Missoula County made slight improvements in air quality over the last year, though it still ranked among the most polluted metro areas in the nation in particle pollution, according to the American Lung Association.

The organization on Tuesday released the results of its 2020 State of the Air report, which found that overall, air quality in several Montana counties improved, though they continue to have unhealthy levels of pollution due mainly to wildfires and wood stoves.

“Trends of increasing wildfires in Montana and neighboring states are consistent with trends seen in a warming climate,” said Ronni Flannery, director of advocacy for the American Lung Association’s Healthy Air Campaign in Montana. “Exposure to wildfire smoke place our health and our lives at risk.”

The Lung Association’s annual air quality “report card” tracks Americans’ exposure to unhealthy levels of particle pollution and ozone during a three-year period.

Ten Montana counties received the lowest grade for 24-hour particle pollution, and most of those were located in the state's western reaches, including Missoula, Flathead, Gallatin, Lewis and Clark, Ravalli and Silver Bow counties.

According to the report, Missoula improved slightly to the seventh most polluted metro area in the nation, improving over its worst-ever No. 5 ranking in last year’s report. On the bright side, the county recorded no unhealthy ozone days and ranked among the cleanest cities for ozone in the nation.

Ravalli County improved to the seventh most polluted county in the nation for short-term particle pollution, up from it's No. 3 ranking in the last report. Lincoln County also tied for the 13th most polluted county, improving from its No. 10 spot last year.

“With nearly half of Americans breathing unhealthy air nationwide, this report shows that because of climate change, we’re heading in wrong direction when it comes to protecting public health,” said Flannery.

This year’s report covers 2016-2018 – three years that stand among the five hottest on record. Changing climate patterns are fueling large and more intense wildfires, which emit dangerous smoke that pours into western Montana's valleys.

A study released last week in the American Heart Association's scientific journal found that wildfires increase the risk for cardiac arrest among those who can't avoid breathing in the harmful particulates.

The results showed the risk for a cardiac arrest was 70% higher on the second day after exposure to heavy smoke density. Both men and women were at greater risk for experiencing cardiac arrest, including groups of people as young as 35 years old who were exposed to heavy smoke, according to the study’s results.

“We all have the right to breathe clean, healthy air,” said Flannery. “We must stand up for clean air, especially to safeguard our vulnerable community members. Our leaders, both here in Montana and federally, must take immediate action to ward off climate change and other threats to the quality of the air we all breathe.”