An Augument Against Developing Tph-Based Tier 1 Ecological Screening Values to Evaluate petroleum Hydrocarbon Releases to Soil and Grounowater

摘要

The tiered approach described in the American Society for Testing and Materials (ASTM) risk-based corrective action (RBCA) standard 9ASTM, 1995) is successful because it provides a technically defensible and efficient means of allocating resources to petroleum release sites. As originally written, the ASTM standard is limited to human health effects, although ASTM acknowledges the need to consoder nopn-human receptors in the RBCA process. Efforts to incorporate ecological risk into an ASTM RBCA-likeframework have been stymied by attempts to develop "Tier l" screening levels for ttal petroleum hydrocarbon (TPH) concentration rather than relying on data for discrete constituents as described in the ASTM standard. The development of such "TPH-based" criteria is fraught with technical difficulties, including (1) the accuracy or reliability of analytical measurements for "TPH" and the fact that TPH concentration have been demonstrated to not dorrelate with toxicity; (2) the lack of available or applicable toxicity data for whole petroleum hydrocarbon mixtures and the implausibility of developing such data due to the complexity of these mixtures and confounding weathering effects; and (3) the diffculty of designing accurate and defensible bioassay studies for multiple constituent mixtures in uncontrolled settings. These difficulties make it unlikely, if not impossible, that technically defensible criteria can be developed, even on a site-specific basis. More importantly, if site-specific criteria are developed, it will be tempting to broadly apply such criteria to other sites, regardless of their technical defensibility for those sites. Therefore, consitent with the ASTM RBCA standard, available resources should be focused on assessing potential ecological risks posed by petroleum hydrocarbons in soil and groundwater based on well-documented toxicity information for the individual chemical constituents within the petroleum hydrocarbon mixture rather than pursuing elusive TPH-based criteria.