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FILE NAME: Phenolic Resins (PHR) DATE: 1975 Dec DOC#: PHR077 DOCUMENT DESCRIPTION: Trade Journal Article - Handling Asbestos, Chrysotile Asbestos in Plastics JOURNAL OF PAINT TECHNOLOGY - . Handling A sbestos i-.irr Chrysotile Asbestos in P la s t ic s l V n u ; "CiJ' . . ..T-V: ,:c'*'' \ *, - ' " , ?- ,, - V- <tr j j * * * 3- ' -v.4-' > i'iy f e ; ..*,* . - ' . . . r .. f . .-..-v ^^K ^E&M r-:.r>-' y.<.' .. Jo h n L.....M....y.e..r...s. -.*-*.-?.... ,feys '.'-xr.huTj sV ;'.yy;- Union Carbide C o rp o ra tio n V C ^ A :^ '^ ^ ^ H > :h - ;y y i r" '" tes**** .&&&$%> - -r*'*'!v-A*r * >'. .r',---.- i ., , .. ... - .. .. ... -./ti^/j^rg ajR H -.Oy.?J~^U' - ' - .Vt,r*' ,f:" **> , -V.. *>.-. -- ~v.-- it-- a great.deal.of attention and publicity in recent years, especially after it was designated a "target health hazard" by OSH A and a hazardous air pollutant" by the EPA. 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 misinterpretation of facts' floor tile and in phenolic molding compounds. It is also used in other plastics such as polypropylene, poly ester, nylon, melamine, epoxy, sili The use of half-truths or unsubstantiated statements has led to general con fusion 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 into 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. Th e health hazards associated with asbestos, both occupational and environmental, and some industrial ex perience with air sampling and dust control^ measures are also covered.-.'-/ cone, and vinyl Asbestos provides a valuable function in such products' as ; brake linings, clutch facings, electrical ` components, automotive parts,' furni-ture, boats, sealants,' coatings, 'adhe-sives^and mastics. The most im portant - functions of asbestos'in plastics are re :-.r -./nC: j .VrV,. v..- ..'r '`'V '. inforcement, dimensional -stability, KEY WORDS- Asbestos; Pla--st=ic--s; A*=i-r---p---o--l-lu-tion;-.Toxicology.^rn" **........... h eat resistance, flow control, and g e n :.'U-'v.vw';T:: /.ir.vl- eral-purpose filling. Most of die func tions are su p p le d : b y : short-fiber chrysotile - asbestos ' fiber," although : What Is Asbestos? _ _ ...........__ it . .. ^ _ i_. _ . Asbestos is a commercial or generic term used to describe six naturally occurring "ashestifonn" 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 crocidolite, amosite, antho- phyllite, tremolite, and actinolite. Chrysotile is by far the most-used variety and accounts for over 95% of U.S. consumption, as noted in Table 1. . .. /.' . . - ... Crocidolite, also known as blue as bestos, is imported from South Africa. Because of its high mechanical strength and good resistance to adds and alkalis, it is used to reinforce a limited variety of plastics w here its pronounced color is not objectionable. Amosite, also imported from South Africa, is used primarily in therm al Presented at the Golden Gate Society's Man* ajrement Seminar held in San Francisco, Calif., June 16. 1975. * Metals Div^ Niagara Falls, N.Y. 14502. insulation. Although there are some deposits of anthophyllite in the U.S., most of it is imported from Finland. I t is used prim arily as a filler for- polypropylene and in insulating ma- terials.v A comparison of the four -varieties of asbestos which are of oom-.: m errial importance is presented .in j Table 2. I t should be noted th at there " are significant differences between chrysotile and amphiboles with regard to chemical composition and certain physical properties. .. . 4. Where is Asbestos ,. .. , Used and Why? . Asbestos has served mankind for more than 100 years in a broad vari ety of applications. The general areas in which asbestos is used in die TJ.S. are shown in Table 3. Based on infor mation from asbestos producers and consumption surveys, it is estimated that the plastics industry uses about 33% of the 800,000 tons consumed an nually, which makes it the largest single user of asbestos fib .. The largest uses of asbestos by die plastics industry are in vinyl-asbestos longer chrysotile fibers and other as bestos varieties are sometimes re quired 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 us age, are world-wide availability, m e chanical strength, flexibility, positive surface charge, low iron content, soft ness, and low refractive index. I t is conservatively estimated th at chryso-. tile asbestos is used in over 3,000 ap plications and, in most of these appli cations, 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 stead ily increasing. This is due partiy to technical advances perm itting die broader use of chrysotile in plastics and the general decline in the use of asbestos in certain fireproofing and in sulating materials. In addition, there is increasing evidence that crocidolite and amosite are more hazardous to Vol. 47, No. 611, December 1975 Table 1-- Apparent U.S. Consumption of Asbestos, Tons* Year Total Chrysotile Amoslte Crocidolite 1967 720383 686,044(95)* 12,558(1.7) . 14,917(2.1) 1968 817365 775,711(95) . 20,467 (23) 13,965(1.7) 1969 784321 , p 749,708(96)^ '1 .14,618(1.^ F * f" 10358(13) 1970 728,131 695,770 (96) *14261(2.0) ^ : 8,936(15)' 1971 758371 : 729572(96) 14380(1.9) 6,953(0.9) 1972 808354 " ' / 791,020 (98)/vT/?- 7.125(0.9) ' 5374 (0.7J, (a) Information bated - on import 'and production data '-"from U . S1 Bureau of Mines' Minerait Yearbook* 0 -, - (b) Percent of total thown in parentheaet. " . a* * * ' ' - ". . * . Table 3-- Apparent U.S. Consumption of Asbestos By General Use Areas Area of Use Percent of Consumption Construction .40 Floor tile " :/ X .15 Felt paper ' 15 Friction and packing 14' .Insulation nA4* -.'siSR. > ' Textile* - 2 Other ,. n human health than chrysotile.* Since 1970, the use of crocidolite in Britain has been restricted after a panel of experts "concluded there was suffi cient evidence to suggest other types of fibre should be substituted for crocidolite wherever possible."*. ***'"" . -.i-, vni 'isas.'s? r' ;: . . . . . s i ' -) What is the Asbestos Hazard?^ It is readily accepted that asbestos, like many other foreign bodies, -oan cause disabling lung damage, (pul monary fibrosis), commonly referred to as asbestosis. This disease and bronchogenic carcinoma (lung can cer) are the two most common as bestos-related diseases. It is im portant 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 .re searcher has reported th at neither of these diseases is peculiarly related to r.' " */ or ca-used -solely by the '.inhalation of ' asbestosfiber.' Another im portant con- sideration .is the relation between f* cigarette smoking and lung cancer, as reported by D r. E. C. Hammond and IDr. I. J. Sehkoff.* In this study, they reported that: "It seems clear, then, ;.' that lung cancer is uncommon among . ' asbestos insulation workers who have /n o history of cigarette smoldng and th a t if dhe risk J s increased, such in -' r crease is -'not g te a t" i^ 'iys-i"ti???& iS****?#* ^ i s ^ nSbthe"KVToini;: '* ' m ore .recently been /associated ;with .persons cpc^d :to asbestos., Meso--r -thKom is anextrem ely rare cancer - of the lining of die cheSt (pleura) or u . the abdominal cavity (peritoneum ). >/. In contrast to the lung cbseases.-there ' / . is some evidence that mesothelioma'. can occur after brief exposures to \ relatively high fiber levels. / According to the 33-member Ad visory Committee on Asbestos Can- :tr lcTt - J >; " *' Formula .! ' Table 2-- Comparative Data for Asbestos Minerals'i'./ T ' '-i' ^ - J' Chrysotile Crocidolite Amoslte Anthophyliite 3Mg02SiO:'2HjO NasO FesO.' 1.5Mg0 5.5Fe0 7Mg0 8Si0, H*0 8SiOr H-0 8SiO* H,0 raTtripca. . , Composition,,% SiO. ... - - ;p - -, .;.V.V 37-44 . ,. 49-53' ' ' ' - ' 49-53 ' '' 56-58 '7: ' Mgo FeO Fe.O, ' : 39-44 // ,; o--s ./"' . V 28--34 !'' ' 0--6 " ' 13--20 ; ' 34--44V''--;'" ' "-3 -1 2 :.'.' " ' ` 0-5 ' 17--20 7* SC* AlsOt . ^ H ,0 0-2 . 12--15 .. ; 2-9 0 -2 2 - 5 :. -ToVr.-g^j-'y m -m e i --6 CaO " "0--5 " ', ; AS '' ~fy r r i i rrn o Na.O CaO-f Na=0 ' ' " ` 4 --8 '" " " -- // /'. .... --. ; ' 0X3 ' . ' . Crystals .. .. Fine fibers Color ... , . ; , Cray green Texture . . Soft silky Flexibility .. Very good Hardness, mohs ; 23-4 Fiber diameter, A 180-300 Tensile, mpsi . ..... 800 Surface charge ^ Positive Resistance to arid Poor . Resistance to alkali Good Brittle fibers Prismatic - Prismatic . Blue . `; - Gray/brown Gray Harsh . , ' Harsh .. . . Harsh Good,,. ;/ . Good ; Poor -4 ; --, 53-6 ........ 53-6 600-900 ,, . 600-900 600-900 , 600 . ,.,..200. . , .; ,< * ; Negative...: Negative , Negative,..- Good ' . Good K-,, i , Vety good ... -Good. ,,...... . . Fair . , - COOdr'T . (a) Source*: Rodent Planks Encyclopedia (1973), and Encyclopedia of Chcm. Tech., VoL S. oers of the International Agency for Research on Cancer (a division of the World Health Organization) : "There is evidence of an association of mso thlial tumors with air pollution in the neighborhood of crocidolite mines and of factories using ridxturoe of-as bestos fiber types. The evidence'ire-7 lates to conditions of many~years".ago.l There is evidence of no excess- risk of mesotheliomas from asbestos air pollution which has eristed an -ihe. between^urban a n d ru m la re a s.ih e causes of which have not been estab-lished. There is no evidence o f a risk. to the general pihH c a t ^resentTFS? - T h e a n e 'body quoted above has also concluded that there is, at pres ent, no evidence of lung damage by asbstos to th e general public; and. such evidence as there is does not in - dicate any risk of cancer resulting from asbestos fibers present in water, beverages, food, or in the fluids used for the administration of d ru g s ///'/';- W hile ther seems -io b e general agreement ' th a t' the public is m ot-in any present-danger .from asbestos, i t is also recognized th at excessive. long term occupational exposure can cause serious health problems. Also, i f man m ad e--emissions are not controlled,, then ` environmental . contamination could could approach harmful levels. During the p ast two years, significant legislation bas b een .enacted by the Federal government to reduce and control occupational exposure to as bestos fibers and to minimize fiber emissions to the environment.-Addi tional standards or regulations bave been proposed -or enacted by many states and local governments.`'nw.;. l. UaRsctMft^onr^j/AbtoySS ..vSotrtA. Summary of OSHA Regulations. - XT/---- --V-:-' t" Fc. " , The William-Steiger Occupational Safety and Health Act of 1970 be came effective on April 28,1971, with J ournal of Paint T echnology Hi the following Congressional purpose: Im proper interpretation of the reg EPA Standards "To assure so far as possible every ulations has created many miscon working man and woman in the na ceptions about equipment and pro Whereas OSHA is responsible for tion safe and healthful working con cedures needed to properly use the protection of the worker, the En ditions and to preserve our human asbestos. If exposure limits are not vironmental Protection Agency (EPA) resources." The Act established the exceeded, -there are no further com- is charged with improving the en Occupational Safety and Health Ad plianoe requirements except fo r med vironment to which the general p u b lic, ministration (OSHA) within the D e ical examinations. Medical examina is exposed. On March .31, 1971, as partm ent of Labor, which has re tions are required for all employees bestos, along with beryllium and sponsibility for administration .and : in any occupation exposed to airborne y mercury, was identified as a'^hazard- - enforcem ent Research a n d 're la te d concentrations of asbestos fibers.. The ' ous air pollutant" by the Administra functions are handled by the Depart ' examinations are relatively sim pleahd ,j to r .of the EPA. . National Emission . ment of Health, Education and Wel y should cost no more than $50 p e r. Standards for asbestos were then pub- ' fare (HEW ) through th e National ' year, p e r employee. - fished by EPA in the Federal Regis- Institute of Occupational Safety and ` ter, Vol. 38, No. 66, April 6, 1973. - ' Health (NIOSH). Five million em Respirators and special clothing Although no numerical emission stan- - ployers and 60 million of th e nations are required in the construction trade 'dards were established, operating cri- 80 million workers are covered by for die spray application of insulation " teri are prescribed^ to prevent o r., OSHA. Specifically excluded from ..and fireproofing materials, and for"the ' limit asbestos emissions to 4he out- r-. coverage are government employees removal of such materials. This spe- side air from asbestos mills, roadways, and operations which are protected d al protection is n o t required for any- certain m anufacturing 'operations, under other federal health and safety.' eth er use of asbestos unless exposure building demolition, -mid the spiay-on laws. In a news release issued January limits are exceeded. This is also true application of materials used to in- 'r"'y. 4, 1972, OSHA announced a Target _for _other items such -as spedally su k te o r fireproof equipment an d Health Hazards Program -aimed -at equippedtools, change rooms, clothes machinery. D ie law further 'requires; improving health factors associated . laundering, a n d -waste disposal. Res that spray-on materials 'used.>to in-;, with working conditions. T he follow pirators are not a substitute for en- su k te or .fireproof buildings, struct ing five substances were designated gineeririg controls, but the law , allow sTj -tures, :pipes,-and conduits shall ^con to be die focus of initial .and con- ' their use while c^tro k ^su eT iein g tain less th an ,IS asbestos on a= dry- certed efforts by OSHA and NIOSH: . implemented, in `-special ; situations ; weight basis. This should significantly asbestos, cotton dust, silica, lead, ^nd where controls are not feasible or ' reduce emissions^ to which die gen-, adequate, in emergencies, and fo rjn - . eralpubfic may to exposed, especially c a i b o n m o n o x i d e ^ : frequent short-term, job assignments. `in large urban areas. . At the present time, new standards ;/ - Caution, labels are required on prod- ' .-yyi'.- . J the Administrator (of EPA) have been established only for asbes ucts containing asbestos except where has determined that, in order to pro-' tos, although, of die 8,000 toxic sub .the fibers have been modified by a vide an ample margin of safety to stances on the NIOSH list, only 500 bonding agent or other m aterial to protect the public health from as me covered by standards and many prevent dusting during any normal bestos, i t is necessary to control em is of those need updating. The new subsequent use or handling. Besides sions from major man-made sources Standard for Exposure to Asbestos raw asbestos fiber, products which of asbestos emissions into d ie atmos D ust was published in die Federal require package labeling could in phere, b u t that it is p o t necessary to Register, VoL 37, No. 110, on June 7, clude: dry acoustical spray products prohibit all emissions.X SH'v - 1972. The basic exposure standard is and joint cements, unsaturated roof- - ; "In this determ ination/ihe Admin- an 8-hr tim e weighted average ing felt ,and textiles, and some in istratoi has relied :on the. National (TWA) of five fibers, longer than 5 sulating products made w ithout ade Academy of Sciences' report on as- - ; micrometers, per cubic centimeter of quate binders. T he labeling of a prod- - bestos, which concludes:-""Asbestos -is - air. The TWA limit is to be reduced uct does not prohibit its nse. It too im portant in our technology an d . to two fibers per cubic centim eter on ' should be noted here that in a t least economy for its essential use to be . ' July 1, 1976. A peak concentration 90S of the products containing as stopped. But, because of the known ' of 10 fibers p er ctibic centimeter is bestos. die fibers are solidly locked serious effects of uncontrolled inha not to be exceeded at any time. AH into the product thereby presenting lation of asbestos minerals in indus of the fiber concentrations are those little danger of dust generation dur- , try, and uncertainty as to the shape to which an employee may b e ex ing normal use and handling of the and character of the dose-response posed w ithout protective clothing and ' product* ...? ...... '. curve in man, it would be highly im- equipment. The first basic require ment of the new standard is monitor ing to determine whether or not fiber concentrations are in excess of die _ exposure limits. Some asbestos sup pliers provide a monitoring service to JO H N L. MYERS, Marketing Manager for the Calidria Asbestos Group in Union Carbide's Metals Div., received customers, and a similar service may be obtained from state health depart ment officials, insurance earners, or private consultants. The law requires that monitoring be repeated as nec his B.S. Degree in Chemical Engineering from Purdue University in 1951. Joining Union Carbide that same year, h e s e r v e d in t h e N u c le a r D iv isio n u n til 1966, w h e n h e b e came a Research Engineer in the asbestos group. He was promoted to his present position in 1970. ' ; : essary to ensure that employees are not exposed to levels in excess of the exposure limits. . ' .; Vol. 47, No. 611, December 1975 prudent to permit additional con tamination of the public environment with asbestos. Continued use at min imal risk to the public requires that the major sources of man-made as bestos emission into the atmosphere be defined and controlled.'"'- What is industry Doirig? '^" The Asbestos Information Assocda- tion/N orth America reports that, dur ing the past 30 years, the asbestos in dustry has spent millions of dollars to improve mining, milling, and manufac- hiring methods.* 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 m edical researchers*^;5^ ' i T h e ultim ate goals of die asbestos industry are: Reduction of work-area dust to minimum, levels; Protection . of workers from asbestos-related d is-: eases; Maintenance of environmental emissions a t levels low enough to pre- ` dude public endangerment.' ; //i- . -r Air Sampling -Z'; . In order to comply with OSHA . standards and to determine the need for dust control measures, air monitor ing should be conducted in areas where asbestos is regularly handled or used. OSHA standards require that "all determinations of airborne con centrations of asbestos fibers shall be m ade by the membrane filter method at 400-450X (magnification) (4 milli m eter objective) with phase contrast illumination."" The equipment for collecting, air samples .costs less than $400 and is readily available. A phase contrast microscope can be obtained for as little as $600, or an existing microscope can be modified for "counting" the asbestos fibers m com pliance with NIOSH criteria." -; Air samples have been collected and analyzed on a regular basis by the asbestos industry for years. Ex cept for a few applications where dust control is an engineering problem, in dustry is finding that dust levels are already within acceptable standards or- that minimum changes are nec essary to achieve compliance. Al though data on many asbestos/plastic applications are not available, the summary in Table 4 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 allow- - Table 4-- Typical Air Sampling Dust-Control Measures Type-Plant Results* Ceiling , - Concentration,. Asbestos producers and users are spending a considerable amount of Or Operation .. Asbestos Fibers/cc time and money on various dust-con-'' .Floor -tile. V i J-8 . / trol measures. Conventional .means t o " " .' -achieve minimum dust levels include: - . filtered ventilation systems on process .'^ eq u ip m en t, local ventilation for saws ~ .,;and ,'isim flar^took;! c o n v eraw p o Gypsum compounds ^ ' 2 - 9 ; ` .^ ^ w etted " operation,'.Teak-proof p ack -' ; aging,vacuum clean-up,-more care In (a) /Source: Union Carbide Corp*. from air m onitoring report. . - rw . - y .v /. . hag disposal and other asbestos w a s t e handling, and autom atic bag openers;.-; . U nusual innovations Include: ' pel-' - . letized asbestos, special packaging, and treated prodiK its/iiarf.^; ;--^ - ^ '., z Only short-fiber duysotile Is avail able OSHA level is 10 fibers/oc. In able as pellets, but this product serves - most cases, the TWA exposure /level `..a /fair portion of the/asbestos m arket would b e well below OSHA 'Stan-. T ellets -pot /only reduce -dust d u rin g '"/ dards. Most of fee data were collected / conventional handling But they '/are - before th e installation 1of uiyspfl- f ~"also -available in bulk hopper oars ancT dust-control measures! Monitoring '"-canbe transferred and used in totally ; te n shows feat dbtuously'dusty xn-\Z: -enclosed systems. Baning leaks in fee 'ditions'ure `caused by^materials Bfeer- - 'system, dust in work!areas is virtually. ^ fhaii asbestos. This 'does not preclude elinunated. 'U sed^^'briD cjipfeestos.^i the need for controkrB ut -it r-could pellets also rd u c e /Shipping -^costs,. '. change their scope and facilitate com eliminate : warehouse ^. storage/`--and .-h pliance wife government Regulations. ' ' Bandling, facilitate automation, reduce U ' Because of *Bad pressT* asbestos' is clean-up, and eliminate bag handling'.'. frequently ordered out o f use without -and disposal. T B e pellets contain no - regard to w hether -or 'n o t a" hazard :r Binder and m e Jtiablejenough to.Be -f . actually exists due to air contamina-' . dispersed in dry form .or.in aqueous ~.*~ tion. " If acceptable d u stTevis Vre ^ or resinous'systems wife conventional feasible, there is no need to replace high-shear grinding equipm ent" .r asbestos at the expense of product , Several types of special packaging ...: quality or economic penalty. Cordon are currently available, and suppliers - v Everett of EPA points out feat in consider customer requests for--unus- -1', formation on the biological effects of ual requirements. The floor tile Indus asbestos is very limited and feat the try can obtain asbestos in plastic bags effects of many substitutes have not which can be added directly to -fee/ been investigated a t all. Before as compounding operation. Asbestos -in _. ' bestos is replaced, it should be cer bleached paper Bags assembled.-wife . tain feat a -safer altem tive is avail . water-soluble glue and printed with - / ' Obviously there are* more people; exposed to products containing asbes tos than there `re to raw asbestos fibers. As noted previously, more than 90% of the asbestos used in this coun try is in products in which fee asbes tos "is "locked' in" -or bound with ce ment, 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 wife locked-in fibers would include: floor tile, polyester water-dispersible -ink: can B e added directly to paper-making .finishes n r .V acoustical tile formulations. ; Although "wetted" asbestos is not generally -available, .m ost. suppliers . are working w ife customers to pro vide "dustless" products. W hen justi-. fied by m arket demand, asbestos can , be treated with water, m ineral spirits,/ -\ glycol, or other materials compatible with the application or system. ... ; "ir' Conclusion resins, phenolics, sealants, coatings, Asbestos is one of industry's many " brake linings, friction materials, rub raw materials which involves a po ber, roofing compounds, and rein tential hazard when not used wife forced plastics. Since an abrading ac reasonable respect and care. Although tion on some of these products could - all forms of asbestos are recognized release asbestos fibers, appropriate as hazardous to health when inhaled ~ m onitoring and/or 'control measures excessively, there is growing evidence should be instituted if it is thought feat such action would release fibers. that crocidolite and amosite are more hazardous than chrysotile. Fortunate- J ournal of Paint T echnology ]y, the plastics industry uses primarily chrysotile asbestos and, in most prod ucts, the fibers are -locked-in to pre vent airborne contamination. Al though asbestos dust levels are gen erally lower than expected, industry continues to expend large amounts of time and money to further improve the quality o f fee'w orlqplace. Al though the general public is r a t cutt] rently in danger,' occupational controls 'h* are required to prevent * ....... vironmental contamination. Chrysotile asbestos is and necessary raw m aterial, the nation's safety and economy; and, w ife proper safely and m ent regulations, government, and industrial personnel m ust continue to w ork'-closely gefeer --- " *' sure limits, and eliminate -Arch. Environ. S ea lth , (Nov. 1973) (2) W agner, J . C., Ann. 15, 61 (1972). (3) W right, G. W ,, statem ent "before ' ,V . Dept, of Labor, ' Safety and Health hearing posed occupational ' dard, M arch 16, 1972, (4) Hammond X C. and "Relation Of Cigarette Smoking T o , Risk of D eath o f Ashestos-Assod- - *: C ated Disease among Insulation W orkers in th e TJ.SA.," presented at meeting of the W orking Group to Assess Biological Effects o f As bestos, International Agency for Re search on Cancer. Lyon, France (Oct. 4, 1972). (5) `R eport of the Advisory Committee on Asbestos Cancers," Brit. J. In- dustr. Med., 30, 180 (1978) . ; (6) "Asbestos," National Safety News . (Oct. 9, 1978). (7) "N ational Emission Standards for Hazardous A ir Pollutants," Federal Register, 38, No. 66, 8820 (April 6, . . 1978). w (8) "Protecting the Asbestos Worker," Booklet No. 101D37, T h e Asbestos In form ation A ssodation/N orth America, p 5. (9) Selikoff, I. J.. Industr. Medicine, 39, No. 4, 21 (April 1970). (10) "Standard for Exposure to Asbestos Dust," Federal Register, 37, No. 110, 11320 O '" 7, 1972). (11) Bayer, S. G,, e t al, "E quipm ent and Procedures for Mounting Millipore Filters and Counting Asbestos Fibres by Phase-Contrast Microscopy," Bureau of Occup. Safety and Health, U S. Dept, of H ealth. Edu cation, 8c W elfare (Feb. 1969). (12) "Asbestos H ealth Q uestion Per plexes Experts," Chem. Eng. Notes, 18 (Dec. 10, 1973)............... " (13) Myers, J . L., "C alidria Asbestos Pel lets," ASBESTOS (Oct. 1971). Vol. 47, N o. 611, December 1975 ** ' 1 Asbestos Information Association* North America > 1660 LStreet, N.W .- ^ I Washington,D.C. 20036.,>