Illinois Part of St. Louis Area Meets Federal Ozone Air Quality Standards
Official: Air Plan Approval; Illinois; Clean Data Determination for the Illinois Portion of the St. Louis Area for the 2015 Ozone Standard
Reading: The EPA is approving Illinois' achievement of the existing 2015 ozone NAAQS and suspending further attainment-planning requirements as long as the standard continues to be met, which maintains the current regulatory framework rather than tightening or relaxing it.
Louis metropolitan area.
In clear language
The EPA has confirmed that the Illinois side of the St. Louis area has met federal air quality standards for ozone pollution based on 2023-2025 air monitoring data. This means Illinois no longer needs to submit detailed plans showing how it will reduce ozone pollution in that region, as long as air quality stays at or above the standard. The approval applies only to the Illinois portion of the St. Louis metropolitan area.
How does this affect you?
Pick the type of resident or organization you most identify with — we'll generate a plain-language breakdown of what changes for you and what you can do about it.
Who does this affect?
- Residents of the Illinois portion of the St. Louis metropolitan area who breathe the air in that region
- Illinois state environmental agencies responsible for air quality planning and compliance
- Local governments in southern Illinois counties that are part of the St. Louis nonattainment area
What can you do?
- Monitor your local air quality forecasts to protect your health during poor air days, even though the region has met the standard
- Support continued efforts to maintain clean air by using public transportation or carpooling when possible
Timeline
- Effective: 2026-09-14
- Effective: 2026-09-14
- Effective: 2026-09-14
- Effective: 2026-09-14
- Effective: 2026-09-14
- Effective: 2026-09-14
- Effective: 2026-09-14
- Effective: 2026-09-14
- Effective: 2026-09-14
- Effective: 2026-09-14
- Effective: 2026-09-14
- Effective: 2026-09-14
- Effective: 2026-09-14
- 2023-2025: Design value period for air monitoring data used in determination
- December 18, 2025: Illinois EPA submitted exceptional events request
- January 12, 2026: EPA concurred with the exceptional events request
- August 13, 2026: Federal Register publication
- September 14, 2026: Rule becomes effective
No New Jersey official has a verified action on this policy yet.
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