In the last decade advances in the analytic methods for quantification of polychlorinated biphenyls (PCBs) have resulted in widespread availability of congener-specific analysis procedures, and large amounts of data on PCB congener profiles in soil, air, water, sediments, foodstuffs, and human tissues have become available. These data have revealed that the PCB residues in environmental media and human tissues may not closely resemble any of the commercial PCB mixtures, depending on source of exposure, bioaccumulation through the food chain, and weathering of PCBs in the environment. At the same time, toxicological research has led to a growing awareness that different classes of PCB congeners have different profiles of toxicity. These advances in analytic techniques and toxicological knowledge are beginning to influence the risk assessment process. As the data from ongoing PCB studies assessing the mediators of neurobehavioral outcomes in children are published, the weight of evidence for PCB effects on neurodevelopment is growing. Studies in Taiwan, Michigan (USA), New York (USA), Holland, Germany, and the Faroe Islands have all reported negative associations between prenatal PCB exposure and measures of cognitive functioning in infancy or childhood. The German study also reported a negative association between postnatal PCB exposure and cognitive function in early childhood--a result that had not been found in previous studies. Only one published study in North Carolina (USA) has failed to find an association between PCB exposure and cognitive outcomes. Despite the fact that several more recent studies have used congener-specific analytic techniques, there have been only limited attempts to assess the role of specific PCB congeners or classes of congeners in mediating neurodevelopmental outcomes. From a statistical standpoint, attempts to determine the role of individual congeners in mediating outcomes are hampered by the fact that concentrations of most individual congeners are highly correlated with each other and with total PCBs. From a toxicological standpoint, these efforts are hampered by the fact that many of the PCB congeners present in human tissues have never been studied in the laboratory, and their relative potency to produce nervous system effects is unknown. More complete information on the health effects of various congeners or congener classes would allow more informed scientific and risk assessment decisions. Key words: children's health, congeners, neurobehavioral outcomes, neuropsychological function, polychlorinated biphenyls. Environ Health Perspect 111:357-376 (2003). doi: 10.1289/ehp.5461 available via http://dx.doi.org/[Online 29 January 2003]
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A number of epidemiological studies to assess the neuropsychological consequences of developmental exposure to PCBs have been initiated over the last decade or so. These studies have extended previous epidemiological research on the developmental neurotoxicity of PCBs, as well as used modern analytic technology for quantification of individual PCB congeners. The U.S. Environmental Protection Agency (EPA) intends to reassess the health effects of PCBs, incorporating information on health effects of PCB congeners or groups of congeners to the extent possible. This review focuses on recent epidemiological studies for which congener-specific exposure data are available. Findings from earlier studies reporting only total PCB concentrations are also summarized to facilitate cross-study comparisons for consistency...