QSAR Parameters for Toxicity of Organic Chemicals to Nitrobacter

Abstract

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.