Polychlorinated dibenzofurans as a causal agent of fetal Yusho.

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dioxin-like PCBs) are highly-toxic environmental pollutants that are still ubiquitous. About 40 years ago, a mass food poisoning, termed "Yusho", occurred in western Japan, and the causal agent of Yusho was thought to be PCDFs. The preserved umbilical cords of babies who were born to mothers with Yusho 2-5 years after the outbreak of Yusho and diagnosed with fetal Yusho were recently obtained, and the concentrations of PCDDs, PCDFs, dioxin-like PCBs and polychlorinated biphenyls (PCBs) in these preserved umbilical cords were determined. Among babies with fetal Yusho, the pollutant concentrations in umbilical cords were compared between "black babies", a term that describes the dermatologic abnormality that is classically seen in fetal Yusho, and "non-black babies". There was almost no difference in the concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) toxic equivalents (TEQ) concentrations of PCDDs, PCDFs and dioxin-like PCBs found in these two groups of babies. Therefore, the Yusho infants with the dark brown skin pigmentation seemed to have a hypersensitive genetic predisposition to the production of melanin pigment in the skin after the exposure to these toxic compounds. The concentrations of PCDDs, PCDFs, dioxin-like PCBs and PCBs in the preserved umbilical cords of infants diagnosed with fetal Yusho and of healthy babies were also determined and compared. PCDDs, dioxin-like PCBs and PCBs were detected in both groups. PCDFs, however, were found at high concentration only in the babies with fetal Yusho. In 2,3,7,8-TCDD TEQ concentrations, 90% of the total TEQ concentrations were attributable to PCDFs after taking into account the baseline concentrations found in healthy babies. This evidence shows that fetal Yusho is caused by PCDF intoxication.