Canadian wildfires in 2023 significantly worsened air pollution in several U.S. cities.

Coraopolis, Pennsylvania experienced the highest pollution levels, with the Upper Midwest and Mid-Atlantic also heavily affected.

Cities like Milwaukee and Elwood saw increased PM2.5 levels, a measure of air quality.

Conversely, the West Coast's air quality improved due to a less severe wildfire season.

Las Vegas achieved the status of the least-polluted major city in the U.S.

The cleanest air was reported in Hawaii, Alaska, and cities on the West Coast.

The American Lung Association reported that over a third of Americans face exposure to life-shortening air pollution.

IQAir's global report ranked over 7,800 locations and found the U.S. to be 102nd out of 134 countries in air quality for 2023.