Recent decreasing trends of exposure to PCDDs/PCDFs/dioxin-like PCBs in general populations, and associations with diabetes, metabolic syndrome, and gout/hyperuricemia

The author reviewed recent reports about the blood levels and dietary intake of polychlorinated dibenzo-p-dioxins (PCDDs)/furans (PCDFs)/dioxin-like polychlorinated biphenyls (DL-PCBs) to investigate the trends of dioxin exposure, and epidemiologic studies on the associations of blood levels of dioxins with metabolic diseases. In recent years, dietary intake of dioxins has been decreasing, and the means are equal to or less than 1.0 pg Toxic Equivalents (TEQ)/kg/day in the general populations of several countries. The blood levels of dioxins are also decreasing, probably because of reduced dietary intake. Many cross-sectional studies reported positive associations between blood levels of some isomers or TEQ-based concentrations of PCDDs/PCDFs/DL-PCBs and diabetes in general populations. Three cohort studies on populations with heavy exposure and two nested case-control studies on general populations have also been published, but the results are inconsistent. Three large-scale cross-sectional studies and two cohort studies reported an association between blood levels of some isomers or TEQ-based concentrations of PCDDs/PCDFs/DL-PCBs and metabolic syndrome. In addition, three cross-sectional studies reported significant positive associations with gout/hyperuricemia. Further prospective studies and experimental studies are needed to establish cause-effect relationships, and to clarify the biological mechanisms for the association between background exposure to dioxins and potential health effects.