A strategy to reduce the use of fish in acute ecotoxicity testing of new chemical substances notified in the European Union

This study explores the applicability of a fish acute threshold (step-down) test approach for the assessment of new chemical substances notified in the EU. The proposed approach basically implies replacing the fish LC50 toxicity test with a simple acute threshold test and thus reducing the number of fish used and also costs. The fish test would be performed only at one concentration, the lowest between the EC50 concentrations obtained with previous testing with algae and daphnia. When fish would be more sensitive than algae and daphnia, testing with fish would be continued at lower concentrations (step-down). From step-down test results the LC50 value can be obtained by applying the binominal method of interpolation. These data can be used together with algal and daphnid data to provide the same Predicted No Effect Concentration values. The acute aquatic toxicity data used in this evaluation were extracted from the New Chemicals Database of the European Chemicals Bureau. The results show that 53.6–71.2% reduction of the number of fish used would be possible when applying this new testing strategy and suggest its use for regulatory purposes.