Occupational Exposure to Diesel and Gasoline Engine Emissions and Bladder Cancer Risk in Men: a Canadian Population-Based Case-Control Study

Abstract

Background: The International Agency for Research on Cancer has classified diesel exhaust as a carcinogen and gasoline exhaust as a possible carcinogen based on evidence for lung cancer. Our goal was to determine whether a positive association exists between occupational exposure to diesel or gasoline exhaust and bladder cancer. Methods: A population-based design was used to recruit 670 cases and 2547 frequency-matched controls from eight Canadian provinces between 1994 and 1997. Lifetime occupational history, including job title, status and duties, and information on possible risk factors was obtained by self-reported questionnaire. Concentration and frequency of occupational exposure to diesel and gasoline exhaust, and a measure of the reliability of exposure assessment, was assigned for each job using a job-exposure matrix supplemented by expert review. Exposure metrics were modeled as ever-never, highest attained concentration, duration, and cumulative exposure. Unconditional logistic regression was used to calculate odds ratios and their 95% confidence intervals. Analyses were restricted to estimates with high reliability and adjustment was made for proxy respondent, province, age, smoking, alcohol, occupational silica and aromatic amine exposure. Results: Relative to unexposed men, elevated odds of bladder cancer were observed for men whose highest attained diesel exhaust exposure concentration was high (1.97, 1.08-3.58) and who spent more than 30% of time at work exposed to diesel (1.80, 1.02-3.15). A statistically significant trend in increased risk of bladder cancer was observed with increasing duration of exposure to medium/high concentrations of diesel exhaust (>20 years, 1.82, 1.07-3.10, p-trend=0.002). We found no association between exposure to gasoline exhaust and bladder cancer. Conclusions: Our results suggest that occupational exposure to diesel exhaust increases bladder cancer risk in men, independent of smoking and other occupational exposures.