LANSING, MI — Michigan regulators are asking the U.S. Environmental Protection Agency to discount several high ozone days tied to wildfire smoke as they seek to ease air quality restrictions in parts of the state.

The Michigan Department of Environment, Great Lakes and Energy (EGLE) has submitted multiple “exceptional event” demonstrations to EPA arguing that smoke from Canadian wildfires in 2023 and 2025 artificially inflated ozone readings at several monitoring sites.

If the EPA agrees, those days would be excluded from calculations and clear the way for Berrien County and part of Muskegon County to be re-designated as meeting the federal ozone standard despite their classification as in “serious” non-attainment.

“There’s two parallel processes going on in West Michigan,” said Tom Shanley, EGLE air quality evaluation manager. “A few things all kind of came together at the same time.”

In January, the EPA automatically reclassified Berrien and parts of Muskegon and Allegan counties as in “serious” nonattainment after they failed to meet improvement deadlines under the Clean Air Act — triggering a requirement that Michigan submit a detailed state implementation plan outlining additional pollution controls.

At the same time, EGLE is asking EPA for an “exceptional event” ruling for Berrien and Muskegon counties tied to wildfire smoke during some of the worst ozone days in 2023.

Federal rules allow states to exclude air quality data caused by natural events that are not reasonably controllable or preventable.

According to EGLE documents, dense smoke from Canadian wildfires coincided with unusually high ozone readings at West Michigan monitoring sites on several days in June and July 2023.

In Berrien County, the Coloma monitor recorded some of its highest ozone concentrations of the year during those smoke episodes, while the Muskegon monitor saw similar spikes during the same period.

In Muskegon County, EGLE is also seeking to exclude a single day in July 2025 when smoke from Canadian wildfires again pushed ozone levels above regulatory thresholds.

A “serious” nonattainment designation requires imposition of stricter permitting, additional pollution controls and detailed planning requirements even if much of the ozone comes from outside the region.

If EPA excludes wildfire smoke days, those obligations would no longer apply in Berrien and Muskegon counties because the areas would again qualify as meeting the federal standard.

However, Allegan County would remain subject to the stricter designation because state officials say the area does not meet the ozone standard even after accounting for wildfire smoke.

For Allegan, “the data does not support re-designation, even if we were to consider wildfire smoke impacts,” said Shanley.

According to EGLE, West Michigan’s ozone problem is largely imported from air pollutants blowing in from upwind states — especially the Chicago metropolitan area and the broader industrial Midwest.

Pollution does not simply drift across Lake Michigan. On hot, sunny days, nitrogen oxides and volatile organic compounds continue to chemically react as air masses move east, effectively “cooking” over the lake and forming ground-level ozone. State modeling shows a significant share of the ozone measured along West Michigan’s shoreline originates outside the state and crosses Lake Michigan on prevailing winds.

Ozone plays a protective role high in the atmosphere, but near the ground it becomes a pollutant that irritates the lungs. The effects can be serious for people with lung disease, children and older adults.

Shanley said imposing additional local controls required under a serious nonattainment classification “can be costly, but it doesn’t necessarily move the needle for ozone concentrations in West Michigan,” he said.

EGLE has also submitted a separate exceptional event request tied to Canadian wildfire smoke in southeast Michigan.

The state’s request centers on four days — June 19, June 29, June 30 and July 25, 2023 — when ozone monitors in Wayne County recorded some of their highest readings of the year during periods of heavy wildfire smoke. EGLE argues those days triggered maintenance plan thresholds despite long-term air quality improvements in the region.

The metro Detroit area has already been re-designated as meeting the federal ozone standard. The exceptional event request is meant to protect the region’s maintenance plan and prevent wildfire-driven spikes from triggering enforcement thresholds, Shanley said.

Public comment on the re-designation requests, exceptional event demonstrations, and the serious ozone SIP ended this month. EPA has up to 18 months to act on the submissions, though state officials say they hope for decisions within a few months.

Shanley said that EPA has previously approved Michigan requests to exclude wildfire-related air quality data for both ozone and fine particulate pollution.