THE RELATIONSHIP BETWEEN AQUATIC TOXICITY QSARS AND BIOCONCENTRATION FOR SOME ORGANIC-CHEMICALS

Aquatic toxicity testing is conducted largely by means of a single experimental protocol.sbd.the concentration-response toxicity test. This procedure has a number of well-known limitations resulting from the fact that the relationship between the waterborne toxicant concentration and the actual body toxicant concentration which is producing the observed biological response is unknown. Hence quantifying the influence of chemical potency, physical, chemical and biological factors and elapsed time on the outcome of toxicity tests is difficult. Interpretation, and even more significantly, predictability may be severely restricted. Using, and further quantifying, the links between octanol-water partition coefficients, bioconcentration and acute and chronic toxicity quantitative structure-activity relationships (QSARs) for narcotic organic chemicals has allowed the following conclusions to be made: Establishing internal toxicant concentration related to acute and chronic effects, as estimated in this paper, will allow the toxicological significance of body burdens of certain organic chemicals, both singly and in certain mixtures, to be determined. Chemical potency, as determined in the exposed organism, appears to be essentially constant for each of the biological responses and organic chemical groups examined. The acute and chronic QSARs discussed herein are all parallel, each having a slope of unity. It appears, as a first approximation, that a one-compartment, first-order kinetics model could provide a quantitative means of studying aquatic toxicity test results, both retrospectively and prospectively. Bioconcentration and toxicity kinetics appear to be similar, but the internal toxicant concentration endpoint is different, fixed for toxicity and variable for bioconcentration.