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CT National Bureau of Standards Special Publication 506. Proceedings of the Workshop on Asbestos; Definitions and Measurement Methods held at NBS, Gaithersburg, MD, July 18-20, 1977. (Issued November 1978) THE STANDARD FOR OCCUPATIONAL EXPOSURE TO ASBESTOS BEING CONSIDERED BY ASTM COMMITTEE E-34 M. Cossette Director, Centre for Technology of the Environment University of Sherbrooke, Canada and A. A. Winer CANMET Industrial Minerals Laboratory Ottawa, Canada Abstract This presentation reviews the consensus reached by the Task Group on Naturally Occurring Inorganic Fibers of ASTM Committee E-34. Significant differences with the OSHA regulation are pointed out on the following topics: Definitions, exposure limits, record keeping, monitoring, and the counting method. The reasons for these differences are outlined and a rationale in support of a dual standard is presented. This Task Group document is now under study according to official ASTM procedures. Key Words: Asbestos; ASTM; consensus; definitions; exposure limits; monitoring; occupational exposure; record keeping. Introduction ASTM Committee E-34 is presently considering a standard for occupational exposure to asbestos. This standard differs from others in one very significant respect, in that it is a consensus document. There is input from both the regulators and the regulated, and this situation makes it a unique document. Scope This ASTM standard is applicable for all occupational exposures including mining and milling, as well as manufacturing and end-use industries. It is intended for use both in the USA, and in other countries where ASTM standards are in current usage. Excluded from the scope of application are situations where the airborne fibrous particulates can be proven to be pathologically inert [1,2]i. Recent epidemiological studies by Ahlmark at the University of Sweden, and by P. Radovan on two asbestos cement factories in Yugoslavia, in addition to a major study by Greg and Weiner at Battelle Pacific Northwest, are said to indicate that the biological activity of asbestos fibers is altered by the autoclave process of producing asbestos cement. 'Figures in brackets indicate the literature references at the end of this paper. 381 N 0 ~ w .+ 0 ~ ~ ~ N

This standard is flexible in application to the extent of recommending the use of only respirators for occasional work that may involve intermittent exposure. This would be the case where asbestos lagging must be removed from a valve, occasionally, in a chemical plant. Definitions The ASTM document presents the following mineralogical definitions: asbestiform - mineral structured in the form of asbestos. asbestos - generic term for naturally occurring, inorganic hydrated silicates that when crushed and processed separate into flexible fibers made up of fibrils [3,4]. Minerals defined as asbestos are the asbestiform varieties of the following: serpen- tine (chrysotile), riebeckite (crocidolite), cummingtonite (amosite), anthophyllite, tremolite, and actinolite [5-8]. fiber - for the purpose of this standard, fiber means naturally occurring inorganic fibers. fibril - a single crystal in the form of a fiber [9]. fibrous particulate - for the purpose of this standard, fibrous particulate designates fibers, fiber fragments, and fiber agglomerates. naturally occurring inorganic fiber - form of mineral characterized by properties of flexibility and length-to-width ratio in the order of 100, composed of definite crystal unit cells oriented with respect to a specific axis [4]. Note 1 - The designated 100:1 aspect ratio is considered to represent a reasonable lower limit for naturally occurring inorganic fibers. Fibers of these dimensions [10] can be broken into parts of fibers that may maintain their same surface properties and activities. Therefore fiber fragments may have to be evaluated for atmospheric monitoring purposes. However, attempting to define a fiber by its aspect ratio alone is inadequate since it is obvious that particles of non-fibrous material do not become fibers as their aspect ratio increases through comminution. Other non-mineralogical definitions include: aspect ratio - ratio of the length of a fibrous particulate to its equivalent diameter [11]. monitored particulate - fibrous particulate with an aspect ratio of at least 5:1, a minimum ' length of 5 pm, a maximum diameter of 3 pm, and the appearance of a fascine (bundle of sticks effect). Only particulates that fit these requirements are counted in the monitoring method [12-16]. peak sample - for the purpose of this standard, a sample taken over a short interval (not exceeding 15 min) to evaluate brief excursions in the airborne fibrous particulate concentration level [17]. Definitions applicable to monitoring include: personal sample - sample collected on a membrane filter that is attached near to the opera- tor or employee's breathing zone. Geographical samples - static sample - sample collected on a membrane filter at a fixed station. dynamic sample - sample collected on a membrane filter transported over a fixed route at N 0 a specific speed. w 0 382

S5 Permissible Exposure Levels The exposure level being considered for mines and mills is 5 fibers/cm3 (same as the present MESA regulation.) The exposure level being considered for manufacturing and end use industries is 2 fibbrs/cm3 (same as the present OSHA regulation). Rationale for a Dual Standard The bases considered in reaching a consensus on a dual standard were the following: Gibbs and Hwang [18] have shown that the particulate size distributions of airborne fibrous particulates differ for different types of asbestos, and for different occupations. For example the percentage of countable fibers (diameter smaller than 0.5 Ym and length greater than 5 pm) was found to be 18.3 percent at one site where amosite insulation was installed, compared against 1.0 percent in a bagging area of a chrysotile mill. This implies that 18.3 percent of the airborne fibrous particulates would be invisible in the optical microscope in one case versus only one percent in the other case. In general, it appears that with each successive step in milling, and manufacturing, the fibers become more finely divided, and more of them become invisible in the optical microscope. On the other hand, the hazard may increase with finer fibers because more of them are likely to reach the lower airways. It has also been demonstrated rigorously [19] that the likelihood of counting a fiber is a function of fiber length. A fiber 40 pm long has about a 10 percent higher probability of being counted than a 5 pm fiber. An 80 pm fiber has about 50 percent more probability of being counted than a 5 pm fiber. Now the manufacturing and end-use industries generally shorten the fibers. For example Gibbs and Hwang [12] have shown that the median length of airborne fibrous particulates in the bagging area of a mill (the last milling operation) was 1.00 pm versus 1.35 pm for the same type of asbestos in the carding area of a textile plant. The International Labor Organization has established [20] that the highest risks are found in the insulation trade (an end-use industry). On the other hand "in chrysotile mining and milling, despite very heavy dust concentrations in the past, the incidence of severe asbestosis, asbestos cancers, and especially mesotheliomas has been low." McDonald [21] has found that the mesothelioma-inducing potential was greater in asbestos manufacture and application than in mining and milling, and he stated: "This may be related to fiber size but also possibly to co-carcinogens in the industrial environment" ...... "mining envi~ronments may well be free from co-carcinogens of the kind found in factories, ports and industrial cities." The sedimentation velocity of airborne fibrous particulates has been shown to be a function of diameter [22]. Gibbs and Hwang [18] have shown that for a given type of asbestos the proportion of fibers finer than 0.5 pm was 67 percent in the ore drying area (beginning of milling process), 82 percent in the bagging area (end of milling) and 88 percent in the carding area (manufacturing). There is no question that fewer of the airborne fibrous particulates are respirable in mining and milling, than in manufacturing and end use industries. In addition fibers in mines and mills show a notably greater propensity to flocculate together, thus reducing their respirability while increasing their countability [23]• Time Weighted Average The formula for the calculation of the 8-hour time weighted average that has been adopted is: 8hTWA=INiTi/FTi where Ni = Number of fibrous particulates in the ith sample, and Ti = Time period over which the ith sample was collected. N 383 a w r 0 U1 Fr -4 ?

C;b Medical Surveillance A preplacement medical examination is mandatory. Enforcement of annual examinations is recommended where legal to do so. The question of -starting medical surveillance at one-half the permissible exposure limits versus the full limit is still unresolved. An interesting document on the diagnosis of asbestosis is annexed to the standard. Medical Records These are to be available to government agencies, and upon written request, to employees, or former employees. Records are to be kept 50 years. This is in recognition of the long latent period necessary for the manifestation of asbestos related diseases. Labeling (Posting) Materials containing asbestos, bound or reacted in such a way as to give off emanations of dust that can be demonstrated to be non-toxic, when produced by foreseeable activities, are exempt from labeling. Monitoring The emphasis is placed upon personal samplers. Static geographical sampling is also called for. Areas above the permissible limits must be monitored every six months. Two to twelve samples per worker per shift are recommended [17]. Monitoring records are also to be kept 50 years. The midget impinger may be used to obtain correlation data since it was the basis for the most reliable epidemiological data, but may not be used for referee testing. Analytical Method The method is based upon the use of a 37 mm diameter membrane with a pore size of 0.8 pm, and personal sampling pumps operating at 2 dm3/min for periods of 15 min to 4h at concentrations of 1 to 20 fibrous particulates per cubic centimeter. Only fibrous particu- lates with a length greater than 5 pm, a maximum diameter of 3 pm, and an aspect ratio of at least 5 to 1 are counted. The 5 to 1 aspect ratio was adopted when it was ascertained that the 3 to I ratio originally adopted by the British was strictly arbitrary [15], and when it was determined that the highen ratio could exclude many acicular rock slivers while making no appreciable difference with true fibrous particulates. For referee purposes, it must be established that the items counted are indeed asbestos, as defined. Typically, 4 to 7 samples per shift are demanded for 8-h TWA. The details of pump calibration, microscope adjustment, and counting rules are like those presented in the NIOSH method, issued 30 Mar 77. In view of the very low precision and accuracy obtained, we are not satisfied with a method of analysis based on counting. A gravimetric method based upon the collection of only the respirable fraction of fibrous particulates, and coupled with the quantitative analysis of asbestos present, would be preferred, and appears feasible. X-ray diffraction of fiber arrays, and acid titration at constant pH [24] appear promising for this purpose. 384

C3 Conclusion In conclusion, it should be emphasized that in spite of its shortcomings (it is the product of a committee) the ASTM document has the single advantage of being a consensus document, reflecting the views of both the regulators and the regulated. References [1] Kogan, F. M., Gerasimenko, A. A., Bunimovic, G. I., Kler, 0. V., Karacarova, V. N., Olsvang, R. A., Hygienic characteristics of the asbestos-cement dust. Collection of papers on silicosis, The Book Publishing Institution of Middle-Ural, Sverdlovsk, p. 173-85, 1966. English translation available from the same source as reference 23. [2] Rhodes, H,. Detection of chrysotile asbestos in airborne dust from thermoset resin grinding, 3rd Int Conf Chem Phys Asbestos Min, Quebec 20 Aug 1975. (Same source as 23). [3] Federal Register, Vol. 38, No. 188 - Friday 28, 1973, page 27076 (Food and Drug Administration). [4] Ann. N.Y. Acad. Sci 132, 23-30, 1965. [5] Asbestos Fundamentals, Berger, H. and Oesper, R. E., Chemical Publishing Company Inc., New York, 1963, p. 1-3. [6] Federal Register, Vol. 39, No. 127 - Monday, 1 Jul. 1974, p. 24316. (U.S. Bureau of Mines). [7] Rutley's Elements of Mineralogy, 25th Ed. H. H. Read, Thomas Murry & Co, London. [B] Thompson, C. S., Proceedings of the Symposium on Talc, p. 22-42, Washington, D.C. 8 May, 1973. (Same source as 23). [9] ASTM Glossary of Terms, p. 585. 02946-71T. [10] Prasad, N. A. and Pooley, F. D., Characteristics of amphibole asbestos dust surfaces in aqueous media with reference to quartz, J. Appl. Chem. Biotechnol. , 23, 675-87 (1973). [11] Federal Register, Vol. 9, No. 87, 3 May 1974, p. 15396. [12] Holmes, S., The measurement of airborne asbestos dust by the membrane filter method, Technical note #1, Asbestos Research Council, Box 40, Rochdale, Lancashire, England, 1971. [13] Timbrel, V., The inhalation of fibrous dusts, Proc. Conf. Biol. Effects Asbestos, N.Y. Acad. Sci. 1964. [14] Field Information Memorandum #74-92, OSHA, 21 Nov. 1974. [15] Holmes, S., The definition of an asbestos fiber, Asbestosis Research Council, P.O. Box 40, Rochdale, Lancashire, England OL12 7EQ. [16] Health Division Instruction Memorandum #8-Definition of asbestos fiber for tremolite occurring in talc, MESA, 13 Dec. 1974. [17] Leidel, N. A., Optimum sampling times for airborne asbestos fibers, NIOSH, 1014 Broadway, Cincinnati, OH 45202, Nov. 1972. [18] Gibbs, G. W. and Hwang, C. Y., Physical Parameters of Airborne Asbestos Fibers in Various Work Environments - Preliminary Findings, American Industrial Hygiene Association Journal, June 1975, pp. 459-466. 385 2063105176

Cot [19] Comments of Johns-Manville Corp. with respect to notice of Proposed Rulemaking Occupational Exposure to Asbestos (Fed. Register, Oct. 9, 1975) to O.S.H.A., U.S. Dept. of Labor, April 1976. [20] International Laboua Organization, Meeting of Experts on the Safe Use of Asbestos, Geneva, 11-18 Dec. 1973, Draft Report, p. 1-32. [21] McDonald, A. and McDonald, C., Epidemiology of Mesothelioma from Estimates of Inci- dence., 18th Int'1 Congress on Occupational Health, Brighton, Sept. 16, 1975, p. 7-8. [22] Timbrell, V., The Inhalation of Fibrous Dust, Ann. N.Y. Acad. Sci., 132, 255-273 (1965). [23] Draft standard for occupational exposure to asbestos, Rationale supporting the selec- tion of a dual ASTM standard, Second draft ASTM Committee E-34, 25 April 1977. [24] Barbeau, C., Roy, J. C., and Dupuis, M., Reactivity of magnesium silicates in acid solutions, Means of distinguishing between antigorite and chrysotile, 3rd Int. Conf. on the Physics and Chemistry of Asbestos Minerals, Laval U. 17-21 Aug. 1977. Discussion NDTE: Discussion of this paper was included in the General Discussion at the end of this session. 386