Occupational exposure to asbestos and lung cancer in men: evidence from a population-based case-control study in eight Canadian provinces
1 Population Studies Division, Health Canada, Ottawa, Ontario, Canada
2 Division of Occupational and Environmental Health, Dalla Lana School of Public Health, University of Toronto, Toronto, Canada
3 Occupational Cancer Research Centre, Toronto, Ontario, Canada
4 INRS-Institut Armand-Frappier, University of Quebec, Laval, Quebec, Canada
5 Division of Epidemiology, Dalla Lana School of Public Health, University of Toronto, Toronto, Canada
6 Prevention and Cancer Control, Cancer Care Ontario, Toronto, Ontario, Canada
7 Health Promotion and Chronic Disease Prevention Branch, Public Health Agency of Canada, Ottawa, Canada
BMC Cancer 2012, 12:595 doi:10.1186/1471-2407-12-595Published: 13 December 2012
Asbestos is classified as a human carcinogen, and studies have consistently demonstrated that workplace exposure to it increases the risk of developing lung cancer. Few studies have evaluated risks in population-based settings where there is a greater variety in the types of occupations, and exposures.
This was a population based case–control study with 1,681 incident cases of lung cancer, and 2,053 controls recruited from 8 Canadian provinces between 1994 and 1997. Self-reported questionnaires were used to elicit a lifetime occupational history, including general tasks, and information for other risk factors. Occupational hygienists, who were blinded to case–control status, assigned asbestos exposures to each job on the basis of (i) concentration (low, medium, high), (ii) frequency (<5%, 5-30%, and >30% of the time in a normal work week), and (iii) reliability (possible, probable, definite). Logistic regression was used to estimate odds ratios (ORs) and their corresponding 95% confidence intervals (CI).
Those occupationally exposed to (i) low, and (ii) medium or high concentrations of asbestos had ORs for lung cancer of 1.17 (95% CI=0.92 – 1.50) and 2.16 (95% CI=1.21-3.88), respectively, relative to those who were unexposed. Medium or high exposure to asbestos roughly doubled the risk for lung cancer across all three smoking pack-year categories. The joint relationship between smoking and asbestos was consistent with a multiplicative risk model.
Our findings provide further evidence that exposure to asbestos has contributed to an increased risk of lung cancer in Canadian workplaces, and suggests that nearly 3% of lung cancers among Canadian men are caused by occupational exposure to asbestos.