Document LKRn9rm8nY4E26m2M6qannZ3b

CHRYSOTILE ASBESTOS IN PLASTICS John L. Myers "CAL I DR!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 INTRODUCTI ON Asbestos has received a great deal of attention and publicity in recent years, especially after it was designated a "target health hazard" by OSHA and a "hazardous air pollutant" by the ERA. Many of the articles on asbestos by the press have been emotionally oriented or distorted and in some cases stories have been sensationalized, based on obvious misinterpretatton 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. The 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 naturaIly-occurring "asbsstiform" 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 amphiboles include crocido life, amosite, anthophyIlite, tremolIte and actinoiite. Chrysotile is by far the most used variety and accounts for over 95^ of U.S. consumption, as noted in Tab lei. . Croc idolite, 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 Iimited '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 anthophy!lite 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 II. It should be noted that there are significant differences between chrysotile and the amphiboles 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 is 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 vinyI/asbestos floor tile and in phenolic molding compounds. It is also used In other plastics such as polypropylene, polyester, nylon, melamine, epoxy, silicones and vinyls. Asbestos provides UCC 014828 p valuable function in such products as brake linings., clutch facings, electrics! components, automotive parts, furniture, boats, sealants, coatings, adhesives and mastics. The most important functions of asbestos in plastics are reinforcement, dimensional stability,' heat resistance, flow control and general-purpose filling. Most of the functions are supplied by short fiber chrysotile asbestos fiber, although longer chrysotile fibers and other asbestos varieties are sometimes required for particular properties. WHY USE CHRYSOTILE? Among the several advantages of chrysotile, which set it 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 Index. 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 I 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 asbestos is. 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 considerat ion 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 rare cancer of the lining of the chest (pleura) or the abdominal cavity (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 33--member Advisory Committae on Asbestos C2.nce.-3 of the International Agency for Research on Cancer (a division of the World Health Organization): "There is evidence of an association of mssothelial tumours with air pollution in the neighbourhood of crocidolite mines 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 existed in the neighbourhood of chrysotiis and amosite mines. There are reported differences on incidence of mesothelioma between urban and rurai 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 general 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-made emissions are not controlled, then environmental contamination 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 VJi 1 liams-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 Administration (OSHA) within the Department of Labor, 'which has responsibility for administration and enforcement. Research and related functions are handled by the Department of Health, Education and Welfare (HEW) through the National Institute of Occupational Safety and Health (NIOSH). Five million employers and 60 mil lion of the nation's 80 mil lion 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, 1972, OSHA announced a Target Health Hazards Program aimed at improving health factors associated v/ith 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 Mho ' UCC 014830 A 076 07 NI OSH list, only 509 are covered by standards and many of these need updating. The new Standard for Exposure to Asbestos Dust was published in the Federal Register, Vo Iume 37, Mo. 110 on Wednesday, June 7, 1972. The basic exposure standard is an 8-hour time-weigh'ied average (TWA) of 5 fibers, longer than 5 micrometers, per cubic centimeter of air. The TWA limit is to be reduced to 2 fibers per cubic centimeter on July l, 1976. A peak concentration of 10 fibers per 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 requirement of the new standard is monitoring to determine whether or not fiber concentrations 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 Iimits. Improper interpretation of the reguis ions has created many misconceptions about the equipment ar orocedures needed to properly use asbestos. Sf exposure lie its are not exceeded, there are no further compliance requirements except for medical examinations. Medical examinations are required for all 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 Iimits 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 the Ir use whiI 8 . 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 does 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 norma I use and handling of the product 75). . ERA STANDARDS Whereas OSHA is responsible for the protection of the worker, the Environmental Protection Agency (ERA) is charged with improving the environment to which the general public is UCC 014831 exposed. On March 31, 1971, ; jbestos, along with beryl lie and mercury, was identified a: a "hazardous air pollutant17 by the Adm i r, i s+rator of the EPA. National Emission Standards to asbestos were then published by the EPA in +thr e Federal Register, Vol. 33, No. 66 - Friday, April 6, 1973. Although no numerical emission standards were established, operating criteria are prescribed to prevent or limit asbestos omissions to the outside air from asbestos mills, roadways, certain manufacturing operations, building demolition, and the spray-on application of materials used to insulate or fireproof equipment and machinery. The law further requires that spray-on materials used to insulate or fireproof buildings, structures, pipes, and conduits shall contain less thanT$ asbestos on a dry weight basis. This should significantly reduce emissions to which the general public may ba 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 the 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 into the atmosphere be defined and controlled."1 (7) WHAT IS 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 ultimate goals of the asbestos industry are: ----- Reduction of work-area dust to minimum levels. ------ Protection of workers from asbestos-related diseases. ----- Maintenance of environmental emissions at levels low enough to preclude public endangerment. 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 determinations of airborne concentrations of asbestos fibers shall be made by tbs membrane filter method at 400-450X (magnification) (4 millimeter objective) with phase contrast illumination." (10) The equipment for collecting air samples costs less than $400 and is readily available. A phase UCC.014832 d0765b contrast microscope can be obtained for as little as 3600 or an existing microscope can be modified for "counting" the asbestos fibers in compliance with NiOSH criteria CM). Air samples have been collected and analyzed on a regular basis by the asbestos industry for years. Except for a 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/plastics 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 EPA 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 90% 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 finings, 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 A07656 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 products. Only short-fiber chryso+lle is available as pellets,, but UCC 014833 & this product serves a fair portion of the asbestos market. Pellets not only reduce dust during conventional handling but they are also available in hulk 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 friable enough to be dispersed in dry form or in aqueous or resinous systems with conventional high- shear 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-soiubIe 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-fiIming 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 anosite are more hazardous than chrysotile. Fortunately the plastics industry uses primarily chrysotile asbssto 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 to further improve the quality of the workplace. Although the general oublic is not currently in danger, occupations controls are required to prevent future environmental contamination Chrysotile 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. Enterline, 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 (March 16, 1972). 4. Hammond, E. C. and I. 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 Working Group to Assess Biological Effects of Asbestos, InternatfonaI Agency for Research on Cancer, Lyon, France (October 4, 1972). 5. "Report of The Advisory Committee on Asbestos Cancers," Brit. J. industr. Med., Vol. 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, 1973). 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. 11320 (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 Weffare, (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 197 fc076&8 UCC 014835 TABLE I APPARENT U.S. CONSUMPTION OF ASBESTOS, TONS* (* of Total Shown In Parentheses) Year 1967 1968 1969 1970 1971 1972 Total 720583 817363 784321 728131 758571 808554 Chrysoti le 686044(95) 775711(95) 749708(96) 695770(96) 729272(96) 791020(98) Atos1te 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 II COMPARATIVE DATA FOR ASBESTOS MINERALS CHRYSOTILE CR0C1D0UTE AMOSITE ANTHOPHYLLITE FORMULA 3MgO-2Sf02-2H2O NajO* FejOy 3FeO' 8S102-H20 l.5MgO5.5Fe083(02" H2O 7MgO* 8S102* H2C COMPOSITION,* SI02 MgO FeO Fe203 A<23 h2 CaO NajO CaO+Na^ 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 2.5-4 180-300 800 Posit1ve 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 Crysta1s Gray Harsh Poor 5.5-6 600-900 <4 Negative Very Good Good Source; Modern Plastics Encyclopedia!11972-3), and Encyclopedia of Chemical Technology, Volume 2, p. 136(1948). A07659 UCC 014836 ' TABLE !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 Author's interpretation of data from the USBM Minerals Yearbook - Asbestos-1972, the Asbestos Information Association/ North America, and personal communications with Mr. R. A. Clifton of the USBM. TABLE IV TYPICAL AIR SAMPLING RESULTS lYP_e P1 ant or Operation Floor Tile PoIyester Phenolic Compounding Hand Iing Phenolie 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. ^?6Qq UCC 014837