Evaluation of the combined toxicity of 15 pesticides by uniform design.
BACKGROUND
Environmental pesticides, including insecticides and herbicides, are frequently encountered as mixtures and threaten non-target organisms in water. Evaluation of the combined toxicity of diverse pesticides with various concentration combinations is important, especially using limited experimental effort. Uniform design (UD) is one optimal experimental technique that can rationally arrange the concentrations of mixture components so that, with a minimum number of experimental runs, the combined toxicity of multiple pesticide mixtures can be evaluated.


RESULTS
The concentration compositions of 18 pesticide mixture points designed by UD covered almost all possible concentration ranges of the mixture components on account of the two merits of 'space filling' and 'multiple levels'. The combined toxicities of 18 mixture rays extended by using the fixed-ratio ray design (FRRD) from 18 UD mixture points were evaluated by concentration addition (CA) and independent action (IA) models. It was found that the concentration-response curves (CRCs) predicted by CA were, on the whole, located between the 95% confidence intervals of the experimental CRCs, which implied that the combined toxicity of the pesticide mixture rays could be evaluated by CA. The CRCs predicted by IA were very similar to those from CA.


CONCLUSIONS
The model developed from the UD mixture rays can effectively simulate mixtures with arbitrary concentration compositions of 15 pesticides. The CA model can accurately evaluate and predict the combined toxicity of the pesticides, which provides a useful tool for risk assessment of a mixture of multiple pesticides in the aquatic environment.
Zhang
Ya-Hui
YH
State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, People's Republic of China.
Liu
Shu-Shen
SS
Liu
Hai-Ling
HL
Liu
Zheng-Zao
ZZ
D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D006540:Herbicides / Q000633:toxicity*; D007306:Insecticides / Q000633:toxicity*; D018675:Toxicity Tests / Q000379:methods*; D014733:Vibrio / Q000187:drug effects; D014874:Water Pollutants, Chemical / Q000633:toxicity*
D006540:Herbicides; D007306:Insecticides; D014874:Water Pollutants, Chemical