Document a4nngRkjXVZY3yOZopm4Rom2B

22642 {. Federal Register / Vol. 51, No. 119 / Friday, June 20, 1986 / Rules and Regulations discussed the advantage of additional which may be experienced by asbestos- expected GI cancers), only seven had information, but remarked that-- ' ` * [T|he total number of cases involved in those two studies is three. So it would be a very large uncertainly of any estimates made with those. And when one averaged it with the much higher levels of the four studies, would not substantially alter the lower value which was chosen in the OSHA document. That is. we would now be using an average of six studies rather than four.. . . |l|f those additional two studies were utilized there may not have been the need to artificially lower the average that was obtained using the four studies that were cited here.. . . [i]n essence, what I'm saying is that if you take exposed workers. In addition, OSHA has examined several alternate combinations of the data, including computing the best estimate of KM from the ratio of KM/KL. As in the lung cancer data, these calculations produce estimates which bracket the 1x10"'. Dr. Crump's preferred estimate of KM of 2x10"* [Ex. 237A, p. 48] was based solely on the studies of predominantly chrysotile-exposed workers and was meant to represent the mesothelioma risk of workers exposed predominantly statistically significant excess Cl cancers (Ex. 84-392 at 13) (Ex. 328, p. 1-21|. However, Dr. Nicholson pointed out at the rulemaking hearing (hat: ' ` * [Ex. 84-392) said 21 studies were listed. Twelve demonstrated an excess gastrointestinal cancer, and eight demonstrated a deficit. One was even. Many of those--several of those--actually were studies in which there was also no excess lung cancers. So there were circumstances where the excess risk to be expected was a very low one. And, thus, one would be within the range of statistical account of all the data, I don't think it would to chrysotile; his preferred estimates fluctuations no matter what the risk was; change the estimate of K* substantially. And, was not meant to characterize the risk since the Gt cancer . . . risk is never in fact, the correction that was made to lower of mesothelioma faced by workers in a expected to be equal to that of the excess the estimate is an appropriate one. It fits variety of workplaces--including the lung cancer risk. most of the data that do exist (Tr. 6/19, p. I138). Dr. Crump also noted the added uncertainty associated with the use of studies containing small numbers of deaths [Ex. 7/9, p.87). . major exposures to mixed fibers that will occur in asbestos removal, demolition, and renovation operations (Tr. 7/9, p. 119). OSHA has therefore determined that Dr. Crump's approach is not adequate to I think, of these 21 studies . . . only 13, if I'm not mistaken, would demonstrate an excess lung cancer risk. And the ones that do not [demonstrate an excess lung cancer risk] are largely the negative ones [for GI cancer) (Tr. 6/19, p. IU7|. OSHA has computed the arithmetic and geometric means of the KM's of the six studies for both the values of K,, from the OSHA model (Including Dement et al. and Weill et al. as computed by Crump) and for the "best fit" model using the KM from the multistage model with one, two or three stages. As Dr. Nicholson suggested, the inclusion of the Dement, et al. and Weill et al. data may "eliminate the need to artificially lower the average" by address the question of the total risk posed by asbestos exposure, and the Agency has chosen instead to base its -best estimate of risk on the six studies with sufficient data to quantify the excess risk of mesothelioma. Hence. OSHA concludes that its best estimate of K,, remains at 1x10"*, as proposed. The addition of the two studies with . small numbers of deaths adds some uncertainty to this estimate but. as indicated, this estimate is likely to In addition, OSHA believes the finding of astatistically significant excess of Cl cancer in seven studies of worker populations to be a substantial body of evidence. As pointed out by Dr. Nicholson, many of the studies in which GI cancer was not observed were unable to detect lung cancer as well. This points perhaps to methodological problems in the studies as well as low exposures. looking at the ratio of KH to Kl, since represent a substantial underestimate of It was also suggested that the these two studies represent the lower the risk of mesothelioma actually observed excesses could conceivably be md of the mesothelioma risk. Using the experienced by asbestos-exposed due to a misdiagnosis of peritoneal data in Table 3, the OSHA model gives workers. mesothelioma. While OSHA believes.lt i. an arithmetic mean of the KM of 2.73x10"*, (almost three times that proposed) and a geometric mean of 0.82 x 10"', approximately equal to OSHA's best estimate of KM given in the proposal. The mean values.of the estimates of Km from each of the six studies from the multistage mode) with the best fit are astonishingly high, with an arithmetic mean of 84.26 x 10"* to 70.92 x 10"', (up to 70 times larger than OSHA's preferred estimate of KM) and a geometric mean of the six KH's of 2.45 x 10"* to 7.2 x 10"*. Further inspection of III. Estimates of Risk for Other Cancers As discussed in Section IV, OSHA has concluded that workers exposed to asbestos are likely to be at an increased risk of gastrointestinal cancer. Though an excess of GJ cancer has not been observed consistently in every study of asbestos workers, and while the ratio of gastrointestinal cancer to lung cancer varies considerably from study to study, there appears to be sufficient evidence to roughly estimate the excess gastrointestinal cancer risk in asbestosexposed populations. A number of submissions to the record recognized the is unreasonable to totally account for these excesses (some as large as 60% of the lung cancer risk) by misdiagnosis, to the extent that the incidence of mesothelioma has been underobserved in these studies, then OSHA's predictions of the risks of mesothelioma are also underestimated. In an attempt to quantify the risk of gastrointestinal cancer, OSHA considered a simple risk model In which gastrointestinal cancer risk was assumed to be equal to 10% of the lung cancer excess risk. As Dr. Nicholson noted: Table 3 demonstrates that using several relationship between asbestos and Based upon the rough finding and given the values of KM from models with only slightly poorer fit (e.g.; .097 vs. 0.99) would produce estimates of risk several orders of magnitude larger. Hence, according to this analysis, OSHA's original choice of a best estimate of K,, of 1x10"* is by no means an gastrointestinal cancer [see, e.g., Exs. 91-40,118,183e, 158, 261A. 277, 297, 321J. In general, the risk ranges from about 5 to 20% of the excess lung cancer risk. The A1A/NA commented that: Although excess GI cancers have been found in some heavily exposed worker fact that there are different dose-response relationships, that overall, considering an increase over lung cancer of 10 percent for gastrointestinal cancer would give an underestimate of possible asbestos-related-CI cancers. One finds that the relationship that 1 just mentioned, comparing excess GI cancer with overestimate, as Dr. Crump apparently studies, no such excesses have been found in excess lung cancer to be such that some contends; indeed, his own calculations many other studies. Of the twenty-one studies demonstrated an increase of GI . show that 1 x 10"'in fact, greatly studies reviewed by OSHA (in each of which cancer about 50-60 percent that of lung ' underestimates the mesothelioma risk there was a minimum of 10 observed or cancer, a very high correlation. Others show, GLEASON-000890