Faculty of Engineering, Hokkaido University, N13W8, Sapporo, 060-8628, Japan.
Graduate School of Engineering, Hokkaido University, N13W8, Sapporo, 060-8628, Japan.
Chemosphere. 2020 Dec;261:127743. doi: 10.1016/j.chemosphere.2020.127743. Epub 2020 Jul 21.
Organophosphorus insecticides are known to be partly transformed to their respective oxons during the chlorination step of drinking water treatment. For most organophosphorus insecticides, the toxicological endpoint for determining acceptable daily intake levels is inhibition of acetylcholinesterase (AChE). Like the parent insecticides, oxons also inhibit AChE, so the presence of oxons in drinking water is also evaluated. However, no attention is paid to the possible presence of transformation products (TPs) other than oxons. In the present study, we determined whether the anti-AChE activity observed for chlorinated solutions of the organophosphorus insecticides malathion and methidathion could be solely attributed to the parent compounds and their oxons. Upon chlorination, both malathion and methidathion were immediately transformed to their oxons; the maximum transformation ratios were 60% and 30%, respectively, indicating that at least 40% and 70% of these compounds were transformed into other TPs. Before chlorination, malathion- and methidathion-containing solutions exhibited little to no anti-AChE activity, but the solutions showed strong activity after chlorination. The contributions of the parent insecticides and their oxons to the activities of the chlorinated samples were calculated from the concentrations of the compounds in the samples and dose-response curves for chemical standards of the compounds. For both the malathion-containing solution and the methidathion-containing solution, the calculated anti-AChE activities were almost the same as the observed activities at every chlorination time. This suggests that the observed activities could be attributed solely to the parent insecticides and their oxons, indicating that other TPs need not be considered.
有机磷杀虫剂在饮用水处理的氯化步骤中会部分转化为各自的氧代物。对于大多数有机磷杀虫剂，确定可接受的每日摄入量水平的毒理学终点是乙酰胆碱酯酶（AChE）的抑制。与母体杀虫剂一样，氧代物也抑制 AChE，因此也评估饮用水中氧代物的存在。然而，人们没有注意到除氧代物以外的转化产物（TPs）的可能存在。在本研究中，我们确定了在马拉硫磷和甲拌磷这两种有机磷杀虫剂的氯化溶液中观察到的抗 AChE 活性是否可以仅仅归因于母体化合物及其氧代物。氯化后，马拉硫磷和甲拌磷立即转化为氧代物；最大转化率分别为 60%和 30%，表明至少有 40%和 70%的这些化合物转化为其他 TPs。在氯化之前，含有马拉硫磷和甲拌磷的溶液几乎没有抗 AChE 活性，但氯化后溶液表现出很强的活性。从样品中化合物的浓度和化合物化学标准的剂量-反应曲线计算出母体杀虫剂及其氧代物对氯化样品活性的贡献。对于含马拉硫磷的溶液和含甲拌磷的溶液，计算出的抗 AChE 活性与每个氯化时间的观察活性几乎相同。这表明观察到的活性可以仅仅归因于母体杀虫剂及其氧代物，表明不需要考虑其他 TPs。
