Long-term exposure to ambient air pollution and bladder cancer incidence in a pooled European cohort: the ELAPSE project

Background The evidence linking ambient air pollution to bladder cancer is limited and mixed. Methods We assessed the associations of bladder cancer incidence with residential exposure to fine particles (PM 2.5 ), nitrogen dioxide (NO 2 ), black carbon (BC), warm season ozone (O 3 ) and eight PM 2.5 elemental components (copper, iron, potassium, nickel, sulfur, silicon, vanadium, and zinc) in a pooled cohort ( N = 302,493). Exposures were primarily assessed based on 2010 measurements and back-extrapolated to the baseline years. We applied Cox proportional hazard models adjusting for individual- and area-level potential confounders. Results During an average of 18.2 years follow-up, 967 bladder cancer cases occurred. We observed a positive though statistically non-significant association between PM 2.5 and bladder cancer incidence. Hazard Ratios (HR) were 1.09 (95% confidence interval (CI): 0.93–1.27) per 5 µg/m 3 for 2010 exposure and 1.06 (95% CI: 0.99–1.14) for baseline exposure. Effect estimates for NO 2 , BC and O 3 were close to unity. A positive association was observed with PM 2.5 zinc (HR 1.08; 95% CI: 1.00–1.16 per 10 ng/m 3 ). Conclusions We found suggestive evidence of an association between long-term PM 2.5 mass exposure and bladder cancer, strengthening the evidence from the few previous studies. The association with zinc in PM 2.5 suggests the importance of industrial emissions.