Risk of mesothelioma and occupational exposure to asbestos and man-made vitreous fibers: evidence from two case-control studies in Montreal, Canada.

OBJECTIVE: To examine the effects of exposure to occupational asbestos and man-made vitreous fibers (MMVF) across a wide range of occupations on risk of mesothelioma.

METHODOLOGY: Two population-based case-control studies (1979-1986 and 1996-2001) provided 35 histologically confirmed mesothelioma cases and 1965 controls. A detailed job history was obtained to evaluate occupational exposure to many agents, including asbestos and MMVF.

RESULTS: The mesothelioma odds ratio for exposure to any asbestos type was 3.7 (95% confidence interval = 1.7 to 7.8). The subset exposed to amphibole fibers experienced an odds ratio = 7.0 (95% confidence interval = 2.7 to 18.5). Effects of MMVF could not be disentangled from those of asbestos.

DISCUSSION: In workers with exposure levels lower than in most historical cohort studies and across a wide range of industries, a strong association was found between asbestos, especially when it was amphibole, and mesothelioma.