PUB - Publikationen an der Universität Bielefeld

Acute-to-chronic ratios (ACRs) and quantitative structure-activity relationships (QSARs) generate continuous interest in particular in chemical risk assessment. Previous studies focusing on the relationship between the size or variation of ACRs to substance classes and QSAR-models were often based on data for standard test organisms, such as daphnids and fish. For the present study, we performed acute and chronic toxicity tests with the nematode *Caenorhabditis elegans* for a total of 11 chemicals covering 3 substance classes (nonpolar narcotics: 1-propanol, ethanol, methanol, 2-butoxyethanol; metals: copper, cadmium, zinc; and carbamates: methomyl, oxamyl, aldicarb, dioxacarb). ACRs were variable, especially for the carbamates and metals, although there was a trend for small and less variable ACRs for nonpolar narcotic substances. The octanol-water partition coefficient was a good predictor for explaining acute and chronic toxicity of nonpolar narcotic substances to *C. elegans*, but not for carbamates. Metal toxicity could be related to the covalent index X2mr. Overall, our results support earlier results from ACR and QSAR studies with standard freshwater test animals. As such, *C. elegans* as a representative of small soil/sediment invertebrates would probably be protected by risk assessment strategies already in use. To increase the predictive power of ACRs and QSARs, further research should be expanded to other species and compounds and should additionally consider chemicals' target sites and toxicokinetics.