The primary risk factor for bladder cancer is cigarette smoking. Using a combined analysis of 11 case‐control studies, we have accurately measured the relationship between cigarette smoking and bladder cancer in men. Available smoking information on 2,600 male bladder cancer cases and 5,524 male controls included duration of smoking habit, number of cigarettes smoked per day and time since cessation of smoking habit for ex‐smokers. There was a linear increasing risk of bladder cancer with increasing duration of smoking, ranging from an odds ratio (OR) of 1.96 after 20 years of smoking (95% confidence interval [CI] 1.48–2.61) to 5.57 after 60 years (CI 4.18–7.44). A dose relationship was observed between number of cigarettes smoked per day and bladder cancer up to a threshold limit of 15–20 cigarettes per day, OR = 4.50 (CI 3.81–5.33), after which no increased risk was observed. An immediate decrease in risk of bladder cancer was observed for those who gave up smoking. This decrease was over 30% after 1–4 years, OR = 0.65 (0.53–0.79), and was over 60% after 25 years of cessation, OR = 0.37 (0.30–0.45). However, even after 25 years, the decrease in risk did not reach the level of the never‐smokers, OR = 0.20. (0.17–0.24). The proportion of bladder cancer cases attributable to ever‐smoking was 0.66 (0.61–0.70) for all men and 0.73 (0.66–0.79) for men younger than 60. These estimates are higher than previously calculated. Int. J. Cancer 86:289–294, 2000. © 2000 Wiley‐Liss, Inc.

Our results indicate that substantial exposure to metals and solvents may be nephrocarcinogenic. There is evidence for a gender-specific susceptibility of the kidneys.

The results of the analysis by bitumen fume exposure do not allow us to conclude on the presence or absence of a causal link between exposure to bitumen fume and risk of cancer of the lung and the head and neck.

European workers employed in road paving, asphalt mixing and other jobs entailing exposure to bitumen fume might have experienced a small increase in lung cancer mortality risk, compared to workers in ground and building construction. However, exposure assessment was limited and confounding from exposure to carcinogens in other industries, tobacco smoking, and other lifestyle factors cannot be ruled out.

Occupational exposure to aromatic amines could not be shown to be as strong a risk factor for urothelial carcinomas as in the past. A possible explanation for this finding is the reduction in exposure over the last 50 years. Our results strengthen the evidence that PAH may have a carcinogenic potential for the urothelium. Furthermore, our results indicate a urothelial cancer risk for the use of chlorinated solvents.