Over one-third of Americans, or about 130 million people, routinely breathe in unhealthy air, according to the newest State of the Air report from the American Lung Association (ALA). That number is larger in 2023 than in years past, despite significant long-term and ongoing efforts to clean the nation's air. And climate change, the report says, is making the job harder.

Hotter temperatures lead to more ozone formation and can make the air dustier, too. But the biggest climate-fueled pollution challenge comes from wildfire smoke, which has added vast quantities of dangerous fine particle pollution to the air. Western states like California and Colorado have found that wildfire smoke is counterbalancing long-term, successful efforts to clean up pollution from human-controlled industrial sources, like coal-fired power plants and diesel truck exhaust.

"Wildfires are changing the landscape, literally and figuratively," says Katherine Pruitt, national policy director at the American Lung Association.

Long-term air improvements interrupted in the West

Since the passage of the landmark Clean Air Act in 1970, the country's air has improved markedly. Measures like adding pollution control to cars, trucks, and fossil-fuel-burning power plants cut down on the amount of fine particles in the air. Those particles can penetrate deep into people's lungs and even cross into the bloodstream, where they contribute to a range of chronic and acute health risks.

Between 1990 and 2020, pollution from those fine particles dropped by about 40% nationwide. The improvements were particularly noticeable in industrial East Coast cities and states.

This year's State of the Air report reiterates that most of the country, most notably the eastern U.S., has gotten cleaner over time as industrial pollution sources have been reined in.

But in the West, 2023 had the most days ever recorded with dangerous or very dangerous air quality, measured by the Air Quality Index. And for the first time in the report's 25-year history, the 25 cities with the worst short-term particle pollution in the country were all in the Western U.S.

"The severity of the pollution is unprecedented," says Pruitt.

The report highlights an increasingly clear challenge, says Susan Anenberg, an air quality expert at George Washington University and a consultant for the EPA. Through regulations over past decades, "we've pretty much addressed the easiest ways of reducing pollution," she says. "So we have catalytic converters on our vehicles, we have diesel particulate filters on our trucks, we have scrubbers on our power plants."

But now, Anenberg says, the challenge is getting harder as human-driven climate change worsens some problems like ozone, a gas that forms near the ground when pollutants and some natural compounds react with sunlight and heat, and wildfire smoke. The easy wins, she says, are gone.

"It just really underscores that we need to do both things at the same time," Anenberg says. "We need to reduce carbon emissions that are causing anthropogenic climate change, and we need to continue to pursue stringent regulations on air pollution emissions."

A soup of unhealthy pollutants

The State of the Air report tracks particle pollution and ozone. Both are harmful to people's health, increasing the risk of respiratory problems like asthma. Fine particle pollution has also been linked to worse heart disease outcomes and even the development of dementia.

Bakersfield, California, has stayed at the top of the report's list for the U.S. city with the worst short-term particle pollution in the country for five years. This time, it also got top billing for year-round particle pollution, too. The region is a major site of oil and gas production as well as agriculture, both of which produce significant local pollution.

"Those industries are the main driver of our economy but also our air pollution," says Jasmin Martinez, an advocate at the Central Valley Air Quality Coalition who has lived most of their life in the San Joaquin Valley, where Bakersfield lies. The area has been heavily polluted for their entire lifetime, despite the federal and state laws mandating local industries to minimize pollution.

They chose to move back home after college even though they were well aware of the dangers. "It's always in the back of my mind, just living here, I may be just losing years of my life," Martinez says.

Air pollution helps hasten tens or even hundreds of thousands of premature deaths each year in the U.S. alone. It is one of the most profound public health risks in the nation, says Pruitt.

Bangor, Maine, and Honolulu, Hawaii, have some of the cleanest air in the country.

Unequal exposure to dirty air

While air in the U.S. got much cleaner overall after Clean Air Act-related regulations, the improvements were far from uniformly shared. Communities of color and low-income Americans have historically breathed in dirtier air than wealthier or whiter communities, a disparity that continues into 2024, the report says.

About 130 million Americans live in places where particle or ozone pollution exceeds levels the EPA considers healthy. About 70 million of those are people of color.

Pruitt stresses people of color are "more than twice as likely as white people to live in a place that gets failing grades" for short and long-term particle pollution and ozone, she says.

Opportunity for progress?

Late last year, the Environmental Protection Agency announced a long-awaited update to its regulatory standard for PM2.5, or fine particle pollution. The agency lowered the allowable pollution from 12 micrograms per meter cubed of air averaged over a year to 9—a major tightening, says Anenberg.

The tighter standard still far exceeds the World Health Organization's recommendation of 5 micrograms or less.

The American Lung Association used the new standard to calculate dangerous exposures. Applying the new value, they found the number of Americans exposed to unhealthy air rose from about 120 million people counted in the previous report to roughly 130 million.

What that really means, says Pruitt, is that "those people have been breathing unhealthy air for years." They simply weren't counted yet.

Meeting the new standard will take years to achieve, but Pruitt welcomes the rules. Next, she says, she hopes to see similar standard tightening for ozone pollution.

Meanwhile, climate change complicates efforts to clean up the air, says Anenberg. "This report tells us that we need to ramp up our carbon mitigation efforts so that we're slowing the rate of climate change because that climate change is putting more pollution into the air," she says. At the same time, "we need to redouble our efforts to reduce pollution from the sources where it's possible to reduce pollution."

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