Effects of prenatal exposure to organochlorines on thyroid hormone status in newborns from two remote coastal regions in Québec, Canada

Several prospective studies have revealed that prenatal exposure to polychlorinated biphenyls (PCBs) and other organochlorine compounds (OCs) affect neurodevelopment during infancy. One of the mechanisms by which PCBs might interfere with neurodevelopment is a deficit in thyroid hormone (TH) concentrations. We investigated the potential impact of transplacental exposure to PCBs and hexachlorobenzene (HCB) on TH concentrations in neonates from two remote coastal populations exposed to OCs through the consumption of seafood products. Blood samples were collected at birth from the umbilical cord of neonates from Nunavik ( n=410) and the Lower North Shore of the St. Lawrence River ( n=260) (Québec, Canada) for thyroid parameters [thyroid-stimulating hormone (TSH), free T 4 (fT 4), total T 3 (tT 3), and thyroxine-binding globuline (TBG)] and contaminants analyses. In multivariate models, umbilical cord plasma concentrations of PCB 153, the predominant PCB congener, were not associated with TH and TSH levels in both populations. Prenatal exposure to HCB was positively associated with fT 4 levels at birth in both populations (Nunavik, β=0.12, p=0.04; St. Lawrence, β=0.19, p