Mortality among capacitor workers exposed to polychlorinated biphenyls (PCBs), a long-term update
Purpose Polychlorinated biphenyls (PCBs) are ubiquitous in the environment. Concerns have been raised about cancer and other disease risks. This follow-up mortality study of PCB workers addresses some of these concerns.
Methods Mortality among 7,061 PCB capacitor workers was updated through 2008 (287,712 person-years; mean follow-up 41 years). Adjusted standardized mortality ratios (SMRs) and 95 % confidence intervals (CIs) were calculated for USA and New York State referent rates. Standardized rate ratios (SRRs) were calculated based on employment duration and latency.
Results Standardized mortality ratios for all causes of death were statistically significantly lower in the total cohort (SMR 92; 95 % CI 89–96) and in males (SMR 88; 95 % CI 83–92), but not in females (SMR 100; 95 % CI 94–106). For all cancers combined, SMRs for the total cohort (SMR 103; 95 % CI 96–111) and for males (SMR 96; 95 % CI 87–105) did not differ from the expected rates, in contrast to females (SMR 114; 95 % CI 103–126). Buccal cavity and pharyngeal cancers were statistically increased in the combined cohort (SMR 169; 95 % CI 108–251) and in females (SMR 273; 95 % CI 131–502). Respiratory system malignancies were statistically lower in males (SMR 83; 95 % CI 70–97), while they were increased in females (SMR 143; 95 % CI 118–172). Melanomas were statistically significantly increased in male salaried workers only. No positive trends (SRRs) with increasing length of employment and increasing latency were found.
Conclusions The positive results lacking exposure–response relationships are subject to confounding and probably do not represent causal associations.