very small Very small Very small Very small Small Considerable Very small Very small Very small Very small Very small Very Good Poor Very Good Poor Poor Average Very Good Poor Very Good Very Good Very Good Very small Very small Very small Very small Small Small Very small Very small Very small Very small Very small Fluorotelomer metacrylates 6:2 FTMAC Poor Very small Poor Very small Fluorotelomer acrylates 6:2 FTAC Poor Very small Poor Very Fluorinated products of incomplete combustion PFM Poor Very small Poor Very PFE Poor Very small Poor Very PFCB Poor Very small Poor Very TFE Poor Very small Poor Very HFP Poor Very small Poor Very PFIB Poor Very small Poor Very With respect to the colour coding for removal from flue gas and removal in the CO2 washer: red = poor, orange = average, yellow = good and green = very good. For the fraction from flue gas in CO2 and the presence of PFASs in the recovered CO2, before cooling and liquefying, the following qualitative indication is used: Green = very small amount, yellow = small amount and red = considerable amount. The calculations for the qualitative assessment are described in Section 6.2.5. small small small small small small small Page 160 of 160 RIVM Committed to health and sustainability