Validation of some extrapolation methods with toxicity data derived from multiple species experiments

For effects assessment several extrapolation methods are used which can be applied to estimate the concentration of toxic chemicals above which ecosystems may be affected. At present, however, it is uncertain whether the values calculated with these methods really represent concentrations harmless to ecosystems. Therefore, a validation is carried out by comparing no-observed-effect concentrations derived from multiple species experiments with extrapolated values. In this study validation was restricted to the methods of Aldenberg and Slob (1993) and Wagner and Løkke (Water Res. 25, 1237-1242, 1991), and a modification of the method of the Environmental Protection Agency (Slooff, 1992). Also, only organic compounds were studied. With restrictions, due to the paucity of data, it is concluded that single species toxicity data are a good starting point for establishing "safe" values for the aquatic ecosystem. Furthermore, extrapolation methods seem to be a good basis for determining these values if sufficient toxicity data are available for sensitive taxonomic groups. From the results of this study it was not possible to give preference to one of the validated extrapolation methods, but on theoretical ground the methods of Aldenberg and Slob and Wagner and Løkke are perferred.