Advances in Inhalation Dosimetry of Gases and Vapors with Portal of Entry Effects in the Upper Respiratory Tract

This report reviews advances in the state of the science for inhalation gas dosimetry related to the URT or nasal tract region that have occurred since the publication of the Methods for Derivation of Inhalation Reference Concentrations and Application of Inhalation Dosimetry; EPA/600/8-90/066F, October 1994 (RfC Methods). The RfC Methods document provides the basis for EPA extrapolation of data from animal toxicology studies to estimate delivered dose in humans as part of the development of inhalation reference values (i.e., RfC values).The primary results from this review include empirical information related to the assumptions underlying the current methodology used by EPA, as well as how the state of the science and advanced dosimetry modeling techniques inform these assumptions. The intent of this report is to serve as a source document for revisions to the Agency’s RfC Methods. The report makes clear that it is intended neither to displace the current procedures for gas dosimetry in RfC Methods nor to reflect on use of these procedures in assessments currently in IRIS.

This is the final report.