T3 AM Ecological Risk Assessment (Part 2)
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in Ballroom 3

(GRE-1117-807730) Using the Rule of Five to determine ecologically protective clean-up goals at Superfund sites.

Greenberg, M^{1, 2}, Charters, D¹, ¹ U.S. EPA Environmental Response Team, Edison, NJ, USA² Wright State University, Dayton, OH, USA

ABSTRACT- Ecological risk assessment (ERA) guidance for Superfund states that clean-up goals for contaminants should be selected within the risk range or between the no observed and low observed effect levels (NOAEL and LOAEL). The Rule of Five, a visual tool based on a geometric progression of five nodes between the NOAEL and LOAEL, provides a flexible framework for selecting a defensible, clean-up goal for ecological receptors. For an assessment endpoint, selection of the ultimate clean-up goal is initiated at the geometric mean of the NOAEL and LOAEL with the assumption that this value is protective of growth and reproduction endpoints. The lines of evidence are then weighed or evaluated. If the data from the measurement endpoint(s) justify refinement of the initial clean-up value, then the risk manager may move about the nodes (i.e., select a higher or lower clean-up value relative to the geometric mean of the NOAEL and LOAEL). The weighing of the lines of evidence and the movement about the nodes in this fashion provide a logical and appropriately conservative approach which results in a scientifically-based clean-up goal. The method is especially useful when the NOAEL and LOAEL risk range spans an order of magnitude or more. Moreover, this approach improves upon the ERA process as some of the more ecologically-based parameters, that have been excluded previously as non-decisional (e.g., species diversity and numerical abundance, functional attributes), can be incorporated into the risk management decisions. This presentation will provide a technical description of the Rule of Five method and a number of case studies where the approach was applied.

Key words: Rule of Five, clean up goal, geometric progression, ecological risk assessment