ANALYZING AND MODELING TOXICITY OF MIXTURES OF ORGANIC-CHEMICALS TO MICROORGANISMS

Inhibition concentrations of 50 organic chemicals acting singly and jo intly in different combinations on activated sludge microorganisms and a surrogate test microbial culture, Polytox, were measured using the respirometric technique. The suitability of the surrogate test culture in toxicity studies was evaluated against activated sludge microorgan isms. The toxicity correlation between the two organisms was highly si gnificant with coefficient of determination of 0.922. The joint toxic effects of several 2-, 8-, and 10-component mixtures on the surrogate cultures were found to be simply additive. Using the single chemical t oxicity data, Quantitative Structure Activity Relationship (QSAR) mode ls were developed to relate toxicity to molecular structures of the ch emicals. The application of these QSAR models in predicting joint effe cts in six 2-, six 8-, and ten 10-component mixtures was demonstrated. These predictions agreed with the experimentally measured values with coefficient of determination of 0.866 at p < 0.0001.