A Monte Carlo Simulation Probabilistic Risk Assessment Using Site-Specific Exposure Duration Data. K. E. Bauman and J. C. Cozzie, Harding Lawson Associates, Arlington, VA; and T. W. Simon, USEPA Region 4, Atlanta, GA
A Monte Carlo simulation probabilistic risk assessment (PRA) was conducted at a Base Realignment and Closure site to assess whether contamination in surface soil and groundwater posed unacceptable human health risk under the proposed land redevelopment scenario-apartment dwelling. Site-specific exposure data were used to establish a probability density function (PDF) for the apartment dweller exposure duration. Data were collected from three nearby apartment complexes similar to the proposed apartment complex and a probit plot was used to establish the PDF. Probit plots were also used to establish PDFs for the three contaminants of potential concern. Other PDFs were established using data obtained primarily from the USEPA Exposure Factors Handbook. The results indicated that 90% of the proposed adult apartment dweller population fell below an excess lifetime cancer risk (ELCR) of 10-6, while only 59% of a hypothetical adult long-term residential adult population (home owners) fell below an ELCR of 10-6. The PRA provides a risk range from exposure to soil and groundwater at this site, and most notably, it allows for the use of site-specific parameters, such as exposure duration. The deterministic Reasonable Maximum Exposure (RME) risk estimate was presented in conjunction with the PRA results for comparison.
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