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5B a - RA: Ranking and Chemical Specific (TU6/8) Integration of the environmental bioavailability of metals in Risk Assessment - the copper example. Delbeke, K.1, Van Sprang, P.2, 1 European Copper Institute, Brussels, Belgium2 Euras, Zwijnaarde, Gent, Belgium ABSTRACT- It is widely recognised that bioavailability is crucial for the understanding of environmental metal toxicity. Recently, in the frame of the ongoing EU metal RAs, the EU Member States agreed to evaluate and incorporate bioavailability into the risk analysis for the water, sediment and soil compartments, as far as scientifically defensible. The presentation will focus on the integration of bioavailability in the risk analysis of metals in water and sediments compartments. For the aquatic compartment, metal bioavailability and metal toxicity depends on (1) the partitioning of the metal to the suspended solids, (2) the speciation of the metal within the dissolved phase and (3) the competition between the free ions for the biological binding sites (the Biotic Ligands). The recently developed Biotic Ligand Model (BLM) integrates the existing knowledge on metal speciation, metal competition and metal toxicity and allows to predict the bioavailability and toxicity of metals to aquatic organisms belonging to different trophic levels under varying water chemistry conditions. The model is currently under review by regulatory agencies in the United States, South America and Europe. For copper for example, acute and chronic BLMs were developed and evaluated/validated across a variety of EU surface waters. Application of the models to copper ecotoxicity data, collected from recent research as well as available literature data, showed that important intra-species variability observed in the aquatic ecotoxicity data can be reduced by the application of the BLMs. Subsequent application of the BLMs to the freshwater copper exposure and effects databases allows to express effects and exposures on the same level of bioavailability and leads to important reductions in uncertainty of the risk analysis. For the sediment compartment, especially the binding of divalent metal ions to the sulphides present in anaerobic sediments is important for the understanding of metal bioavailabilty in sediments. Again, incorporation of the metal - sulphide binding into the risk analysis can drastically reduce the uncertainty related to the assessment of metal toxicity in sediments and hence increase the ecological relevance of the risk assessment. Key words: copper, metals, risk assessment, bioavailability |
