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(M/MF135) Mixture toxicity of zinc, cadmium, copper and lead to the potworm Enchytraeus albidus. Lock, Koen1, Janssen, Colin1, 1 ABSTRACT- Organisms inhabiting contaminated habitats are almost always exposed to various chemicals simultaneously. Ecological risk assessments and soil quality standard derivations are, however, predominantly based on laboratory toxicity data with single-substance exposure. The use of toxicity tests in which each chemical is tested separately is inadequate for assessing the potential risk of mixtures of chemicals for soil ecosystems. In the present study, central composite designs were used to develop surface response relationships for predicting the chronic toxicity of mixtures of zinc, cadmium, copper and lead to the potworm Enchytraeus albidus. Surface response relationships were obtained for all binary mixtures of zinc, cadmium, copper and lead as well as for mixtures with all four metals. For the binary mixture of zinc and cadmium, this approach and the toxit unit approach gave similar results. However, with the toxit unit approach no such surface response models can be developed. The experimental results indicated that effect predictions based on the concentration addition model were always higher than those obtained with the independent action model. The observed effect was lower than the effect predicted by the concentration addition model for all metal mixtures. It can therefore be concluded that the concentration addition model represents a reasonable worst case scenario for the risk assessment of metal mixtures in terrestrial ecosystems. Key words: central composite design, concentration addition, independend action, toxit unit |
