On December 22, 2022, EPA’s Integrated Risk Information System (IRIS) Program released its ORD Staff Handbook for Developing IRIS Assessments (IRIS Handbook). EPA began working on the approaches in the IRIS Handbook after a 2011 National Research Council report recommended several improvements to the overall IRIS assessment process. In 2020, EPA released a draft IRIS Handbook for public comment and commissioned a peer review by the National Research Council.
Established in 1985 to ensure Agency-wide consistent toxicity evaluations, IRIS assessments provide chemical toxicity values for noncancer and cancer human health effects resulting from chronic exposure to chemicals. These values are often utilized in EPA regulations under the Clean Air Act (CAA), the Safe Drinking Water Act (SDWA), and the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). While chemical risk evaluations conducted under the Toxic Substances Control Act (TSCA) require more information and analysis than that provided by an IRIS assessment, IRIS assessments will likely continue to be used to inform TSCA risk evaluations. State agencies and international bodies also rely on IRIS assessments.