# Air Plan Approval; Approval of Missouri Air Quality Implementation Plans; Revisions to St. Louis 1997 PM2.5 Maintenance Plan
> **Rule** · Final rule. · Published 2021-09-30 · Effective 2021-11-01 · 86 FR 54106
## Document
- **Document number:** 2021-20972
- **Category:** air-emissions
- **Federal Register citation:** 86 FR 54106
- **CFR reference:** 40 CFR 52
- **Publication date:** 2021-09-30
- **Effective date:** 2021-11-01
- **State:** MO
- **EPA docket:** EPA-R07-OAR-2021-0405
## Abstract

The Environmental Protection Agency (EPA) is taking final action to approve a State Implementation Plan (SIP) revision submitted by the State of Missouri on November 12, 2019, revising the maintenance plan demonstrating continued maintenance of the 1997 PM<INF>2.5</INF> National Ambient Air Quality Standards (NAAQS) in the St. Louis area. This revision demonstrates that the St. Louis area no longer needs to rely on the vehicle Inspection and Maintenance (I/M) program and the use of Reformulated Gasoline (RFG) for continued maintenance throughout the maintenance period for the 1997 PM<INF>2.5</INF> NAAQS. The EPA has determined that this revision meets the requirements of the Clean Air Act (CAA).

## Source
- [Federal Register document](https://www.federalregister.gov/documents/2021/09/30/2021-20972/air-plan-approval-approval-of-missouri-air-quality-implementation-plans-revisions-to-st-louis-1997)
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