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


CONCLUSIONS
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.
Vida
Stephen
S
Research Center of CHUM, School of Public Health, Université de Montréal, Montréal, Québec, Canada.
Pintos
Javier
J
Parent
Marie-Elise
ME
Lavoué
Jerome
J
Siemiatycki
Jack
J
D000395:Air Pollutants, Occupational / Q000506:poisoning*; D002170:Canada / Q000453:epidemiology; D016022:Case-Control Studies; D006801:Humans; D019570:Inhalation Exposure / Q000009:adverse effects; D008175:Lung Neoplasms / Q000139:chemically induced* / Q000453:epidemiology; D008297:Male; D009784:Occupational Diseases / Q000139:chemically induced* / Q000453:epidemiology; D016273:Occupational Exposure / Q000009:adverse effects*; D018570:Risk Assessment; D012822:Silicon Dioxide / Q000506:poisoning*
D000395:Air Pollutants, Occupational; D012822:Silicon Dioxide