This document describes EPA's methodology for estimation of inhalation reference concentrations (RfCs) (earlier terminology was "inhalation reference dose" or "RfD") as benchmark estimates of the quantitative dose-response assessment of chronic noncancer toxicity for individual inhaled chemicals. Noncancer toxicity refers to adverse health efects other than cancer and gene mutations. The overview chapter discusses general prinicples of dose-response assessment for noncancer assessment process. Subsequent chapters of the document discuss criteria and information to be considered in selecting key studies for RfC derivation, provide an overview of the respiratory system and its intra- and interspecies variables and discuss areas of uncertainty and data gaps in relation to the proposed methodology.

• Methods for Derivation of Inhalation Reference Concentrations and Application of Inhalation Dosimetry (PDF)(389 pp, 5 MB, October 1994, 600-8-90-066F)