Occupational exposure to lead and lung cancer: results from two case-control studies in Montreal, Canada

Objectives We investigated the association between workplace lead exposure and lung cancer risk, separately for organic lead and for inorganic lead, from either engine emissions or from other sources. Methods Two population-based case-control studies were carried out in Montreal (1979–1986 and 1996–2002) to investigate occupational factors in relation to lung cancer among 1593 men with histologically confirmed incident lung cancer, and 1426 controls from the general population. Interviews elicited information on sociodemographic characteristics, lifetime smoking and occupational history. Chemists translated each job into potential chemical exposures. Cumulative indices of exposure were derived and classified into non-substantial and substantial exposure. ORs adjusted for several potential confounders including smoking, and 95% CIs were estimated by logistic regression. Results Lifetime prevalences of exposure in Study I were 3% for organic lead, 40% for inorganic lead from engine emissions and 17% for inorganic lead from other sources; corresponding prevalences in Study II were 4%, 19% and 16%, respectively. No associations were observed when comparing ever to never exposed subjects in pooled analyses (organic lead, OR=1.39, 95% CI 0.77 to 2.52; inorganic lead from engine emissions: OR=0.89, 95% CI 0.72 to 1.09; inorganic lead from other sources: OR=0.99, 95% CI 0.76 to 1.29). Nor were these exposures associated with lung cancer in subjects with substantial cumulative exposure. Conclusions In this large study, using a blinded expert-based assessment of lifetime occupational exposure and adjustment for several potential confounders, we observed no increased risk of lung cancer with exposure to lead compounds.