CENTER FOR THE STUDY OF METALS IN THE ENVIRONMENT Annual Report

The Center for the Study of Metals in the Environment is a multi-institutional consortium of scientists and engineers working to further the understanding of processes affecting the fate and effects of metals in aquatic and terrestrial ecosystems. Significant gaps in the ability to predict the fate and effects of metals in both aquatic and terrestrial systems continue to hamper appropriate risk assessments and cost-effective risk management. In these situations, decisions include many assumptions and the application of safety factors. The focus of the Center is to develop appropriate information so that regulatory decisions will be based on sound scientific principles. Much of the existing methodology for hazard identification and for risk assessment is based on experience with persistent organic pollutants such as DDT and PCBs. The large differences in environmental behavior and potential for toxicity between organic compounds and metals are not incorporated into these methods. Assessment methodology is currently focused on the extent to which chemicals exhibit PBT (persistent, bioaccumulative, and toxic) characteristics. All three characteristics are important aspects of the assessment of risk, but their applicability to metals and the evaluation of metals data for these criteria differ from organic compounds. As a replacement for the current methods for evaluating the effect of metals in the environment, the Center is developing a model for the behavior of metal compounds that can be used as a tool in the hazard assessment of metals and metal compounds. This model will include the physical and chemical mechanisms that control the fate and resulting bioavailability of metals discharged to natural waters. In particular the transformations that affect metal fate and toxicity will be included. It is anticipated that it would be similar to the Unit World models, for example EUSES that are used for evaluating PBT organic chemicals. Metal behavior in watersheds, streams, lakes and reservoirs will be considered. The focus of the research efforts is to provide the information necessary to formulate and parameterize the model. Introduction There is a clear need for methods that can be used for evaluating the environmental hazard associated with the release of metals and metal compounds to the environment (Adams et al., 2000). The purpose of the Unit World Model (UWM) is to provide such a framework. The idea for a UWM comes from the fugacity and regional models developed for organic chemicals (Mackay 1979, 1991, Mackay et al. 1992). Models of this sort have …