Cavallaro Michael C, Morrissey Christy A, Headley John V, Peru Kerry M, Liber Karsten
School of Environment and Sustainability, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Environ Toxicol Chem. 2017 Feb;36(2):372-382. doi: 10.1002/etc.3536. Epub 2016 Aug 12.
Nontarget aquatic insects are susceptible to chronic neonicotinoid insecticide exposure during the early stages of development from repeated runoff events and prolonged persistence of these chemicals. Investigations on the chronic toxicity of neonicotinoids to aquatic invertebrates have been limited to a few species and under different laboratory conditions that often preclude direct comparisons of the relative toxicity of different compounds. In the present study, full life-cycle toxicity tests using Chironomus dilutus were performed to compare the toxicity of 3 commonly used neonicotinoids: imidacloprid, clothianidin, and thiamethoxam. Test conditions followed a static-renewal exposure protocol in which lethal and sublethal endpoints were assessed on days 14 and 40. Reduced emergence success, advanced emergence timing, and male-biased sex ratios were sensitive responses to low-level neonicotinoid exposure. The 14-d median lethal concentrations for imidacloprid, clothianidin, and thiamethoxam were 1.52 μg/L, 2.41 μg/L, and 23.60 μg/L, respectively. The 40-d median effect concentrations (emergence) for imidacloprid, clothianidin, and thiamethoxam were 0.39 μg/L, 0.28 μg/L, and 4.13 μg/L, respectively. Toxic equivalence relative to imidacloprid was estimated through a 3-point response average of equivalencies calculated at 20%, 50%, and 90% lethal and effect concentrations. Relative to imidacloprid (toxic equivalency factor [TEF] = 1.0), chronic (lethality) 14-d TEFs for clothianidin and thiamethoxam were 1.05 and 0.14, respectively, and chronic (emergence inhibition) 40-d TEFs were 1.62 and 0.11, respectively. These population-relevant endpoints and TEFs suggest that imidacloprid and clothianidin exert comparable chronic toxicity to C. dilutus, whereas thiamethoxam induced comparable effects only at concentrations an order of magnitude higher. However, the authors caution that under field conditions, thiamethoxam readily degrades to clothianidin, thereby likely enhancing toxicity. Environ Toxicol Chem 2017;36:372-382. © 2016 SETAC.
非目标水生昆虫在发育早期容易受到慢性新烟碱类杀虫剂暴露的影响，这是由于反复的径流事件以及这些化学物质的长期残留。关于新烟碱类对水生无脊椎动物的慢性毒性研究仅限于少数物种，且是在不同的实验室条件下进行的，这往往妨碍了对不同化合物相对毒性的直接比较。在本研究中，使用摇蚊进行了全生命周期毒性试验，以比较3种常用新烟碱类杀虫剂的毒性：吡虫啉、噻虫胺和噻虫嗪。试验条件遵循静态更新暴露方案，在第14天和第40天评估致死和亚致死终点。羽化成功率降低、羽化时间提前和雄性偏向的性别比是对低水平新烟碱类暴露的敏感反应。吡虫啉、噻虫胺和噻虫嗪的14天半数致死浓度分别为1.52μg/L、2.41μg/L和23.60μg/L。吡虫啉、噻虫胺和噻虫嗪的40天半数效应浓度（羽化）分别为0.39μg/L、0.28μg/L和4.13μg/L。通过在20%、50%和90%致死和效应浓度下计算的等效值的三点响应平均值，估算了相对于吡虫啉的毒性当量。相对于吡虫啉（毒性当量因子[TEF]=1.0），噻虫胺和噻虫嗪的慢性（致死率）14天TEF分别为1.05和0.14，慢性（羽化抑制）40天TEF分别为1.62和0.11。这些与种群相关的终点和TEF表明，吡虫啉和噻虫胺对摇蚊具有相当的慢性毒性，而噻虫嗪仅在浓度高一个数量级时才产生相当的效应。然而，作者提醒，在田间条件下，噻虫嗪很容易降解为噻虫胺，从而可能增强毒性。《环境毒理学与化学》2017年；36：372 - 382。©2016 SETAC。
