Abstract
Dioxins are highly toxic to foetuses and prenatal exposure leads to adverse health effects; however, the metabolic pathways involved in dioxin excretion are poorly understood. We determined the dynamics of maternal-to-foetal dioxin transfer during normal pregnancy and how foetuses eliminate polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and non-ortho polychlorinated biphenyls. Dioxin levels in maternal blood, cord blood, placenta, vernix caseosa, meconium, and amniotic fluid were analysed by high-resolution gas chromatography/mass spectrometry. The average levels of total dioxins, expressed as picograms of toxic equivalency quantity per gram of lipid and in parentheses, dioxin fraction, with maternal blood levels arbitrarily set as 100%, were as follows: maternal blood, 15.8 (100%); placenta, 12.9 (81.5%); cord blood, 5.9 (37.2%); vernix caseosa, 8.4 (53.2%); meconium, 2.9 (18.2%); and amniotic fluid, 1.5 (9.2%). Similar proportions were observed for each dioxin congener. Thus, the highest content of foetal dioxins was observed in the vernix caseosa, indicating that this is the major site of dioxin excretion in human foetuses.
Highlights
Prenatal exposure to dioxins can result in various adverse health effects[1]
The highest content of dioxins in foetuses was observed in the vernix caseosa, followed in descending order by cord blood, meconium, and amniotic fluid
We observed that the level of dioxins in cord blood was approximately 40% of that in maternal blood
Summary
Yusho disease is caused by exposure to rice oil contaminated with non-ortho polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs), and polychlorinated dibenzo-p-dioxins (PCDDs). A previous study, in which we assessed dioxin levels in maternal blood, placenta, and cord blood[6], demonstrated that 1) the dioxin level in cord blood is approximately half of that in maternal blood, 2) congeners with a high toxic equivalency factor (TEF) value, such as 1,2,3,7,8-penta CDD and 2,3,4,7,8-penta CDF, are transferred from maternal blood to the placenta, and 3) PCDDs display an enhanced capacity for maternal blood-to-foetus transfer through the placenta as compared to PCDFs and non-ortho PCBs. the metabolic pathways responsible for dioxin excretion in the human foetus are not fully understood. It is thought that the material discharged from the foetus, including meconium and vernix caseosa, directly reflects the quantity of dioxins. The vernix caseosa has not been examined This pilot study aimed to determine the dynamics of maternal-to-foetal dioxin transfer, including vernix caseosa, during normal pregnancy
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