Occupational Exposure to Engine Exhausts and Prostate Cancer Risk.

Background: Some engine exhausts (EEs) have been classified as carcinogens and/or can have hormone-modulating properties that could play a role in prostate cancer development.

Objective: We investigated associations between lifetime occupational exposure to various EEs and prostate cancer risk, overall and for aggressive cancers.

Methods: In a population-based case-control study conducted in Montreal, Canada, 1,924 incident histologically-confirmed prostate cancer cases (436 aggressive) and 1,989 population controls were recruited. Socio-demographics, lifestyle factors and a detailed occupational history were collected during in-person interviews. Industrial hygienists conducted evaluations of intensity, frequency and reliability of exposure to EEs resulting from the combustion of several fuels (any diesel, light- and heavy-duty diesel, leaded and unleaded gasoline, propane and jet fuel) in each job held ≥ 2 years. Odds ratios (ORs) and 95% confidence intervals (CI) were estimated for exposure to each EE, in association with prostate cancer risk, adjusting for age and then for potential lifestyle and occupational confounders, accounting for a 5-year latency period. As most associations were not linear, we fitted functions for changes in percentile distributions based on natural cubic splines.

Results: There was no evidence of associations between exposure to the various EEs and overall prostate cancer. However, for high-grade cancers, based on the fully-adjusted model, a change from the 25th to the 75th percentile of the exposure distribution of any diesel EE yielded an OR of 1.24 (95%CI 0.96-1.61), and of 1.27 (95% CI 0.80-2.01) for a change from the 75th to the 95th percentile. These increases reflected exposure to diesel EE from light-duty vehicles, associated with similar ORs. For leaded gasoline EE, a change from the 75th to the 95th percentile resulted in an age-adjusted OR of 1.36 (95%CI 0.88-2.11), which was attenuated to 1.12 (95%CI 0.63-2.02) after full adjustment. There were no associations with EE from unleaded gasoline, diesel from heavy-duty vehicles, jet fuel and propane.

Conclusion: There was suggestive evidence for a deleterious role of occupational exposure to EE resulting from the combustion of any diesel, light-duty diesel and from leaded gasoline in the development of aggressive prostate cancer. Results were independent from prostate cancer screening patterns.