The U.S. Environmental Protection Agency (EPA) should make changes to its integrated risk information system (IRIS) assessments handbook to ensure it provides clear operational instructions for those conducting assessments, and transparency regarding the assessment process, says a new report from the National Academies of Sciences, Engineering, and Medicine.

The handbook guides agency scientists who perform IRIS assessments — analyses of the potential health effects from exposure to chemicals found in the environment — which inform environmental health regulations and risk management decisions made by federal, state, local, and other agencies.  

The report says the handbook reflects significant improvements made by EPA to the IRIS assessment process, including systematic review methods for identifying chemical hazards. However, the handbook does not consistently convey the methodology of the assessment process in a clear and even manner.

Recommendations for improving the handbook include:

• Clearly stating when systematic review methods are being employed in the assessment process.
• Describing how to detect and assess funding bias and publication bias on the confidence of study ratings.
• Restructuring the handbook to reflect the order in which assessment steps are undertaken, and clearly indicating each written product that should result from the planning process.
• Providing a clearer, step-by-step description of how the agency selects studies to include when deriving toxicity values.
• Engaging a professional editor to assist with revising the handbook, and to enhance the handbook’s transparency and ease-of-use. The editor should focus the handbook’s material on the concepts, definitions, and instructions needed to complete the main steps in the assessment process; eliminate repetition; and make terminology consistent across chapters.

DETAILS: Review of U.S. EPA’s ORD Staff Handbook for Developing IRIS Assessments: 2020 Version is available for immediate release. Media inquiries should be directed to the National Academies’ Office of News and Public Information; tel. 202-334-2138 or e-mail news@nas.edu.