Document LgQgmpzjp7p9RNaR9jBjLBn7z

Federal Register / Vol. 51, No. 119 / Friday, June 20, 1986 / Rules and Regulations 22641 10"6) and concluded that "this indicates workers--based upon exposure cancer was 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/K,. used in OSHA's determination of an overall K,,. predominantly tochrysotile. 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 (Tr. 7/9. p. 87J. 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 ajl 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)' Years since firs! exposure (AvflJ Observed mesothel iomas Personyears Absolute risk* tO (5)........... 1020(15)___ 2000 (25}___ 0 n.390 0 0 10,621 0 0 8.055 0 Crump admitted that-- * * * |T|he chrysotile estimates l 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. 119]. Although the asbestos manufacturing industry may confine itself primarily to roughly comparabte ratios for chrysotile. amo8ite and mixed exposure. Crocidolite has approximately a two-fold greater number of mesotheliomas as percent of excess adjusted lung cancer. However, as noted previously, the untraced individuals in the various crocidolite cohorts may lead to'sn overestimate of this ratio. Though somegreater potency may be considered for crocidolite regarding mesothelioma (a factor of two perhaps), the uncertainty associated SO + (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 |Er. 237A. Table 4). `Absoluts risk(number ot deaths/person.yoars)x 1,000. . Table 5.--Number of Mesothelioma Deaths and Absolute Risk by Years From First Ex posure, Weill et al. (1972)* Tears since first exposure (Avq) Obsarvod mesotho- Komaa Personyears Absolute risk* 10-15 (12.5).......... .. ......... 15-20 (17.5)...............-.... 25-30 (27.5)______ ___ __ 30-35(32.5) 36 -f (37.5)......... ............. 0 31,160 2 29.473 25.080 0 14,016 0 3,632 0 1.565 0 0.0676 0 0. 0 time of the proposal, that the major sources of exposure to asbestos workers in the next 20 to 40 years will be in the demolition, renovation, and removal of asbestos products (for example, insulation) which were installed 30 to 40 years ago. These products generally contain amphiboles. This was brought out by Dr. Nicholson during cross* examination, when he noted.that: I should make the point though we are concerned in much of the regulation of the future with exposures that will be to 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, the suggestion 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 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, Tsbk) 4). * Absolute risk = (number of deaths/persori-yearsJxt.OOO. Table 5 gives the results of the calculation of Ku for the WeiU'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 ail of the (hose exposures to (hose 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 Bhows an inadequate .fit to the data (P=0.001) with a KM of 7.0 x 10",0. The three-stage multistage model showed excellent fit to the data (P=0.90) and gave a KM of 1.6 x 10"10, almost 100 times smaller, than the overall KM calculated by OSHA in the proposal. Dr. Crump pointed to the calculation of Ku for the six studies, three with mixed exposures (Sellkoff et 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.. . . [I}f you materials will be of a mixed fiber type. And Mesothelioma has been documented in a so I think that's what we have to deal with. You can find in some 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. variety of non-occupational circumstances; including among family contacts of asbestosexposed individuals.. . . Notable is that family contact cases are 6cen with exposure to chrysotile. amosite and crocidolite. Relative to the risk at work, there appears to be little difference in the family contact risk 6/19- p. 1-1440- by fiber typo. Animal studies substantiate the above Hence, OSHA believes it is wholly analysis and suggest that all varieties of . correct in using esitmates of Ku from asbestos should be considered equally potent studies of mixed exposures as well as with respect to the production of either lung single-fiber type exposures in cancer or mesothelioma. Table 6 [of Ex. determining an overall estimate of 303A) lists the data of Wagner et al. (1974) mesothelioma risk.. (Ex. 84-96} from inhalation studies using Moreover, in a post-hearing different forms of asbestos. Canadian 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 chrysotile produced as mony 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 al. 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 89 a percentage of adjusted excess lung base used for the overall calculation of Ku 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