Cancer Risk following Residential Exposure to Airborne Polychlorinated Biphenyls: A Danish Register-Based Cohort Study

BACKGROUND: Polychlorinated biphenyls (PCBs) are biopersistent chemicals classified as human carcinogens. This classification is primarily based on evidence on higher-chlorinated PCBs found in food. The carcinogenic potential of airborne lower-chlorinated PCBs remains largely unexplored. OBJECTIVES: We aimed to investigate cancer risk following residential exposure to airborne PCBs. METHODS: Cancer risk was examined in the Health Effects of PCBs in Indoor Air (HESPAIR) cohort of 38,613 residents of two partly PCB-contaminated residential areas in Greater Copenhagen, identified by nationwide registries. PCB exposure was based on relocation dates and indoor air PCB measurements in subsets of apartments. Cancer diagnoses were extracted from the Danish Cancer Registry for the follow-up period of 1970–2018. We estimated adjusted hazard ratios with time-varying cumulative exposure and a 10-y lag using Cox regression. RESULTS: Overall risk of cancer was not associated with [Formula: see text] , [hazard ratio (HR) for high-exposed vs. low-exposed [Formula: see text]; 95% confidence interval (CI): 0.88, 1.09], but residents exposed to [Formula: see text] [Formula: see text] had higher risk of liver cancer (HR [Formula: see text]; 95% CI: 1.28, 6.15) and meningiomas (HR [Formula: see text]; 95% CI: 1.84, 6.64), with indications of exposure–response relationships. Results were suggestive of a higher risk of pancreatic cancer (HR [Formula: see text]; 95% CI: 0.95, 2.64) at the highest aggregated PCB level. For testis cancer, a higher risk was observed among residents exposed to [Formula: see text] [Formula: see text] relative to residents exposed to [Formula: see text] [Formula: see text] (HR [Formula: see text]; 95% CI: 1.41, 6.28), but the risk was not higher for residents exposed to [Formula: see text] [Formula: see text]. Apart from this, the risk of specific cancers was similar across exposure groups. DISCUSSION: In this, to our knowledge, first population-based cohort study of residential exposure to airborne PCBs, we found no association between exposure to PCBs in indoor air in private homes and the risk for most of the specific cancers. Higher risk of liver cancer and meningiomas were observed. https://doi.org/10.1289/EHP10605