Ecotoxicological effects assessment: a comparison of several extrapolation procedures

In the future, extrapolation procedures will become more and more important for the effect assessment of compounds in aquatic systems. For achieving a reliable method these extrapolation procedures have to be evaluated thoroughly. As a first step three extrapolation procedures are compared by means of two sets of data, consisting of (semi)chronic and acute toxicity test results for 11 aquatic species and 8 compounds. Because of its statistical basis the extrapolation procedure of Van Straalen and Denneman is preferred over the procedures of the EPA and Stephan et al. The results of the calculations showed that lower numbers of toxicity data increase the chance of underestimating the risk of a compound. Therefore it is proposed to extend the OECD guidelines for algae, Daphnia, and fish with chronic (aquatic) toxicity tests for more species of different taxonomic groups.