The incidence of bladder cancer is unusually high in aluminium smelter workers. An epidemiological study showed that workers in Soderberg potrooms are at highest risk for bladder cancer, the adjusted overall relative risk being 2.39 (1.34-4.28). Exposure to polycyclic aromatic hydrocarbons, of which benz(a)pyrene (BaP) served as an indicator, seems to be the causative factor. The relative risk was evaluated at 12.38 for workers with 20 or more equivalent years of BaP exposure. Cigarette smoking contributed significantly to the appearance of bladder cancer in the population studied. There is a synergistic effect when cigarette smoking and BaP exposure are combined; the numbers in our population are too small to determine whether this interaction effect is multiplicative or additive. It is concluded that bladder cancer is associated with aluminium smelting (primarily with the Soderberg process).
The existence of polycyclic aromatic hydrocarbons (PAH) in the particulate phase of diesel engine exhaust has raised concern about a carcinogenic effect in workers exposed to exhaust from diesel engines. Some of the PAH are carcinogenic following inhalation by experimental animals and are associated with excess cancer mortality in some occupational exposures. Studies of occupational exposure to diesel exhaust show concentrations of PAH are above ambient levels but below the very high levels in occupations with demonstrated excess cancer mortality. A critical review of the epidemiologic evidence on the carcinogenicity of workplace exposure to diesel engine exhaust is suggestive of a carcinogenic effect but the existing data are sparse and contradictory. Further epidemiologic studies of this question are needed.