Background

Toxicants often occur simultaneously. Some combinations show synergistic combined effects that go far beyond what is predicted with current effect models. Up until now, only the combined additive effects of similar acting chemicals have been assessed accurately, whereas the combined effects of dissimilar acting chemicals have been greatly underestimated in many cases.

Results

Here, we use the individual tri-phasic concentration–response relationship of two toxicants with different modes of action to model their combined synergistic effect on Daphnia magna. The novel stress addition approach (SA) predicted the combined effects (LC₅₀) of different esfenvalerate and prochloraz combinations with an uncertainty factor of 2.8 at most, while the traditional effect addition (EA) and concentration addition (CA) approaches underestimated the combined effect by a factor of up to 150 and 660, respectively. Data of the single substance concentration–response relationships and on their combined effects enable to determine the degree of synergism. For the evaluation of the combined toxicant effect, we provide the approach as R package and as Indicate model (http://www.systemecology.eu/indicate/).

Conclusion

Adding stressors arithmetically, considering non-monotonic cause–effect relationships, is a decisive component in predicting the combined effects of multiple stressors within test systems. However, the extent of the synergistic effects that multiple stressors exert on populations within the ecosystem context is still highly controversial. Various processes are relevant at the ecosystem level, which are not considered in laboratory studies. However, the present work serves as a building block for understanding the effects of multiple stressors in the field.

中文翻译：

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模拟有毒混合物的协同效应

背景

毒物通常同时发生。一些组合显示出协同的组合效果，远远超出了当前效果模型所预测的效果。迄今为止，仅准确评估了相似作用化学品的组合加和作用，而在许多情况下，大大低估了不同作用化学品的组合加和作用。

结果

在这里，我们使用两种具有不同作用方式的毒物的各自的三相浓度-响应关系来模拟它们对大型蚤的综合协同作用。新的应力增加方法（SA）预测了综合效果（LC ₅₀）的不同esfenvalerate和prochloraz组合的不确定度最大为2.8，而传统的效果添加（EA）和浓度添加（CA）方法分别将组合效果低估了150和660。单一物质浓度-反应关系及其组合效应的数据可以确定协同作用的程度。为了评估组合的毒物效果，我们以R包和指示模型（http://www.systemecology.eu/indicate/）的形式提供了该方法。

结论

考虑到非单调的因果关系，以算术方式添加压力源是预测测试系统中多个压力源的组合影响的决定性组成部分。但是，多种压力源对生态系统环境中的种群产生协同效应的程度仍然存在很大争议。各种过程都与生态系统水平相关，而实验室研究中并未考虑这些过程。但是，当前的工作是了解该领域中多种压力源的影响的基础。