[Polychlorinated biphenyl(PCBs, PCDDs, PCDFs)]

Dioxins include polychlorinated dibenzo-p-dioxins(PCDDs), polychlorinated dibenzofurans(PCDFs), and part of polychlorinated biphenyls(PCBs). Only the compounds that are chlorinated at the 2,3,7, and 8 positions have characteristic dioxin toxicity. PCDDs, PCDFs and PCBs accumulate in the food chain due to their high lipophilicity, high stability, and low vapor pressure. They are not metabolized easily, however their hydroxylate are detected in feces. PCBs and dioxins cause a wide range of endocrine disrupting effects in experimental animals, wildlife, and humans. Endocrine related effects of PCBs and dioxins on thyroid hormones, neurodevelopment and reproductive development are summarized. In addition, some studies of exposure and endocrine-related effects in human populations are presented.