Methods for derivation of inhalation reference concentrations and application of inhalation dosimetry
U.S. Environmental Protection Agency, Office of Research and Development, Office of Health and Environmental Assessment, Environmental Criteria and Assessment Office
Research Triangle Park, NC
This document describes the U .S . Environmental Protection Agency (EPA) methodology for estimation of inhalation reference concentrations (RfCs) (earlier terminology was inhalation reference dose or RfDi) as benchmark estimates of the quantitative doseresponse assessment of chronic noncancer toxicity for individual inhaled chemicals. Noncancer toxicity refers to adverse health effects other than cancer and gene mutations. This overview chapter discusses general principles of dose-response assessment for noncancer toxicity, the development of the RfC methodology, and its role within the context of the risk 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.