Prenatal Exposure to Polychlorinated Biphenyls in Indoor Air and Neurodevelopmental Disorders

Lower-chlorinated polychlorinated biphenyls (LC-PCBs) likely act through toxicological mechanisms distinct from higher-chlorinated PCBs, which have been studied more extensively. Although LC-PCBs more readily cross the placenta and may disrupt foetal development, their contributions to neurodevelopmental disorders remain unclear. We aimed to investigate the association between prenatal exposure to LC-PCBs in indoor air and attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). We included 3797 children whose mothers lived in one of two partially PCB-contaminated housing areas in Greater Copenhagen at some point during the 3.6-year period before conception through pregnancy. PCB exposure was based on indoor air measurements of seven indicator PCBs (PCB-28, -52, -101, -118, -138, -153, and -180) and cumulated according to years of maternal residence. ADHD and ASD diagnoses were obtained from national registers. We estimated adjusted hazard ratios (aHRs) and corresponding 95% confidence intervals (CIs) using Cox regression models. Prenatal PCB exposure ≥ 300 ng/m3 × year was associated with higher risk of ADHD (aHR 1.53 95% CI: 1.09–2.15) and showed a tendency towards higher risk of ASD (aHR 1.35 95% CI: 0.87–2.08) compared with exposure < 300 ng/m3 × year. Our findings suggest that prenatal exposure to LC-PCBs in indoor air may disrupt neurodevelopmental programming and increase risk of ADHD and ASD when living one year with levels above the Danish Health Authority’s lower action level (300 ng/m3).