Analysts collected daily and annual air pollution data from 2019-2021 for what the association called the most widespread and dangerous air pollutants – fine particles and ozone. They ranked each metropolitan area from the most polluted to the cleanest for annual particle pollution, annual ozone pollution and short-term particle pollution.
Top 25 cities with the worst air pollution
Los Angeles takes the top spot for the worst ozone pollution this year, as it has for 23 of the 24 years this report has been calculated.
Several places in California's Central Valley take top spots for particle pollution. Bakersfield and Fresno top the list for failing short-term particle pollution grades. Visalia and Bakersfield share the crown for worst annual particle pollution.
"Although cities most affected by western drought and wildfires, including eight in California, three in Oregon, and three others in Alaska, Arizona, and Washington, still represented the largest share, cities with high power plant emissions as well as local industrial and mobile sources of year-round particle pollution continued to show up on this list," stated the report about annual particle pollution.
Only Pittsburgh and Lancaster, Pennsylvania, made the short-term particle pollution fail list east of the Mississippi River.
These cities have the cleanest air in the US
Seven cities are on the cleanest-air list for all three measures: annual particle pollution, ozone pollution and short-term particle pollution. All had zero days in high particle and ozone pollution.
- Asheville-Marion-Brevard, North Carolina.
- Bangor, Maine.
- Greenville-Kingston-Washington, North Carolina.
- Lincoln-Beatrice, Nebraska.
- Rochester-Batavia-Seneca Falls, New York.
- Urban Honolulu, Hawaii.
- Wilmington, North Carolina.
Dangers of pollution
Particles from exhaust, smoke, dust storms and construction that are smaller than the width of a human hair can not only be inhaled but get trapped in the lungs. The finest particles can pass through the lungs into the bloodstream, according to the American Lung Association.
Inhaling fine particulate matter and pollution (less than 2.5 micrometers in diameter) and ozone at high levels can cause lung irritation that may take days to recover from. Research published by the National Institutes of Health indicated that both short-term and long-term air pollution exposure is linked to premature death.
Researchers found a "significant" increase in deaths within two days of high air pollution levels for people over 65 years old. The number of deaths rose as the ozone and particulate levels increased.
"We found that the mortality rate increases almost linearly as air pollution increases," wrote Dr. Francesca Domenici, author of the study. "Any level of air pollution, no matter how low, is harmful to human health."
Another study linked low birth weight in newborns and preterm labor for moms to air pollution.
Ozone at the Earth’s surface mixes with other pollutants (nitrogen oxides emitted by cars, power plants and other high-heat combustion) and VOCs (volatile organic compounds emitted by cars, factories, refineries and paint) to create smog. Ozone is harmful to inhale in high concentrations and can even be deadly.
Ozone, composed of three oxygen molecules, attacks lung tissue. Most at risk are kids, seniors, people who work or exercise outdoors and those with existing lung disease. The more a person breathes in, the more at risk they are of damage.
The most likely area to experience smog is downwind of the source, which can be miles away.
Besides premature death, ozone can cause shortness of breath, asthma attacks and can lead to an increased risk of respiratory infections for all ages. The EPA also reported that ozone pollution may cause cardiovascular harm (heart attacks, strokes) and damage the central nervous system.
One in three people, or 119.6 million of us, live in cities that the report gave failing grades for unhealthy levels of ozone and particle pollution. The report found that 63.7 million Americans are living in counties with "daily spikes in deadly particle pollution," which is the most ever reported under current national standards.
There is a silver lining, 17.6 million fewer of us breathe unhealthy air compared to last year's report.