Comparison of Soil Cleanup Goals for Acute, Subchronic, and Chronic Exposures. K. M. Johnson, Tetra Tech, Inc., 3746 Mt. Diablo Blvd., #300, Lafayette, CA 94549; K. Swingle, GeoTrans, Inc., 4888 Pearl East Cr., #300E, Boulder, CO 80301; and K. Jennings, University of San Francisco, Department of Environmental Science, 2130 Fulton St., H-327, San Francisco, CA 94117
Soil cleanup goals are generally developed on the basis of chronic long-term exposure to contaminants in soil. Examples of these types of goals are the risk-based concentrations (RBCs) developed by the U.S. EPA Region III and the preliminary remediation goals (PRGs) developed by the U.S. EPA Region IX. One of the unstated assumptions supporting the use of these goals is that chemical concentrations sufficiently low to be health protective for chronically exposed receptors do not represent health risks for persons exposed for shorter time periods. Most sites for which risk-based cleanup goals are developed do not provide an opportunity to test this assumption. Tetra Tech was asked to review an initial set of cleanup goals developed for potentially acute and subchronic exposures to selected chlorinated pesticides, volatile organic compounds (VOCs), and heavy metals for future recreational visitors and industrial workers at Rocky Mountain Arsenal. Tetra Tech's review found that a number of the cleanup goals for short-term exposures were not consistently higher than those developed for long-term, chronic exposures. Depending on the compound, two counter-intuitive types of results also occurred: 1) cleanup goals for chronic exposures could be higher than either acute or subchronic exposures, and 2) cleanup goals for subchronic exposures could exceed goals developed for either acute or chronic exposures. The factors contributing to this unexpected set of results were determined as part of Tetra Tech's review. For certain compounds (e.g., dieldrin) the toxicity values were the primary factors contributing to unexpected cleanup goals, whereas the exposure parameters used in estimating acute or subchronic chemical intakes resulted in unexpected cleanup goals for other compounds (e.g., endrin). Finally, this paper examines the ramifications of the review results so that other groups involved in the development of cleanup goals can take advantage of the lessons learned.
Work supported by the State of Colorado, Office of the Attorney General.