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This methodology document seeks to provide risk assessors with the guidance necessary to estimate the health risks that result from exposure to toxic pollutants in combustor emissions by pathways other than inhalation. The organization of the document reflects the four-step process of risk assessment (hazard identification, dose-response assessment, exposure assessment and risk characterization). This methodology is not intended to be prescriptive; that is, it does not comprise a set of guidelines or recommended approaches that the U.S. EPA believes should be applied in all circumstances. Rather, it provides a set of procedures that the risk assessor can draw upon, where applicable, to a given assessment. The document describes analytical procedures and computer models that can be used to estimate exposure and risk by a variety of environmental pathways. In addition, it serves as a preliminary source of data for carrying out the risk calculations. The degree of scientific support or uncertainty attendant to each calculation varies widely. Therefore, the appropriate use of these procedures and the discussion of uncertainties surrounding the results remain important responsibilities of the risk assessor.