Mortality and industrial hygiene study of workers exposed to polychlorinated biphenyls

Because of the demonstrated toxic effects on animals resulting from exposure to polychlorinated biphenyls (PCBs), the National Institute for Occupational Safety and Health conducted a retrospective cohort mortality study of 2,567 workers in two plants where PCBs were used in the manufacture of electrical capacitors. All workers included in the study were employed for at least 3 months in areas of the plants where PCBs were used. The vital status of 98% of the two cohorts was determined, and 39,018 person-years were accumulated. All-cause mortality was lower than expected (163 obs. vs 182.4 exp.) as well as all cancer mortality (39 obs. vs 43.8 exp.). Excess mortality was noted for rectal cancer (4 obs. vs 1.19 exp.) and liver cancer (3 obs. vs 1.07 exp.), although neither excess was statistically significant. In one of the plants the observed mortality due to cirrhosis of the liver was also elevated. The results of detailed industrial hygiene surveys conducted in each plant are also presented.