Occupational variation in bladder cancer in Nordic males adjusted with approximated smoking prevalence

Background: Occupational exposure has been identified as the most important risk factor for bladder cancer second to smoking. The objective of this study was to estimate the occupational variation in risk of bladder cancer that is not attributable to smoking. Material and methods: In the Nordic Occupational Cancer study (NOCCA), 111,458 cases of bladder cancer and 208,297 cases of lung cancer cases were observed among men in Denmark, Finland, Iceland, Norway and Sweden during 1961–2005. Relative smoking prevalence in an occupation was estimated based on standardized incidence ratio (SIR) for lung cancer in the given occupation. Crude and smoking-adjusted SIRs with 95% confidence intervals (CI) for bladder cancer were calculated for each occupation. Results: The smoking-adjusted SIR for most of the occupations was closer to 1.00 than the unadjusted SIR. The highest statistically significant smoking-adjusted SIRs were observed among chimney sweeps (SIR 1.29, 95% CI 1.05–1.56), waiters (1.22, 1.07–1.38) hairdressers (1.14, 1.02–1.26), cooks and stewards (1.12, 1.01–1.25), printers (1.11, 1.04–1.18) and seamen (1.09, 1.03–1.14). Conclusions: Smoking is a strong risk factor for bladder cancer but there may also be other factors in some specific occupations in addition to smoking. The occupational variation in risk of bladder cancer is small when adjusted for smoking, but risk increasing factors are indicated in some occupations.