PREDICTING MICROBIAL TOXICITY OF NONUNIFORM MULTICOMPONENT MIXTURES OF ORGANIC CHEMICALS

Three schemes proposed in the literature for analyzing joint toxic effects of multicomponent mixtures on fish, namely the additivity index (AI), the mixture toxicity index (MTI), and the similarity parameter (λ) are evaluated in this study for microbial toxicity. A new approach is proposed to establish acceptance limits for the similarity parameter, λ, based on experimental errors and uncertainties. Quantitative structure activity relationship (QSAR) techniques are then used to develop a model to predict the concentrations of components in mixtures that would jointly cause 50% inhibition of microbial respiration. The application of this approach is demonstrated on the experimental toxicity data of six eight-component organic chemical mixtures on microorganisms.

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