According to the American Lung Association’s annual report (PDF, 2.51 MB), 141.1 million Americans—that’s four in 10—live in areas with unhealthy levels of particle pollution or ozone. Unfortunately, it’s an increase from last year’s report.
The latest findings capture data from 2015 to 2017 on particle and ozone pollution across the country.
A key takeaway from this year’s findings: the nation’s number of days with hazardous air quality is higher than ever. Here’s a breakdown of other air quality trends:
Cities in the West and Southwest continue to lead the most ozone-polluted list, as California has 10 of the 25 most-polluted cities. Los Angeles is again the city with the worst ozone pollution—a position its held for 19 of the report’s 20-year history. Other cities with low ranking are in Texas, Colorado, Arizona, Nevada and Utah.
Only seven cities on the most ozone-polluted list are east of the Mississippi River. In the Northeast and Mid-Atlantic zones, these locations include the New York City metro area, Philadelphia, Washington, D.C.-Baltimore, and Hartford, Connecticut.
The Midwest has two low rankings—Chicago and Sheboygan, Wisconsin.
Atlanta is the only Southeast city on the most ozone-polluted list.
California continues to dominate the year-round particle pollution list, with six of the 10 most-polluted, and topping the list with the Fresno-Madera-Hanford area.
Regionally, the Midwest has five cities on this list; Southeast has four; and the Northwest has three.
Wildfires often cause spikes in unhealthy air quality. Eight cities west of the Mississippi River recorded their highest number of days with short-term spikes.
Bakersfield, California, is the most polluted city for short-term particle pollution levels, and has been eight times in the past decade. Pittsburgh is the only city in the 25 short-term list that is east of the Mississippi River
Six cities ranked on all three cleanest lists for ozone, year-round particle pollution and short-term particle pollution:
To see where your city or area ranks, check out more key findings.