Developing Risk-Based Screening Levels at Petroleum Release Sites. D. J. Vorhees, Menzie-Cura & Associates, Inc. One Courthouse Lane, Suite Two, Chelmsford, MA 01824; and W. H. Weisman, U.S. Air Force, OH AL HSC/OET, 2856 G Street, Building 79, Wright-Patterson AFB, OH 45433-7400
Because it is impractical to analyze environmental samples for hundreds of individual petroleum constituents, many states regulate petroleum as total petroleum hydrocarbons (TPH). However, TPH composition varies from site to site, so there is no single TPH toxicity criterion for developing human health risk-based cleanup goals. Instead, diverse and sometimes arbitrary TPH standards are applied that may reduce human health risk by an unknown amount. New approaches based on fractions of petroleum (i.e., C9-C10 hydrocarbons) have been developed by the Massachusetts Department of Environmental Protection and the TPH Criteria Working Group for estimating non-cancer risk and establishing risk-based screening levels (RBSLs) or cleanup goals. Analysis of petroleum fractions rather than whole product or TPH provides more information about weathering of spilled product. Using the fraction-based approach, we calculate fraction RBSLs and TPH RBSLs for soil samples collected from several U.S. sites contaminated with #2 fuel oil, jet fuel, and diesel. TPH RBSLs are calculated from the weight percent contribution of each fraction to the mixture, assuming toxicity is additive across fractions. We assess the influence of petroleum source type, aging, soil characteristics, chemical saturation limits, and other sources of uncertainty on RBSLs.
Work Supported by US Air Force Contract No. F41624-97-C-9013.
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