Evidence of a multiplicative effect between cigarette smoking and occupational exposures in the aetiology of bladder cancer.

A case-control study on urinary tract cancer in men is ongoing in the Province of Torino. The analysis of tobacco smoke and occupational histories of the first 225 case-control pairs is described. The overall relative risks (RR) for tobacco smoke and for occupations known to entail a risk for bladder cancer were respectively 4.8 (95% confidence limits (C.L.) 2.4--9.3) and 1.7 (1.0--2.7). There was a clearcut dose-response relationship between different categories of cigarette consumption and risk for urinary tract cancer. For each level of cigarette consumption, relative risks were compared between men reporting and non-reporting occupation at risk. This analysis suggested a multiplicative effect between the 2 factors.