| hile experimental studies have demonstrated the carcinogenicity of certain types of commercially available polychlorinated biphenyls (PCBs), the data from human populations exposed to PCBs have been inconsistent. A retrospective cohort mortality study was undertaken of 44,497 workers at three electric utilities in the United States. The cohort consisted of full-time, male employees who had worked six months or more, had not been employed exclusively in nuclear units, and had been employed between January 1, 1950 and December 31, 1986. Vital status followup for the cohort was undertaken through December 31, 1988 and was 99% complete. The study was undertaken to determine the possible long-term health effects, particularly cancer, resulting from low level occupational exposures to PCBs for workers in the electric utility industry.;The exposure assessment for the study was conducted using expert panel and industrial hygiene walkthrough survey methods at each of the companies. A job exposure matrix, linking estimates of potential exposure to PCBs to work history information from personnel records, was developed. The results of the exposure assessment indicated that more than one third (36%) of the active person-years for the cohort were potentially exposed to PCBs, where potential exposure was defined as the presence of the chemical within electrical equipment in the worker's environment. Four occupational categories of workers (electricians, linemen, cable splicers, and riggers) were estimated to have direct contact with PCBs at each of the companies.;The combined cohort of electric utility workers experienced an overall mortality rate and an all cancers mortality rate that were lower than expected. The overall standardized mortality ratio (SMR) for all causes of death was 0.79 (0.77-0.81; 6,836 deaths); the all cancer SMR was 0.87 (0.83-0.92, 1513 deaths). The SMRs for liver cancer were elevated across all three companies in the cohort with an overall SMR of 1.23 (0.86-1.71, 35 deaths). Excess deaths due to skin cancer were evident for workers "ever exposed to PCBs" with an SMR of 1.21 (0.77-1.80, 24 deaths). Internally standardized rate ratio (SRR) analyses by cumulative hours of exposure to PCBs yielded a monotonically increasing dose-response gradient for skin cancer (33 deaths). The SRRs for the four consecutive exposure levels were 1.06, 1.62, 2.62, and 3.45, with a significant test for the linearity of trend (p... |
