BACKGROUND AND AIM: The epidemiological evidence on associations between ambient air pollution and bladder cancer is limited. We aimed to evaluate the associations between long-term exposure to ambient air pollution and bladder cancer incidence in a pooled European cohort. METHODS: We pooled data from six European cohorts enrolled between 1985 and 2005 (N = 302,493). Residential exposure to annual 2010 mean concentrations of fine particulate matter (PM2.5), nitrogen dioxide (NO2), Black Carbon (BC), warm season ozone (O3) and eight PM2.5 elemental components (copper, iron, potassium, nickel, sulfur, silicon, vanadium, and zinc) were assessed based on Europe-wide land use regression models at 100 × 100 m spatial scale. We applied Cox proportional hazard models with adjustment for potential confounders at individual- and area-level. We also performed two-pollutant models and sensitivity analyses including using exposures back-extrapolated to baseline years. RESULTS:During an average of 18.2 years follow-up, 967 bladder cancer cases were diagnosed. In single pollutant models, we observed a positive association between PM2.5 and bladder cancer incidence (Hazard Ratio (HR) and 95% confidence interval (CI): HR 1.09; 95% CI: 0.93, 1.27 per 5 µg/m3), which attenuated for PM2.5 back-extrapolated to baseline years (HR 1.06; 95% CI: 0.99, 1.14 per 5 µg/m3). Effect estimates for NO2, BC and O3 were very close to unity. Regarding elemental composition in PM2.5, we observed a positive association between zinc and bladder cancer incidence (HR 1.08; 95% CI: 1.00, 1.16 per 10 ng/m3). The effect estimates were robust in two-pollutant models and sensitivity analyses. CONCLUSIONS:There was suggestive evidence of an association between long-term exposure to PM2.5 and bladder cancer incidence, especially with zinc in PM2.5, which is primarily associated with industrial emissions. We found no evidence of an association between traffic-related air pollution and bladder cancer. KEYWORDS: Air pollution, Particulate matter, Particle components, Long-term exposure, Cancer and cancer precursors