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

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


Background: 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.

Methods: 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.

Results: 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.

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

Impact: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Air Pollutants, Occupational / poisoning*
  • Canada / epidemiology
  • Case-Control Studies
  • Humans
  • Inhalation Exposure / adverse effects
  • Lung Neoplasms / chemically induced*
  • Lung Neoplasms / epidemiology
  • Male
  • Occupational Diseases / chemically induced*
  • Occupational Diseases / epidemiology
  • Occupational Exposure / adverse effects*
  • Risk Assessment
  • Silicon Dioxide / poisoning*


  • Air Pollutants, Occupational
  • Silicon Dioxide