Both ozone and particle pollution are risky to public health and can increase the risk of premature death and other serious health effects such as lung cancer, asthma attacks, cardiovascular damage, and developmental and reproductive harm.
An increasing number - more than 20.5 million people - lived in counties with year-round particle pollution problems. Eugene-Springfield is now the 19th most polluted for short-term particle pollution.
"We must confront the reality that climate change is making the job of cleaning our air much more hard, " said Will Barrett, ALA's director of clean advocacy in California.
"We were ranked eighth a year ago, so we did have more days where the air quality was bad", said JoAnna Strother, director of advocacy for the American Lung Association of Arizona. The report analyzes particle pollution in two ways: through average annual particle pollution levels and short-term spikes in particle pollution.
The City of Trees is one of the most ozone-polluted cities in the United States, according to a new report from the American Lung Association. Topping that list was the Fresno-Madera-Hanford, California, area; followed by Bakersfield, California; Fairbanks, Alaska; Visalia, California; Los Angeles-Long Beach, California; San Jose-San Francisco-Oakland, California; the Pittsburgh-New Castle Weirton, Pennsylvania-Ohio-West Virginia area; El Centro, California; the Cleveland-Akron-Canton, Ohio, area; and Medford-Grants Pass, Oregon. Under President Trump, the Environmental Protection Agency has softened emissions rules for the auto and coal industries, threatening to worsen pollution levels.
Climate change is likely to make ozone pollution worse in the future, by making the hot temperatures necessary to create smog more common.
Multnomah County scored a C for particle pollution. "It's like getting a sunburn on your lungs".
And it can be damaging especially for people living with lung disease.
The warning comes as part of ALA's annual "State of the Air Report". California dominated the list of most-polluted cities. Compared to the 2018 report, this is considerably worse.