Environmental risks are typically characterized in the risk assessment framework by considering the ratio between exposure concentrations and critical effect concentrations. In the Organisation for Economic Co-operation and Development (OECD) countries, critical effect concentrations are based on Predicted No Effect Concentrations (PNEC), which are typically derived from long-term laboratory-based ecotoxicity tests using well-defined protocols on a limited number of species. Such information is usually retrieved from relevant literature and/or internationally recognized databases or direct ecotoxicity testing. Because the quality of the extracted data may vary considerably among individual source documents, it is important to evaluate all ecotoxicity data with regard to their reliability and relevance for PNEC derivation and risk assessment. This fact sheet provides clear guidance on how to perform such evaluation for the freshwater sediment compartment including criteria for acceptance (or rejection) of a study in accordance with the purpose of the assessment and examples how these data can be applied in the European Union Environmental Risk Assessment for Nickel and Nickel Compounds.
Earlier attempts to develop sediment toxicity data for nickel using laboratory toxicity tests were unsuccessful, largely because nickel spiked into natural sediments diffused from the sediment into overlying water, resulting in overlying water concentrations sufficiently high to cause toxicity (Vandegehuchte et al., 2007). A workshop sponsored by the European Chemicals Agency (ECHA) identified new scientific developments within sediment risk assessment and made recommendations on incorporating these advances into sediment risk assessment guidance (ECHA, 2014). The nickel sediment research program addressed many of the developments that were discussed at the ECHA workshop and represents an example for how research findings can be implemented into sediment risk assessment. The conceptual model of the integrated bioavailability based approach that was developed within the nickel sediment research program for assessing the risks of nickel to freshwater sediment ecosystems is given in Figure 2.
Figure 2: Conceptual model of the integrated bioavailability based approach for assessing
the risks of nickel to freshwater sediment ecosystems (Schlekat et al., 2016)