Detroit region's 'worst ozone summer in a decade' reopens pollution debate

Southeast Michigan experienced its 13th clean air or ozone action day on Wednesday, more than twice the number of action days declared by the state in each of the past two years and representing what one expert called Metro Detroit's worst ozone summer in a decade.

The action days signal that conditions are right for the formation of ground-level ozone, a pollutant that is created as a result of vehicle and industrial emissions reacting with sunlight, Michigan Department of Environment, Great Lakes, and Energy, spokesman Hugh McDiarmid Jr. said Wednesday.

Ground-level ozone or smog can be unhealthy for sensitive groups, including the elderly, children and people with asthma or other respiratory issues. When ozone levels are high, the state's environmental department recommends people modify their behavior to reduce air pollutants, such as driving less, not using gas-powered lawn equipment, refueling vehicles after 6 p.m. and avoiding outdoor exercise in a bid for the region to avoid violating Clean Air Act standards.

This comes as the region has also endured Canadian wildfire smoke that dumped unprecedented levels of particulate matter pollution, worsening Metro Detroit's air quality. Particulate matter pollution is dangerous to health and is part of the state's redesigned clean air action day warning, which is like an ozone action alert but now includes fine particulates, such as wildfire smoke, in the forecast.

The seven-county Metro Detroit region experienced five ozone actions days each in 2021 and 2022, according to the Southeast Michigan Council of Governments, which publicizes the state's alerts. The largest number of ozone action days in the past seven years was nine days each in 2016, 2018 and 2020, according to SEMCOG. EGLE also issued its first ozone action alert this year on April 14, the earliest date of unsafe ozone levels the department has recorded.

More: What is an ozone or clean air action day in Michigan?

The spike in clean air or ozone action days comes after Southeast Michigan earlier this year was reclassified as an attainment area based on ground-level ozone pollution data from 2019 to 2022. The counties of Monroe, Washtenaw, Livingston, Wayne, Oakland, Macomb and St. Clair had been previously considered out of compliance with federal air quality standards for ozone pollution since 2018, based on data from 2014-17.

"While forecasters have called 13 ozone action days this season, our region is still in compliance with EPA's ozone standard because air quality monitors did not exceed the ozone standard on all forecasted days," said Kelly Karll, SEMCOG's environment and infrastructure manager.

The EPA's attainment area determination in May allowed the state to toss plans for a vehicle emissions testing program, something it hadn't done in decades, and other required moves to cut emissions and come into compliance. Critics argue the state and EPA erred by declaring the region in compliance — in part by tossing two days of unsafe ozone level readings collected by the East Seven Mile monitor in Detroit in June 2022 because the Whitmer administration argued those levels were caused by wildfires in Canada.

One environmental activist predicted ozone concentrations in southeast Michigan will exceed the National Ambient Air Quality standard again this year.

"It's very likely that ozone concentrations in southeast Michigan will cause an exceedance of the National Ambient Air Quality Standard again," said Nick Leonard, executive director of the Great Lakes Environmental Law Center. "Based on a quick review of the data, it looks like that's already occurred at the East Seven Mile monitor."

The center would still like to see the area designated as an ozone nonattainment area, Leonard said. This designation would require more aggressive emissions-cutting moves, including mandatory vehicle emission inspection and maintenance programs, creating a plan to reduce the emission of certain pollutants by 15% in six years and a requirement for factories and other major stationary sources of ozone pollutants to install "reasonably available control technology," he said.

"We also think it’s appropriate given the fact that this summer looks like it’s going to be our worst ozone summer in a decade," Leonard added.

How state does alerts

Michigan this year so far has issued 21 air alerts across the state, 11 of which involved the Canadian wildfires, EGLE's McDiarmid said.

The state issues an alert after making a forecast that conditions — hot temperatures, sunny skies and a lack of a breeze — are ripe for smog to form.

The Clean Air Act directs the EPA to set national ambient air quality standards for levels of ozone and other pollutants such as carbon monoxide, lead, nitrogen oxides, particulate matter and sulfur oxides. The ozone standard is currently set at 70 parts per billion, measured in a three-year average of the annual fourth-highest daily maximum eight-hour average ozone concentrations.

The 70 ppb standard is set through 2035, and the ozone season runs from March 1-Oct. 31, according to the U.S. Environmental Protection Agency.

Areas that do not meet this standard, or contribute to air quality in a nearby area that does not meet this standard, are classified as nonattainment areas or out of compliance by the EPA. The EPA found that the Detroit area attained the standard for the 2019-21 three-year period and 2020-22 three-year period.

Debating how much state should do

"The EPA has significant discretion in determining whether or not to pursue redesignation," Leonard said. "In this instance, I think they've made it fairly clear that even if ozone pollution levels rise above the standard, they will rely on EGLE implementing a wide range of contingency measures."

The federal agency credited state and federal programs aimed at reducing emissions, such as vehicle emissions standards, nonroad engine emissions standards and programs to reduce emissions from power plants with helping to keep the Detroit region in compliance.

In its proposal for the EPA to redesignate southeast Michigan as an attainment area, EGLE outlined contingency measures if ozone levels meet action or warning level response criteria. These measures include adopting and updating reasonably available control technology rules for sources of volatile organic compounds, known as VOC, and NOx.

Other options include reduced idling and trip reduction programs, traffic flow and transit improvements, and working with the state Department of Licensing and Regulatory Affairs to encourage natural gas utilities to increase the turnover of legacy distribution pipelines.

Leonard said these measures give EGLE too much leeway to determine which measures are appropriate when ozone concentrations increase.

But supporters of keeping the attainment status note the region's pollution levels have dropped. Since the mid-1990s, state air monitors in southeast Michigan have shown gradual reductions in the number of days of unsafe ozone levels, while federal pollution rules have become stricter. Monitors in Detroit have recorded a 28% decline in ozone concentrations in the past 20 years, EPA spokeswoman Rachel Bassler said in May.

Adding stricter requirements for southeast Michigan, such as mandatory car emissions inspection and maintenance, would add an annual cost for residents that would have hurt economic growth, Liethen noted. The redesignation of southeast Michigan as in compliance was based on verified, good-quality data submitted by EGLE, she added.

"There's a number of additional requirements that would be triggered under the ... moderate nonattainment designation. That would have also resulted in an essentially no growth policy for the region," Liethen said.

The state "wouldn't be able to attract business as far as sources of emissions to that region," she added.

hmackay@detroitnews.com

Staff Writer Carol Thompson contributed.

Correction: The story has been updated to correct the number of ozone action days in 2020 to nine.