Study: Western U.S. wildfires undo 2 decades of air quality progress

What they found: From 2000 to 2020, air quality has worsened in the western U.S. due to wildfires.

• Black carbon concentrations have risen 55% on an annual basis, mostly due to the wildfires, researchers found.
• The fires have also caused an increase of 670 premature deaths per year in the region in the two-decade span.

Meanwhile, the eastern U.S. had no major declines in air quality during the same time period.

Yes, but: Daniel Swain, a climate scientist at UCLA, noted in a Monday night phone interview that most of the eastern half of North America had "terrible air quality from these record shattering wildfires in Canada" last summer.

• So if researchers examined the past couple of years, "that trend might have started to look a little bit different even in the rest of the country," said Swain, who was not involved in the study.

Of note: Air pollution contributes to almost 11,000 deaths in the U.S. annually, according to a 2021 estimate, while a 2022 study estimated that it contributed to at least 1.8 million excess deaths in 2019.

• Pollutants in wildfire smoke can cause a range of health problems, from wheezing and difficulty breathing to asthma, lung and heart conditions, and even increase heart attack risks, per the EPA.

What they're saying: "Our air is supposed to be cleaner and cleaner due mostly to EPA regulations on emissions, but the fires have limited or erased these air-quality gains," said Jun Wang, the study's lead corresponding author and chair of the University of Iowa's Department of Chemical and Biochemical Engineering, in a statement.

• "[A]ll the efforts for the past 20 years by the EPA to make our air cleaner basically have been lost in fire-prone areas and downwind regions," Wang added. "We are losing ground."

Context: Fires are likely to become more frequent and intense due to climate change.

• Multiple studies show climate change is a key driver behind increased wildfire risk.
• "If fires increase or become more frequent, our air quality will get worse," Wang said.

Between the lines: Jeremy Hess, a professor of environmental and occupational health sciences at the University of Washington, said the study findings were concerning but not unexpected.

• "We are worried that climate change will undermine and potentially reverse the progress that public health has made in this and other areas and are concerned to be seeing this happening now, as we can expect the climate to warm considerably more in the next several decades," Hess said in a Monday night email.

• Swain said the findings were consistent with other studies that contribute to the same overall picture that after the air quality regulations' great success, "the extremes of those air pollution episodes are actually now increasing again" due to wildfires.
• "On average, the air quality is still better, but the problem is, it's during these episodes of just-near apocalyptic conditions where we're really losing a lot of ground and that really is because the size and the intensity of wildfires has increased greatly," he said.

Be smart: Given climate change is a wildfire driver, keeping global heating to the lowest level possible will help. "But we're still going to see more warming no matter what moving forward, and so there will be further increases in the wildfire hazard," Swain said.

• There's emerging consensus among American, Australian and European experts that adopting fire management practices, such as prescribed, controlled or traditional Indigenous burning, could help mitigate fire risks, according to Swain, who co-wrote a study in October on how climate change is impacting prescribed fire windows in the U.S. West.
• Research indicates that smoke from managed burns is "less in volume and perhaps also less toxic," as crews wait for the right conditions and the fires don't consume vegetation, Swain noted.

Go deeper: How to protect yourself from wildfire smoke