Occupational exposure to polychlorinated biphenyls and cancer risk.

Polychlorinated biphenyls (PCBs) are a class of chemicals characterized by a long-term persistence and diffusion in the environment, and by bioaccumulation through the food chain. The highest exposures occurred in occupational cohorts through inhalation or skin absorption in work environments. These cohorts can therefore provide important information on health risk from exposure to PCBs in the general population. To provide comprehensive evidence on cancer risk from PCB exposure, we have thus reviewed the epidemiological studies on workers occupationally exposed to PCBs. Overall, no excess for all cancer mortality was observed in the six studies providing information (573 cancer deaths versus 630.4 expected, corresponding to a standardized mortality ratio (SMR) of 91). Among neoplasms potentially related to PCB exposure, there were 12 deaths from liver cancer compared with 9.5 expected (SMR=126). No excess was found for cancers of the breast (40 observed versus 47.4 expected, SMR=84) and of the lymphatic and haematopoietic system (51 observed versus 53.2 expected, SMR=96). Therefore, studies on occupational exposure to PCBs do not show any excess in all cancer mortality, or in mortality for specific cancer sites of interest.