Missouri's Air Gets EPA Green Light: St. Louis Ozone Win
Published Date: 2/26/2026
Proposed Rule
Summary
The EPA says the Missouri part of the St. Louis area has cleaned up its air enough to meet the 2015 ozone pollution rules. This means Missouri won’t have to do some extra pollution control planning as long as the air stays clean. People living and working in the area can expect better air quality, and the state can save time and money on extra paperwork.
Analyzed Economic Effects
3 provisions identified: 3 benefits, 0 costs, 0 mixed.
Missouri St. Louis Meets 2015 Ozone Standard
The EPA proposes to find that the Missouri portion of the St. Louis nonattainment area attained the 2015 8-hour ozone standard based on the 2023-2025 design value of 0.070 parts per million (ppm). This proposed Clean Data Determination is based on quality-assured, certified monitoring data for 2023-2025 and EPA concurrence on part of Missouri's exceptional events request (concurrence date January 27, 2026).
EPA Concurred on Wildfire Exceptional Days
The EPA concurred (on January 27, 2026) that certain ozone monitor days in 2023 were influenced by Canadian wildfire smoke and may be excluded from regulatory design-value calculations. The concurred exclusions are: West Alton (AQS ID 29-183-1002) for May 24, June 3, June 6, June 10, June 17, and June 24, 2023; and Maryland Heights (AQS ID 29-189-0014) for June 6, 2023.
State Planning Submissions Suspended If Finalized
If the EPA finalizes the Clean Data Determination, the requirements for the Missouri portion of the St. Louis area to submit attainment demonstrations and associated reasonably available control measures (RACM), reasonable further progress (RFP) plans, contingency measures, and other attainment-related plan elements under 40 CFR 51.1318 would be suspended for as long as the area continues to attain the 2015 ozone NAAQS.
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