Applying the Three Rs in Acute Ecotoxicity

The assessment of the adverse effects of chemicals and other stressors on the environment is a difficult task because of the complex network of species and physicochemical factors interrelated in a given ecosystem. Since it is almost impossible to perform tests in complete ecosystems, ecotoxicity testing has to rely on simplified testing systems, but should still be as representative for the whole ecosystem as possible. The classical approach for Environmental Risk Assessment (ERA) combines calculations of exposure, hazard identification and risk characterisation. Regulatory testing guidelines identify two environmental compartments: terrestrial and aquatic, depending on the exposure scenario. For hazard identification/classification, the first step is to determine the acute ecotoxicity and then, based on this, the Predicted No Effect Concentration (PNEC) is established. Acute ecotoxicity is based on LC50 tests with single species, usually one species per trophic level (aquatic and terrestrial primary producers, invertebrates and vertebrates). Single species LC50 data have been required for more than 30 years in the regulatory guidelines (EC, 1967), although their value is highly questionable with respect to toxicological relevance. To base environmental risk assessment on the death of individuals after short-term exposure to high toxicant concentrations is even more questionable – perhaps with the exception of accidental spills – but is still what we have in hand and what is accepted by the regulatory community. Today there is a strong political ambition to reduce animal experiments and replace them with alternatives. For a rough estimation of toxicity for classification and labelling purposes it is not justified to kill a large number of vertebrates. Alternatives in ecotoxicology focus on replacement of tests performed with vertebrates. Currently, acute LC50 data on vertebrates are required in ERA of chemicals, active substances of plant protection products (PPP), biocides and human and veterinary medicines (EC, 1991; 1992; 1998). Serious ethical concern has been raised about the use of vertebrates in ERA, since they suffer severe distress and pain when subjected to acutely toxic concentrations of chemicals, which is clearly not acceptable in view of animal welfare. Therefore, it is becoming more and more urgent to find solutions to avoid, or in the worst case to reduce, vertebrate testing, either with more rational testing strategies and/or by developing animal alternatives that can provide data on this first step in estimating toxicity. Applying the Three Rs in Acute Ecotoxicity