OCCUPATIONAL EXPOSURE TO POLYCYCLIC AROMATIC-HYDROCARBONS AND THE RISK OF BLADDER-CANCER - A FRENCH CASE-CONTROL STUDY

Background. The risk of bladder cancer has been shown to be increased in occupations which are likely to involve exposure to polycyclic aromatic hydrocarbons (PAH), but up to now, most studies have considered this exposure in terms of job title. Methods. A hospital-based case-control study of 658 male cases of bladder cancer and 658 male controls was carried out in five areas of France from 1984 to 1987. For each subject, occupational exposure to PAH was assessed from questionnaires by an expert according to a semi-quantitative index of exposure. Results. The overall odds ratio for PAH exposure, adjusted for smoking, coffee drinking and occupational exposure to aromatic amines was estimated at 1.3 (95% CI : 1.0-1.7, P < 0.05). A slight but clear dose-response relationship was observed, and the trend remained significant after adjustment for cumulative smoking, with odds ratios of 1.2 (95% CI : 0.9-1.7), 1.4 (95% CI :0.9-2.2) and 1.8 (95% CI :0.8-3.9) for low, medium and high average exposures respectively compared to subjects unexposed to PAH (P for trend < 0.05). Moreover, the association between bladder cancer and PAH exposure was also investigated in a category of smokers homogeneous with respect to their tobacco consumption. In this heavy-smoker group, a stronger association with PAH was detected. Conclusions. These results support the hypothesis of a causal relationship between occupational exposure to PAH and bladder cancer risk.