Exposure to airborne polychlorinated biphenyls during childhood and risk of asthma, allergic rhinoconjunctivitis, atopic eczema, and respiratory infections: a register-based cohort study

Background: Polychlorinated biphenyls (PCBs) are industrial chemicals commonly used in building materials before their ban decades ago. PCBs are immunotoxic and childhood exposure may impair the developing immune system. We examined the risk of asthma, allergic rhinoconjunctivitis, atopic eczema, and respiratory infections among children exposed to lower-chlorinated PCBs in indoor air. Methods: The study included 13 633 children residing in one of two partly PCB contaminated residential areas in Greater Copenhagen, Denmark at least one day before their 15th birthday during the period 1970–2018. Exposure was quantified using indoor air measurements combined with register-based relocation dates (ng/m3 PCB_total × years at the address). Register-based hospital discharges and medication claims defined the outcomes. We estimated hazard ratios (HR) and 95% confidence intervals (CI) using Cox regression with time-varying cumulated exposure lagged six months, adjusted for child sex, ancestry, and calendar year. Results: We identified 890 (7%) asthma cases, 1379 (10%) allergic rhinoconjunctivitis cases, 46 (<1%) atopic eczema cases, and 2058 (16%) respiratory infections cases. We observed no association between PCB and any of the outcomes: adjusted HR per interquartile range increase in PCB_year for asthma: 1.00 (95% CI: 0.99-1.01); allergic rhinoconjunctivitis: 1.00 (95% CI: 1.00-1.00); atopic eczema: 1.02 (95% CI: 1.00-1.04); respiratory infections: 1.00 (95% CI: 0.99-1.00). Conclusion: We found no evidence in support of changes to risk of developing asthma, allergic rhinoconjunctivitis, atopic eczema, and respiratory infections among children exposed to PCBs in indoor air.