Background exposure to PCDDs/PCDFs/PCBs and its potential health effects : a review of epidemiologic studiesT

Herewe reviewepidemiologic studies dealingwith the dietary intake and the body burden of polychlorinated dibenzo-p-dioxins (PCDDs)/polychlorinateddibenzo-furans (PCDFs)/ polychlorinated biphenyls (PCBs) in the general population, and potential adverse health effects of these substances, especially on the risk of diabetes mellitus and endometriosis, and on thyroid function and the neurodevelopment of infants. Themean ormedian intake of dioxin-related compounds among the general populations of various countries is lower than the maximum tolerable daily intake (TDI) set by the WHO in 1998 (4pg TEQ/kg/day). However, there have been few reports on the distribution of intake and the proportion of subjects whoseexposure levels exceed themaximumTDI. Atpresent, it remains unclearwhether background exposure to dioxin-related compounds is associated with increased risk of diabetes (because of lack of longitudinal studies), endometriosis (because of lack of studieswithsufficient statistical power), or altered thyroid function (because of inconsistent results on humans). Consistent results have been reported for the association between exposure to background levels of PCBs/dioxins, especially trans-placental PCBs, and defective neurodevelopment of infants intheU. S. andEurope. Thus, efforts shouldbemadetofurtherdecreasethebodyburden among women of reproductive age by reducing the release of PCDDs/PCDFs/PCBs into the environment.