Environmental Fate and Human Bioaccumulation of Endosulfan after Its Prohibition: Evidence from Exposure Assessment and Molecular Docking Analyses

Endosulfan, an organochlorine insecticide composed of two isomers, α-endosulfan (isomer I) and β-endosulfan (isomer II), was completely banned in China in 2019. Nevertheless, its environmental persistence and human bioaccumulation remain major concerns. In this study, Taizhou, Zhejiang Province, was selected as the research area, where concentrations of endosulfan isomers were systematically measured in multiple environmental media (soil, air, indoor dust, and food) and in human serum samples collected in 2022. The results showed that the median concentration of endosulfan II in human serum (83.46 ng/g lw) was significantly higher than that of endosulfan I (37.17 ng/g lw). Selective bioaccumulation of endosulfan II in the human body through combined exposure and metabolic mechanisms. Exposure assessment indicated that food was the dominant exposure pathway; however, the contribution of dust to endosulfan II exposure (33.5%) was notably higher than that of endosulfan I (16.1%). Furthermore, molecular docking analysis revealed that endosulfan II exhibited stronger binding affinity to the Megalin protein (binding energy: –5.26 kJ/mol), but weaker binding to cytochrome P450 enzymes (–6.32 kJ/mol), suggesting slower metabolism and delayed excretion. Overall, this study provides new molecular-level evidence for understanding the persistence of banned pesticides, contributing to improved residue management and understanded for accumulation of pollutants in the body.