Air quality in U.S. cities improved overall last year, a new report from the American Lung Association (ALA) concluded.
The report, which measures ozone and particulate matter pollution levels as an indicator of air quality, found that the number of Americans exposed to dangerous levels of both pollutants decreased in recent years.
But the report also found an increase in temporary spikes of particulate matter in numerous cities. Those are often due to wood burning, such as increased fireplace use or wildfires.
“This year’s ‘State of the Air’ report is a testament to the success of the Clean Air Act, which has reduced air pollution in much of the nation,” Harold Wimmer, the group’s president, said in a statement.
“However, this report adds to the evidence that the ongoing changes in our climate make it harder to protect human health. As we move into an ever warmer climate, cleaning up these pollutants will become ever more challenging, highlighting the critical importance of protecting the Clean Air Act.”
He called it “simply unacceptable” that people in some cities still live with unhealthy air pollution, and called on leaders to do more to reduce it.
The annual report, dubbed “State of the Air,” found that 125 million Americans are exposed to unhealthy pollution levels between 2013 and 2015, compared with 166 million between 2012 and 2014.
Residents of those counties account for 38.9 percent of the United States’ population, ALA said.
The ALA defined the unhealthy levels as “code orange” air quality days under the Environmental Protection Agency’s benchmarks, and passing grades for the annual particulate levels.
California cities had the worst air in all three categories the ALA examined.
Los Angeles is still the city with the worst ozone pollution. Bakersfield, Calif., still has the highest short-term particle pollution, while the Visalia-Porterville-Hanford area in California rose to the worst annual particle pollution.