[05/08] Recently it was discovered that the version posted here previously had an incorrect equation listed on page 4-49 in the PDF. When we checked a bound paper copy of the guidance, the equation was different (corrected), it had a different equation number, and it was on a different page. Clearly, we had two different versions of the guidance even though both versions of the guidance have the same reference (EPA/600/8-90/066F; October 1994). After consulting within the IRIS Staff, we determined that the previous version on the IRIS web site was an early version and that corrections had been made before it was published. Many years after the guidance was published, IRIS developed a web site. A copy of the RfC guidance was posted on the IRIS website, but unfortunately it was the wrong version.

If you have a previous copy of the RfC guidance that came from the IRIS website, you may want to replace it with the latest (correct) version available below.


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 "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.


U.S. EPA. METHODS FOR DERIVATION OF INHALATION REFERENCE CONCENTRATIONS (RfCs) AND APPLICATION OF INHALATION DOSIMETRY. U.S. Environmental Protection Agency, Office of Research and Development, Office of Health and Environmental Assessment, Washington, DC, EPA/600/8-90/066F.

Additional Information

*Please note that we are in the process of making this document accessible to those requiring assistive technology devices. A fully accessible version of this document will be posted when we complete this process. The content and general nature of the document will otherwise remain unchanged.

This document has been reviewed in accordance with U.S. Environmental Protection Agency policy and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.