The Michigan Department of Environment, Great Lakes, and Energy (EGLE) regulates levels of ground-level ozone in the outdoor air by making sure Michigan is meeting or “attaining” United States Environmental Protection Agency (USEPA) national ambient air quality standards.
Ozone is a regional pollutant that is formed in the atmosphere over time from emissions of Volatile Organic Compounds and Nitrogen Oxides. When these pollutants combine on warm, sunny days, harmful ground-level ozone may form.
When an area is not meeting the standard EGLE takes additional steps to bring that area back into attainment.
The West Michigan nonattainment area includes Berrien County and the western portions of Allegan and Muskegon counties. EGLE held a public comment period for the five related documents The public comment periods closed on December 5, 2025. All comments received during the public comment period are being reviewed, and a formal response to comments will be posted.
One document covers the West Michigan nonattainment area as a whole, while the other four include demonstrations addressing two specific portions: Berrien County and the western portion of Muskegon County. Information on the documents, are detailed below.
2015 Ozone National Ambient Air Quality Standard - current classifications Through this document EGLE shows how the elements of the Serious Ozone classification are being addressed. This document covers the three separate West Michigan areas with nonattainment statuses under the 2015 NAAQS for ozone.
Fact Sheet on West Michigan serious elements
This document in addition to the Exceptional Events Demonstration shows that Berrien County now meets the 2015 ozone standard. EGLE is asking USEPA to change the area’s status to attainment, approve the maintenance plan and emissions inventories, and accept the vehicle emissions budgets for the maintenance period.
Fact Sheet on Berrien County Ozone Attainment Status
This document explains how smoke from Canadian wildfires in June and July 2023 significantly impacted ozone readings at the Coloma monitor in Berrien County. The wildfires were widespread across Canada during an unusually active season. USEPA concurred with this demonstration on January 12, 2026.
Fact Sheet on the Exceptional Event Demonstration for Berrien County
This document, along with the Exceptional Events Demonstration, shows that Muskegon County now meets the 2015 ozone standard. EGLE is asking USEPA to change the area’s status to attainment, approve the maintenance plan and emissions inventories, and accept the vehicle emissions budgets for the maintenance period.
Fact Sheet on redesignation of the western portion of Muskegon County
This document shows how smoke from Canadian wildfires in June and July 2023 and July 2025 significantly affected ozone readings at the Muskegon monitor. Both years had active wildfire seasons, with smoke from Canada drifting into Michigan during several periods. USEPA concurred with this demonstration on January 12, 2026.
Fact sheet on Exceptional Event Demonstration for Muskegon County
Reduce air pollution! Michigan and the USEPA have been working to lower ozone levels since 2018 and attain the standard in the West Michigan nonattainment areas (Allegan Partial-County, Berrien County, and Muskegon Partial-County).
The nonattainment areas can be redesignated as attainment once the standard is met and the required regulatory steps are taken.
If ozone concentrations remain above the standard, the nonattainment area would not be able to be designated as being in attainment.
West Michigan currently has areas designated as "Serious Nonattainment". This includes Berrien County and the western portions of Allegan and Muskegon counties.
Concentrations of ozone in the outdoor air helped determine when the area was not attaining the standard, as well as when the area was measuring concentrations below the standard.
Yes! Outdoor air concentrations of ozone in the Berrien County and Muskegon Partial-County nonattainment area for the 2015 ozone NAAQS have improved since being designated.
However, just measuring lower concentrations is not enough to redesignate an area into attainment. To do that, the state needs to show that the area has legally enforceable limits on how much NOx and VOCs can be emitted. Getting those enforceable limits in place takes time.
2023 Wildfire Exceptional Event Demonstration for Ground-Level Ozone in Southeast Michigan – Allen Park and East 7-Mile Monitors
For Air Quality Rules and State Implementation Plans (SIP)
