The Environmental Protection Agency (EPA) is approving a State Implementation Plan (SIP) revision submitted by the Illinois Environmental Protection Agency (IEPA) on July 8, 2022. Illinois revised its air pollution control rules entitled ``Part 243--Ambient Air Quality Standards'' and updated the ``List of Designated Reference and Equivalent Methods'' in response to EPA rulemakings and changes to the National Ambient Air Quality Standards (NAAQS) that EPA adopted in 2021.