Understanding ozone attainment and exceptional events: Why these decisions matter

We’ve been getting a lot of questions lately about Michigan’s recent ozone attainment designation requests in Southeast and West Michigan and how exceptional events factor into these decisions. It’s understandable — air quality is deeply tied to public health, community well being, and trust in environmental oversight. This article walks through what’s happening, why it matters, and how the Michigan Department of Environment, Great Lakes, and Energy (EGLE) continues working to protect residents across the state.

What is attainment and why is it a sign of progress

First, it’s important to recognize what attainment means. When a region is designated as meeting the federal ozone standards, it’s an acknowledgment of real, measurable improvement in air quality. This progress didn’t happen overnight.

Over many years, reductions in ozone forming pollutants have come from lower emitting vehicles, modern pollution control technologies, and the retirement of coal fired power plants, among other changes. These long-term efforts have made Michigan’s largest and most industrialized areas cleaner and healthier. When an area is designated as being in attainment, it does not mean work stops on improving air quality. The rules implemented and emission reductions achieved are permanent and plans are made to ensure continued progress toward reducing pollution. 

Cleaner air overall — and work still ahead

It is recognized that smoke from wildfires and ground-level ozone, along with exposure to other pollutants can have health impacts on people, especially sensitive groups like those with respiratory conditions like asthma, and children and the elderly. Federal standards are intentionally health based and become more protective over time as new science emerges.

Substantial progress has been made to reduce ozone in Detroit and the rest of the state. Levels of ozone being measured in the outdoor air are significantly reduced from the time when ozone was frequently in the unhealthy range. The controls we have put in place have done what they were intended to do and areas previously above the standard are now meeting it. Unlike the past, ozone levels in Detroit are now meeting the standard and in some places are well below the standard, like more rural areas of the state.

This year, Detroit did not see any violations of the ozone standard despite substantial wildfire smoke impacts experienced throughout the state. 
Even with attainment, EGLE’s work is far from finished. Returning an area to attainment requires a plan demonstrating that it can maintain those cleaner air levels over time. Michigan’s maintenance plans outline how air quality will be preserved for the next decade, even accounting for future population and industrial growth. If ozone levels rise again, these plans guide the steps needed to address the problem.

Why Exceptional Events matter — and what they don’t do

The most common question we’re hearing is: Why does EGLE use the federal Exceptional Events Rule to exclude certain wildfire-influenced ozone readings?

Here’s the simple answer: Wildfire smoke — especially from large, out-of-state or international fires — is not something Michigan can regulate or prevent. The federal Clean Air Act recognizes this and allows states to set aside data that is clearly and demonstrably influenced by these uncontrollable events when making regulatory decisions.

Exceptional event demonstrations do not erase data, hide pollution, or diminish the importance of real health impacts residents may have experienced during heavy smoke days. The data remains fully available to the public. EGLE meteorologists issue air quality alerts and educate communities about wildfire smoke because health impacts are real and significant.

But when it comes to assessing whether Michigan’s daily, year round emissions are improving or worsening, using data influenced by transported wildfire smoke would lead to inaccurate conclusions and potentially ineffective regulatory responses. The Exceptional Events Rule helps ensure Michigan is evaluated on the pollution levels we can control — not impacts from natural disasters.

EGLE’s continued work to reduce ozone

Even with attainment-designated areas and exceptional events correctly applied, protecting Michigan’s air remains a daily effort. EGLE continues forward on several fronts:

• Operating 45 monitoring stations across the state, with 200+ monitors measuring a variety of pollutants. This includes 26 ozone monitors (eight in southeast Michigan), with public data accessible on EGLE’s Air Monitoring webpage.
• Improving and expanding the air monitoring network, including new particulate matter and black carbon monitors in Detroit, Marquette, and additional tribal and community locations.
• Advised the City of Detroit as it built out a new network of community air monitors.
• Developing strategies for wider deployment of community air sensors through partnerships with local organizations.
• Conducting inspections and enforcement initiatives focused on environmental justice communities.
• Working with community groups, health partners, and federal agencies to increase public knowledge and reduce exposure.
• Continuing to issue air quality alerts when ozone or fine particulates are expected to reach levels of concern for sensitive populations.

Keeping Michigan on the right path

Attainment is an important benchmark, but it’s not the end of the story. It reflects years of investment, cleaner technology, and thoughtful policy — and it allows Michigan to focus its regulatory efforts where they’re most effective.

EGLE’s Air Quality Division staff continue to work every day to uphold our mission of protecting public health and the environment. Our commitment to careful monitoring, transparent communication, and reasoned decision making remains constant, no matter the attainment designation status. The work continues — and our team will keep listening, measuring, and taking action to ensure Michigan’s air is healthy for everyone.