School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada.
Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Environ Toxicol Chem. 2019 May;38(5):1093-1103. doi: 10.1002/etc.4386. Epub 2019 Apr 3.
Receiving waters from agricultural areas can contain multiple pesticides such as the neonicotinoid imidacloprid and the fungicide tebuconazole, leading to the potential for aquatic life to be exposed to such mixtures. In the present study, the effects of tebuconazole were tested alone and in binary mixtures with imidacloprid on 4 aquatic invertebrates: Chironomus dilutus, Hyalella azteca, Lumbriculus variegatus, and Neocloeon triangulifer. Acute (96-h) median lethal concentrations (LC50s) were derived for individual compounds and used to design a binary mixture study to determine cumulative effects. The LC50s showed that imidacloprid was more potent than tebuconazole by 1 to 3 orders of magnitude for the 4 species. Lethality data from mixture experiments were analyzed using MIXTOX to determine deviations from independent action, followed by the model deviation ratio (MDR) technique to determine the biological significance and reproducibility of observed mixture effects. MIXTOX showed that the cumulative toxicities of imidacloprid-tebuconazole differed between the species: for C. dilutus there was no deviation from independent action; however, for H. azteca the mixture was antagonistic (specifically dose ratio-dependent), and for N. triangulifer it was synergistic. The MDR method showed that only observations with H. azteca significantly deviated from independent action. Because of the lack of evidence of a clear deviation from independent action and the much greater potency of imidacloprid, the weight of evidence indicates that the presence of tebuconazole is unlikely to appreciably increase the hazard from imidacloprid exposure to aquatic invertebrates. Environ Toxicol Chem 2019;00:1-17. © 2019 SETAC.
受农业区影响的接收水域可能含有多种农药，如新烟碱类杀虫剂吡虫啉和杀菌剂戊唑醇，这使得水生生物有可能接触到这些混合物。在本研究中，单独测试了戊唑醇以及与吡虫啉的二元混合物对 4 种水生无脊椎动物（摇蚊幼虫、美洲螯虾、赤子爱胜蚓和三叶真蚓）的影响。为了设计二元混合物研究以确定累积效应，分别得出了各化合物的急性（96 小时）半数致死浓度（LC50）。LC50 表明，吡虫啉对 4 种物种的毒力比戊唑醇高 1 到 3 个数量级。通过 MIXTOX 分析混合物实验的致死数据，以确定是否存在独立作用的偏差，然后使用模型偏差比（MDR）技术确定观察到的混合物效应的生物学意义和重现性。MIXTOX 表明，吡虫啉-戊唑醇混合物对不同物种的累积毒性存在差异：对于摇蚊幼虫，不存在独立作用的偏差；然而，对于美洲螯虾，混合物具有拮抗作用（特别是剂量比依赖性），对于三叶真蚓，混合物具有协同作用。MDR 方法表明，只有美洲螯虾的观察结果明显偏离独立作用。由于缺乏明显偏离独立作用的证据，而且吡虫啉的毒性要大得多，因此证据表明，戊唑醇的存在不太可能显著增加水生无脊椎动物接触吡虫啉的危害。Environ Toxicol Chem 2019;00:1-17. © 2019 SETAC.
