Asbestos and Carcinogenicity

Abstract

It is alleged that there have been 67 or more cases of mesothelioma among Quebec chrysotile miners and millers. Of the many thousand individuals employed by the Quebec chrysotile mining and milling industry since its inception, no one known how many have died or of these how many from mesothelioma. At a 1989 meeting in Ottawa, Ontario, Canada, it was stated that a cohort of 11,379 persons born between 1891 and 1920 and employed for 1 month or more, there had been 11 cases of mesothelioma among 4,547 deaths to the end of 1975; by 1978 there were 18 cases, and a follow-up to 1990 will soon be completed. More than 70% of the cohort have now died, and a study of a subsample indicates that the eventual number of cases of mesotheliomas may be about 30. A disproportionate number of these (at least seven) were exposed to crocidolite in a small local factory, and one had substantial exposure to amosite. Could the remaining cases be attributed to fibrous tremolite contamination Whether or not chrysotile per se is capable of inducing mesothelioma, it is clear that workers whose exposure has been only to commercial chrysotile have suffered much less frommore » mesothelioma than, for example, those exposed for even a few months to crocidolite in gas mask filter manufacture or cigarette filter manufacture, in whom 16 to 19% of all deaths were attributable to this cause. In the general population of the Quebec chrysotile mining towns, exposed over generations to chrysotile concentrations far greater than anything encountered in public buildings, there have been few if any cases of mesothelioma attributable to nonoccupational exposure.« less