Centre for Environmental Sustainability, The School of the Environment, University of Technology, Sydney, NSW 2007, Australia.
Chemosphere. 2011 Nov;85(10):1568-73. doi: 10.1016/j.chemosphere.2011.07.061. Epub 2011 Sep 16.
Pesticides predominantly occur in aquatic ecosystems as mixtures of varying complexity, yet relatively few studies have examined the toxicity of pesticide mixtures. Atrazine, chlorothalonil and permethrin are widely used pesticides that have different modes of action. This study examined the chronic toxicities (7-d reproductive impairment) of these pesticides in binary and ternary mixtures to the freshwater cladoceran Ceriodaphnia cf. dubia. The toxicity of the mixtures was compared to that predicted by the independent action (IA) model for mixtures, as this is the most appropriate model for chemicals with different modes of action. Following this they were compared to the toxicity predicted by the concentration addition (CA) model for mixtures. According to the IA model, the toxicity of the chlorothalonil plus atrazine mixture conformed to antagonism, while that of chlorothalonil and permethrin conformed to synergism. The toxicity of the atrazine and permethrin mixture as well as the ternary mixture conformed to IA implying there was either no interaction between the components of these mixtures and/or in the case of the ternary mixture the interactions cancelled each other out to result in IA. The synergistic and antagonistic mixtures deviated from IA by factors greater than 3 and less than 2.5, respectively. When the toxicity of the mixtures was compared to the predictions of the CA model, the binary mixture of chlorothalonil plus atrazine, permethrin plus atrazine and the ternary mixture all conformed to antagonism, while the binary mixture of chlorothalonil plus permethrin conformed to CA. Using the CA model provided estimates of mixture toxicity that did not markedly underestimate the measured toxicity, unlike the IA model, and therefore the CA model is the most suitable to use in ecological risk assessments of these pesticides.
农药主要以复杂程度不同的混合物形式存在于水生生态系统中，但相对较少的研究考察了农药混合物的毒性。莠去津、百菌清和氯菊酯是广泛使用的农药，它们具有不同的作用模式。本研究考察了这些农药在二元和三元混合物中对淡水溞类 Ceriodaphnia cf. dubia 的慢性毒性（7 天生殖损伤）。将混合物的毒性与混合物独立作用（IA）模型预测的毒性进行了比较，因为对于具有不同作用模式的化学物质，IA 模型是最合适的模型。之后，将其与混合物浓度加和（CA）模型预测的毒性进行了比较。根据 IA 模型，百菌清加莠去津混合物的毒性符合拮抗作用，而百菌清和氯菊酯的毒性符合协同作用。莠去津和氯菊酯混合物以及三元混合物的毒性符合 IA，这意味着这些混合物的成分之间没有相互作用，或者在三元混合物的情况下，相互作用相互抵消，导致 IA。协同和拮抗混合物与 IA 的偏差分别大于 3 和小于 2.5。当将混合物的毒性与 CA 模型的预测进行比较时，百菌清加莠去津、氯菊酯加莠去津的二元混合物和三元混合物均符合拮抗作用，而百菌清加氯菊酯的二元混合物符合 CA。与 IA 模型不同，CA 模型用于这些农药的生态风险评估时，提供的混合物毒性估计值不会明显低估实测毒性。因此，CA 模型是最适合使用的模型。
