Occupation and prostate cancer.

The descriptive epidemiology of prostate cancer, including international comparisons of incidence, temporal trends, social class gradients, and migrant studies, suggests that incidence varies greatly and that exogenous factors may play an important etiologic role (1, 2). Despite attempts to investigate the roles of several classes of exogenous agents, there are still no definitely recognized exogenous risk factors for prostate cancer. While there is still limited physiologic evidence on the extent to which different exogenous chemicals may affect the prostate gland, the principle that such chemicals can alter enzymatic activity is established (3, 4). Further, animal experiments have demonstrated that prostate tumors can be induced by administration of certain chemicals by various routes (5). It has been hypothesized, though not yet proven, that such carcinogenic effects may be mediated by hormonal influences. Experimental evidence indicates the possible role of androgens as initiators in prostate carcinogenesis (6, 7), while other studies have shown that estrogens can induce DNA damage (8). Various exogenous chemicals may affect hormone levels, which may, in turn, affect estrogen levels and androgenic stimulation of the prostate (2, 9-11). In this presentation, we consider evidence regarding the possible role of occupation and occupational exposures. Investigating cancer risks in relation to occupational exposures is important because exposure levels in the workplace may be higher than elsewhere and because most workplace substances find their way into the general environment in one form or another. A thorough review of possible associations between prostate cancer and all occupations and occupational agents would have been beyond the scope of this brief review; instead, we restricted our attention to a handful of occupations and occupational agents which have, in one way or another, already come under particular suspicion and scrutiny. These (partially overlapping) occupations and agents are: farming, pesticides, cadmium, metal working, polycyclic aromatic hydrocarbons, and the rubber industry. Considerable attention has recently been paid to farming, and we will consequently devote particular attention to this