Cancer risk after cessation of asbestos exposure. A cohort study of Italian asbestos cement workers

Corrado Magnani ^1*, Daniela Ferrante ¹, Francesco Barone Adesi ², Marinella Bertolotti ¹, Annalisa Todesco ¹, Dario Mirabelli ² and Benedetto Terracini ³

¹ University of Eastern Piedmont, Italy
² CPO Piemonte, Italy
³ University of Torino, Italy

^* To whom correspondence should be addressed. E-mail: corrado.magnani{at}cpo.it.

Accepted 28 July 2007

Abstract

Objectives: We aimed at studying mortality for asbestos related diseases and incidence of mesothelioma in a cohort of Italian asbestos cement workers after cessation of asbestos exposure. Methods: The Eternit factory operated from 1907 to 1986. The cohort included 3434 subjects active in 1950 or hired in 1950-86, recorded from company books, without selections. Local reference rates were used for both mortality and mesothelioma incidence. Results: Mortality was increased in both sexes for all causes (overall 1809 obs vs 1312.3 exp; p<0.01), pleural (135 obs vs. 3.6 exp; p<0.01) and peritoneal (52 vs 1.9; p<0.01) malignancies and lung cancer (249 vs. 103.1; p<0.01). In women, ovarian (9 vs 4.0; p<0.05) and uterine (15 vs 5.8; p<0.01) malignancies were also in excess. No statistically significant increase was found for laryngeal cancer (16 obs vs. 12.2 exp). In Poisson regression analyses the RR of death from pleural neoplasm linearly increased with duration of exposure while it showed a curvilinear increase with latency and time since cessation of exposure. RR for peritoneal neoplasm continued to increase by latency, duration and time since cessation of exposure. RR for lung cancer showed a reduction after 15 years since cessation of exposure and leveled off after 40 years of latency. Conclusion: This study of a cohort of asbestos exposed workers with very long follow-up confirmed the reduction of risk of death from lung cancer after the end of exposure. It also suggested a reduction of risk for pleural mesothelioma with over 40 years of latency while risk for peritoneal mesothelioma showed a continuing increase.

Keywords: asbestos, cessation of exposure, lung cancer, peritoneal mesothelioma, pleural mesothelioma

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