How clean is the air you breathe? For the past 19 years, the American Lung Association has released an annual "State of the Air" report, using data from official air quality monitors to look at pollution levels in cities across the U.S.
Over 133.9 million Americans now live in counties with unhealthy levels of air pollution, the organization says -- more than two of every five people. That's up from 125 million people in the 2017 report.
The American Lung Association evaluated cities for three types of air pollution: ozone (often called "smog"), year-round particle pollution, and short-term particle pollution.Particle pollution refers to the small liquid and solid particles that come from burning fossil fuel and other sources, small enough to float in the air and get inhaled into the lungs.
The health risks include lung cancer, asthma attacks, and developmental problems among children, among other issues.
Here's a look at the 16 communities with the highest year-round particulate levels -- some of the places where air pollution could pose the greatest risk to your health.
#15 (tie): Houston-The Woodlands, TX
Houston tied 15th highest year-round particle pollution out of 187 metro areas included in the report. It also ranked 11th out 227 cities for high ozone days.
#15 (tie): Harrisburg-York-Lebanon, PA
This metro area tied for 15th highest annual particle pollution levels. It ranked 22nd for 24-hour particle pollution.
In addition to fossil fuels, "burning firewood and trash are among the major sources of particle pollution (soot) in many parts of the country," the report notes.
#15 (tie): Birmingham-Hoover-Talladega, AL
The Birmingham metro area tied for 15th highest annual particle pollution levels. But it was #1 on the list of cleanest metro areas in 24-hour particle pollution.
#14: Detroit-Warren-Ann Arbor, MI
Motor City and its neighbors ranked 14th out of 187 metro areas for annual particle pollution levels, but scored somewhat better when it comes to high ozone days: 40th out of 227.
#13: Indianapolis-Carmel-Muncie, IN
The Indianapolis-Carmel-Muncie metro area of Indiana had high year-round levels of particle pollution, ranking 13th out of 187. Studies have shown that chronic exposure to particle pollution can shorten life by one to three years.
#12: Philadelphia-Reading-Camden, PA-NJ-DE-MD
The metropolitan area encompassing Philadelphia ranked 12th out of 187 in the country for year-round particle pollution. It was also 24nd out of 227 cities for its high ozone levels.
"The burden of air pollution is not evenly shared. Poorer people and some racial and ethnic groups are among those who often face higher exposure to pollutants," the report says.
#10 (tie): San Jose-San Francisco-Oakland, CA
The San Jose-San Francisco-Oakland metropolitan area tied for 10th out of 187 cities for annual particle pollution, and was 6th out of 201 cities for 24-hour particle pollution. It ranked 13th for high ozone levels.
#10 (tie): Cleveland-Akron-Canton, OH
This area was number 10 out of 187 metropolitan areas for yearly particle pollution but scored much better -- No. 68 -- for 24-hour particle pollution. It ranked 30th for high ozone.
#8 (tie): Pittsburgh-New Castle-Weirton, PA-OH-WV
This region was 8th out of 187 metropolitan areas for annual particle pollution. It ranked 10th for 24-hour particle pollution and 32nd for high ozone days.
#8 (tie): Lancaster, PA
Lancaster ranked 8th for annual particle pollution out of 187 metropolitan areas. But its ozone levels were better, placing the community at No. 62 out of 227 metro areas in the rankings.
#7: El Centro, CA
El Centro, near the Southern California border, ranked 7th out of 187 cities for yearly particle pollution. It ranked high in the other categories as well -- 9th for 24-hour particle pollution and 15th for high ozone days.
The health risks of air pollution can be especially worrisome for children, the report notes, "because their lungs are growing and because they are so active."
#6: Modesto-Merced, CA
The Modesto-Merced area in California's Central Valley had poor air quality by all measures in the American Lung Association report. It ranked 6th for annual particle pollution, 5th for 24-hour particle pollution and 7th for high ozone days.
#5: Fresno-Madera, CA
The Fresno-Madera metro area in California ranked 5th out of 187 metropolitan areas for yearly particle pollution. It also ranked very high in the other categories, coming in 3rd for 24-hour particle pollution and 4rd for high ozone days.
#4: Los Angeles-Long Beach, CA
Notorious for its smog, the Los Angeles-Long Beach, California, area has seen air quality improve in recent years, but it still placed 4th for annual particle pollution and 7th for 24-hour particle pollution.
L.A. ranked worst out of 227 metropolitan areas for high ozone days.
To protect yourself, the American Lung Association advises avoiding outdoor exercise when air pollution levels are high, and avoiding exercise near high-traffic areas.
#3: Bakersfield, CA
Bakersfield has some unhealthy air. Beyond being ranked third for yearly particle pollution, it ranked worst for 24-hour particle pollution and 2nd for high ozone days.
#2: Visalia-Porterville-Hanford, CA
Coming in second on the list was the Visalia-Porterville-Hanford metro area in California's San Joaquin Valley. It's a bit of an improvement over 2017's #1 worst ranking.
It also ranked 2nd for 24-hour particle pollution and 3rd for high ozone days.
#1: Fairbanks, AK
This city in central Alaska ranked worst for annual particle pollution levels for the first time, due to the burning of wood and other solid fuels to heat homes during the long winter.
But on the bright side, it also tied for first place on the list of cleanest cities when it comes to ozone pollution.