QSAR PARAMETERS FOR TOXICITY OF ORGANIC-CHEMICALS TO NITROBACTER

Concern for the effects of toxic chemicals on the environment leads the search for better bioassay test organisms and simpler test procedures. Nitrobacter was used successfully as a test organism, and the serum bottle technique presented in this paper is an effective and simple method for determining the 50% inhibition concentration(IC50) of toxic chemicals. A total of 43 phenols, benzenes, and aliphatics, including many chlorinated chemicals, were used in the experiments. The test results (IC50) correlate well with the quantitative-structure-activity-relationship parameters, such as log P, the solvatochromic parameters, and molecular connectivity indexes. Specifically, the QSARs (either with log P or with log S) for nonphenolic toxicants may be used to predict potential toxicity to Nitrobacter. The log P QSAR for phenolic toxicants also is adequate. The solvatochromic parameter QSAR correlates well with all toxicants and is free from a collinearity problem. The molecular connectivity indexes QSAR for each class of toxicant show good correlation. The QSAR for all toxicants also is adequate and free of degrading collinearity.