Objectives To determine whether occupational exposure to gasoline engine emissions (GEE) increased the risk of lung cancer and more specifically whether leaded or unleaded GEE increased the risk.
Methods Two population-based case–control studies were conducted in Montreal, Canada. The first was conducted in the early 1980s and included many types of cancer including lung cancer. The second was conducted in the late 1990s and focused on lung cancer. Population controls were used in both studies. Altogether, there were 1595 cases and 1432 population controls. A comprehensive expert-based exposure assessment procedure was implemented and exposure was assessed for 294 agents, including unleaded GEE, leaded GEE and diesel engine emissions (DEE). Logistic regression analyses were conducted to estimate ORs between various metrics of GEE exposure and lung cancer, adjusting for smoking, DEE and other potential confounders.
Results About half of all controls were occupationally exposed to GEE. Irrespective of the metrics of exposure (any exposure, duration of exposure and cumulative exposure) and the type of lung cancer, and the covariates included in models, none of the point estimates of the ORs between occupational exposure to leaded or unleaded GEE and lung cancer were above 1.0. Pooling two studies, the OR for any exposure to leaded GEE was 0.82 (0.68–1.00).
Conclusions Our results do not support the hypothesis that occupational exposure to GEE increases the risk of lung cancer.
- gasoline engine emissions
- lung neoplasms
- occupational exposure
- diesel engine emissions
- case–control studies
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Contributors Each author has directly participated in the planning, execution or analysis of the study. JS and LR designed the study. MX, JS and VH designed the study’s analytic strategy and interpreted the results. JL, RP, MCR and JP provided advice in study design or data analysis. MX and VH drafted the manuscript. All authors critically revised and commented on the manuscript.
Funding Funding for the study was provided by the National Cancer Institute of Canada, the Fonds de recherche en santé du Québec, and the Canadian Institutes for Health Research (MOP-14704). JS’s research team was supported in part by the Canada Research Chairs programme and the Guzzo-SRC Chair in Environment and Cancer. VH is currently supported by the Cancer Research Society, Fonds de recherche du Québec–Santé (FRQS) and Ministère de l'Économie, de la Science et de l’Innovation du Québec (MESI).
Competing interests None declared.
Ethics approval For the lung cancer study, ethics approvals were obtained from all participating hospitals as well as from Institut Armand-Frappier Research Centre, Montreal University Hospital Centre and McGill University. For the multisite cancer study, authorisations were obtained from professional directors of all participating hospitals as well as from Institut Armand-Frappier Research Centre, Montreal University Hospital Centre and McGill University.
Provenance and peer review Not commissioned; externally peer reviewed.