Development of Health-Based Soil Cleanup Levels Based on Monte Carlo Analysis of Occupational Exposures. H. Carlson-Lynch and N. W. Harrington, ChemRisk - A Division of McLaren/Hart, 1685 Congress Street, Portland, ME 04102
Many hazardous waste sites exist at facilities that have had a long history of industrial use. In many cases, plausible future use of such sites is limited to industrial or commercial operations due to location, zoning regulations, and site structures. In such instances, derivation of health-based cleanup levels (HBCLS) should reflect exposure scenarios that are consistent with the likely occupational use. In this analysis, we present a Monte Carlo assessment of interindividual variation in exposure and the application of the assessment to derive HBCLs for an active chemical manufacturing facility in an urban, industrialized area. A hypothetical maintenance worker was selected to represent current conditions and a most likely future scenario at the site. The risks associated with potential future conversion of the site to a business park were considered with the evaluation of exposures to a construction worker involved in the conversion and to a landscaper responsible for maintaining the grounds of the future business park. For all three scenarios, exposures through ingestion of and dermal contact with soil were considered, as was inhalation of soil particulates and vapors. A careful review of site-specific information and published sources was performed to characterize the parameter distributions used in the analysis. Using these exposure scenarios and routes, Monte Carlo techniques were used to calculate distributions of health-based soil cleanup levels corresponding to an acceptable risk level 10-6 for surface and subsurface contamination. HBCLs of 17 ppm and 90 ppm PCBs (surface and subsurface soils, respectively) were found to meet the acceptable risk level for 95% of the individuals under the highest exposure scenario. Similarly, HBCLs of 130 ppm and 1,100 ppm were estimated for surface and subsurface benzene contamination.