Quantitative structure-activity relationship for aromatic hydrocarbons on freshwater fish.

A quantitative structure-activity relationship (QSAR) was determined, according to Hansch's approach. The acute toxicity of nine aromatic hydrocarbons (benzene, toluene, ethylbenzene, o-xylene, m-xylene, p-xylene, isopropylbenzene, n-propylbenzene, butylbenzene) was evaluated in an Argentinean freshwater fish species. Solubility, molecular weight, and the octanol-water coefficient of partition (K(ow)) were taken as macroscopic molecular descriptors. Slopes obtained from regression analysis were similar with respect to those of the standard fish, Pimephales promelas. A potential nonpolar narcosis power (NP) concept was defined on the basis of the mode of toxic action of the assayed chemicals. Following Ferguson's principle and the critical volume doctrine for nonpolar narcosis, NP was defined as log MW*K(ow). Experimental data fitted better than regression analysis did only with log K(ow). NP improves the quantitative relationship between nonpolar narcotic compounds and their toxicity. It was more suitable to describe the physiological aspects relative to the mode of action of the chemicals assayed.