Document 6RL5Z1DB8ZjqR3QqXgDvDazRm

This document was submitted by: Reiner Friedrich; Merck Electronics KGaA, Darmstadt, Germany, on June 1st, 2023 under the following link: https://comments.echa.europa.eu/comments_cms/AnnexXVRestrictionDossier.aspx?RObjectId=0b0236 e1885e69de Comments for ANNEX XV restriction report Specific Information requests 9: Degradation potential of specific PFAS subgroups Section IV: non confidential information Executive summary In this document we compiled scientific data from literature and independent research organizations that justify additional entries to the list of fully degradable PFASs under Annex B.4.1.4. of the proposed restriction of Per and polyfluoroalkyl substances (PFASs). Over last decades Merck KGaA Darmstadt, Germany invested significant resources in the search for more sustainable solutions in the field of PFAS. The main driver of this effort was to focus on molecular structures that can be produced on an industrial scale, provide sufficient technical performance, and show as little impact for the environment as possible. To estimate the environmental impact of these compounds we relayed on the competence of highly recognized research institutions like the Department of Atmospheric Chemistry at the MaxPlank Institute for Chemistry in Mainz, Germany, the Atmospheric Chemistry Observations and Modeling Laboratory of the National Center for Atmospheric Research in Boulder, Colorado, USA or Department of Chemistry of the University of Toronto in Ontario, Canada and other. In particular we focus the use of Perfluoroalkyl vinyl ether as building block for degradable fluorinated compounds due to their intrinsic low stability. In this document we provide evidence of the nonpersistence nature of some PMVE adducts and therefore request to be added under Annex B.4.1.4.: PMVE (Perfluoro methyl vinyl ether; CASNo.: 1187935; EC/List No.: 2147037) and its low molecular reactions products made from alcohols and mercaptans In addition, we estimate that PMMVE is a viable candidate for fully degradable PFASs and therefore request to be add under Annex B.4.1.4.: PMMVE (Perfluoro methoxy methyl vinyl ether; CASNo.: 700874879; EC/List No.: 6150640) and its low molecular reactions products made from alcohols and mercaptans We also request to consider PPVE based PFAS as alternative to existing C6 telomeric materials since they do not contain C8 impurities from manufacturing processes and show very short lifetime and a high mineralization rate in atmospheric degradation. PPVE (Perfluoro propyl methyl vinyl ether; CASNo.: 1623058; EC/List No.: 2166002) and its low molecular reactions products made from alcohols and mercaptans Since there is still research in progress, we also expect additional results and publication by our cooperation partners in the near future to support our findings. Introduction Fluorinated compounds are manmade material which offer special properties in technical applications. These properties can be assigned to the unique physical characteristic of the fluorine atom, which are among others: High electronegativity, high oxidative potential, small atomic radius and low polarization rate. Although having a common root these characteristics reveal themself in different behavior: high electronegativity forms strong CF bonds, high oxidation potential leads to high chemical stability, small atomic size is accounted for low refractive index and the low polarization yields low intermolecular attraction which is used in water and dirt repellent application. For most application only a one or two of these attributes are needed. Especially the chemical and thermal resistance of fluorinated chemicals seems to be "overengineered" for many applications and life cycle of fluorinated moiety will exceed the product life cycle by far. The extensive use of fluorinated compounds over the last 80 years and the increasing sensitivity of analytical measurements reveal that fluorinated compounds can be detected in remote areas far away from their point of release in the environment. This combination of broad distribution and persistency of fluorinated compounds is the motivation of a restriction proposal which was started in the EU in 2020. Although there is no scientific evidence that all fluorinated compounds have a similar physiological or toxicological profiles this group of so called Perand polyfluorinated alkyl substances (PFAS) is raising concern. The goal of the legislation is "to phase out all nonessential uses of PFAS and to accelerate the development of safe and non persistent alternatives to all uses of PFAS". The high persistency of fluorinated compounds is the main concern among environmental scientists regarding this chemical group. The demur regarding distribution, bioaccumulation or ecotoxicity would be less profound, if fluorinated organic substances could become degradable and therefore would poses a much shorter life span in the environment. Although this seems to be contradictive to the oftenstated high stability of CF bonds there are some fluorinated alkyl structures that are quite sensitive against radical and hydrolytically cleavage. The aim of this document is to summarize publications and add some of our research results to offer an insight to this research area. We try to give a comprehensive overview to some of these new fluorinated compounds in respect to synthesis, technical performance and its potential for degradation in the environment. Degradable fluorinated compounds design considerations OECD has identified over 4700 substances by CAS number, which have in common that they at least contain one CF2 orCF3moiety and are therefore grouped as PFAS. During the time these chemicals were developed persistency was not seen as a potential threat. High chemical stability was and is a guarantee for long shelf life of the products. The extraordinary stability of fluorinated compounds results can be attributed according to Kissa to (1) the high electronegativity of fluorine, (2) the three non bonding electron pairs on fluorine, and (3) the excellent match between the 2s and 2p orbitals of fluorine and the corresponding orbital of other second period elements1. This generally yields a strong CF bond formation in per or poly fluorinated molecules, but since organic fluorine chemistry is an exeptional broad branch within organic chemistry there are also examples which show a remarkable low stability. Primary perfluoro alcohols for example are thermally unstable and will decompose at room temperature due to facile HF elimination2: Rf-CF2-OH O Rf C + HF aqua F O Rf C + HF OH Figure 1: Disproportionation of fluorinated alcohols and subsequent hydrolyzation of the carboxyl fluoride group under aqueous conditions The instability of the fluorinated alcohols is merely due to the presence of the OH group. The strong electron withdrawing character of the fluorine weakens the OH bond, which leads to a facile deprotonation of the alcohol. Fluorine is abstracted as fluoride and a carbonyl function is created. In the presence of water, the carbonyl fluoride will further hydrolyze to corresponding carbonic acid. The rearrangement liberates two fluorides per "CF2OH group". For CF3OH this breakdown even advances further and yields CO2 and 3 HF in total, which makes this compound a fully degradable fluorinated compound (Figure 2): F3COH + + O aqueous HF F C 2 HF CO2 F solution Figure 2: Complete degradation of Perfluoro methanol in the presents of water to yield Fluoride and CO2 The stability of the molecule is largely enhanced, if the hydrogen is replaced by an alkyl group. The resulting hydrofluoroethers (HFEs) are currently used in industry as refrigerants and are referred to as "third generation replacements to chlorofluorocarbons (CFCs), hydrochlorofluorocarbons,(HCFCs) and perfluorocarbons (PFCs)"3. Trifluoromethylmethyl ether (CF3OCH3; HFE143a) being the simplest of these materials was proven to be fully degradable in the atmosphere yielding HF and CO2 as expected4,5. 1 Fluorinated Surfactants and Repellents: Second Edition, Revised and Expanded Surfactant Science Series. Volume 97. By Erik Kissa (Consultant, Wilmington, DE). Marcel Dekker: New York. 2001 2 A. Baxter et al., Chem. Eur. J. 2018, 24, 16737 - 16742 3 WenTien Tsai, Journal of Hazardous Materials A119 (2005) 69-78 4 L. Chen, S. Kutsuna, K. Nohara, K. Takeuchi,T. Ibusuki , J. Phys. Chem. A 2001, 105, 1085410859 5 David A. Good, Mike Kamboures, Randy Santiano, and Joseph S. Francisco, J. Phys. Chem. A 1999, 103, 92309240 If the CF3O group is attached to a fluorinated alkyl chain the stability of the molecule is enhanced further and the structure becomes inert towards chemical attack. Trifluoromethyl ether (CF3OCF3) is regarded as persistent and will only decompose at elevated temperatures (> 400 C) to yield to CF4 and COF26,7. These examples illustrate that it cannot be concluded just by the presence of a CF2 or a CF3 group whether a molecule is persistent or not, but that neighboring groups must be brought into considerations. Like OH groups also Thiol, Amino and Silicongroups will weaken the CF bond, if they are directly attached to a linear fluorinated chain8. This chemically oddity is helpful in designing non persistent fluorinated compounds. In 2008 a paper was published describing the preparation of a CF3O containing surfactant 1. It was also reported that this material will degrade under aerobic conditions with defluorination rate of 90% occurred within 90 days9. F3CO 1 SO3Na Figure 3: Fully mineralizable fluorinated surfactants Other suitable chemical structures which possess F3CO end groups are 2 and 3 10 F3CO O O OCF3 3 O O 3O O SO3Na 2 NaO3S 3 OCF3 O O O O 3 5 OCF3 5 OCF3 Figure 4: Examples of fluorinated surfactants which have the potential to mineralize completely In this context also other degradable moieties were reported like OSF511. Despite their nonpersistent nature these molecules had little promise to be commercially successful. Due to their extremely short fluorinated chain the surface tension reduction achieved by these substances was in the order of 2330 mN/m @ 0.1 % active compound in aqueous solution, whereas conventional C6 telomer fluorosurfactants reach levels of around 1618 mN/m. To improve the performance the fluorine content within the molecule must be increase, but without jeopardizing the degradability of the fluorinated building blocks. One option could be the use CF2O Building blocks and synthesis a Poly(oxyperfluoromethylene) type of alcohol like 4. 6 J. Pacansky, R.J. Waltman, Journal of Fluorine Chemistry 82 (1997) 7983 7 J. Pacansky, R.J. Waltman, Journal of Fluorine Chemistry 83 (1997) 4145 8 R. N. Haseldinme, J.Newlands, J. B. Plumb, Proc. Chem. Soc. 1960, 147 9 M. Peschka et al., Chemosphere 72 (2008) 1534-1540 10 WO2009141053A1; WO2010003567 A2 11 DE102011114650A1 F F F FO F O F n FOH 4 Figure 5: Poly(oxyperfluoromethylene)hydroxide The amount of fluorine could be varied over a broad range and could be adjusted to different applications. Since primary fluorinated alcohols are not stable as mentioned above the degradation should progress according to the following mechanism: F FO F F O F F H n O F -HF F FO F F F H O O F n-1 F -CO2 F FO F F O O n OH F F FO F F O F O n F +H2O -HF Figure 6: Expected degradation cycle of a Poly(oxyperfluoromethylene)hydroxide in the presence of water. Note the stepwise degradation process which yield no residual components except CO2 and HF. It is worth mentioning that for this cycle the present of moisture/water would be essential, and that the degradation would proceed in stepwise manner (figure 6): 1) rearrangement and HF elimination, 2) hydrolysis of carbonyl fluoride, 3) decarboxylation Although the molecule would be regarded as a perfluorinated substance, it is expected to be non persistent and has the potential to degrade completely to HF and CO2. The mere presence of CF2 and CF3 groups within a molecule is therefore not a suitable criterion for upcoming regulation. The potential drawback of this approach is that the Poly(oxyperfluoromethylene) compounds are expensive to produce and complicated to store. Recent developments on nonpersistent PFAS based on Perfluoroalkyl vinyl ether (PAVE) Another interesting building block to design degradable fluorinated compounds are Perfluoroalkyl vinyl ethers. These commercially available material class is used as comonomers for different fluoropolymers. Figure 7 summarizes the structure and boiling points of these compounds: b.p. [C] Perfluoropropyl vinyl ether (PPVE) 36 Perfluoroethyl vinyl ether (PEVE) 8 Perfluoromethyl vinyl ether (PMVE) -22 Figure 7: Commercially available Perfluoro alkyl ethers and their boiling points at ambient conditions The vinyl group in these compounds is susceptible to react with H2O or OH to form again unstable perfluorinated alcohols which degrade accordingly. Since the abovementioned vinyl ethers have high vapor pressure investigations of the environmental fate of these compounds in the atmosphere were conducted by the MaxPlank Institute for atmospheric chemistry, Mainz, Germany12,13,14,15. 12 J. N. Crowley at al.; Phys.Chem.Chem.Phys., 2015, 17, 18558 13 G. Srinivasulu, A. J. C. Bunkan, D. Amedro and J. N. Crowley Phys. Chem. Chem. Phys., 2018, 20, 3761 14 A. J. C. Bunkan, G. Srinivasulu, D. Amedro, L. Vereecken, T. J. Wallington, J. N. Crowley Phys. Chem. Chem. Phys., 2018, 20, 11306 15 L. Vereecken, J. N. Crowley and D. Amedro Phys. Chem. Chem. Phys., 2015, 17, 28697 The detailed degradation mechanism of Perfluoroalkyl vinyl ethers and their terminal end products are summarized in Figure 8. Figure 8: Atmospheric degradation of Perfluoroalkyl vinyl ether shown for PPVE based on findings of MPI, Mainz In all cases it could be verified that the corresponding vinyl ether rapidly degrade through OHinitiated photooxidation processes within 35 days yielding CO2 and HF as main degradation products. HF will be washed out of the atmosphere and converted to CaF2 (Fluorspar) once it comes in contact with Ca(OH)2. Whereas PPVE and PEVE yield next to CO2 and HF perfluoro propionic acid or trifluoroacetic acid, PMVE will completely mineralize! Furthermore, it should be noted that perfluoroalkyl vinyl ethers in general have zero ozone depletion properties (ODP) and that their global warming potential (GWP) is neglectable due to their very short life time in the atmosphere. Since PPVE and PEVE degrade to fluoride and smaller fragments (PPVE: 5 out of 10 CF bonds are broken and fluoride liberated 50% mineralization rate; PEVE: 5 out of 8 CF bonds are broken and fluoride liberated 62% mineralization rate), these compounds can be described as partly mineralizable fluorinated substance, whereas PMVE could be consequently described as fully mineralizable fluorinated substance. It is also worth mentioning that in the REACH registration dossier PMVE here named Trifluoro(trifluoromethoxyethylene) "is neither considered as PBT nor as vPvB, since the P, vP, B, vB and T criteria are not fulfilled"16. The relevant screen shot from the dossier is show in Figure 9. Figure 9: Screenshot of ECHA `s registration dossier regarding PMVE. Although this material consists of a CF3 and a CF2 group the substance is not regarded as persistent. From the consideration above it can be concluded that perfluoro vinyl ethers appear to be suitable building blocks for degradable fluorinated compounds. In the following sections a brief description of the chemical structures arising from PPVE and PMVE, there potential performance and applications as well as their environmental fate will be is described. Although fully mineralizable fluorinated compounds seem to be the preferred substitute for persistent PFAS there could be limitations in the case of PMVE based material since the fluorine content per molecule is quite low. This disadvantage can be compensated somewhat through a smart design by combining several PMVE moieties in one molecule, but it also has its limitations. Since the "fluorine content" of PPVE is twice the amount of PMVE a less complex design and higher technical performance can be expected. 16 (https://echa.europa.eu/de/registrationdossier//registereddossier/13408/2/3) Finally, there is another variation of PMVE produced on industrial scale that have the potential to serve as building block for fully degradable PFAS, which is called PMMVE (Perfluoro methoxy methyl vinyl ether, see Fig.10). Figure 10: Chemical structure of Perfluoro methoxy methylvinyl ether (PMMVE) Following the atmospheric degradation scheme of Perfluoroalkyl vinyl ethers in Figure 8 PMMVE would decompose to Poly(oxyperfluoromethylene) intermediates like CF3OCF2OCOF and CF3OCF2OH only, which are unstable and will further degrade in the presence of water to CO2 and HF as explained in detail in Figure 6. Since the material was not available due to logistic reasons at the time the degradation studies were conducted, PMMVE based material could not be included in this survey. Degradable building blocks made from PFVE compounds, general synthesis approach Perfluoroalkyl vinyl ether can be processed further by nucleophilic addition at the fluorinated double bond. Under base conditions and elevated temperature, they react e.g. with alcohol or thiols to the corresponding (thio)ether. Figure 11: Reaction scheme of PFVE with Alcohol or Thiols Note that the double bond is unlocked, and the hydrogen atom is attached to the carbon next to the Rf O group. This structure is the fundamental design to facilitate easy degradation. If the hydrogen atom is substituted against OH, the structure would be a primary alcohol which as explained above is intrinsically unstable and will trigger further degradation. For our research we created numerous different chemical structures using this approach and exploited further the technical performance of such materials in different applications17. 17 WO2015/124290A1 FESOH a fluorinated building block based on PPVE A very useful intermediate is FESOS which can be prepared in high yield by the reaction of mercapto ethanol with PPVE according to Figure 11: + F F F FFF F F OH K2CO3 F F S F O FF HS solvents F F F O H OH F F F F PPVE Mercapto ethanol FESOH Figure 12: Reaction of PPVE with Mercapto ethanol. Note that the reaction product (FESOH) is not a perfluorinated ether but contains a Hatom next to the Oxygen atom of the fluorinated unit. FESOH can further be converted into fluorosurfactants (e.g. diFESOS see Fig 13) or (meth)acrylate to be used e.g. in emulsion polarization for dirt and water repellent application of garments (see below). Despite what application the material will be used in, FESOH will be the fluorinated compound, which will be released into the environment. Therefore, intensive studies of the environmental fate of this compound were conducted at the University of Toronto. The experiments include aerobic biotransformation, atmospheric degradation, and in vivo transformation studies. Aerobic Biotransformation of FESOH The study of the aerobic biotransformation was conducted using the surfactants diFESOH18. The overall degradation pathway is illustrated in Fig 13. Figure 13:Proposed degradation scheme of diFESOS and its metabolites in wastewater treatment plant inoculum. Grey dashed boxes = not detected in this work. Double arrows represent multiple reaction steps. As expected, the diFESOS hydrolyses fast to liberate FESOH, which is further oxidizes to the corresponding carboxylic acid (FESCA). Once the sulfur linkage is detached less fluorinated transformation products like C3F7OCHFCOOH (2H3:2 PFECA) and perfluoropropanoic acid (PFPrA) were detected suggesting that FESOS degrades to less bioaccumulative molecules in the environment. 18 Shira Joudan, Scott A. Mabury; Environ. Sci.: Processes Impacts, 2022,24, 62-71 Figure 14: Biotransformation of diFESOS to FESOH and FESCA in 10% sludge over 38 days. Data points are normalized to the first measurement of diFESOS, correction for the 1:2 moles of polyfluoroalkyl chain present in diFESOS vs. its transformation products. Error bars represent standard deviation of the replicate experiments (n = 3). The time scale of the overall biotransformation from diFESOS to the terminal fluorinated carboxylic acid (PFPA) seems relatively long (see Fig 14). S. Joudan et al. suggest that the reason for this is slow degradation lays in the deactivation of the Hatom in the CHF group by the electron withdrawing action of the fluorine atoms. Even though the experience was performed in closed bottles a complete molar balance could not be observed, indicating loss of material either through absorption or transfer in the gas sphere (semi volatile intermediates). In vitro and in vivo transformation studies of FESOH In addition to the aerobic biotransformation the Mabury group also investigated the breakdown of diFESOH and FESOH by in vitro studies using rat liver S9 fractions and in vivo Sprague-Dawley rat experiments19. An overview of the conducted experiments is shown in Fig 15 Figure 15: Experimental scheme for both in vivo and in vitro experiments For the in vitro studies they reported a fast conversion of diFESOH or FESOH to FESCA (few hours compared to several days for the biotransformation experiments with wastewater inoculum). FESCA also seemed to be the terminal degradation product since no other degradation products were detected. In the in vivo studies they could confirm the degradation pathway of diFESOH and FESOH down to PFPA, although they could detect different intermediates within the degradation pathway compared to the aerobic biotransformation (2H 3:2PFESA instead of 2H 3:2PFECA; see Fig 14) 19 Folkerson, Andrew P.; Joudan, Shira; Mabury, Scott A.; D'eon, Jessica C.; Environmental Toxicology and Chemistry (2021), 40(12), 33283336 Figure 16: Predicted biotransformation pathways of di(polyfluoroether thioether(S)-oate) sulfonate (diFESOS) to a polyfluoroether thioether(S)alcohol (FESOH) and polyfluoroether thioether(S) carboxylic acid (FESCA), oxidation of the thioether to the 2H 3:2 polyfluorinated ether sulfonate (2H 3:2 PFESA) and a terminal product of perfluoropropionic acid (PFPrA). Solid arrows and boxes indicate confirmed pathways and products; dotted arrows and boxes indicate proposed pathways and intermediate products (Arakaki et al., 2010; Butt et al., 2014). The product of thioether oxidation of FESCA to produce 2H 3:2 polyfluorinated ether carboxylic acid (2H 3:2 PFECA) was not observed. Liter In addition, it was found that the degradation to metabolites and their excretion from the organism is quite fast. The half-lives of FESCA in the intravenously and orally dosed rats were 4 0.2 h and 6.6 0.65 h, respectively. The half-lives of 2H 3:2 PFESA were 14 1.1 h and 20 1.6 h in the intravenously and orally dosed rats, respectively. Concentrations of FESOH itself were below the detection limit in all samples, apparently because of a combination of rapid oxidation and exhalation of the volatile compound from the rats. They conclude, that adding the ester- and electron-rich ether and thioether functional groups into the design of FESOH facilitates the degradation into the observed smaller water- soluble metabolites and that none of these compounds appear to be bio accumulative in rats, due to their fast elimination. Since it became obvious during the conducted trials, that FESOH is a semi volatile compound, it also was of interest to investigate its atmospheric fate. Atmospheric degradation of FESOH Detailed test procedures and results is published20. Here we give only a short summary of the findings. The suggested degradation pathway of FESOH in the atmosphere is depicted in Figure 17. Figure 17: Proposed mechanism of atmospheric FESOH oxidation in the presents of Cl or OH radicals The experiments were performed in a stainlesssteel chamber interfaced to an FTIR to determine reaction kinetics and gasphase products. A reaction rate constants of k (Cl + FESOH) = (1.5 0.6) 10-11 cm3 molecule-1 s-1 and k (OH + FESOH) = (4.2 2.0) 10-12 cm3 molecule-1s-1 was reported, which leads to a calculated FESOH gasphase lifetime of only 2.8 1.3 days with respect to reaction with OH radicals. It should also be noted that the overall degradation of FESOH will again only yield the terminal products HF, CO2 and PFPA (see Figure 18) 20 Shira Joudan, John J. Orlando, Geoffrey S. Tyndall, Teles C. Furlani, Cora J. Young, Scott A. Mabury; Environ. Sci. Technol. 2022, 56, 10, 6027-6035 Figure 18: Schematic degradation process of FESOH in the atmosphere FESOH and its mother compound PPVE exhibit similar degradation kinetics (2.8 1.3 days for FESOH and 34 days for PPVE) and yield the same terminal products, indicating that the chemical modification of the OCF=CF2 group does not impact atmospheric degradation. Due to the very short lifetime in the atmosphere the GWP of both molecules are neglectable and possess due to their chemical structure no ozone depletion potential. Conclusion of degradation studies on PPVE containing material Three studies concerning environmental fate and degradation of a modified PPVE version were conducted by independent research institutes. They concluded, that FESOH has a significantly lower persistence in the environment than standard PFAS. Degradation is triggered by the special design of the molecule, which involves intermediates that can be degraded further to PFPA as the terminal product. Since the intermediates themselves have different lifetime under different environmental conditions it can be estimated that der degradation will take between a few days (degradation in the atmosphere) and few weeks (under aqueous aerobic conditions e.g. waste water). From the 10 CF bonds, which are present in FESOH, 5 fluorine atoms are "mineralized" (converted to fluoride) which eventually forms natural minerals like CaF2; the other terminal degradation product is CF3CF2CO2H. Short chain perfluorinated carboxylic acids like PFPA are not regarded to be bioaccumulate in humans or other organisms like fish and mammals) and therefore impose a minor threat to the environment21. Although FESOH therefore is "only" partly mineralizable, the material clearly shows significantly environmental advantages over existing PFAS materials. FESOH and none of its degradation intermediates appear to be bioaccumulative in rats, because they are quickly eliminated. In contrast to telomer C6 materials where higher molecular impurities such as C8, C10... can be found, FESOH is a welldefined compound consisting of only 5 fluorinated carbon atoms. 21 Conder, J.; Hoke, R.; de Wolf, W.; Russell, M. H.; Buck, R. C. Environ. Sci. Technol. 2008, 42 (4), 995-1003. Technical application and performance level of PPVE containing material Performance wise FESOH seems to reach a similar level or slightly inferior level than 6:2 FTOH in terms of surface tension reduction and oil repellency on textile garments. Although FESOH itself contains less fluorine than 6:2 FTOH an overall excellent surface tension of 16.0 mN/m for diFESOH is found (0,1% active substance in aqueous solution using the Wilhelmy pate method). The reason for this is that by attaching more than one (shorter) fluorinated chains to a surfactants molecule its performance can be increased by a high extend compared to single chained surfactants. Examples and performance data are published22. Since there are many different technical applications of fluorosurfactants a general statement, if such PPVE based surfactants would be a proper placement for C6 telomer chemistry cannot be made. But in cases where no extreme chemical or thermal stability is requested this material class could provide suitable alternative. For dirt and oil repellent applications (meth)acrylates of the C6 telomer alcohols are generally used together with long chain aliphatic ester acrylates in emulsion polymerization to create water soluble formulations, which are used to impregnate textiles. Oil repellency can only be achieved through fluorinated compounds and is normally measures according AATCC Test Method 11823. In this test one drop of a liquid with defined low surface tension is set on an impregnated fabric. After 30 seconds it is evaluated whether the droplet still "sits" on the fabric or began to wet the textile. Non wetting is regarded as passing the test. The test is conducted with 8 different fluids having decreasing surface tension. The test oils are numbered from 1 to 8 starting from 31.5 mN/m (Kaydol) down to 19.8 mN/m (nHeptane). Commercially available C6 containing finishing product claim an oil repellency of up to oil nr. 7 (nOctane) (e.g. Asahi Guard AGE082, Novoguard NL 1600, RucoGuard EPF 3111) First trials replacing 6:2 FTOH with FESOH yield oil repellency around oil nr. 4. In addition to this we also found a slightly reduced water repellency in comparison to C6 telomer based material. Currently it is unclear to what extend the performance of an optimized formulation could be lifted, but due to the uncertainty in the upcoming restriction of ECHA concerning PFAS no additional efforts were taken in this direction. 22 US2019/276397A1, WO2015/124290A1 23 American Association of Textile Chemists and Colorists (1997). "AATCC 118 Oil repellency: hydrocarbon resistance test" Degradable PFAS based on PMVE Like PPVE, PMVE can be converted to functional alcohols which are suitable candidates for fully degradable PFAS. Next to the thioether compound MeFESOH also a diether alcohol MeFdiEOH was synthesized. Figure 19: Thioglycole and glycole based PMVE derivates as representatives for a Methylpolyfluoroetherthioether alcohol (MeFESOH) and a Methylpolyfluorodiether alcohol (MeFdiEOH). Note that both products are not a perfluorinated but contain a Hatom next to the oxygen atom within the fluorinated unit. Since the fluorine contents of both alcohols is only half of the amount of FESOH a more complex design of the final active compound is needed. Figure 20 depicts the structure of an anionic surfactants based on a tricarboxylic acid. This citric acid derivate contains three shortchain fluorinated moieties lifting the fluorine content to 18 fluorine atoms per molecule. Figure 20: Anionic surfactants based on tricarboxylic acid derivatives containing MeFESOH or MeFdiEOH units Performance wise such surfactants exhibit surface tensions of ~ 19 mN/m @ 0,1% in aqueous solution, which is considerably lower than diFESOH with 16.0 mN/m @ 0,1% in aqueous solution despite the fact of similar fluorine contents on both molecules (triMeFESOH 18 Fatoms vs. diFESOH 20 Fatoms), which also indicates that although it is essential to increase the fluorine content per molecule this does not equal in performance increase to the same level. The environmental fate of MeFESOH and MeFdiEOH was investigated by different research groups. The biotransformation of triMeFESOH and triMeFdiEOH was subject to EU funded project named Perforce 324 were as the atmospheric degradation of MeFESOH and MeFdiEOH are again investigated by Mabury group from the university of Toronto. The research results are currently in the process to be published and are therefore not comprehensively available. Biotransformation of PMVE based material Microbial transformation studies were performed for 126 days under aerobic conditions using activated sludgewastewater medium25. Qualitative and quantitative determination of parent compounds and transition products with reference material was performed by liquid chromatography-tandem mass spectrometry (LCMS/MS). Although a semiclosed system approach was chosen which only permitted a short venting time to minimize the loss of volatile degradation the mass balance of the intermediates is only about 3045% to the total expected concentration at the end of the incubation time. This indicates to the irreversible sorption of the molecules to the sludge. Like the biotransformation process of diFEHOS, the biodegradation of triMeFESOH and triMeFdiEOH is a rather slow process involving the following transition products: Figure 21: Bio transformation pathways of triMeFESOH under aerobic conditions in activated sludge and its identified transition products After 126 days only a small amount of 2H1:2 PFECA (~4%) which is created by the first mineralization step (MeFESCA > 2H1:2 PFECA). Although no significant further degradation of 2H1:2 PFECA could not be detected in the studies they conclude that "based on fundamental chemical knowledge, it should completely degrade at some point, even if it takes a long time." 24 https://perforce3itn.eu/workpackages/solutions/ 25 Finding a way out? Comprehensive biotransformation study of novel fluorinated surfactants; Viktria Licul Kucera et al., in press Atmospheric degradation of PMVE based material Due to their volatile character, it is expected that for MeFESOH and MeFdiEOH the main pathway into the environment would be through release into the atmosphere. In a similar set up as described under the atmospheric degradation of FESOH20 atmospheric lifetime and their degradation products for both materials were investigated. The results were presented by Andrew Folkerson from University of Toronto at the Canadian Chemical Conference and Exhibition in Calgary in 202226. A detailed publication is in preparation. The breakdown scheme of the observed intermediates and its concentration profiles are depicted in Figure 22. Note that the smaller degradation products O=CF2 and O=HCF will immediately hydrolyze in humid air and to yield HF and CO2 as terminal products. Figure 22: Atmospheric degradation. (Left) Breakdown products of MeFESOH identified under experimental conditions in the presents of OH + NOx, relative timedepending concentration of intermediates; (Right) proposed degradation pathway in atmosphere. In addition to the aerobic bio degradation the atmospheric degradation experiment shows that 2H1:2 PFECA is further decomposed to full mineralization. Similar degradation path is found for MeFDiEOH reviling that both materials can be regarded as examples of fully degradable PFAS. The estimated reaction rate constants were reported to be k (OH + MeFESOH) = (3.18 0.32) 10-12 cm3 molecule-1 s-1 and k (OH + MeFDiESOH) = (1.13 0.11) 10-12 cm3 molecule-1 s-1, indication a gasphase lifetime of 3.64 days for MeFESOH or 10.2 days for MeFDiESOH respectively. These results indicate that for PFAS based on PMVE the atmospheric degradation provides a very efficient and fast breakdown process leading to full mineralization (H20, CO2 and CaF2 as terminal products). Based on its composition the material has zero ODP potential and neglectable GWP due to their very short atmospheric life span. 26 https://www.xcdsystem.com/cic/program/bMlXk1m/index.cfm?pgid=2690&sid=24296&abid=91810 Force degradation experiments In addition to the environmental degradation test we also focused on chemical reactions, which allow simple and complete degradation of the material. These so called "forced degradation" experiments allow to evaluate the overall stability of these compounds and compare then to standard PFAS. To monitor the degradation 19FNMR was used. Intensity and shift of the fluorine signals are characteristic for compounds and intermediates and can therefore be used without additional reference. We found that in strong basic conditions PMVE (and PPVE) based material will degrade at elevated temperature over time. As a general procedure a small amount of fluorinated alcohol (0.05 g) was dissolved in ethanol (0.2 g), added to 30% aqueous KOH (0.6 g) and transferred to into an NMR tube. The first measurement was taken immediate after sample preparation. After that the NMR tube kept at 80C for several hours and the measurement were repealed periodically. Two representative spectra are shown in Fig. 23 and 24. Figure 23: 19F NMR of MeFESOH in aqueous KOH/Ethanol mixture. Chemical shift and intensity of the signals can be clearly assigned to the fluorinated functional groups of the molecule. Figure 24: 19F NMR of MeFESOH in aqueous KOH/Ethanol mixture after 18h at 80C. Chemical shift and intensity of the signals can be clearly assigned to the fluorinated functional groups of MeFESOH, 2H1:2 PFECA as well as Fluoride (signal G). A comparison of both spectra show clearly that the MeFESOH is decomposed under the give condition to yield 2H1:2PFECA and fluoride (Signal G in Figure 24). Since the fluorine mass balance does not change during reaction, the molecular ration of the compounds can be calculated indicating that after 15 h at 80C 37% of MeFESOS is still present, 7% converted to 2H1:2 PFECA and 56% mineralized. It is worth mentioning that 2H1:2PFECA is again not the terminal product but decomposes further under full mineralization. Standard PFAS like telomer based C6 materials do not degrade under the given reaction conditions. Technical performance of PMVE based material As stated above MeFESOH and MeFdiEOH can be converted into an anionic surfactant (e.g. triMeFESOH and triMeFdiEOH, see figure 19) with reasonable good surface tension reduction of 19 mN/m in a 0.1 wt% aqueous solution. Due to the low fluorine content per alkyl chain in MeFESOH or MeFdiEOH a more complex design is used to increase the total fluorine content per molecule. This concept has its limitations and cannot be seen as a general substitute for all existing PFAS applications. Especially when it comes to dirt and oil repellent formulations in textile applications (meth)acrylic monomers based on MeFESOH are not very effective. Formulation prepared in our lab made from Poly MeFESOHacrylate completely fail the AATCC 118 Oil repellency: hydrocarbon resistance test. It should not be concluded that oil repellency is not possible with PMVE based material, but it must be stated that due to the unclear regulatory situation all efforts proceeding to solve this problem were discontinued. Conclusions Based on scientific evidence it can be concluded that the mere presents of a CF3 or CF2 group is not a sufficient condition to assume persistency of a molecule. Neighboring groups and the present of heteroatoms influence the stability of fluorinated compounds drastically. We compiled scientific information that shows that CF3O groups could be used as building blocks for nonpersistent PFAS. Especially materials based on Perfluoroalkyl vinyl ether seem to have the potential to yield fully mineralizable fluorinated substances due to its reduced chemical stability. They possess very short life span in the atmosphere (few days only), have zero ozone depletion potential and due to their short life span a neglectable global warming potential. 1) For this reason, we are request that PMVE (Perfluoro methyl vinyl ether; CASNo.: 1187935; EC/List No.: 2147037) and its low molecular derivates are added as fully degradable PFASs under Annex B.4.1.4. of the proposed EU wide PFAS restriction. The structural elements of the exemption should also include MeFESOH and MeFDiESOH, which were in focus of recent degradation studies. For all these compounds full degradation in the atmosphere accomplished within a few days only yielding CO2, H2O and HF. PMVE can be reacted with a variety of different thiols/alcohols without jeopardizing its ability to degrade, therefore we request that a more structural approach like PMVEAdducts is considered for exemption. 2) A commercially available variation of PMVE is PMMVE (Perfluoro methoxy methyl vinyl ether; CASNo.: 700874879; EC/List No.: 6150640). Although this material was not part of the degradation experiments, it can be concluded from its chemical similarity that it will also fully mineralize in the atmosphere. Therefore, we request to add PMMVE and possible PMMVE Adducts to the exemption list. 3) For essential technical application where PMVE based design will have its limitations, it should be considered to allow the use of PPVE based materials like FESOH. PPVE (Perfluoro propyl methyl vinyl ether; CASNo.: 1623058; EC/List No.: 2166002) has the advantage over C6 telomer chemistry that no residual PFOA related impurities are created during manufacturing process. The degradation process of PPVE and its low molecular reaction products like FESOH in the atmosphere is in the order of a few days only and will results in a 50 % fluorine loss of the molecule (5 out of 10 fluorine atoms will mineralize). S'''''''''''' OH FESOH In vivo biotransformation studies in rates have also indicated that FESOH and its degradation products are excreted within hours. 4) For the vast majority of PFASs regulatory standard tests for persistence are missing, and the assessment of full degradability is based on the general scientific literature and expert judgement. The search for degradable PFAS was started a few years ago and the compiled information here reflexes scientific results we are currently aware of. Therefore, in the proposed Annex B.4.1.4. a passus should be implemented that allows molecular structures to be added beyond the public consultation phase if fully degradability can be proven. The materials suggested for exemption could be suitable for technical application where low surface tension is required (wetting, leveling and antifogging agent as well as oil and dirt repellency applications on textiles). The compiled information represents the current status of this research area to the best of our knowledge. Darmstadt, June 1St, 2023 For further information please contact: @merckgroup.com