On July 6, 2023, the Board proposed amendments to keep Illinois’ ambient air quality standards identical in substance to the National Ambient Air Quality Standards (NAAQS). The amendments reflect action taken by the United States Environmental Protection Agency (USEPA) during the second half of 2022. Specifically, USEPA updated its List of Designated Reference and Equivalent Methods to modify existing method designations and designated a new Federal Equivalent Method (FEM) for fine particulate matter (PM2.5) in ambient air. In addition, although it requires no Board action, the Board noted that on October 7, 2022, USEPA redesignated the Chicago area as moderate nonattainment under the 2015 eight-hour ozone NAAQS.
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