About four out of 10 Americans are living in areas with "unhealthy levels of air pollution" and spikes in particle pollution, or soot, are the highest in 25 years, the American Lung Association said in a report released Wednesday.

The organization's "State of the Air" report found that "despite decades of progress cleaning up air pollution, 39% of people living in America - 131.2 million people - still live in places with failing grades for unhealthy levels of ozone or particle pollution. This is 11.7 million more people breathing unhealthy air compared to last year's report."

Particle pollution, which the report says is caused by wildfires, wood-burning stoves, coal-fired power plants, and diesel engines, can trigger asthma attacks, heart attacks, strokes and cause lung cancer.

The report breaks down particle pollution - also known as PM2.5 or soot - into short-term, or daily spikes, and the annual average "year-round" level.

It said the short term is an example of the impact of climate change, citing changing weather patterns that cause more "frequent and severe" wildfires.

About 65 million people are living in counties that saw "unhealthy spikes" in particle pollution.

"In the three years covered by this report, individuals in the U.S. experienced the highest number of days when particle pollution reached 'very unhealthy' and 'hazardous' levels in the 25 years of reporting the 'State of the Air,' the report said.

It also listed the top five cities most polluted by short-term particle pollution.

Bakersfield, Calif.
Fresno-Madera-Hanford, Calif.
Fairbanks, Alaska
Eugene-Springfield, Oregon
Visalia, Calif.

The report said more than 90.7 million people live in counties where year-round particle pollution levels were below the EPA's new, stricter air quality standards - the highest number in the report's history.

The top five cities in this category are:

Bakersfield, Calif.
Visalia, Calif.
Fresno-Madera-Hanford, Calif.
Eugene-Springfield, Oregon
San Jose-San Francisco-Oakland, Calif.

"State of the Air" also listed the five cities with the worst ozone pollution, which can cause shortness of breath, coughing and asthma attacks.

They are:

Los Angeles-Long Beach, Calif.
Visalia, Calif.
Bakersfield, Calif.
Fresno-Madera-Hanford, Calif.
Phoenix-Mesa, Ariz.

The five cleanest cities, which must " experience no high ozone or particle pollution days and rank among the 25 cities with the lowest year-round particle pollution levels" are:

Bangor, Maine
Johnson City-Kingsport-Bristol, Tenn.-Va.
Lincoln-Beatrice, Neb.
Urban Honolulu, Hawaii
Wilmington, N.C.