On May 12, 2022, the Board adopted amendments to keep Illinois’ ambient air quality standards identical in substance to the National Ambient Air Quality Standards (NAAQS). The amendments reflect two actions taken by the United States Environmental Protection Agency (USEPA) during the first half of 2021: (1) USEPA designated one new federal reference method for sulfur dioxide and one new federal equivalent method for coarse particulate matter in ambient air; and (2) USEPA issued the Round 4 area designations under the 2010 primary NAAQS for sulfur dioxide, which had the effect of revoking the 1971 primary NAAQS for sulfur dioxide in all areas of Illinois effective April 30, 2022. Responding to the first USEPA action, the Board updated the incorporation by reference of the List of Designated Reference and Equivalent Methods. And responding to the second USEPA action, the Board removed the 1971 NAAQS for sulfur dioxide from the Illinois rules.
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