Modeling Joint Effects of Mixtures of Chemicals on Microorganisms UsingQuantitative Structure Activity Relationship Techniques. Phase 3

摘要

A laboratory procedure was developed to measure the toxicity of 35 organicchemicals in the soil medium using the respirometeric technique. These toxicity assays were carried out using a commercially available surrogate test culture of microorganisms. Reproducibility test were done on 12 of the chemicals yielding an average standard deviation of 0.034 and a coefficient of variation of 0.08. These tests were also repeated at different moisture holding capacities of 33%, 50%, 80% and 100% for six chemicals yielding an average standard deviation of 0.20 and coefficient of variation of 0.27. Using a part of the experimental IC50 results as a training set, Quantitative structure Activity Relationship (QSAR) models were developed to predict the toxicity of 12 chemicals in the testing set. Joint toxicity of 35 different combinations of mixtures in the soil were also measured at equitoxic ratios. The joint effects in there mixtures were analyzed for simple additivity. Result indicate that the test chemicals exhibited simple additivity when acting jointly in a uniform mixture. A QSAR approach is proposed to predict mixture toxicity based on single chemical QSAR models.