Air quality in the U.S. improved from 2021 to 2022, a new report found, with the biggest increases in the West.
Pollution lessened in more than 8 out of every 10 cities in the country in 2022, according to an NBC News analysis of data from air pollution monitor IQAir.
Chet Wayland, director of the Air Quality Assessment Division at the Environmental Protection Agency, attributed the rise in air quality to 2022’s milder wildfire season. “That’s where we saw the biggest drop” in one of the main air pollutants, he said.
Redding, California, and the Denver suburb of Lakewood were among the cities that saw the largest improvement in air quality. The Dixie Fire in 2021, which burned close to Redding, had sent the town’s air pollution spiking.
There are caveats: IQAir’s data is collected from government monitors and an array of low-cost sensors, which have risen in popularity in recent years. The low-cost sensors can overstate the amount of pollution in the air, and, with cleaner air, sometimes understate it, Wayland said.
The amount of fine particulate matter in the air, or PM2.5, is one of several contributing factors to air pollution. PM2.5 per cubic meter represents how much of the air has inhalable particles measuring a fraction of the width of a human hair. PM2.5 is what causes the haze on hazy days, and exposure to it can lead to lasting health effects. The World Health Organization estimates that air pollutants are responsible for more than 4 million premature deaths per year.
The WHO and the EPA each have standards for annual PM2.5 levels: The EPA set its at 12.0 micrograms per cubic meter, though the agency is in the process of revising it. The WHO updated its standard in 2021 to 5 micrograms per cubic meter. While 95% of the 300 largest cities in the U.S. met the EPA’s current standard in 2022, only 8% met the WHO’s standard, NBC News’ analysis found.
Each region deals with its own air quality challenges, Wayland said. In the Western U.S., wildfires are a uniquely significant contributor to the fine particulate pollution caused by PM2.5.
Urban areas across the country face emissions-related pollution. In the Midwest, most particulate air quality issues stem from vehicle and industrial emissions. That describes the Northeast too, Wayland said, but in addition to that, the region is downwind of the rest of the country and suffers from pollutants blown in from elsewhere.
Particular to the South are natural “biogenic” emissions, which are emitted from soil and vegetation, Wayland said.