Dose-response in perinatal exposure to polychlorinated biphenyls (PCBs): the Michigan and North Carolina cohort studies.

Two prospective, longitudinal studies-one in North Carolina and one in Michigan-have examined effects of prenatal polychlorinated biphenyl (PCB) exposure on behavioral and cognitive development in infants and children. The Michigan cohort was selected to overrepresent the offspring of women who had eaten relatively large quantities of Lake Michigan fish; the North Carolina cohort was drawn from the general population. Both studies collected umbilical cord serum and maternal serum and milk samples. In both studies, the children were assessed at birth, during infancy, and during the preschool period, and multivariate statistical analysis was used to control for confounding. When exposure was assessed in terms of maternal body burden, effects were seen only in the most heavily exposed children: the top 3-5% of the general population North Carolina sample and the top 11% of the fisheater sample in Michigan.