Los Angeles wildfires show growing health threat of wildfire smoke
Research links deadly 2025 California fires to a spike in deaths and hospital visits, as smoke erodes air quality gains.
LOS ANGELES — Ecologist Olivia Sanderfoot evacuated her West Los Angeles home with her infant son in January 2025 as the Palisades Fire approached, terrified of the dangerous fumes she studies.
"Even just thinking about the smoke in small quantities, I was like: 'I am not doing this to my kid,'" said Sanderfoot.
The Palisades and Eaton fires killed 31 people, destroyed nearly 16,000 structures and forced more than 200,000 to evacuate.
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Hundreds more people died in Los Angeles that month compared to a typical January, with poor air quality from the fires likely a major reason.
At one emergency room in the 90 days after the fires, visits for pulmonary illness surged 24 percent and heart attacks rose 46 percent, according to Cedars-Sinai cardiologist and researcher Susan Cheng.
Abnormal blood work linked to general illnesses also more than doubled, a surprising and highly significant finding, Cheng said.
She said the consequences for the millions exposed will take years to unravel, and she is collaborating on a 10-year research program to understand the health effects.
Such investigations are increasingly important as larger wildfires generate more air pollution across North America, often far beyond the flames.
Smoke from wildfires is stalling and even reversing invaluable air quality gains made since the Clean Air Act of 1970, said Marshall Burke, director of Stanford University’s Environmental Change and Human Outcomes Lab.
"What the data really show is how rapidly we’re unraveling decades of progress we had made," said Burke.
His research estimated that wildfires between 2016 and 2022 erased 25 percent of particulate matter (PM 2.5) air quality improvements since 2000 in nearly three-quarters of the United States.
These tiny particles, emitted when something burns, work deep into lungs and the bloodstream, exacerbating respiratory ailments, increasing cardiovascular disease risk and shortening lifespans, said University of Wisconsin-Madison air quality expert Tracey Holloway.
"When they study whether almost any adverse health outcome gets worse with air pollution, the answer is: It does," Holloway said.
Holloway notes smoke is not as pervasive as historic industrial pollution, but its effects can be severe and are projected to worsen with climate change.
Wildfires in North America are expected to continue emitting more greenhouse gases and air pollutants, with other regions similarly at risk, according to the World Meteorological Organization.
For Sanderfoot, who studies how birds fare when smoke pollutes the air, the intense smoke events confirmed her research was on the right track.
"In wildlife ecology, we had often thought about air pollution as a done deal; we have the Clean Air Act," she recalled.
In an era of intensifying wildfires, she said, we may need to think again.
With files from National Audubon Society