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Cancer Epidemiol Biomarkers Prev. 2010 Jun;19(6):1602-11. doi: 10.1158/1055-9965.EPI-10-0015. Epub 2010 May 25.

Occupational exposure to silica and lung cancer: pooled analysis of two case-control studies in Montreal, Canada.

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Research Center of CHUM, School of Public Health, Université de Montréal, Montréal, Québec, Canada.



Respirable crystalline silica is a highly prevalent occupational exposure and a recognized lung carcinogen. Most previous studies have focused on selected high-exposure occupational groups. This study examines the relationship between occupational exposure to silica and lung cancer in an occupationally diverse male population.


Two large population-based case-control studies of lung cancer were conducted in Montreal, one in 1979-1986 (857 cases, 533 population controls, 1,349 cancer controls) and the second in 1996-2001 (738 cases and 899 controls). Interviews provided descriptive lifetime job histories, smoking histories, and other information. Industrial hygienists translated job histories into histories of exposure to a host of occupational substances, including silica. Relative risk was estimated, adjusting for several potential confounders, including smoking.


The odds ratio for substantial exposure to silica was 1.67 (95% confidence interval, 1.21-2.31) and for any exposure was 1.31 (95% confidence interval, 1.08-1.59). Joint effects between silica and smoking were between additive and multiplicative, perhaps closer to the latter. In this population, it is estimated that approximately 3% of lung cancers were attributable to substantial silica exposure.


The carcinogenicity of inhaled crystalline silica was observed in a population with a wide variety of exposure circumstances.


The finding of carcinogenicity across a wide range of occupations complements prior studies of specific high-exposure occupations. This suggests that the burden of cancer induced by silica may be much greater than previously thought.

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