The effects of prenatal exposure to polychlorinated biphenyls (PCBs) and related contaminants on the CNS function of infants born to women who had consumed Lake Michigan sports fish have been investigated in 236 children previously evaluated for PCB-related deficits in infancy and reassessed at four years of age in the Psychology Department, Wayne State University, Detroit, MI and the Michigan Department of Public Health, Lansing, MI. Prenatal exposure, indicated by umbilical cord serum PCB levels, was associated with poorer short term memory function on both verbal and quantitative tests and the adverse effects were dose dependent and not attributed to other variables. Exposure from nursing was unrelated to cognitive performance. The study demonstrates continuation of toxic effects through early childhood. 
COMMENT. Polychlorinated biphenyls were once used in industrial products and were banned in the United States in 1970. Residues persist in air, soil, water and sediments in lakes and can be detected in residents of industrialized countries. PCB levels are unusually high in sports fish from Lake Michigan and transplacental exposure to PCBs has been documented.