Introduction Some engine exhaust components are carcinogenic or have hormone-disrupting properties.

Objective To investigate the association between lifetime occupational exposure to various engine exhausts (EE) and prostate cancer risk.

Methods In the context of a case-control study conducted in Montreal, Canada, 1,924 histologically-confirmed prostate cancer cases (436 aggressive) and 1,989 population controls were recruited. Complete occupational history, socio-demographic and lifestyle factors were collected during in-person interviews. Industrial hygienists conducted semi-quantitative evaluations of intensity, frequency and reliability of exposure to leaded and unleaded gasoline EE, any diesel EE, heavy diesel EE, light diesel EE, jet fuel EE, and propane EE in each job held ≥2 years. Odds ratios (ORs) adjusted for age, ancestry and education, and 95% confidence intervals (CI), were estimated with unconditional logistic regression, modelling the association between each EE and prostate cancer risk.

Results Ever exposure to leaded gasoline EE was associated with a slight increase in risk of overall prostate cancer (OR=1.13, 95%CI 0.98 to 1.31), after restricting to probable and definite exposures, and applying a 5-year lag. Although no formal statistical heterogeneity in risks appeared, the association was slightly stronger for non-aggressive cancers than aggressive ones. No dose-response relationships emerged for total duration or cumulative exposure. Men who had ever been exposed to jet fuel EE showed a decreased odds of the tumor (OR=0.34 95%CI 0.19 to 0.61). No association was found with exposure to any other EE. Mutual adjustments for other EE and sensitivity analyses restricting controls to men recently screened for prostate cancer yielded results consistent with the main findings.

Conclusion We found limited evidence for a deleterious role of occupational exposure to leaded gasoline EE in the development of prostate cancer. This is the first study to examine the distinct role of leaded and unleaded gasoline EE in the etiology of this cancer.