Preliminary Findings for Pleural Mesothelioma among Women in the Quebec Chrysotile Mining Regions

Abstract

Introduction. We conducted a descriptive study to compare cases of pleural mesothelioma among female residents of Quebec’s asbestos mining regions to matched controls for residential, domestic and occupational asbestos exposures. Methods. We visited hospitals throughout the province of Quebec to identify women aged ≥50 yr whose hospital records mentioned any possible mesothelioma between 1970 and 1989. Hospital records and biological materials were reviewed by three expert pathologists to identify individuals who had lived in a mining region in Quebec at the time of diagnosis. For each case, 15 controls matched for year (±2) of birth and area of residence were selected from a previously interviewed sample of 817 female asbestos mining area residents alive in 1989. Relatives of the cases were similarly interviewed regarding lifetime occupational and residential histories and cohabitation with asbestos worker(s). Cumulative exposure from each source was estimated in fibers/ml-yr from indirect data. Results. We identified six ‘definite or probable’ and four ‘possible’ pleural mesothelioma cases. All resided in Thetford Mines (none in the town of Asbestos) and were born before 1935. Five cases (50%) worked in the asbestos industry (versus 2.7% of controls; relative risk = 53.8). Nine (90%) had lived with one or more asbestos workers (versus 65% of controls); six (60%) with two or more workers (versus 36% of controls). Mean cumulative exposure (residential, domestic, and occupational combined) was estimated as 226.1 fibers/ml-yr (range 84–525) for cases and 84.1 fibers/ml-yr (range 0–189) for controls, with a plausible 5-fold error on either side.