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CHRYSQTILE ASBESTOS IN PLASTICS John L. Myers "CAL I DR I A" ASBESTOS UNION CARBIDE CORPORATION MINING AND METALS DIVISION NIAGARA FALLS, NEW YORK A0765C Presented on May 14, 1974 at the 32nd Annual Technical Conference of the Society of Plastics Engineers in San Francisco. UCC 014827 I NTRODUCi 10-J Asbes tos has received a great eea I of attention and publicity in recent years, especially after if was designated a "target health hazard" by OSHA and a "hazardous air pollutant" by ihe ifPA. Many of the articles on asbestos by the press have been emotionally oriented or distorted and in same cases stories have been sensationalized, based on obvious misinterpretation of facts, the use of half-truths or unsubstantiated statements has led to general confusion and the unfair castigation of asbestos and products containing asbestos. Ihe purpose of this paper is to put the matter of asbestos use and asbestos hazards in a logical and practical perspective. In this paper the different types of asbestos and their many uses are discussed along with government regulations controlling the use of asbestos. The health hazards associated with asbestos, both occupational and environmental, and some industrial experience with air sampling and dust control measures are also covered. WHAT IS ASBESTOS? Asbestos is a commerical or generic term used to describe six nafuraI Iy-occurring "asbes+iform" minerals that are fibrous, hydrated metal silicates. The six varieties are divided into two classes, serpentine and amphibole, based on their crystal structure. Chrysotile is the only member of the serpentine class while the amphiboies include eroded ite, amosite, anthophy! I i te, tremolite and actino life. Chrysotile is by far the most used variety and accounts for over 95% of U.S. consumption, as noted in Table I. Crocidolite, also known as blue asbestos, is imported from South Africa. Because of its high mechanical strength and good resistance to acids and alkalis, it is used to reinforce a limited variety of plastics where its pronounced color is not objectionable. Amosite, also imported from South Africa, is used primarily in thermal insulation. Although there are some deposits of anthophyiIite in the U.S., most of it is imported from Finland. It is used primarily as a filler for polypropylene and in insulating materials. A comparison of the four varieties of asbestos which are of commercial importance is presented in Table If. It should be noted that there are significant differences between chrysotile and the amphiboies with regard to chemical composition and certain physical properties. WHERE IS ASBESTOS USED AND WHY? Asbestos has served mankind for over 100 years In a broad variety of applications. The general areas in which asbestos fs used in the United States are shown in Table III. Based on information from asbestos producers and consumption surveys, it is estimated that the plastics industry uses about 1/3 of the 800,000 tons consumed annually, which makes it the largest single user of asbestos fiber. The largest uses of asbestos by the plastics industry are in viny(/asbestos floor tile and in phenolic molding compounds. If is also used in other plastics such as polypropylene, polyester, nylon, melamine, epoxy, silicones and vinyls. Asbestos provides UCC 014828 2 valuable tunc Mon in such products as brake linings, clutch facings, electrical components, automotive parts, furniture, boats, sealants, coot inns, adhesives and mastics. 1 ho n;osi important functions of asbestos in plastics are rei nf crooner, t, dimensional stability, heat resistance, flow control and general-purpose filling. Most of the functions are supplied by short fiber chrysotile asbestos fiber, although longer chrysolite fibers and other asbestos varieties are sometimes required for particular properties. WHY USE CH9Y30TILE? Among the several advantages of chrysolite, which set if apart from the amphibole minerals and account for its widespread and increasing usage, are world wide availability, mechanical strength, flexibility, positive surface charge, low iron content, softness and low refractive indc-x. it is conservatively estimated that chrysotile asbestos is used in over 3,000 applications and in most of these applications it is an essential ingredient for which no replacement is readily available. The information in Table 1 shows that the use of chrysotile asbestos and its share of the total market are steadily increasing. This is partly due to technical advances permitting the broader use of chrysotile in plastics and the general decline in the use of asbestos in certain fireproofing and insulating materials. In addition, there is increasing evidence that crocidolite and amosite are more hazardous to human health than chrysotile (I). Since 1970 the use of crocidolite in Britain has been restricted after a panel of experts "concluded there was sufficient evidence to suggest other types of fibre should be substituted for crocidolite wherever possible." (2) WHAT IS THE ASBESTOS HAZARD? It is readily accepted that asbestos, like many other foreign bodies, can cause disabling lung damage (pulmonary fibrosis), commonly referred to as asbestosis. This disease and bronchogenic carcinoma (lung cancer) are the two most common asbestos-related diseases, it is important to note that, based on epidemiological data, these diseases have occurred primarily in workers with high, long-term exposures to asbestos dust. It is of further interest that one noted researcher has reported that neither of these diseases is peculiarly related to or caused solely by the inhalation of asbestos fiber (3). Another important consideration is the relation between cigarette smoking and lung cancer as reported by Dr. E. C. Hammond and Dr. I. J. Selikoff (4). In this study they reported that: "It seems clear, then, that lung cancer is uncommon among asbestos Insulation workers who have no history of cigarette smoking and that if the risk is increased, such increase is not great." A third disease, mesothelioma, has more recently been associated with persons exposed to asbestos. Mesothelioma is an extremely rjrare cancer of the lining of the chest (pleura) or the abdominal Q7 0^ *-cavjty (peritoneum). In contrast to the lung diseases, there is some evidence that mesothelioma can occur after brief exposures to relatively high fiber levels. UCC 014829 According to the 35-member Advisory Committee on Asbestos Cancers of the Internetionai Agency for Research on C3ncer (a division of th-o World Health Organization): "There is evidence of sn association of mesathe I ia I tumours with air pollution in the neighbourhood of croc idolite .nines and of factories using mixtures of asbestos fibre Types. The evidence relates to conditions many years ago. There is evidence of no excess risk of mesotheliomas from asbestos air pollution which has exisied in the neighbourhood of chrysotile and amosite mines. There are reported differences on incidence of mesothelioma between urban and rural areas, the causes of which have not been established. There is no evidence of a risk to the general public at present." (5) The same body quoted above has also concluded that there is at present no evidence of lung damage by asbestos to the genera! public; and such evidence as there is does not indicate any risk of cancer resulting from asbestos fibers present in water, beverages, food or in the fluids used for the administration of drugs. While there seems to be general agreement that the public is not in any present danger from asbestos, it is also recognized that excessive, long-term occupational exposure can cause serious health problems. Also, if man-rri3de emissions are not controlled, then environmental eontamination could approach harmful levels. During the past two years, significant legislation has been enacted by the Federal Government to reduce and control occupational exposure to asbestos fibers and to minimize fiber emissions to the environment. Additional standards or regulations have been proposed or enacted by many state and local governments. SUMMARY OF OSHA REGULATIONS The VIi1 Iiams-Steiger Occupational Safety and Health Act of 1970 became effective on April 23, 1971, with the following Congressional purpose: "to assure so far as possible every working man and woman in the Nation safe and healthful working conditions and to preserve our human resources." The Act established the Occupational Safety and Health Administrafion (OSHA) within the Department of labor, which has responsibility for adminisfration and enforcement. Research and related functions are handled by the Department of Health, Education and V/elfare (HEW) through the National Institute of Occupational Safety and Health (NIOSH). Five million employers and 60 million of the nation's 80 million workers are covered by OSHA. Specifically excluded from coverage are government employees and operations which are protected under other Federal health and safety laws. In a news release issued January 4, 1912, OSHA announced a Target Health Hazards Program aimed at improving health factors associated with working conditions. The following five substances were designated to be the focus of initial and concerted efforts by OSHA and NIOSH: Asbestos, Cotton Dust, Silica, Lead and Carbon Monoxide. At the present time new standards have been established only for asbestos; although, of the 8,000 toxic substances on 'the UCC 014830 A 07fi f-ilOSM [ i st, only 590 are covered by sinnderco and many of theso need updating. The new Standard for Exposure to Asbestos Dust cos published in the Federal Reg i s * er , Vo I umo 37, t:o. 110 cn 'Wednesday, Juno 7, 1072. The basic exposure standard is an 3-hour tine-weighted average (TV/A) of 3 fibers, longer than 5 micrometers, per cubic centimeter of sir. The TWA iimi'r is to be reduced to 2 fibers per cubic centimeter on July I, 1975. A peat concentration of 10 fibers por cubic centimeter is not to be exceeded at any time. All of the fiber concentrations are those to which an employee may be exposed without protective clothing or equipment. The first basic requirament of the new standard is monitoring to determine whether or not fiber concen+rafions are in excess of the exposure limits. Some asbestos suppliers provide a monitoring service to customers and a similar service may be obtained from state health department officials, insurance carriers, or private consultants. The law requires that monitoring be repeated as necessary to ensure that employees are not exposed to levels in excess of the exposure limits. Improper interpretation of the regulf ions has created many misconceptions about the equipment at procedures needed to properly use asbestos. if exposure 1; its are not exceeded, there are no further compliance requirements except for medical examinations. Medical examinations are required for ail employees in any occupation exposed to airborne concentrations of asbestos fibers. The examinations are relatively simple and should cost no more than $50 per year, per employee. Respirators and special clothing are required in the construction trade for the spray application of insulation and fireproofing materials, and for the removal of such materials. This special protection is not required for any other use of asbestos unless exposure limits are exceeded. This is also true for other items such as specially-equipped tools, change rooms, clothes laundering and waste disposal. Respirators are not a substitute for engineering controls but the law allows their use while controls are being implemented, in special situations where controls are not feasible or adequate, in emergencies, and for infrequent short-term job assignments. Caution labels are required on products containing asbestos except where the fibers have been modified by a bonding agent or other material to prevent dusting during any normal subsequent use or handling. Besides raw asbestos fiber, products which require package labeling could include: dry acoustical spray products and joint cements, unsaturated roofing felt and textiles, and some insulating products made without adequate binders. The labeling of a product doss not prohibit its use. It should be noted here that in at least 90$ of the products containing asbestos, the fibers are solidly locked into the product thereby presenting little danger of dust generation during normal use and handling of the product (6). ERA STANDARDS Whereas 0SHA is responsible for the protection of the worker, the Environmental Protection Agency (ERA) is charged with improving the environment to which the genera I public is UCC 014831 expos ed. On Punch 31, 1971, asbestos, a lot's with b ary 1 ! i un and m.0 Cl.. ry, was identitied as a "hazard ous air poi lutsr.t" by th e A.dm: n i s+.-a tor of (he fcPA. National Emission Standards for <j s o > tos \uore then cub 1 ished by fho EPA in the Fed-re i Register, Vo I . 38, I'to. 55 - Friday, April 6, 1973. A!though no numerical omission standards were established, operating criteria are prescribed to prevent or limit asbestos emissions to the outside air from asbestos mills, roadways, certain manufacturing operations, bu i I d i r.g demo! i i ion, and tho spray-on application of materials used to insulate or fireproof equipment and machinery. Tha lew further requires that spray-on materials used to insulate or fireproof buildings, structures, pipes, end conduits shall contain less than 1^ asbestos on a dry weight basis. This should significantly reduce emissions to which the general public may be exposed, especially in large urban areas. ''...the Administrator (of the EPA) has determined that, in order to provide an ample margin of safety to protect the public health from asbestos, it is necessary to control emissions from major man-made sources of asbestos emissions into the atmosphere, but that it is not necessary to prohibit all emissions. In this determination, the Administrator has relied on The National Academy of Sciences' report on asbestos, which concludes: 'Asbestos is too important in our technology and economy for its essential use to be stopped. But, because of the known serious effects of uncontrolled inhalation of asbestos minerals in industry and uncertainty as to the shape and character of tha dose-response curve in man, it would be highly imprudent to permit additional contamination of the public environment with asbestos. Continued use at minimal risk to the public requires that the major sources of man-made asbestos emission inlo the atmosphere be defined and controlled."' (7) WHAT 1$ INDUSTRY DOING? The Asbestos Information Association/North America reports that, during the past 30 years, the asbestos industry has spent millions of dollars to improve mining, milling, and manufacturing methods (3). The establishment of safer working conditions has been a prime target and this work continues unabated and in close association with government agencies and independent medical researchers (9). The ultimata goals of Ihe asbestos industry are: ----- Reduction of work-area dust to minimum levels. ----- Protection of workers from asbestos-re!ated diseases. ----- Maintenance of environmental emissions at levels low enough to preclude public endangermenf. AIR SAMPLING In order to comply with OSHA Standards and to determine the need for dust control measures, air monitoring should be conducted in areas where asbestos is regularly handled or used. OSHA Standards require that "all deferminations of airborne concentrations of asbestos fibers shall be made by the membrane filter method at 4Q0-450X (magnificat ion) (4 mi I Iimeter objective) with phase contrast illumination." (10) The equipment for collecting un samples costs less than $400 and is readily available. A phase UCC.0I4832 40765b contrast microscope can be obtained for as little as 1600 or an existing microscope can be modified for ''counting" the asbestos fibers in compliance with NI05H criteria (I!). Air samples have been collected and analyzed on a regular basis by the asbestos industry for years. Except for 3 few applications where dust control is an engineering problem, industry is finding that dust levels are already within acceptable standards or that minimum changes are necessary to achieve compliance. Although data on many asbestos/p Iastics applications are not available, the summary in Table IV is typical of our measurements of dust levels during asbestos handling in various types of plants and operations. The dust levels reported are Ceiling Concentrations and it should be noted that the allowable OSHA level is 10 fibers/cc. in most cases, the TWA exposure level would be well below OSHA Standards. Most of the data were collected before the installation of any special dust control measures. Monitoring often shows that obviously dusty conditions are caused by materials other than asbestos. This does not preclude the need for controls but it could change their scope and facilitate compliance with government regulations. Because of "bad press," asbestos is frequently ordered out of use without regard to whether or not a hazard actually exists due to air contamination. If acceptable dust levels are feasible, there Is no need to replace asbestos at the expense of product quality or economic penalty. Mr. Gordon Everett of ERA points out that information on the biological effects of asbestos Is very limited and that the effects of many substitutes have not been investigated at all. Before asbestos is replaced, it should be certain that a safer alternative is available (12). Obviously there are more people exposed to products containing asbestos than there are to raw asbestos fibers. As noted previously, over 902 of the asbestos used in this country is in products in which the asbestos is "locked in" or bound with cement, plastics or other binders so that there is no release, or at least no significant release, of fibers in work areas or to the environment. Materials or products with locked-in fibers would include: floor tile, polyester resins, phenolics, sealants, coatings, brake linings, friction materials, rubber, roofing compounds and reinforced plastics. Since an abrading action on some of these products could release asbestos fibers, appropriate monitoring and/or control measures should be instituted if it is thought that such action would release fibers. DUST CONTROL MEASURES A07C56 Asbestos producers and users are spending a considerable amount of time and money on various dust control measures. Conventional means to achieve minimum dust levels include: filtered ventilation systems on process equipment, local ventilation for saws and similar tools, conversion to a "wetted" operation, leak-proof packaging, vacuum clean-up, more care in bag disposal and other asbestos waste handling, and automatic bag openers. Unusual innovations include: pelletized asbestos, special packaging, and treated product's. Only short-fiber chryso+Ile Is available as pellets, but UCC 014833 this product serves a fair portion cf the asbestos market. Pellets not only reduce dust during conventional handling but they are a I so available in bulk hopper cars and can be transferred and used in totally enclosed systems. Barring leaks in the system, dust in work areas is virtually eliminated. Used in bulk, asbestos pellets also reduce shipping costs, eliminate warehouse storage and handling, facilitate automation, reduce clean-up, and eliminate bag handling and disposal. The pellets contain no binder and are triable enough to be dispersed in dry form or in aqueous or resinous systems with conventional highshear grinding equipment (13). Several types of special packaging are currently available and suppliers consider customer requests for unusual requirements. The floor tile industry can obtain asbestos in plastic bags which can be added directly to the compounding operation. Asbestos in bleached paper bags assembled with water-soluble glue and printed with water-dispersible ink can be added directly to paper-making furnishes or acoustical ceiling tile formulations. Water-proof bags are available to permit slurrying of the asbestos in the bag. Wider use of shrink-filming is being offered to reduce dust during bag handling, transportation and storage. Although "wetted" asbestos is not generally available, most suppliers are working with customers to provide ''dustless" products. When justified by market demand, asbestos can be treated with water, mineral spirits, glycol or other materials compatible with the application or system. CONCLUSION Asbestos is one of industry's many raw materials which involves a potential hazard when not used with reasonable respect and care. Although all forms of asbestos are recognized as hazardous to health when inhaled excessively, there is growing evidence that crocidolite and amosite are more hazardous than chryso+ile. Fortunately the plastics industry uses primarily chrysoti!e asbestos and in most products the fibers are locked-in to prevent airborne contamination. Although asbestos dust levels are generally lower than expected, industry continues to expend large amounts of time and money tc further improve the quality of the workplace. Although the general oublic is not currently in danger, occupational controls are required to prevent future environmental con tarnination. Chrysoti(e asbestos is an important and necessary raw material, vital to the nation's safety and economy; and, with proper control, it can be used safely and in compliance with government regulations. Medical, scientific, government, and industrial personnel must continue to work closely together to establish reasonable exposure limits, provide safe work areas, and eliminate any possibility of public endangerment. UCC 014834 REFERENCES: 1. Enter line, P. E. and V. Henderson, "Type of Asbestos and Respiratory Cancer in the Asbestos Industry," Arch. Environ. Health/Vol. 27, pp. 312-317 (Nov. 1973). 2. Wagner, J. C., "Current Opinions On The Asbestos Cancer Problem," Ann. Occup. Hyg., Vol. 15, pp. 61-64 (1972). 3. Wright, G. W., Statement before U.S. Dept, of Labor, Occupational Safety and Health Hearing on Proposed Occupational Asbestos Standard, p. 3 (I4arch 16, 1972). 4. Hammond, E. C. and 1. J. Selikoff, "Relation Of Cigarette Smoking To Risk of Death Of Asbestos - Associated Disease Among Insulation Workers In The United States," presented at the meeting of the V/orking Group to Assess Biological Effects of Asbestos, !nternationaI Agency for Research on Cancer, Lyon, France (October 4, 1972). 5. "Report of The Advisory Committee on Asbestos Cancers," Brit. J. industr. Med., Vo). 30, pp.180-186 (1973). 6 "Asbestos," National Safety News (October 9, 1973). 7 "National Emission Standards for Hazardous Air Pollutants," Federal Register, Vol. 38, No. 66, p. 8820 (April 6, 19735. 8 "Protecting The Asbestos Worker," Booklet No. I0ID37, p. 5, The Asbestos Information Association/North America. 9 Selikoff, I. J., "Partnership For Prevention," Industrial Medicine, Vol. 39, No. 4, pp. 21-25 (April 1970). 10. "Standard For Exposure To Asbestos Dust," Federal Register, Vol. 37, No. NO, p. ! 1320 (June 7, 1972). 11. Bayer, S. G. et a I, "Equipment and Procedures For Mounting Mi I Ijpore Filters and Counting Asbestos Fibres By Phase Contrast Microscopy," Bureau of Occupational Safety and Health, U.S. Dept, of Health, Education, and Welfare, (February 1969). 12. "Asbestos Health Question Perplexes Experts," Chemical and Engineering News, pp. 18-19 (December 10, 1973) 13. Myers, J. L., "Calidria Asbestos Pellets," ASBESTOS (October 1971) &076o8 UCC 014835 TABLE I APPARENT U.S. CONSUMPTION 0* AS8ESTCS, TONS* (f of Total Shown In Parentheses) Year 1967 1968 1969 1970 1971 1972 Total 720583 817363 784321 728131 758571 808554 Chrysotlle 686044(95) 77571 U95) 749708(96) 695770(96) 729272(96) 791020(98) Amoslte 12558(1.7) 20467(2.5) 14618(1.9) 14261(2.0) 14580(1.9) 7125(0.9) Croc Idolite 14917(2.1) 13965(1.7) 10558(1.3) 8936(1.2) 6953(0.9) 5374(0.7) information based on import and production data from United States Bureau of Mines Minerals Yearbooks. TABLE 11 COMPARATIVE DATA FOR AS5ESTQS MlfJEP-ALS FORMULA CHRYSOTILE 3Mg0-25i02-2H20 CROClDOLiTE NazO* Fe203- 3FeO' 8SI02-H20 AMOSITE I.SMgO*5.5FeO- 8Si02" HjO ANTHQPHYLLiTE 7Mg0*8SI0z- H20 COMPOSITION,* SI02 MgO FeO F-203 Al203 H2O Cat) Na^ CaO+NajO 37-44 39-44 0-6 0-5 0-2 12-15 0-5 49-53 0-3 13-20 17-20 2-5 4-8 49-53 1-7 34-44 2-9 2-5 0-3 56-58 28-34 3-12 0-2 1-6 CRYSTALS COLOR TEXTURE FLEXIBILITY HARDNESS, Mohs FIBER DIA., A TENSILE, Mpsi SURFACE CHG. RES. TO ACID RES. TO ALK. Fine Fibers Gray/Green Soft/Silky Very Good 2.5-4 180-300 BOO Positiwe Poor Good Brittle Fibers Blue Harsh Good 4 600-900 600 Negative Good Good Prismatic Crysta Is Gray/Brown Harsh Good 5.5-6 600-900 200 Negative Good Fair Prismatic Crystals Gray Harsh Poor 5.5-6 600-900 <4 Negative Very Good Good Source: Modern Plastics Encyclopedia!1972-3), and Encyclopedia of Chemical Technology, Volume 2, p. 136(1948). 407659 UCC 014836 ' TABLE I I I APPARENT U.S, CONSUMPTION OF ASBESTOS BY GENERAL USE AREAS Area of Use % of Consumption* Construction FIoor Tile Felt and Paper Friction & Packing Insulation Textiles Other 40 15 15 14 3 2 II *Author*s interpretation of data from the USBM Minerals Yearbook - Asbestos-1972, the Asbestos Information Association/ North America, and persona! communications with Mr. R. A. Clifton of the USBM. TABLE IV TYPICAL AIR SAMPLING RESULTS Type Plant or Operation Floor Tile Polyester Phenolic Compounding Hand Iing PhenoIic Caulks and Sealants Gypsum Compounds Ceiling Concentration, Asbestos Fibers/cc 1-3 1-3 2-5 3-14 0-8 2-9 Source: Union Carbide Corporation, from air monitoring reports. 40766c UCC 014837