Adaptation of Preliminary Risk Evaluation (PRE) Approach to Accelerate Soil Risk Assessments. K. G. Caesar, C. J. Saranko, H. L. Williams, T. A. Peel, and R. P. DeMott; GeoSyntec Consultants, and NASA
An expedited human health risk assessment process, Preliminary Risk Evaluation (PRE), was adopted by the Kennedy Space Center RCRA remediation team to facilitate rapid risk characterization where groundwater impacts were apparent. In this approach, the maximal site concentrations of individual constituents are divided by established screening levels. The resulting ratios are then summed to provide an estimate of overall risk. Based on successes expediting site evaluations with this approach, potential use for soils risk assessment at sites that might not warrant remedial action was considered. The PRE process was adapted to incorporate comparisons between maximum detected site soil concentrations and Florida default Soil Cleanup Target Levels (SCTLs). One difficulty was reasonably accounting for potential cumulative non-cancer risks. For carcinogens, published SCTLs are based on the more conservative endpoint, typically carcinogenesis, and values relevant for non-cancer endpoints are not readily available. Using a cancer risk-based SCTL for the cumulative non-cancer risk summation considerably overestimates the risk, limiting the ability to establish whether site assessments can be closed without remedial action. Therefore, SCTLs based on non-carcinogenic endpoints were calculated using the method adopted by Florida. In addition, default SCTLs were modified to fit site-specific receptors and exposure scenarios, where appropriate. As adapted, the PRE process has become a useful tool for soil risk assessment and accelerated site assessment and management. This adapted PRE could be applied to other situations where expedited risk assessment is desired, including brownfields assessments.
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