In the first 90 days after the devastating Palisades and Eaton fires that destroyed entire Los Angeles neighborhoods, there was a 46% increase in ER visits for heart attack symptoms at LA’s Cedars-Sinai hospital, according to a newly released study.
“Rates of heart attacks in January 2025 actually surpassed heart attack rates during all the prior Januaries, even during the Covid years,” Dr Susan Cheng, director of public health research at Cedars-Sinai and the study’s senior author, told the Guardian.
Residents in the zip codes directly affected by the January wildfires or located adjacent to a fire-affected area also reported a 24% increase in pulmonary illness and a staggering 118% increase in blood test abnormalities.
The Palisades fire was the most destructive fire in Los Angeles history, destroying 6,800 structures and killing 12 people. To the east, the Eaton fire devastated the neighborhood of Altadena, with 19 confirmed deaths. More than 9,400 structures were destroyed across Altadena and neighboring Pasadena and Sierra Madre.
The findings, which were released in the Journal of the American College of Cardiology, are part of a research project on the short- and long-term impact of the fires on human health.
Cedars-Sinai medical center is located approximately 10 and 20 miles from the epicenters of the Palisades and Eaton fires, respectively.
“What we saw during the wildfires was an excess of respiratory illness showing up in our ER that matched the worst years of Covid,” Cheng said. “And that was striking.”
While some increased respiratory illness was expected due to the effects of wildfire smoke,Cheng said she was surprised not only by the percentage of increase, but also by the jump in heart attack incidences and blood test abnormalities.
“For a very large number of people, the January wildfire exposures led to a biochemical or metabolic stress on the body that likely affected, not just one, but multiple organ systems,” she said.
The blood test data came from patients who reported physical symptoms that did not have a clear diagnosis, such as dizziness without clear signs of dehydration or chest pains without other signs of a heart attack. Cheng noted that the patients’ blood tests revealed subtle abnormalities.
“The blood tests could show their electrolytes were a little bit off, like sodium, potassium, or there’s a slight imbalance in their protein levels,” she said. “Or there’s a slight change in markers of kidney and liver function.”
The Palisades and Eaton fires were particularly harmful to human health due to their classification as a “wildland-urban interface fire (WUI)”. This type of fire spreads more easily than a wildfire-only or urban-only fire, burning a combination of organic materials and industrial fuels, such as plastic, batteries, and electronics.
While the data collected by Chang and her colleagues is a start, there are still many questions left to be answered on the long-term effects of January’s fires on human health. “There’s a lot of work to do,” she said. “We’re still working hard to put the pieces together.”
This story was amended on 17 December 2025 to correct a misprint in the journal study. The was a 118% increase in blood-test abnormalities after the January wildfires.
