US EPA

The National Center for Environmental Assessment has prepared this methodology in response to the 1993 Combustion Strategy for Hazardous Waste Incinerators released by the Administrator of EPA. Among other mandates regarding the regulation of this industrial sector, the strategy involved the requirement of EPA and/or the regulated community to conduct indirect exposure assessments to evaluate the impact of stack emissions. Although this mandate was specific to hazardous waste incinerators, the importance of the indirect pathways has extended to all combustors. The available methodologies at that time to conduct an indirect risk assessment were a 1990 ORD document titled, "Methodology for Assessing Health Risks Associated with Indirect Exposure to Combustor Emissions" (IEM) and the 1992 NCEA dioxin exposure reassessment document, "Estimating Exposure to Dioxin-Like Compounds". In order to develop a response to the Administrator's strategy, a workgroup comprised of ORD, OSWER, OAQPS, and others, convened. The result of this workgroup was an "Addendum" document to the 1990 Indirect Exposure document, released in November of 1993. This document described updates and other changes to the 1990 document; the two documents, together with other relevant information such as that from the dioxin exposure document or the Exposure Factors Handbook, would provide guidance on conducting indirect risk assessments.

U.S. EPA. Methodology For Assessing Health Risks Associated With Multiple Pathways Of Exposure To Combustor Emissions. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-98/137, 1998.