National Risk Assessment Methodology to Support EPA’s Air Characteristic Study. C. M. Bertrand, U. S. Environmental Protection Agency, Washington, DC; T. K. Pierson, A. C. Lutes, and A. B. Marimpietri, Research Triangle Institute, Research Triangle Park, NC
As part of ongoing efforts to review the adequacy of the Resource Conservation and Recovery Act’s (RCRA) hazardous waste characteristics, the US EPA has analyzed the potential direct inhalation risks that may result from uncontrolled waste management unit emissions. The purpose of this analysis, known as the Air Characteristic Study, is to inform future efforts the Agency may undertake to revise the present RCRA characteristics and include wastes that may pose a human health risk from direct inhalation. Included as part of the Study is a national scale risk assessment that is designed to highlight areas where inhalation risks may occur. The overall objective of this assessment is to estimate waste concentrations that can be present in certain waste management units without posing a threat to human health. This paper describes the technical approach used for generating the results for the Air Characteristic Study. Over 3,400 waste management units located throughout the continental US were modeled and a Monte Carlo analysis was used to capture variability in receptor characteristics. Chronic exposures were evaluated for 104 constituents, and acute and subchronic exposures were considered for 35 and 64 constituents, respectively. The results are a range of constituent specific estimates of threshold concentrations in waste below which the risk to human health would not be of concern. The results of the study produced several findings that merit further exploration. Trends evident in the results indicate that children and adult residents surrounding a waste management unit are at greater than workers and that waste water management in tanks generates a greater inhalation risk than wastes managed in other types of units.
Work supported by U. S. EPA under Contract 68-W6-0053.
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