Six Iowa counties get an F for unhealthy ozone levels

State of play: The report uses rolling three-year monitoring data.

• Iowa's latest ozone results, covering 2022–2024, are mostly unchanged from the previous year's report.

Yes, but: The measure of "bad air days" caused by tiny particles — often from sources like wildfire smoke or diesel exhaust — improved slightly in the latest report.

Zoom in: Bremer, Clinton, Harrison, Linn, Palo Alto and Scott counties received failing ozone grades.

• No Iowa county failed because of high particle pollution days in the latest report.

Caveat: The report includes only counties with official air pollution monitoring data from federal, state, local or tribal monitors. In Iowa, that means 15 of 99 counties were listed.

• In the Des Moines area, Dallas, Warren, Jasper and Story counties were not included.

The big picture: More than 152 million people in the U.S. live in places that received failing grades for unhealthy levels of ozone or particle pollution.

• That includes just over 500,000 people in Iowa.