6 Iowa counties get failing grades for air quality. What's to blame?

Almost half of all Americans are living in counties that get failing grades for unhealthy levels of ozone or particle pollution.

The American Lung Association's annual State of the Air report uses data from the U.S. Environmental Protection Agency’s Air Quality System to assign counties across the country a letter grade based on data from 2022 to 2024.

In Iowa, only nine of the state's 99 counties track ozone pollution in the system, and only 12 track particle pollution. None of Iowa's counties earned an A grade.

For ozone pollution, the highest grade achieved was a C and six counties received an F, according to the State of the Air report. Five counties received a B grade for particle pollution.

Here's a breakdown of the data from the 2026 State of the Air report.

How did Polk County rank in the State of the Air report?

Polk County was graded a "D" for both high ozone and particle pollution, according to data from the American Lung Association.

How did other Iowa counties rank in the State of the Air report?

Here's how other counties ranked for high ozone:

• Bremer: F
• Clinton: F
• Harrison: F
• Linn: F
• Montgomery: C
• Palo Alto: F
• Scott: F
• Van Buren: C

And how counties rank for particle pollution:

• Black Hawk: B
• Clinton: D
• Johnson: D
• Linn: D
• Montgomery: B
• Muscatine: C
• Palo Alto: B
• Pottawattamie: B
• Scott: D
• Van Buren: B
• Woodbury: C

How does bad air quality affect me?

"Breathing ozone irritates the lungs, resulting in inflammation — as if your lungs had a bad sunburn," according to the State of the Air website.

Poor air quality can also contribute to wheezing and coughing, respiratory illnesses and lung cancer. Air quality is of particular concern for children, who are especially vulnerable to the effects of air pollution because their lungs are still developing.

Nearly half of American children live in counties that received a failing grade for at least one measure of air pollution. Ten percent of children live in counties with failing grades for all three measures.

Why did Iowa receive low grades for air quality?

Extreme heat in many central states pushed ozone levels higher than expected, the report details in its Key Findings section. An "unprecedented blanket" of smoke from wildfires in Canada in 2023 also contributed to the rise in ozone and particle pollution levels.

The report explains how climate change is related to the extreme heat, drought and wildfires.

Lucia Cheng is a service and trending reporter at the Des Moines Register. Contact her at [email protected] or 515-284-8132.