Document 2R0jnLOrnZkV6En7enLgv4V7p

Federal Register / Vol. -51. No. 119 / Friday, June 20, 1986 / Rules and Regulations 22641 10~s) and concluded that "this indicates workers--based upon exposure cancer wa9 calculated for four studies of that the assumption Implicitly made by measurements--'Workers exposed . interest. This analysis showed OSHA of a constant ratio is not universally valid" [Ex. 237A, p. 41]. Using Crump's preferred estimate of risk for Kl (0.023) gives a ratio of 9.5 x 10"*, approximately 10 times smaller than the average KM/Kt used iri OSHA's determination of an overall KM. predominantly to.chrysotile. The value of potency used by OSHA was 1, which is smaller than the estimates for the upper studies, but as you can see. it is considerably greater than the estimates made for populations exposed mainly to chrysotile ITr. 7/9. p. 87). However, during questioning, Dr. reasonable agreement .with the analysis done by OSHA. Dr. Nicholson concluded: in comparing the different ratios of pleural mesothelioma to adjusted lung cancer for all studies in which the major exposure was to . one fiber type, one can see that there are- Table 4.--Number of Mesothelioma Deaths and . Absolute Risk by Years From First Exposure, Dement et al. (1983)* Yoon since first exposure (Avg) Observed mesothel iomas Personyears Absolute risk* tO (5)............... ................ . 1020 (15)_________ _____ 2030(25)........... ...... -.... 0 11.390 0 0 10,921 0 0 8,055 0 Crump admitted that-- * * * (T|he chrysolile estimates 1 was making. I was thinking about exposures which are today predominantly chrysotile. 1 wasn't thinking of necessarily applying those in situations where the exposures were to mixed fibers in removal operations (Tr. 7/9, p. 1191. Although the asbestos manufacturing industry may confine itself primarily to roughly comparable ratios for chrysotile, amosite and mixed exposure. Crocidolile has approximately a two-fold greater number of mesotheliomas as percent of excess adjusted lung cancer. However, as noted previously, the unlraced individuals in the various crocidolile cohorts may lead.to'an overestimate of this ratio. Though somegreater potency may be considered for crocidolite regarding mesothelioma (a factor of two perhaps), the uncertainty associated 30 + (35)______________ Total_____ __ ____ . 1 2.775 0.3604 the use of chrysotile fiber in its products, with other factors in a given exposure 1 OSHA believes now, as it did at the circumstance lead to much greater From Crump (Ex. 237A, Table 4). kAbsolute riske(number ol deaths/person-yosrs)x 1,000. . time of the proposal, that the major sources of exposure to asbestos workers Table 5.--Number ol Mesothelioma Deaths in the next 20 to 40 years will be in the and Absolute Risk by Years From First Ex demolition, renovation, and removal of posure. Weill et al. (1972)* asbestos products (for example, insulation) which were installed 30 to 40 Veers since first exposure (Avg) Observed mesothe- lomas Personyears Absolute risk* years ago. These products generally contain amphiboles. This wa9 brought 10-15 (12.5)____________ 15-20 (17.5)..-......---.... out by Dr. Nicholson during cross- 0 2 31,180 29.473 0 0.0678 examination, when he noted .that: differences. For example, as was seen in the case of lung cancer, different exposure circumstances with the same fiber led to nearly 100-fold differences. Thus, thesuggestion that there are dramatic differences between different asbestos varieties has no basis in fact. Much greater differences would appear to be related to process, to fiber size distribution effects within a single asbestos variety (note the difference between textiles and mining, e g.), or to methodological 20-25 (22.5)------------ -----25-30 (27.5)........... ......... 30-35 (32.5)____ . ... 35 + (37.5)_________ . 0 25.080 0 0 14.018 0 0 9.832 0 . 0 1.565 0 1 should make the point though we are concerned in much of the regulation of the future with exposures that will be to differences in cohort studies (e.g., the asbestos cement studies of Weill et al. and of Finkelstein) (Ex. 303A, p. 6]. .Total----------------------- 2 * From Crump (Ex. 237A, Table 4). * Absolute rteJt s (number ol deaths/person-years) x 1,000. Table 5 gives the results of the calculation of KH for the Weilt'et al. materials that have already been put in place, In the insulation materials,.the sprayed bn asbestos materials, all these loosely friable [sic) insulation materials that have been applied over the years. Virtually all of the those exposures to those In addition to the data from occupational cohorts, Nicholson also pointed to some evidence of environmental exposures as supportive evidence. He noted that: study. Data from the Weill et al. cohort gives, by far, the smallest values of KM. The OSHA model shows an inadequate .fit to the data (P=0-001j with a KM of 7.0 x 10't0. The three-stage multistage model showed excellent fit to the data (P=0.90) and gave aXM of 1.6 x 10*"` almost 100 times smaller than the overall KM calculated by OSHA in the proposal. Dr. Crump pointed to the calculation of KM-for the six studies, three with mixed exposures (Selikoffet at., Seidman et al., and Finkelstein) and three with predominantly chrysotile exposures (Peto et al., Dement et al., and Weill et al.}and observed that: What one sees here is a large difference between the potency estimates in the upper three studies involving the mixed exposures - and those in the lower three involving exposures primarily to chrysotile.. . . [Ijf you materials will be of a mixed fiber type. And so 1 think that!a what we have to deal with. You can find in Borne circumstances, some manufacturing circumstances, pure fiber , exposure. I don't know what their risk started at, as the discussion has indicated, because of the variabilities inherent in those studies. But most of the exposures that we have in the future will be mixed fiber exposures [Tr. B/.19. p. 1-144]. Hence, OSHA believes it is wholly correct in using esitmates of KM from studies of mixed exposures os well as single-fiber type exposures iri determining an overall estimate of mesothelioma risk.. Moreover, in a post-hearing submission. Dr. Nicholson gave some additional analysis of the carcinogenic response to different asbestos fiber types [Ex. 303A]. In an effort to make a broader comparison of mesothelioma Mesothelioma has been documented in a variety of non-occupetional circumstances; including among family contacts of asbestosexposed individuals.. . . Notable is that family contact cases are 6een with exposure to chrysotile, amosite and crocidolite. Relative to the risk at work, there appears to be little difference in the family contact risk by fiber type. Animal studies substantiate the above analysis and suggest that all varieties of asbestos should be considered equally potent with respect to the production of either lung cancer or mesothelioma. Table 6 [of Ex. 303A j lists the data of Wagner et al. (1974) (Ex. 84-96) from inhalation studies using different forms of asbestos. Canadian chrysotile produced as many mesotheliomas as crocidolite and more than amosite or anthophyllite. Further, it produced lung cancer with a single day's exposure [Ex. 303A, p. 6-7). look at the geometric mean, there is about a according to exposure by mineral type, The addition of the Weill et al. study 20-fold difference in the risk. Although there Dr. Nicholson compared the risk of and the Dement et at. study to the data is more uncertainty in the numbers in the lower group because of smaller numbers of mesotheliomas, these values are still not - consistent with the ones in the upper group. 1 feel that, taken together, they do show a pattern of a smaller risk experienced by the pleural and peritoneal mesothelioma with that of lung cancer in a variety of studies. After various appropriate adjustments, the ratio of mesothelioma as a percentage of adjusted excess lung base used for the overall calculation of KM raises several points. First, the small number of mesothelioma deaths in the two studies makes the estimates of risk much less reliable. Dr. Nicholson GLEASON-000889