Indianapolis' air quality gets failing grades as pollution worsens nationwide
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Marion County is one of just 20 counties that failed every pollution test in the American Lung Association's annual State of the Air Report, released this morning.
Why it matters: The county is home to hundreds of thousands of Hoosiers who face an elevated risk of health conditions linked to air pollution, ranging from wheezing and coughing to premature death.
Driving the news: About 44% of Americans (152.3 million people) are living in places that get failing grades for unhealthy levels of ozone or particle pollution, per the report.
- That includes 33.5 million children, 10% of whom live in places like Marion County with "F" air quality grades across the board.
How it works: The report used local air quality data to grade and rank locations in the categories of ozone pollution, daily particle pollution and annual particle pollution.
- It includes data from 2022-24, "the most recent three years of quality-assured nationwide air pollution data publicly available."
- Ozone is a gas that, at ground level, is a harmful irritant. Particle pollution involves tiny airborne particles from wildfires, fossil fuel burning and more.
Zoom in: The Indianapolis-Carmel-Muncie area ranked No. 11 nationally for worst annual particle pollution out of 211 U.S. metros.
- It ranked No. 14 for worst for short-term particle pollution and No. 55 for worst ozone pollution.
- Marion ranked No. 16 on the list of the 25 worst counties for annual pollution and No. 22 for short-term pollution. It joins Lake as the only other Indiana county to fail all three measures.
- Hamilton County — included in the Indy metro analysis — got a "C" for ozone, a "D" for daily particle pollution and failed annual particle pollution.
The other side: Delaware County was among the cleanest, earning a "C" for ozone, a "B" for daily particle pollution and passing annual particle pollution.
- Brown County earned a "B" for ozone.
Caveat: Not every county listed in the report includes results for all three tests.
- The report adds that many rural communities lack the monitoring data needed to be assigned a grade for at least one pollutant, meaning those populations lack official information about their air quality.
State of play: The ALA found that ozone pollution worsened across much of the U.S. over the past two years after a run of successful reductions, "demonstrating that past progress is fragile."
- The report warns that recent EPA rollbacks, such as the repeal of the 2009 Endangerment Finding in February 2026 and the weakening of vehicle and power plant emission standards, threaten to reverse decades of air quality gains.
- The rise of data centers was also identified as a new threat.
What they're saying: "The increase in ozone in this year's report was especially remarkable given that the previous report already showed a drastic worsening and that more counties in this year's report reported incomplete data," the report states.
What you can do: The ALA says to keep yourself and others safe by checking daily air pollution forecasts at Airnow.gov and reducing vehicle and home energy use to reduce emissions.
Go deeper: The fallout from EPA's pollution shift