Finding of Failure To Attain for the Missouri Portion of the St. Louis Nonattainment Area for the 2015 Ozone National Ambient Air Quality Standards

The Environmental Protection Agency (EPA) is accepting comment on a determination that the Missouri portion of the St. Louis, MO-IL bi-state nonattainment area failed to attain the 2015 8-hour ozone National Ambient Air Quality Standards (NAAQS) by the applicable attainment date. The effect of failing to attain by the applicable attainment date is that the area is reclassified by operation of law to "Serious" nonattainment for the 2015 ozone NAAQS. On November 25, 2024, the EPA published a final action in the Federal Register which determined that the St. Louis area failed to attain the 2015 ozone NAAQS by the Moderate area attainment date. That action also reclassified the area to Serious by operation of law with an effective date of December 31, 2024. On January 24, 2025, the EPA received a petition for reconsideration of that final action from the State of Missouri. On March 5, 2025, EPA Region 7 granted the petition for reconsideration and stated our intention to undergo a notice and comment rulemaking. Therefore, the EPA is accepting comment on the determination that the St. Louis area failed to attain by the attainment date. The Illinois portion of the St. Louis, MO-IL bi-state area is addressed separately.