Residual dioxins in Chinese schistosomiasis region and its eco-environmental risk

Dioxin is a general designation of polychlorinated dibenzo-p-dioxins （PCDDs） and polychlorinated dibenzofurans （PCDFs）. They are two series of tricyclic, almost planar, aromatic compounds, which are composed of 75 PCDD and 135 PCDF congeners,respectively. Among them, the most toxic congener is 2, 3, 7, 8-TCDD, with the suggested permissible level for human 10×10-9mg/（kg·d）-1. The environmental scientists have expressed much concern over these compounds since the 1980s. Chlorine-containing aromatic