Department of Biology and Centre for Environmental and Marine Studies, University of Aveiro, Aveiro, Portugal.
Aquat Toxicol. 2011 Mar;102(1-2):114-22. doi: 10.1016/j.aquatox.2011.01.007. Epub 2011 Jan 25.
The toxicological assessment of chemical compounds released to the environment is more accurate when mixtures of chemicals and/or interactions between chemicals and natural stressors are considered. Ultraviolet radiation can be taken as a natural stressor since the levels of UV are increasing due to the decrease of its natural filter, the stratospheric ozone concentration. Therefore, a combination of chemical exposures and increasing UV irradiance in aquatic environments is likely to occur. In the current study, combined effects of carbendazim and ultraviolet radiation were evaluated, using selected life traits as endpoints on Daphnia magna. To design combined exposures, first single chemical and natural stressor bioassays were performed: a reproduction test with carbendazim and a reproduction, feeding inhibition and Energy budget test with ultraviolet radiation. Following single exposures, the combinations of stressors included exposures to UV radiation and carbendazim for a maximum exposure time of 4h, followed by a post-exposure period in chemically contaminated medium for a maximum of 15 days, depending on the endpoint, where the effects of the combined exposures were investigated. Statistical analyses of the data set were performed using the MixTox tool and were based on the conceptual model of Independent Action (IA) and possible deviations to synergism or antagonism, dose-ratio or dose-level response pattern. Both ultraviolet radiation and carbendazim as single stressors had negative impacts on the measured life traits of daphnids, a decrease on both feeding rates and reproduction was observed. Feeding rates and reproduction of D. magna submitted to combined exposures of ultraviolet radiation and carbendazim showed a dose-ratio deviation from the conceptual model as the best description of the data set, for both endpoints. For feeding inhibition, antagonism was observed when the UV radiation was the dominant item in combination, and for reproduction, synergism was observed when UV radiation dominated the exposure. From these results, the combined exposure of ultraviolet radiation and chemical compounds should also be considered for risk assessment as this study has shown that more severe effect than expected by single chemical assessment might be observed.
当考虑化学混合物和/或化学物质与自然胁迫之间的相互作用时，对释放到环境中的化学化合物的毒理学评估更为准确。紫外线可以被视为一种自然胁迫，因为由于平流层臭氧浓度的自然过滤器减少，紫外线水平正在增加。因此，在水生环境中，化学暴露和紫外线辐射增加的组合可能会发生。在当前的研究中，使用大型溞的选定生命特征作为终点，评估了多菌灵和紫外线辐射的联合效应。为了设计联合暴露，首先进行了单一化学物质和自然胁迫物的生物测定：使用多菌灵进行繁殖试验，使用紫外线进行繁殖、摄食抑制和能量预算试验。在单一暴露之后，包括紫外线辐射和多菌灵暴露的胁迫组合，暴露时间最长为 4 小时，然后在化学污染介质中进行最长 15 天的暴露后期，具体取决于终点，在此期间研究了联合暴露的影响。数据集的统计分析使用了 MixTox 工具，并基于独立作用（IA）的概念模型和协同作用或拮抗作用、剂量比或剂量水平反应模式的可能偏差。紫外线辐射和多菌灵作为单一胁迫物对大型溞的测量生命特征都有负面影响，观察到摄食率和繁殖都降低。紫外线辐射和多菌灵联合暴露的大型溞的摄食率和繁殖率显示出与概念模型的剂量比偏差，这是对数据集的最佳描述，对于这两个终点都是如此。对于摄食抑制，当紫外线辐射是组合中的主要因素时，观察到拮抗作用，而对于繁殖，当紫外线辐射占主导地位时，观察到协同作用。从这些结果可以看出，对于风险评估，也应该考虑紫外线辐射和化学化合物的联合暴露，因为本研究表明，与单一化学评估预期的相比，可能会观察到更严重的影响。
