Further Exploring Linear Concentration Addition and Independent Action for Predicting Non-interactive Mixture Toxicity

Since it is unrealistic to do an experimental mixture assessment on every possible combination, mathematical model plays an important role in predicting the mixture toxicity. The present study is devoted to the further application of linear concentration addition（CA）-based model（LCA） and independent action（IA）-based model（LIA） to predict the non-interactive mixture toxicity. The 26 mixtures including 312 data points were used to evaluate the predictive powers of LCA and LIA models. The models were internally validated using the leave-one-out cross-validation and y-randomization test, and the external validations were evaluated by the test tests. Both LCA and LIA models agree well with the experimental values for all mixture toxicity, and present high internally（R2 and Q2 〉 0.98） and externally（Q2F1, Q2F2, and Q2F3 〉 0.99） predictive power. The use of LCA and LIA led to improved predictions compared to the estimates based on the CA and IA models. Both LCA and LIA were found to be appropriate methods for modeling toxicity of non-interactive chemical mixtures.

Mixture Toxicities of Three Pesticides Having Different Time-Toxicity Profiles

In the environment,chemical pollutants always exist as mixtures.To evaluate mixture toxicity,we should ex-amine the concentration ratios and the concentration levels of mixture components as well as the interactive time between the components and testing organism.Selecting three pesticides,metribuzin(MET),dodine(DOD)and ri-domil(RID),as mixture components,Vibrio qinghaiensis sp.-Q67 as testing organism,and 96-well microplate as exposure experiment carrier,the luminescence inhibition toxicities of the pesticides and their binary mixtures at six exposure time points(0.25,2,4,8,12,and 16 h)were determined.The results showed that the three pesticides have different time-toxicity profiles.The toxicity of MET increases over time,and those of DOD and RID show a slight decrease or increase in the first 4 h,respectively,and then remain unchanged to 16 h.The toxicities of the binary mixtures consisting of the three pesticides depend on not only the mixture composition but also the exposure time.The time-toxicity profiles of all rays in MET-DOD mixture system are U-shaped curves,those in MET-RID system are basically monotonically increased and those in DOD-RID system are basically monotonically decreased.How-ever,our findings indicate that for the test substances,mixture toxicity can be predicted by the extended concentra-tion addition model.