Document kmgZZZeNR1w28v5BGbOMV4g5V

SOUTHERN CALIFORNIA SECTION AMERICAN INDUSTRIAL HYGIENE ASSOCIATION SYMPOSIUM November 16, 1972 Supported in part by a conference grant from: National Institute for Occupational Safety and Health, United States Public Health Service, Department of Health, Education, and Welfare Under the Direction of: H. V. BROWN, Dr. P.H. CHEV BB 0003167 Ai / Symposium ASBESTOS AND ASBESTOS-RELATED DISEASES REGISTRATION: 8:30-9:00 o.m. MORNING SESSION Welcome Address........................... ......... _______ J. S. Felton, M.D. Medical Director Occupational Health Service Department of Personnel County of Los Angeles "Geology and Mineralogy of Asbestos" _______ Arden L Albee, Ph.D. Professor of Geology California Institute of Technology Pasadena "Epidemiology and Epidemiological Investigations of Asbestos-Related Diseases", and "Development of a Threshold Limit Value"_______________ Joseph K. Wagoner, S. D. Hyg. Director ' Division of Reid Studies and Clinical Investigations Notional Institute for Occupational Safety and Health William M. Johnson, M.D. ' "Medical Aspects of Asbestos and Acting Deputy Director Division of Reid Studies end Clinical Investigations 'National Institute for Occupational Safety and Health Asbestos-Related Disease"............... ............ ............... Irving J. Selikoff, M.D. AFTERNOON SESSION Director Environmental Sciences Laboratory Mount Sinai School of Medicine New York "Sampling and Evaluation of the Work Environment"__________ John M. Dement, B.S. "Uses, Manufacturing Methods, and Engineer Environmental Investigations Branch Division of Reid Studies and Clinical Investigations National Institute for Occupational Safety and Health Industrial Hygiene Controls"....................................... I. H. Weaver Corporate Director Environmental Control ' Raybestos Manhattan Manheim, Pennsylvania CHEV BB nnn3i Measurement of Asbestos Exposure JEREMIAH R. LYNCH HOWARD E. AYER he sampling stratkgy decisions Tmade at tiie time of the luisic epidemiologic study of an industrial dust hazard ultimately de termine the methods that will be used to evaluate exposures in later regulatory or control situations. Threshold Limit Values (TLV) are based on a correlation between health effects and exposures as measured by a particular method. Since no method, with the possible exception of electron microscopy, measures all of the dust and no two methods measure exactly the same fraction, the correlation of exposures with health effects should not be expected to be the same where different methods of exposure measurement are used. Al though it is possible to establish a transition from one method to another by means of simultaneous companion sampling, the number of samples re quired is large, making this approach difficult. Therefore, the methods used in the original study arc important not only because of their contribu tion to the success of that study but also because succeeding industrial hygiene surveys will be largely committed to the use of those methods. Ftam the Bureau of Disease Prevention and Environ* mental Control, Motional Center far Urban and Industrial Health, Occupational Health Program, VS. Public Health Service (HEW), Cincinnati, Ohio. Journal of Occupational Medicine Threshold Limit Value for Asbestos The present TLV for asbestos has its origin in a linear or "one time" epidemiologic study of the asbestos textile industry conducted by Dreesen et al.1 in the Nineteen-Thirties. The then avail able impinger method was used to sample the dust; all particles, both grains and fibers, were counted since few.fibers were seen. Dreesen et al. stated that, "... if the dust concentration in asbestos factories could be kept below 5 million particles per cubic foot (mppcf) new cases of asbestosis probably would not appear." Elsewhere, they described this suggested TLV as tentative. The reason for their hesitancy in recommending a definite exposure limit was that only four of the workers studied had been exposed to levels under 5 mppcf for over 10 years. This is not surprising when one considers the conditions of these mills at that time as compared with present conditions (Table I). The incidence of frank disease was so great that prior to the beginning of the study out of a total of less than 600 employees the plants discharged 150 workers suspected of having asbestosis. Engineering controls have reduced dust con centrations by an order of magnitude over the past 30 years. The economics of dust control are such that the cost of further improvement, if necessary, may well equal the cost of all improvements made 21 CHEVBB Asbestos Exposure SURVEY OF OPERATION Fiber Preparation Cardinq Spinninq Twittinq Waavina __________ TABLE I_________________ Oust Concentration* -- Asbastas Taxtila Survey* PENNA. PHS 1938 1934 WITHOUT WITH CONTROL CONTROL Mean Concentration in mppcf 67.0 36.0 31.1 25.7 16.2 7.1 3J II.I 19.8 14.0 6.0 3.3 -- -- 2.1 PUBLIC HEALTH SERVICE 196* 2.3 1.2 1.2 1.9 0.8 to date. It`is, therefore, necessary for the benefit of both the worker and the industry that precise knowledge of the health hazards of asbestos be obtained. Present Epidemiologic Study The present epidemiologic study of the asbestos products industry by the United States Public Health Service has been adequately described elsewhere,2-* and will only be summarized here. The reasons for the study are as follows. L The substantial changes in the size and tech nology of the industry have created new exposure situations in need of evaluation. 2. Over-all reductions in asbestos dust levels now make it possible to examine the relation of asbestos to asbestosis in workers with long-term lower level exposures. 3. The relationship between types and magni tudes of exposures and the occurrence of lung cancer needs to be defined. The study is divided into the following seg ments. (A) . The present exposure of groups of work ers will be measured by baseline surveys. Past exposures will be obtained from plant or regula tory agency records; and future exposures from periodic resurveys so as to yield a history of ex posure spanning at least 20 years. (B) . Death certificates and, where available, autopsy records will be obtained for those mem bers of the exposed group on whom social se curity death claims have been filed. From these data (age and cause) specific death rates will be constructed and related to exposure. (C) . More sensitive measures of health status will be obtained from medical examination of a selected sample of the study population. (D) . Techniques of future medical and en vironmental evaluation and hazard control will be developed. 22 This present paper is concerned with the first segment only, measurement of exposure. Impinger Sampling and Counting Impinger samples were collected routinely in both the baseline surveys and resurveys of the present epidemiologic study because only by this sampling method could dust levels be related to the present TLV, which is based on dust concen tration measurement by impinger. Impinger sam ples collected simultaneously with other sample types are also used to establish relationships be tween methods to permit estimation of past ex posures in terms of other fractions of the airborne dust. Since the confidence limits of a dust count improve as the number of particles counted in creases and only a few fibers are seen in impinger samples the original investigators chose to count all particles and, thus, arrive at a measure of over all dustiness. The success of this approach as ap plied to dust control in that era of massive ex posures is evidenced in the improvement in the industry (Table I). However, in modern asbestos product plants, such as asbestos cement pipe plants, we find ourselves in the anomalous posi tion of counting airborne dust known to consist mostly of cement against a TLV intended to apply only to asbestos dust. The lack of fibers in the impinger samples was not due to the absence of fibers in the air. The impinger, an impaction device, has a collection ef ficiency related to the aerodynamic size of par ticles and is not efficient for particles with falling speeds less than that of one micron (/*), unit den sity spheres. Further, the 10X objective, light field, counting technique used does not resolve par ticles much smaller than one micron. Laboratory experiments showed that the impinger passed fibers and from field sampling it is estimated that only about one out of 100 fibers in the air as seen in electron micrographs was seen in the impinger samples. Jaimari/ IDGft Volume 10 No. I CHEV BB Fiber Counls on Membrane Fillers It is evident from the preceding that another method is needed if we are to obtain a statistically useful index of airborne fiber concentration. In terest in fibers stems from the need to measure that factor in the environment that is most rele vant to the disease-causing mechanism and will, therefore, yield a significant correlation between health and exposure. Fibers have long been im plicated as the causative agent in asbestosis and may be significant in cancer. Timbrell's4 work showed that because of the peculiar aerodynamic properties of fibers (i.e. that their falling speed is dependent on diameter only when aspect ratios are greater than 10) it is possible for'much larger objects (longer and heavier) to penetrate deep into the lung in the shape of fibers than in the shape of grains. This appears to be a most sig nificant biologic property considering that the parent minerals involved (amphibole and serpen tine) are not considered biologically active. Based on methods developed in Great Britain,8 a method of collecting and counting fibers on membrane filters was developed.8 These fibers have pore sizes of 0.8 n but are almost 100% ef ficient down to several hundredths of a micron because of surface effects. They are rendered transparent with a 1-to-l mixture of diethyl oxa late and dimethyl phthlate and counted with a 4 mm. objective (430X) under phase contrast il lumination. By examining a suitable number of fields, it is possible to count enough fibers to make a statistically useful estimate of fibrous dust con centration. In addition, longer duration personaltype samples which are not possible with the impinger method may now be used. Some comments on the relationship between the impinger and the membrane filter with respect to the question of sensitivity will reveal a further limitation of the impinger method. From large numbers of companion impinger-filter pairs col lected in asbestos textile mills an equivalence be tween the two sampling methods has been ob tained.7 Thus, when impinger samples yield, on the average, a concentration near the TLV of 5 mppcf, the fiber concentrations as measured by membrane filter samples would be expected to be as shown in Table II. Although there is no formal TLV applicable to English asbestos textile mills, a goal of 4 fibers longer than 5 per cc. has been mentioned.* If the above equivalence is approximately valid, this indicates that the TLV by impinger would be on the order of 1 mpeef. If the safe level of exposure Joumnl o/ Occupational Medicine Lynch. Ayer ___ ____ . _ table ii _ 'rYpf COUNT ` ' ............ *" CONCENTRATION _____________ _ __ __ FjSFRS/CC__ ToMl fib*!**-. 50 Fibers longer 5 js Fib*'i longer than IQ m 30 1$ should fall in this lower range, dust concentra tions would be so near the lower practical limit of sensitivity for the impinger that accurate meas urements would be impossible. Consequently, the shift in emphasis in the present study from the impinger to the membrane filter method is based not only on increased relevance, but also on the greater sensitivity of the latter method. Weight Methods for Asbestos Even though the greater precision of gravi metric methods over count methods is unques tioned, the ability to capitalize on this lessened variability is limited by the natural variability of the environment. When used as an index of as bestos exposure a measurement of the gross weight of airborne dust suffers from the same problem as impinger counts. If the relevant factor is the airborne concentration of respirable fibers, a gross mass measurement yields only an index of over-all dustiness, which includes much dust of lower biologic significance, especially in mixed.dust environments. Size-selective presampling de vices suitable for long-period respirable mass sampling have been developed. However, airborne dust, even in the' respirable fraction, contains mostly grains, both in number and in weight. Some of these grains are particles of the parent rock ad jacent to the asbestos vein, chemically and crystallographically indistinguishable from fibrous asbes tos. Other particles are grains of process materials and of ambient dust. With the non-respirablc dust excluded by a presampling device, the asbestos and parent rock fraction can be determined by x-ray diffraction or, in the case of chrysotile, by magnesium analysis. No analytical method has been developed for measuring only fibrous asbes tos in the presence of particles of associated rocks. Airborne Carcinogens All of the foregoing has been concerned with exposure measurement for the prevention of asbestosis. Although the mechanism of cancer among asbestos workers is not clear, apparently airborne asbestos fibers are a factor. Thus, the methods of fiber concentration measurement serve to measure this fiber factor with respect to cancer as well. Other asbestos contaminants of interest are polynuclear aromatic hydrocarbons and cer- 0HEV BB 23 Asbestos Exposure tain trace metals, especially nickel, chromium, co balt and manganese. In all of the early plants sur veyed in this study, high volume (30 to SO cfm) samples on glass fiber filters were collected for airborne polynuclear aromatic hydocarbon meas urement Levels in the work places were not sig nificantly above ambient air pollution levels. However, trace metal analyses, of similar high volume samples collected on glass fiber and, more recently, membrane filters, do show significant amounts of nickel, chromium, cobalt and man ganese and it can be presumed that past levels were higher.8 Since these data are collected with out exact information on the specific factor to measure for cancer-risk correlation no conclu sions can be drawn at this time. Selection of a Standard Method As an outcome of an epidemiologic study, a safe level of exposure should be set in terms of a meth od of exposure measurement which meets the following criteria in the order given: 1. The environmental factor measured should be sufficiently relevant to the disease mechanism to correlate with health status even in environ ments where exposures to mixed dust occur. 2. The sensitivity of the method should be such as to measure levels well below the TLV. 3. The method should lend itself to an appro priate sampling strategy; e.g., long-period personal samples in the case of asbestos. 4 The expense of conversion from existing methods should be reasonable. The impinger method of measuring asbestos ex posure does not meet any of the criteria well with the exception of expense. Weight methods would be preferred if there were an analytical break through At present fiber counts on membrane filters are the best method of estimating exposure as related to the risk of asbestosis and the air borne fiber concentration as a factor in the risk of lung cancer. VS. Public Health Service Cincinnati, Ohio <5202 References: 1. Duzssx, W. C; Daua Vamx. J. M.; Edwajus, T. I; Mru.nt, J. U. and Saras, R R.: A Study of Asbestssis in the Asbestos Textile Industry, Public Health Bulletin No. 241, U.S. Government Printing Office, Washington, D.C, 1938. 2. Ciau.iy, L. J.: Objectives and General Plan for Oc cupational Health Study of the Asbestos Products Industry. Division of Occupational Health, Public Health Service, Department of Health, Education and Welfare, 1962. 3. Lynch, J. R.: Asbestos Study--Procedures and Find ings. Trans 27th Aim Meet Am Conf Governmental Indus Hygienists, 196S. 4. Tniwtu,, V.: The Inhalation of Fibrous Dusts, Ann NT Acad Sci 132:1,1965. ii. Amwoxt, C. G.: Asbestos Dust and its Measurement Ann Occupa Hygiene 9:2, 1966. 6. Eowams, G. H. and Lynch, J. R.: The Method Used by the U.S. Public Health Service for Enumeration of Asbestos Dust on Membrane Filters Ann Occupa Hygiene 11:1, 1967. 7. Am, H. E.; Lynch, J. R. and Fanncy, J. H.: A Com parison of Impinger and Membrane Filter Techniques for Evaluating Air Samples in Asbestos Plants Ann NT Acad Sci 132:1, 1965. 8. Roach, S. A.: Measurement of Airborne Asbestos Dust by Instruments Measuring Different Parameters Ann NT Acad Sci 132:1,1965. 9. CsAu.tr, L. J.; Hainan, R. G. and Lynch, J. tu Exposure to Trace Metals in the Manufacture of As bestos Textile Products. Presented at the American Industrial Hygiene Conference, Chicago, Illinois, 1967. Allergy to Work Some people axe literally allergic to work, according to a report submitted to an. Italian medical conference. The report said that muscular activity could release an excessive amount of histamine, a powerful chemical stimulant in the body tissues, to cause rashes and allergies. Renters dispatch from Caramanico, Italy, as quoted in New York Times, August 30.1067. 24 Janunry IfWS Volume 10 No. I CHEV BB A merican industrial Hygiene dissociation Southern dali^omia Section "Mineralogy and Geology of Asbestos" Arden L. Albee Abstract The term "asbestos" includes the fibrous varieties of a number of different hydrous silicate minerals. These minerals are common and widespread, but to be of cocnmercial\alue the fibers must be unusually well-developed, permitting easy disaggrega tion of the fibers. The differences in the crystal structure, chemical composition, and physical habit of the asbestos minerals and of minerals which commonly occur as impurities in commercial asbestos will be outlined since the different minerals may have different effects upon body tissue. The geologic occurrences of asbestos, as well as mining and mill ing practices, will be summarized. Asbestos Symposium November 16, 1972 CttEVBB A Jn merican tfftene i%fyoorrmnt,a "Medical Aspects of Asbestos and Asbestos-Related Diseases" Irving J. Selikoff Abs tract Asbestos exposure was identified as a potentially fatal occupational risk in 1907 and again in 1972. The hazard was clear, specific and unambiguous, and provided a classic opportunity for prevention by industrial hygiene measures. Yet 50 years later, serious disease i3 found among asbestos workers in mine, mill and industry; pneumoconiosis (asbestosis), cancer of lung, pleural and peritoneal mesothelioma, gastro-intestinal cancer. A major cause for this public health failure is the long period (20 or more years) of clinical latency between onset of work exposure and appearance of overt disease. Disease now being seen was initiated during or before World War XI, in many instances. At that time, few precautions were taken. Our lapse, then, was complacency in the 1930's to 1950's. It follows, that to prevent asbestos disease in the year 2,000, appropriate measures need be taken now. Clinical-epidemiological correlations are discussed from this point of view. Asbestos Symposium November 16, 1972 CHEV BB merican du6trial ^JJ-^iene -dlddociation Southern daii^ornta Section "Asbestos & Industrial Hygiene" I. H. Weaver Abs trac t Paper briefly reviews history of asbestos/health problem pointing out industry research and action toward corrective and preventive measures. Cites need for cooperation between industry, labor, and government in arriving at solutions. Uses and needs for asbestos - past, present and future - are outlined. Basic manufacturing techniques and industrial hygiene controls are discussed, and slides are presented showing examples of old versus new methods and conditions. Some thoughts concerning future control efforts and the complexity of the problem are presented. Asbestos Symposium November 16, 1972 CHEVBB 0003171