On December 22, 2022, the U.S. Environmental Protection Agency (EPA) released two important documents from its Integrated Risk Information System (IRIS) Program: The Office of Research and Development (ORD) Staff Handbook for Developing IRIS Assessments (IRIS Handbook) and the final IRIS Toxicological Review of Perfluorobutanoic Acid and Related Salts. The IRIS Handbook gives clear instructions for how IRIS assessments are made, including how to use systematic review methods. Systematic reviews use scientific methods that have already been set up to find, choose, evaluate, and combine the results of similar but separate studies. In IRIS assessments, these kinds of studies are used to find the health risks that come from being exposed to chemicals in the environment and to figure out the toxicity values for the health effects that come from being exposed. Five IRIS PFAS assessments have been done by EPA researchers. The PFBA assessment is the first IRIS PFAS assessment to be finished. PFHxA, PFHxS, PFNA, and PFDA are the other four IRIS PFAS assessments that are being made.