PCB-induced neurodevelopmental toxicity in human infants and its potential mediation by endocrine dysfunction.

Polychlorinated biphenyls (PCBs) cross the placenta and expose the fetus to the body burden of the mother. Additionally, the breastfed baby is postnatally exposed to PCBs in maternal milk. Among the broad spectrum of biological effects interaction with endocrine systems and developmental neurotoxicity are prominent features of these chemical mixtures. Associations between neurodevelopmental delay and prenatal or early postnatal PCB-exposure at environmental levels have been reported in several cohort studies. Adverse effects were found to be associated with early developmental PCB-exposure, although there are discrepancies between studies in terms of confounding, effective PCB-matrix, as well as spectrum and persistence of effects. From these cohort studies alone the causative role of PCBs in producing neurodevelopmental adversity still cannot be considered proven, but experimental findings do provide evidence for the developmental neurotoxicity of PCBs. The underlying mechanisms of this action is still unknown. However, interaction with endocrine systems, namely the estrogen/androgen and, particularly, the thyroid hormone systems are discussed as a possible explanation for PCB-induced neurodevelopmental adversity. Some evidence in this respect is being reviewed.