Document p2knjMLpLGmz80K3GEQMz6dgd

PLAINTIFF'S EXHIBIT Sources and Interpretations of Asbestos Exposure Data by Michael Gough, Office of Technology Assessment, United States Congress The attached paper was presented' at a workshop "Exposure Assessment: Problems and Prospects" Sponsored by the Task Force on Environmental Cancer and. Heart and Lung- Disease- National Institutes of Health. September 14, 1982 008178 2 understanding of the relationship between asbestos and cancer. Individual case studies and reviews of ease series began to appear in the literature in the 1930's. However, according to Selikoff (1981) the establishment of an association in populations between occupational exposure to asbestos and lung cancer depended on the classic study of Doll (1955). From the standpoint of cancer, there was no reason to measure exposure levels to asbestos until an association between the fibers and disease was shown. Not unexpectedly, there are few references in the literature to measured exposure levels during the 1930's, 40's, and 50's. Of course, given the long latent period for cancer, those are the exposures chat are associated with today's cancer cases. Despite the fact that asbestos was positively identified as a cause of lung cancer in the 1950's and that exposure to it was known to be widespread, no published estimate of its impact on nationwide mortality was were until 1978. In that year, two estimates were made. Selikoff (according to a footnote in the paper that is next mentioned) estimated that the annual number of asbestos-related cancer deaths was about 50,000. Hi's estimate elicited little public attention. The other 1978 estimate, which was titled "Estimates of the Fraction of Cancer in the United States Be1st ad to Occupational Factors,** was prepared by the National Cancer Institute (NCI), the National Institute for Environmental Health Sciences (NIEHS), and the National Institute for Occupational Safety and Health (NI0SH). Ten employees of those institutes were listed as contributors to the estimates paper. Because no one was identified as the author of the paper, it is difficult to make reference to it in the usual shorthand method used for scientific publications, and it la now often called 006178 3 the "estimates paper." As is veil known, the estimates paper was not published in a journal. Instead it was placed in the Occupational Safety and Health Administration hearing record about that agency's proposed generic cancer policy. I think it's worth wondering if the paper would have passed largely unnoticed if being deposited in the hearing record had been ita only fate. However, Che findings of the estimates paper were widely publicised when then-Secretery of Health, Education and Welfare Califano cited them in a speech. Based on the estimates paper, he stated that it was apparent that workplace exposures caused at least 20 percent of all cancer in this country. Asbestos alone was responsible for 13 Co 18 percent. The projections of the estimates paper were controversial as soon as they were publicised, and they attracted many attacks. Thay also resulted in a spate of articles that presented other estimates of the cancer risk associated with occupational exposure to asbestos. The subsequent papers cen be divided into two general groups: The first group used methods similar to the estimates paper to project numbers of cancer deaths based on estimates of numbers of workers exposed, exposure rates, and mortality rates at various exposure levels. The papers of the second kind presented measurements of the number of deaths from mesothelomias, which are closely associated with asbestos exposure, and then multiplied that number by some factor to estimate all asbestos-caused cancer deaths. The Estimates Paper The estimates paper said that between 8 and 11 million workers had been 4 exposed to asbestos since the beginning of World War II. Of those, 4 million were classified as "heavily exposed," and an additional 1.5 to 3.5 were classified as "significantly exposed." No details or documentation was provided for these estimates. Thirty-five to 44 percent of the heavily exposed population ware projected to die from asbestos-related cancers. This,jpfopprtion-pf.asbestoscaused cancer death was reported from a study of asbestos insulation workers by Selikoff, Hammond, and Seidman (1979; 1980). Assigning that proportion of deaths to asbestos resulted in an estimate of 1,600,000 ebestos-ceused cancer deaths among the 4,000,000 heavily exposed workers (Table 1). The significantly exposed population was projected to suffer one-quarter the asbestos-related mortality estimated for the heavily exposed workers. The estimates paper associated 400,000 to 700,000 deaths in that population with asbestos. Thirteen to 18 percent of all cancer mortality being associated with a single substance is a frighteningly large percentage, but, at the same time, it holds great promise". It suggests that reducing asbestos exposure would significantly impact on overall cancer mortality rates. From the standpoint of this conference, the estimates paper is especially interesting because it did not include a single estimate of the amount of asbestos that workers had been exposed to. It did depend, as does nearly every estimate that I will mention, on Selikoff and his colleagues' measurements of risks and mortality in the heavily-exposed Insulation workers. The estimates paper has been faulted because it included all exposed. 008180 5 workers, even those dead st the time the estimates were made, in the projections of future deaths. It has also been criticized because it projected that there should be well over 10,000 deaths annually from mesotheliomas at the present time. The best estimate of the number of thoae deaths, which is based on cancer incidence data collected from about 10 percent of the United States population is almost 10 times less. Even though mesotheliomas are underreported (Selikoff, 1981), no one has suggested that the undercount is sufficient to account for the 10 fdld difference. Hogan and Hoel, 1981 The techniques used in this paper followed closely those used in the estimates paper. However, much greater detail is provided about population estimates and estimates of the number of exposed workers. Hogan and Hoel estimate that between 7.1 and 8.2 million workers were exposed to asbestos. From data about World War II shipbuilding, they estimate that between 4.3 and 5.4 million workers were exposed to asbestos in those shipyards. The remainder of the exposed workers was estimated from, data collected by NIOSH and by Research Triangle Institute. Hogan and Hoel estimate that about half of all exposed workers are now dead, significantly more than the 9 to 12 percent found in the estimates paper. Furthermore, they subtract the number of estimated dead from the total of exposed workers before estimating cut rent and future trends. That substraction was not made in the estimates paper. There is little difference between the total number of exposed workers in the estimates paper and in the Hogan and Hoel paper. There is, however, a 6 striking difference between the number of workers classified as heavily exposed. Hogan and Hoel cite a paper by Cochrane et al (1980) that reports that 17 of 92 senior staff members of a large South African asbestos/cement company had been heavily exposed to asbestos. They suggest that this 18.5 percent heavily exposed subset might be representative of the whole asbestos, industry. 1 think that most of us would agree that extrapolating from exposure levels in a single company to estimates of exposure in a population of 7 to 8 million workers isnot something to be done lightly. Bogan and Hoel apparently shared that view, and they also made a projection from date of Enterline (1978) that 3.4 percent was a best estimate for the proportion of all asbestos workers that are heavily exposed. The range around Enter.line's best estimate was very wide, from 0.5 percent to something less than 25 percent, or about 50-fold. Combining estimates of 18.5 and 3.4 percent, in a way that is none too clear to me, Bogan and Hoel settled on a best estimate that 15 percent of Che 7 to 8 million workers were heavily exposed. Hie remaining "less-heavily" exposed workers were assumed to have been exposed at one-eighth to one-quarter the rate of the heavy exposure group. The number of workers estimated Co be heavily exposed by Hogan and Hoel is becveen 1.06 and 1.23 million as compared Co Che 4.0 million from Che estimates paper. This reduction by e factor of almost 4 has, of course, a pronounced efface on the the estimated number of asbestos-related cancers. Further reducing Che estimate Is the elimination of the 50 percent of the exposed workers who were already dead from the projections of current and future death rates. Hogan and Hoel's best estimate is that 3.1 percent of current cancer deaths are caused `<7 asbestos with a range from 1.4 to 4.4 006182 percent. That percentage ia expected to increase slightly through the 1980'a and Cher, to decline slowly. The total number of asbestos-caused deaths is estimated at 497,000. Hogan and Hoel made two efforts to verify their risk estimations. First, they calculated the number of deatha from mesothelioma that would be expected from their estimates of the number of Writers exposed to dgb'eatoa and compared that calculated number to the number of nosotheHama "dfedth* repbrfcbsi in the United States. The calculation was done by the method' Wed for all' cancers, but, in this case, including-SeltkoBf%'estimate that i-to 10'-percent of heavily exposed workers' die from mesotheliomas. The calculated lower limit of about 1,000 mesothelioma:' dfeaths -for,l978r%'*ll: undW -which: iis i0': "tflies"-'- the Surve 11 lance Epidetaiology`ahdi'inlf'i`R'fesiirts' (8EER)-'tepOTt'ed swsothelomiis for that year. Because the- feES&._prdrla> collects' date-. ow:''about'-';10-"percent- of ' the United States population times-''its' total--is a- rough- approximation of the total number of cases in. the'country.' Hogan and Hoei's calculated'best estimate of about 2,100 mesothelomias i's somewhat higher than,, but in reasonable proximity to, the'95 percent upper confidence limit (1620 cases) of the SEER data. The other comparison was made to data from studies done in the Pearl Harbor Naval Shipyard-by;`15bl0nel et 1 (1980)', which"reported a relative riak of 1.34 for lung cancer among shipyard' workers exposed to asbestos. That paper also estimated that-only S3 percent of all shipyard workers-were exposed to asbestos. Using those numbers and assuming that there is an overall 20 percent risk of dying from cancer, Hogan and Hoel calculated from Kolonel et 8 al's data 0.63 X (7.1 - 8.2 X 106) * QUmber of exposed workers * 4.5 - 5.2 X 106 (4.5 - 5.2 X 106) X (1.34 - 1.0) (0.2) - 310,000 - 350,000 excess cancer deaths. The calculation from Kolonel et al's data agreed even better with Hogan and Hoel's estimate when the relative risk of 1.34 was corrected for the relative risk observed in the nonexposed shipyard workers, rr - 0.B8. When the calculation was done on that basis, there were 470,000 to 540,000 estimated excess cancer deaths. The range of this calculation neatly brackets Hogan and Hoel's estimate of 497 thousand excess cancer deaths. Hogan and Boel used many of the same techniques as the estimates paper. However their best estimate for the annual asbestos-caused death rate was between 0.18 and 0.24 of the number from the estimates paper. The Hogan and Hoel paper and the estimates paper demonstrates Che absence of readily available data for estimating exposures. As is apparent from comparing the two studies, estimates of excess deaths depend on projections of the percentage of workers who were heavily exposed. There are few data available for identifying that population. The Hogan and Hoel paper was circulated as a preprint and accepted for publication during 1980, but it was not published until a year later. During that year, e number of other papers dealing with estimates of asbestos-related cancer were presented at a Banbury House Conference at the Cold Spring Harbor Laboratory on Long Island (Peto and Schneiderman, 1981). Those papers will now be discussed. Interline (1981)  Enterline has done a number of studies of deaths from asbestosis among asbestos industry workers. In his paper for the Banbury House Conference, he recounts the arguments that asbestosis represents a disease that occurs after long and heavy exposures. Then he summarizes the number of asbestosis deaths that have been recorded in his longitudinal studies and a study of male insulation workers by Selikoff et si (1980). Interline-finds - that about half of all asbestos deaths reported in the United States occurred in those two study populations. Be then calculates the. size of a.population of heavilyexposed workers large enough to account for all asbestosis deaths* From his own data, he estimates that the population of heavily-exposed workers alive in 1981 to be about 75,000; from Selikoff's data, about 85,000. In a note commenting on Hogan end Hoel's (1981) paper, Nicholson (1981) states that Enterline's method for estimating the heavily exposed asbestos wc leer population probably underestimates the size of the population. Asbestosis develops only after a long latent period, end Nicholson argues that that disease is a poor marker for exposures more recent than 80 or more years ago. From census data. Enterline made yet another estimate of the number of people employed in asbestos products plants and in insulation work, the most heavily exposed workers. Enterline reports that his studies show that multiplying the daily census of workers by 3 provides a reasonable estimate for the number of workers employed for at least one year in the asbestos industry over the period 1947 - 1976. Three times the daily census produced an estimate of a total of 120,000 heavily exposed workers during those 30 years. He les that about 90,000 were alive in 1981. 006185 iO Eaterline's best estimate, based on three sources of date. Is that 80,000 heavily-exposed workers were alive in 1981. That nunber, 80,000, is very much lower than the corresponding number in the estimates paper (4,000,000) and in Hogan and Hoel (about 500,000 assuaming that half of the heavily exposed workers in their study were alive in 1981). Enterline borrows an estimate from Selikoff's work that heavily-exposed workers were exposed to 8-12 fiber per cubic centimeter (f/cc), as is shown on Table 1. Enterline cites three sources of data for lung cancer death rataa among workers heavily exposed to asbestos. Selikoff t al (1980)' -found that 22 percent of insulation workers died from lung cancer. Measurements of asbestos-caused lung cancer death rates are lower among workers in asbestos factories. Fourteen percent of retired workers from a Johns Manville plant died from asbestos-caused lung cancer (Henderson and Entarline, 1979); 15 percent in a British plant (Peto, et al, 1977). Enterline takes 20 percent as a reasonable average for death rates from asbestos-caused lung caneer and calculates that there are now 530 annual deaths from that cause among primary asbestos products workers and insulators and retirees from those trades. Enterline applied Kolonel et al's estimate that about 60 percent of shipyard workers were exposed to asbestos and thereby reduces Hogan and Hoe-1's estimate of 2.5 million living persons having been exposed in World War 11 shipyards to 1.5 million. Be also argues that exposure levels were lower in the shipyards than among the most heavily exposed workers. J. Thorton, who is not otherwise identified in Enterline's psper, is credited with making an educated guess that World War 11 shipyard workers were exposed at a rate about one quarter of that observed in primary asbestos workers, hs is shown on the table, working through those numbers produces an annual number of 900 006186 11 asbestos-caused lung cancer deaths among World War II shipyard workers. This number is little mors than 0.1 of the Hogan and Hoel estimate, who considered the risk of cancer in shipyard workers to be the same as thst seen among insulation workers. Enterline gathers together estimates of exposure in other occupational settings, and, based on straight line extrapolation from exposure levels and years of exposure calculates the percentage of asbestos-caused lung cancer to be expected in each population. The summation of those estimates Is-2,500 annually. To' that number, he adds deaths from other cancers associated with asbestos exposure and comes to a total of 4^080 asbestos cancer deaths annually. This estimate is about 0.33 of Hogan and Hoel's and only 0.06 to 0.08 of the estimates paper. In fact, it is the lowest estimate using the methods that depend on estimates of numbers of people exposed and levels of exposure. Nicholson, Perkel, Selikoff, and Seidman (1981) This paper estimates that the total exposed population is 13.2 million, higher than any other estimate. Of that number, 9.2 million were thought to be alive in 1981. The 13.2 million workers were segregated into 11 job categories. The highest risk of cancer was found in insulation workers; 35 to 44 percent of those workers died from asbestos-caused cancer. The risks borne by workers in other Industries were estimated by (1) coopering directly measured mortality rates, especially for 006187 12 mesothelioma and lung cancer, between the insulators and other workers, (2) measured concentrations of asbestos, and (3) the prevalence of X-ray abnormalities associated with asbestos. Xn some cases, none of these matures was available, and then relative risk estimates were based on the number of mesotheliomas identified in a nationwide survey (McDonald and McDonald, 1980). As is shown on Table 1, the projected percentages of deaths eaused by asbestos were all related Co the risks found for asbestos workers Using those risk estimates and estimates of the number of people exposed (X could not easily derive those numbers from data presented in the paper), Nicholson et ml calculate that the current annual number of deaths from asbestos-caused cancer is about 8,500. This number fits neatly between the 4,000 estimated by Interline and the 12,000 by Hogan and Hoel. It is a relatively simple matter to go through the categories of occupations in those four papers and to aee where the estimates vary. The variations depend on different estimates of the numbers of workers exposed and on different estimates of exposure levels. The most remarkable thing about all the estimates may be that each depends heavily on Selikoff's estimates of asbestos-caused mortality in insulators. Almost all the other estimates are fractions of that estimate. McDonald and McDonald (1981) McDonald and McDonald have been leaders in collecting and analyzing data 006188 13 about mesothelioma deaths. They have depended on data iron three sources: (1) the Third National Cancer Survey (TNCS), which was conducted in 1969 through 1971, (2) the SEER Program of the NCI which has been ongoing since 1973, and (3) their own efforts at complete ascertainment, of. mesothelomia deaths through surveys of pathologists (McDondd. and McDonald, 1980).McDonald and McDonald's best estimate of the annual rates 'for mesothelioma deaths are 8 per million for males and 2.5 per million for females, and the rate in males is increasing. From an examination of all cohort studies that reported<both mesotheliomas and other cancers, McDonald-and McDonald'estimated that there re 3.3 lung cancers and 0.9 digestive cancers for every mesothelioma* To calculate the total number of cancers.caused by asbestos, the.number of mesotheliomas can be multiplied by 3.3, as is shown on Table 2. The final step in.the McDonald and McDonald calculation was to estimate the proportion of mesothelioma cases which was associated with occupational exposure to asbestos. Their best estimate, based on .a .case control study conducted by them, was 0*75 for men and less than 0.10 for women* 9 They calculate, based on best estimates, that there were 920 mesotheliomas among American sales in 1975 and chat 0.75 of that number was caused by asbestos. Eased on their literature review, they estimate that ther<; Is a ratio of 3.3 asbestos-caused cancers to 1.0 mesotheliomas. That result' in about 3,000 asbestos cancer deaths among males or 1.4 percent of all male ctncer deaths. On the same bases, they estimate that the number of 006189 14 asbestos-caused feaale cancer deaths is lower by an order of magnitude. The McDonald and McDonald estimate is dependent on the percentage of mesotheliomas caused by asbestos and the ratios between asbestos-caused mesotheliomas and other cancers. They argue that the fraction of mesotheliomas caused by asbestos cannot be less than O.S and, of course, no greater than 1.0. Also the rstio between other cancers and mesotheliomas must lie between 1.0 end 5.0. These reasonably tight ranges produce a lower limit for their calculation of 0.5 percent of all male cancer deaths (about 1,000 annually), and an upper limit of 2.9 percent (about 6,000 annually). J. Peto, Henderson, and Pike (1981) This paper is a critical look at the time of appearance of mesothelioma following exposure to asbestos. The authors report that combined pleural and peritoneal mesotheliomas increase es a function of the time after first exposure raised to the 3.5 power. The appearance of mesothelioma in an exposed population is independent of age at first exposure, length of exposure, and type of asbestos fiber. The paper presents estimates of the number of mesotheliomas to be expected in males from exposure in World War 11 shipyards (5,000), from other exposures during World War 11 (3,000), and from all exposures prior to 1965 (37,500). As is shown on Table 2, multiplying those figures by 3 and adding 37,500 mesotheliomas results in an estimate of about 150,000 cancers from all pre-1965 exposures. The current annual number of asbestos-caused mesothelioma deaths among ales is about 930. Assuming that the death rate from other asbestos-caused 006190 IS cancers is about 3 tines that, the total of asbestos caused cancers in sales would be about 3,000 annually or 1.4 percent of total cancer mortality among males. Higginson et al (1980) I have not read this paper, and my brief description of it depends on a synopsis in Enterline (1981). A number of estimates place the annual mortality from mesotheliomas at about 1,000. Higginson et al reported that there are about 1.5 bronchogenic cancers related to aebestos for every mesothelioma. Multiplying l.S times 1,000 produces an estimate of 1,500 lung cancer cases, to those are added cancers at other sites, and Higginson et al concluded that asbestos causes about 4,000 cancer deaths annually. Because I have not read this paper directly, I cannot comment on its quality, but it was not referenced by anyone other than Enterline at the Banbury House conference, and it may have been deficient in its presentation of details. 1, for one thing, cannon understand how the total of 4,000 was reached if mesothelomia and lung cancer together were only 2,500. Doll and R. Peto (1981) 1 have a special fondness for this paper because 1 contracted for it when 1 directed the Assessment of Technologies for Determining Cancer Risks from the Environment (OTA, 1981), which was completed last summer. Doll and Peto, as is shown on the table, estimated that asbestos causes "a few thousand" 16 cancer deaths annually because it is known to cause a few hundred mesothelioma deaths. They provide no other information about their calculations. The agreement between the McDonald and McDonald estimate based on mesothelioma mortality and Enterline's estimate did not go unnoticed at the Banbury House Conference. I am of two minds about the agreement between the estimates. The fact that both studies project that asbestos is responsible for about 1 percent of cancer deaths can be taken as evidence that that number is, in fact, a close approximation of Che true magnitude. However, I don't think more than a moment's reflection is necessary to generate a note of caution. There are a large number of assumptions in all Che estimates and the congruent numbers may be partially a matter of chance* The fact that all four estimates baaed on mesotheliomas ~ those of McDonald and McDonald, J. Feto et al, Higginson et al, and Doll and R. Peto -- are similar reflects Chat the same sources of data and methods of analysis were used. Whatever reservations exist about Che accuracy of the estimate that 1 percent of cancer mortality is due to asbestos, the participants at the Banbury House conference agreed that the lower estimates were more likely correct than the much higher ones reported in the estimates paper. The lower number means that we can expect a barely discernible impact on total cancer mortality m asbestos exposures decrease, nevertheless, even 1 percent of cancer mortality represents 4,000 deaths annually. Elimination or reduction of those deaths should accompany decreasing exposures. Exposure Assessment The estimates of asbestos-related cancer are a clear example 003192 17 of strictly United exposure deta. Such limited information ia likely to be the case for most exposures that occurred more than a very few years- ago. In the case of asbestos, scientists interested in extrapolating from study generated data to estimates of national cancer mortality were certainly aided by the fact that asbestos causes asbestosis and mesotheliomas. Both those diseases are reasonably rare and reasonably diagnostic for asbest.-a exposure. And both are subject to undercounting which limits the accuracy of estimates based on them. In the absence of the mesothelioma data, we-would,now have three ,estimates of total asbestos cancer mortality of about 1, 2 and-3 percent of all cancers based on analysis of other available data. The Bogan and Hoel paper, the Nicholson et id paper, and the.Interline paper all followed the same general method. The different numbers they project reflect different decisions made about what numbers of workers were heavily exposed. Those decisions can be criticized because they were not made on the basis of firm information. However, that sort of information doesn't exist, and in its absence documented assumptions are the best that can be provided. One thing that all the estimates depend on is estimates of the disease burden borne by heavily exposed asbestos workers. The work of Selikoff et al C1980) was repeatedly cited in this regard. I think that this illustrates that there will frequently bo- no information for making exposure estimates. In fact, we will often remain dependent on impact data from epidemiologic studies. 006193 References Cochrane, J. C., I. Webster and A. Solomon. 1980. Prolonged and variable exposure to asbestos fiber. Current Cancer Research on Occupational and Environmental Carcinogenesis. Washington, 0.C.: Department of Health Education and Welfare. Doll, R. 1955. Mortality from lung caacer in asbestos workers. Br. J. led. Mad. 121 81. Doll, R. and R. Peto. 1981. The cause" of cancer: Quantitative estimates of avoidable risks of cancer in the United States today. J, Natl. Ca. Inst. 66:1191-1308. Enterline, P. E. 1978. Memorandum. Comments on "Estimates of the Fraction of Cancer in the United States Related to Occupational Factors." Washington, D.C.:Asbestos Information Association. 1981. Cancer caused by asbestos, in Peto and Schneiderman. pp 19-33. Estimates of the fraction of cancer in the United States related to occupational factors. Prepared by the National Cancer Institute, the National Institute of Environmental Health Sciences, and the National Institute for Occupational Safety and Health. September 15, 1978. Henderson, V. and P. E. Enterline. 1979. Asbestos exposure; Factors associated with excess cancer and respiratory disease mortality. in I. J. Selikorf and E. C. Hammond (ed) Health Hazards of Asbestos Exposure. Ann. N. !, Acad, of Sci. 330: 117 . Higglnson, J., J. C. Bahar, J. Clemmesen, H. Demopoulos, L. Carfinkel, T. Hirayama, and D. Schottenfeld. 1980. Proportion cf cancers due to occupations . Prev. Med. J9 :180. Hogan, K. D. and D. G. Hoe 1. 1981. Estimated cancer risk associated with occupational asbestos expc"!re. Risk An-lysis 1:67-76. Kolonel, L. N., T. Hirohcta, B. V. Chappell, F. V. Viola and D. E. Harris. 1980. Cancer mortality in a cohort of naval shipyard workers in Hawaii: Early findings. J. Natl. Ca. lust. 64;7 39743. McDonald, J. C. and A. D. McDonald. 1980. Malignant mesothelioma in North America. Cancer 46:1550 ___________ 1981. Mesothelioma as an index of asbestos impact. in Peto and Schneiderman. pp 73-81. 006194 Nicholson, W. J. 1981. The role of occupation in the production of cancer. Risk Analysis _1_: 7 7 -- 78. Nicholson, W. J., G. Ferkel, I. J. Selikoff, and K. Seidman. 1981. Cancer from occupational asbestos exposure projections 1980-2000. in Peto and Schneideraan. pp 87-108. Office of Technology Assessment. 1981. Assessment of Technologies for Determining Cancer Risks from she Environment. Washington, D. C.:Government Printing Office. Peto, J., B. E. Henderson and M. C. Pike. 1981 Trends in mesothelioma incidence in the United States and Che forecast epidemic due to asbestos exposure during World Var II. in Peto and Schneiderman. pp 51-69. Peto, J., R. 'Dolli S. V. Howerd, L. J. Klnlen, and B C. Lewinsohn. 1977. A mortality study among workers in an English asbestos factory. Br. J. Ind. Med. 34:169. Peto, R. and M. Schneideraan. 1981. (eds) Quantification of Occupational Cancer: Banbury Report 9. Cold Spring Harbor, NY:Cold Spring Harbor Laboratory. 756 p. Selikoff , I. J. 1981 Constraints in estimating occupational cancer mortality. In Peto, J. and M. Schneideraan. pp. 3-13. Selikoff , I. J., E. C. Hammond, and H. Seidman. 1979. Mortality experience of Insulation workers in the United States and Canada. Ann. N.Y. Acad. Sci. 330: 91. _____________ 1980. Latency of asbestos disease among insulation workers in the United States and Canada. Cancer 46: 2736. 006195 18 Table I Sitiattei of Cancer Mortality fro* Exposure to Asbestos Based on Estimates of Numbers of Workers Exposed and Estimates of Risks Authors Occupational Groups Estimated Exposure Levels Number of Projected % Projected Workers Ex- of Deaths Due Number of posed to Asbestos Deaths Projected Annual Deaths Z of Annual Cancer Deaths Estimates Paper "heavy" 4,000,000 35 to 44 1,600,000 46,000 to 52,000 "aignlficant" 1,500,000 to 35 to 44 3,500,000 4 400,000 to 700,000 2,000,000 to 2,300,000 12,000 to 23,000 58,000 to 75,000 13-18 {estimated total number of workers exposed, 8 to II millions; I million dead at time of estimate) Hogan & shipyard Heel workers "heavy" 640,000 to 35 to 44 810,000 "less heavy" 3,700,000 to 35 to 44 4.600,000 4 to 8 8,200 2,1 others "heavy" 150,(W0 35 to 44 "less heavy" 850,1X10 4 to 8 35 to 44 automotive "heavy" 270,000 35 to 44 "less heavy" 1,530,000 35 to 44 4 to 8 4,000 1.0 497,000 12,200 3,1 (1.4 to 4.4) (estimated total number of workers exposed 7 to 8 million; about half alive at time of analysis.) al calculated Iron data In paper by M.G. 261800 Table 1 (continued) Enterline 1 asbsestos Industy ami Insulation 2 asbestos industry Wtl ship- yards poat-iMIl shipyards automotive all others 19 8-12 (living in (1981) f/se 80,000 (lung ca.only) 20 16,000 530 4 f/cc 540,000 5 27,000 too 2 f/cc 1,500,000 0.2 3,300 165 I f/cc 285,000 0.3 f/cc 1,700,000 9.3 f/sc 3,500,000 2.7 7,695 0.4 6,375 0.4 13,140 other cancers esotheloaas (non-occupattonal asbestos-caused cancers 256 212 438 2,501 1,250 330 4,084 361) Nicholeon at al. 1 asbestos Industry 2 asbestos Industry insulation shipbuilding and repair construction RR engine repairmen utility services engineers & firenen chewlcal plants automotive marine engineers 35 to 44 35 to 44 2 35 to 44 35 to 44 2 35 to 44 4 to 6.6 35 to 44 5 35 to 44 3.3 35 to 44 6.6 35 to 44 6.6 35 to 44 50 ILtgJ* 991 455 2,747 2,423 179 375 881 285 353 85 -8,770 ~ 1.0 2.1 006197 006198 20 Table 2 Estimates of Cancer Hortallty froa Exposures*t Asbestos RetIsatea Baaed on Numbers of Mesotheliomas and a Relationship Between that Number and the Nuaber of Total Cancers Authors Basis of Calculation HcDonald ml McDonald J. Peto et al 8 esothelioaas/aillion esi I population X 0.75s nuaber of nesothelioaas caused by occupational ex posure to asbeatoa: Cl + 3,3)(nuaber of Mesotheliomas)* nuaber of all cancera caused by occupational exposure to asbestos. Estlasted nuaber of aesothelioaes expected from WWII shipyards (5,000), other mill exposures (3,,QGQ), and all pre-1965 exposures (37,500). (about 3) X (nuaber of aesothelloMs) * nuaber of lung cancera caused by asbestos Hlgginoon (1 + 1.5)(nuaber of aesotheiloaas) 4- (soae other et al cancers) total nuaber asbestos-caused cancera. Doll aid Peto "since in the late 1970's soae hundreds of aesotheliasms were due to asbestos, at least a feu thousand other cancers tust have been attributable to asbestos' Projected Nuaber of Deaths Projected % of Annual Annual Cancer Deaths Deaths 3,000 (4 1.4 (p 300 (0.5 to 2.9) 37,500 112,500 150,000 751 a 2.253 (/) 3,004 1,000 1,500 1,500 4,000 ^ (d) 1.4 1.0 feu thousand 1 or 2 SOURCES AND INTERPRETATION OF ASBESTOS EXPOSURE DATA Michael Gough Office of Technology Assessment United States Congress Washington, DC 20105 My talk'differs from many at this meeting because it focuses on-how scientists have made do with limited exposure data. It'doesn't make suggestions for improvements, but it draws attention to the importance of basic epidemiologic research in learning about the impacts of exposures. Recent years have seen increasing concern about tha workplace as a source of carcinogenic exposures. To some extent, those concerns reflect the general fear of cancer, but the focus on the workpiece has been sharpened by the occupational health disaster that has accompanied exposure to a single substance, asbestos. 1 will review recent estimates of the amount of cancer associated with occupational exposures to asbestos. Those estimates provide examples of the sorts of situation that are certainly more common than situations 9 characterized by good exposure data. In the case of asbestos, levels of past exposure are seldom known, the limited exposure information has not always 'been incorporated into assessments of risk, and slightly different guesses bout exposure levels and risks associated with particular levels have produced widely varying estimates of the impact of asbestos. Selikoff (1981) provides a short description of the development of our