ESTIMATION OF ACUTE TOXICITY BY FITTING A DOSE-TIME-RESPONSE SURFACE

In acute toxicity testing, organisms are continuously exposed to progr essively increasing concentrations of a chemical and deaths of test or ganisms are recorded at several selected times. The results of the tes t are traditionally summarized by a dose-response curve, and the time course of effect is usually ignored for lack of a suitable model. A mo del which integrates the combined effects of dose and exposure duratio n on response is derived from the biological mechanisms of aquatic tox icity, and a statistically efficient approach for estimating acute tox icity by fitting the proposed model is developed in this paper. The pr oposed procedure has been computerized as software and a typical data set is used to illustrate the theory and procedure. The new statistica l technique is also tested by a data base of a variety of chemical and fish species.