Laboratory of Evolutionary Stress Ecology and Ecotoxicology, University of Leuven, Leuven 3000, Belgium.
Environ Sci Technol. 2020 Sep 15;54(18):11476-11484. doi: 10.1021/acs.est.0c03848. Epub 2020 Aug 31.
The exposure order may strongly affect the impact of stressors, yet is largely ignored for the frequently occurring combinations of toxicants with natural stressors. We tested how exposure order shaped the interactive effects of serial exposure to the pesticide chlorpyrifos and to a heat spike in the larvae of the mosquito . Notably, the chlorpyrifos-induced mortality was much more magnified by the heat spike and a synergism was already detected at the low concentration when exposure to chlorpyrifos followed the heat spike. This suggests that the preceding heat spike weakened the larvae as reflected in their lower net energy budget, moreover the chlorpyrifos-induced inhibition of its target enzyme (acetylcholinesterase) was only magnified by the heat spike when it was the first stressor. Also the chlorpyrifos-induced reduction in heat tolerance was stronger when the pesticide pulse followed the heat spike, and was buffered by the heat spike when this was the second stressor. Our results provide the first evidence that the exposure order can strongly change the magnifying effect of an important climate change factor on the toxicity of a pesticide. This highlights the importance of exposure order in ecological risk assessment of toxicants under realistic combinations with natural stressors.
暴露顺序可能会强烈影响应激源的影响，但对于经常同时存在的有毒物质与自然应激源的组合，这一因素在很大程度上被忽视了。我们测试了暴露顺序如何塑造连续暴露于杀虫剂毒死蜱和蚊子幼虫热峰的相互作用效应。值得注意的是，热峰大大加剧了毒死蜱引起的死亡率，而且当暴露于毒死蜱后紧接着暴露于热峰时，即使在低浓度下也已经检测到协同作用。这表明，先前的热峰削弱了幼虫的活力，表现为其净能量预算降低；此外，只有当热峰是第一个应激源时，毒死蜱才会加剧其靶酶（乙酰胆碱酯酶）的抑制作用。而且，当农药脉冲紧随热峰时，毒死蜱引起的耐热性降低更为强烈，而当热峰是第二个应激源时，热峰会缓冲这种降低。我们的研究结果首次提供了证据，表明暴露顺序可以强烈改变气候变化因素对杀虫剂毒性的放大效应。这凸显了在现实条件下考虑有毒物质与自然应激源的组合时，暴露顺序在生态风险评估中的重要性。
