Maternal exposure to polychlorinated biphenyls in indoor air and asthma, allergic rhinitis, atopic eczema, and respiratory tract infections in childhood

Polychlorinated biphenyls (PCBs) are industrial chemicals commonly found in food and building materials. PCBs are immunotoxic and may disturb the fetal programming of the immune and respiratory systems. We evaluated the association between maternal PCB exposure in indoor air and asthma, allergic rhinitis, atopic eczema, and respiratory infections in the offspring in the Health Effects of PCBs in Indoor Air (HESPAIR) cohort. This register-based study examined 7982 children born to mothers residing in two partially PCB contaminated residential areas in Greater Copenhagen before and/or during pregnancy. Children were included if their mothers at any point had lived in a contaminated or uncontaminated apartment in the period from 3.6 years prior to conception until the date of birth. PCB exposure was defined as mothers' number of years in an apartment prior to birth of the child multiplied with the PCB concentration in indoor air based on air measurements. Information on the outcomes was retrieved from the Danish health registers from 1977 to 2018. We estimated adjusted hazard ratios using Cox regression. Our main analyses revealed no association between maternal exposure to PCBs in indoor air and any of the studied allergic and respiratory outcomes. Findings of sensitivity analyses were consistent with main analyses. While these findings may appear reassuring for the considerable number of people living or working in PCB contaminated indoor environments, they should be interpreted with caution due to the indirect measure of exposure, incomplete registration of diagnoses, and lack of supporting evidence from comparable studies.