Microbial Toxicity of Mixtures of Organic Chemicals: Modeling and Validation for Non-Uniform Mixtures.

Abstract : Joint effects of binary and multi-component, uniform and non-uniform mixtures assayed in our microbial toxicity studies were found to be simply additive, or essentially simply additive. These results are in agreement with the conclusions reported in the literature on fish toxicity studies. Using QSAR models to predict single chemical toxicity and assuming perfect simple additivity, concentrations of the components in mixtures that would cause 50% inhibition were predicted. These predicted concentrations agreed well with the measured values over nearly three orders of magnitude with r2=0.80 at p=0.0001% for 610 sets of data points from 40 different mixtures on two different microorganisms. The overall average factor of error of these predictions was 1.82. The results of this study provide an impetus to utilize the large number of single chemical QSAR models reported in the literature by other researchers in predicting joint effects in the aquatic toxicology and ecotoxicological fields.