Mortality among capacitor workers exposed to polychlorinated biphenyls (PCBs), a long-term update.
Kimbrough RD, Krouskas CA, Xu W, Shields PG
Int Arch Occup Environ Health 88 85-101 01/01/2015
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.