Ecological Soil Levels—Next Steps in the Development of Metal Clean-up Values
Randy Wentsel and Anne Fairbrother, Exponent
A session was held to present the results of a workshop titled “Ecological Soil Levels—Next Steps in the Development of Metal Cleanup Values.” The workshop was held 17-21 September 2012 in Sundance, Utah. The purpose of the workshop was to provide managers and decision makers at contaminated sites in North America with appropriate methods for developing soil cleanup values that are protective of ecological resources. The workshop focused on metals and other inorganic contaminants because of their ubiquity at contaminated sites and because their natural occurrence makes it difficult to determine adverse effect levels.
Ecological soil screening levels (EcoSSLs) were developed by the US Environmental Protection Agency (EPA) in 2003 (www.epa.gov/ecotox/ecossl). In the nearly 10 years since the EcoSSLs were developed, there have been significant improvements in the test methods used to develop soil toxicity data, particularly for plants and soil invertebrates. This research was conducted in support of regulatory requirements of the European chemical registration program known as REACH and accounts for differences in bioavailability and organism response as a function of soil parameters. Additionally, new approaches to setting toxicity threshold values have gained acceptance resulting in more accurate predictions. Recent major terrestrial research projects in Europe, Australia and China have significantly advanced our understanding of metal behaviours and toxicity in soils, establishing quantitative relationships between toxicity of metals in soils and soil properties.
Regulatory applications include: adjusting soil concentrations for bioavailability using aging and leaching factors for plants and soil invertebrates, including soil microbial processes, using toxicity databases that are now available to calculate effects levels (e.g., ECx) upon which risk ranges can be developed, selection of cleanup levels from within the risk range, support for the increased use of species-sensitivity distributions (SSDs) in the ecological risk assessment process and in the selection of ecologically protective soil cleanup values by risk managers. A manuscript is being prepared by each workgroup for inclusion in a special publication of the SETAC journal Integrated Environmental Assessment and Management. If you are interested in further information about the workshop, a 10-page pamphlet is available. Please email either of the co-chairs for the pamphlet or with questions about the session.
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