Contact

Jay Olaguer, Air Quality Division
OlaguerJ@Michigan.gov
517-512-0059

West Michigan currently has areas designated as "Serious Nonattainment" and there are areas of Southeast Michigan designated as "Moderate Nonattainment."  To learn more about the history of ozone attainment in Michigan and how three-year design values are used to determine attainment status, see "Michigan's Ozone History" below. To get to where Michigan is today, several things happened:

• 2021: At the end of the ozone monitoring season, data from ambient air monitoring stations in the seven-county Southeast Michigan nonattainment area (NAA), showed attainment with the standard based on data from 2019 through 2021. EGLE submitted a request to the USEPA on January 3, 2022, requesting the area formally be redesignated to attainment.
• July 4, 2021: Monitoring data recorded on July 4, 2022, resulted in a tentative violation of the ozone NAAQS at one of the air monitors in Southeast Michigan. This tentative violation caused the USEPA to pause their review of the redesignation request.
• November 7, 2022: Three areas in West Michigan were reclassified from marginal to moderate nonattainment.
• January 26, 2023: Through routine data validation, it was determined that Canadian wildfire smoke on June 24 and June 25, 2022, was the cause of the tentative violation in Southeast Michigan. An Exceptional Events Demonstration was submitted to the USEPA on January 26, 2023. 
• May 19, 2023: The USEPA finalized a Clean Data Determination and Michigan’s redesignation for the Southeast Michigan counties.
• July 17, 2023: The USEPA’s Redesignation of Southeast Michigan was challenged at the US Court of Appeals for the Sixth Circuit.  The area retained its “Attainment – Maintenance” status while the challenge was pending. 
• August 3, 2024: Based on 2021 to 2023 ozone monitoring data the West Michigan ozone NAAs failed to attain the 2015 Ozone NAAQS.
• December 17, 2024: The USEPA published a final determination notice determining that the West Michigan ozone NAAs failed to attain the standard by the applicable attainment date. 
• January 16, 2025: The West Michigan 2015 Ozone NAAs were reclassified to "Serious" nonattainment for the 2015 ozone NAAQS.
• December 26, 2025: EGLE submitted Exceptional Events Demonstrations and Redesignation Requests for both Berrien and Muskegon ozone NAAs. The Exceptional Events Demonstrations were for several days in June and July of 2023; and July 2025.
  • 2023 Ozone Exceptional Events Demonstration for Berrien County
  • 2023 and 2025 Ozone Exceptional Events Demonstration for Muskegon County
  • Berrien County Redesignation Request
  • Muskegon Partial County Redesignation Request 
• January 12, 2026: The USEPA concurred with the ozone Exceptional Events Demonstrations submitted for Berrien and Muskegon monitoring data in West Michigan. 
• January 12, 2026: EGLE submitted the required West Michigan 2015 Ozone NAAQS Serious Element SIP for Allegan, Berrien, and Muskegon NAAs.
• February 24, 2026: The US Court of Appeals for the Sixth Circuit issued a mandate, effectively implementing its December 5, 2025, opinion regarding a challenge to the USEPA’s redesignation of the Southeast Michigan area to attainment for the 2015 Ozone National Ambient Ozone Standard.  The mandate returns the 7-county area of Southeast Michigan to a “Moderate” nonattainment designation.
• May 5, 2026: EGLE submitted an Addendum to the required West Michigan 2015 Ozone NAAQS Serious Element SIP to address the remaining VOC and NOx RACT requirements for the Berrien County and Muskegon partial-county ozone nonattainment areas.

Attainment / Maintenance Areas

The southeast Michigan redesignation request includes Michigan’s maintenance plan detailing how air quality will be maintained considering projected growth for a period of 20 years. If future monitoring shows that ozone levels are no longer meeting the criteria, the maintenance plan helps determine when and how the problem will be addressed through adoption of contingency measures.

Serious Nonattainment Areas

Michigan currently has three areas in West Michigan that were reclassified to serious nonattainment on January 16, 2025. The Clean Air Act requires several responses / actions be taken for areas designated as serious, including:

• VOC / NO_x Reasonably Available Control Technology (RACT) rulemaking for Major and CTG Sources. Under serious classification a Major is defined as sources of VOC or NOx > 50 tpy.
• Reasonable Further Progress (RFP) 9% VOC / NOx reduction over three years (2024-2026) based on baseline 2017 15% VOC Decrease (over six years 2017 - 2023)
• Attainment Demonstration
• Basic Inspection and Maintenance (for larger population areas: 200,000+ based off 1990 census – this does not apply to West Michigan)
• Contingency Measures for Failure to Attain or meet RFP requirements (can consist of VOC and/or NO_x reductions)
• Transportation control demonstration
• NSR offset ratio increases from 1.15:1 for moderate to 1.2:1 for serious.

Michigan's 2015 Ozone National Ambient Air Quality History

The United States Environmental Protection Agency (USEPA) revised the primary and secondary ozone National Ambient Air Quality Standard (NAAQS) to 70 parts per billion (ppb) October 26, 2015, and published ozone nonattainment designations with an effective date of August 3, 2018. The Michigan counties initially designated as nonattainment were Berrien, Livingston, Macomb, Monroe, Oakland, St. Clair, Washtenaw, and Wayne, and western portions of Allegan and Muskegon counties.

Ozone nonattainment areas are classified based on the severity of their ozone concentrations. The ozone concentration uses a calculation called the "design value." The nonattainment counties were classified as marginal nonattainment, which means that ozone concentrations were less than 10 parts per billion (ppb) above the standard at the time of initial designations. Marginal nonattainment is the lowest classification requiring less actions than more severe classifications.

Michigan had until August 3, 2021, to bring the design values at or below the 2015 Ozone NAAQS. Michigan was not able to attain the standard based on data from 2018 – 2020 and was "bumped-up" to a moderate nonattainment classification for all nonattainment areas. This “bump-up” became effective November 7, 2022, for the West Michigan nonattainment areas and March 1, 2023, for the Southeast Michigan nonattainment areas. On May 19, 2023, Southeast Michigan was redesignated by the USEPA to attainment. The USEPA’s redesignation of the Southeast Michigan area was challenged in the US Court of Appeals for the Sixth Circuit and on February 24, 2026, the court issued a mandate vacating the redesignation of the Southeast Michigan area, effectively returning the area to a Moderate nonattainment designation.

West Michigan had until August 3, 2024, to bring the design values at or below the 2015 Ozone NAAQS. Michigan was not able to attain the standard based on data from 2021-2023 and was reclassified (or commonly referred to as “bumped-up” ) to a Serious nonattainment classification for the 3 nonattainment areas in West Michigan. This “bump-up” became effective January 16, 2025.