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22630- Federal Register / Vol. 51.'No. 119'/ 'Friday. June 20. 1986 / Rules and Regulations compared to the untreated asbestos fibers. Drs. Lemon and Groth of NtOSH (Tr. 6/21, pp. 189-191) testified at the public hearings that, to date, in vitro studies do not show with any degree of certainty that modification of asbestos fibers can prevent adverse health effects. They contend that the in vitro studies did not measure the fiber sizes of the.modified asbestos fibers to determine whether the treatment shortened the fiber. Dr. Groth cited a study by Monchaux (Ex. 84-438) that showed that acid leaching of chrysotile decreased its mesothelioma toxicity in rats; however, the treatment also shortened the fiber. He was not cerlain, therefore, whether the reduced toxicity derived from the treatment or the shortening of the fiber. In addition, no evidence was presented in the record to indicate that modified fibers are incapable of causing adverse effects after administration into laboratory animals. Mr. Warren, of the SNA, in his testimony agreed with this position. "Talcs containing asbestos minerals. . . appear to pose a signficant health risk to exposed workers, and talc workers exposed to asbestos should receive the protection afforded by the asbestos standard" (48 FR 51120). Specifically. Brown et a). (Ex. 84-029) of NIOSH conducted a historical prospective study of talc miners and millers employed at a New York State talc facility operated by the R.T. Vanderbilt Company. Although the company reported that the talc at this facility contained no asbestos. NIOSH (Exs. 84-39,84-181) reported finding asbestiform tremolite and anthophyllite following analysis of personal and bulk samples by election microscopy and xray diffraction techniques. As measured by optical microscopy, average air concentrations of fibers greater than 5 urn in length ranged from 1.7 f/cc to 9.8 f/cc as an 8-hour TWA in the mine. In the mill, average 8-hour TWA exposures for these fibers ranged from 1.5 f/cc to 8.4 f/cc. The cohort Btudied by Brown et al. When asked whether OSHA should deregulate modified chrysotile, Mr. Warren responded; (Ex. 84-029) consisted of 398 workers employed between 1947 and 1959. Cause-specific mortality rates were SNA's position is not that it wants (modified fibers) to be exempted from regulation. Indeed. It expects to be covered. And that is certainly true because the in vivo testing is not completed. There is no present basis available for making any biological' . distinction (between modified and unmodified fibers). (Tr. 7/5, p. 49) Based on these considerations, OSHA has decided that it is prudent from a public health viewpoint to continue to include chemically treated asbestos in the Agency's definition of asbestos (See Section IX. Summary and Explanation for General Industry). compared to those of U S. white males, adjusted for age and calendar period. Brown et al. reported signficantly elevated increases in cancer mortality (9 observed vs. 3.3 expected) and nonmalignant respiratory disease mortality (8 observed vs. 2.9 expected). One death from mesothelioma was reported, but the death could not be specifically attributed to exposure to tremolite or anthopyllite. Of the 10 individuals who died of cancer. 3 worked previously for other New York State talc companies. Gamble et al. (Ex. 84-181) of NIOSH also conducted a cross-sectional morbidity study of the same facility. Of C. Tremolite and Anthophyllite 158 male miners, 121 participated in a Burvey consisting of a respiratory In the November. 1984 notice, OSHA questionnaire, chest X-ray, and reviewed a number of epidemiological spirometric testing. Hie morbidity studies that suggested that the talc experience of this cohort was compared miners and millers are at excess risk of. to that of coal miners, potash miners, mortality from lung cancer, chrysotile asbestos workers, and mesothelioma, and non-malignant . synthetic wool textile workers. Coal and respiratory: disease(Exs. 84-025,84-141,. potash miners were used as comparison 84-181, 4-211), and have a high groups because they were likely to be prevalence of pleural thickening and similar to talc miners in many non- calcification, decreased pulmonary occupational respects that affect function, and lung fibrosis (Ex. 84-181). _ respiratory morbidity. Gamble et al. (Ex. Il ls known that many, but not all, ' 84-181)found that, compared to coal commercial talc deposits contain and potash miners, talc miners with no serpentine and amphibole asbestos and previous work history at other talc the minerals tremolite and anthophyllite, mines had a signficantly elevated which,may be found in amorphous, . - prevalence of pleural thickening and fibrous, or asbestiform habits (Ex. 84- calcification. When all talc workers 039). At the time; based largely on were combined, with or without prior epidemiological studies conducted by talcexposure, the researchers found NIOSH (Ex. 84-029, 84-181), OSHA increased prevalences of cough, phlegm concluded that production, dyspnea, and x-ray abnormalities. Talc workers also had significantly decreased pulmonary function, which was associated with duration and intensity of exposure. OSHA also reviewed a third study that presented conflicting findings in workers at the same facility (48 FR 51118). Stifle and Tabershaw (Ex. 84198) studied all male workers employed sometime between 1948 and 1977 at this facility. Vital status and information on control variables were determined for 655 men. Cause-specific mortality rates were compared to U.S. white males, adjusted for age and calendar period. Non-signficant excesses of mortality from lung cancer and non-malignant respiratory disease were observed in the cohort; these excesses were attributed to a "smoking effect," rather than to an effect from occupational exposure (Ex. 84-198). As a further analysis, Stille and Tabershaw (Ex. 84-196) separately analyzed.the mortality experience of cohort members with a history of any prior work experience and cohort members with no prior work experience. Among the subcohort of 540 males with prior work experience, significant elevatious were found for mortality from all cancers, liver cancer, lung cancer, lymphopietic cancer, and non-malignant respiratory diseases. No elevated causes of death were found for the subcohort of 115 males with no prior work. experience. Stille and Tabershaw concluded that "Since the cancers and lung diseases typically have long latencies, the possibility exists that . exposures prior to work at the. study mine and mill.were responsible for at least some of . . . (the increased incidences of diseases observed]" Ex. 84-198, p. 482). They also concluded that "workers with `exclusive- .... [study mine and mill] employment seem to be at no considerable risk of. ; . lung cancer. ..." (Ex. 84-196, p. 483). OSHA also presented comments by Brown et al. on the Stille and Tabershaw study (48 FR 51119). To summarize, Brown et al. [Ex. 84-218, pp. 178-179) commented- that Stille and ; Tabershaw failed to analyze mortality' by length.of followup period. The analysis ofsubcohoFt with or without prior work history was "not likely to be very informative," because, of the small size and young age of the cohort that had no prior work history. Because of these and other concerns about the Stille and Tabershaw study, Brown et al. concluded as follows:. "(the Stille aiid Tabershaw] report fails to address adequately the question of whether or not there is an increased risk from lung cancer specifically associated with working GLEASON-000878