Emergency room visits for heart attacks at Cedars-Sinai Medical Center in Los Angeles increased by 46% in the 90 days following the Palisades and Eaton fires that erupted in January 2025, according to a new study. The research highlights the significant, and often overlooked, cardiovascular impacts of wildfire smoke exposure on public health.
In addition to the surge in heart attack cases, researchers observed a 24% rise in visits related to respiratory illnesses and a 118% increase in unusual blood test results during the same period, compared to the previous seven years. These findings were published Wednesday in the Journal of the American College of Cardiology.
The study, part of an ongoing research project documenting the long-term health effects of the fires, adds to a growing body of evidence suggesting that wildfires pose a greater threat to human health than previously understood. While other U.S. Wildfires have impacted larger areas or resulted in more direct fatalities, the Palisades and Eaton fires were particularly dangerous due to the unique composition of materials burned.
“The Eaton and Pacific Palisades fires had an immediate effect on people’s health,” said researchers at Cedars-Sinai. The fires burned not only trees and brush, but also a “toxic stew” of cars, batteries, plastics, electronics, and other man-made materials.
Researchers noted that there is no precedent for this level of exposure to such a complex mixture of smoke. “Los Angeles has experienced wildfires before, and will experience them again, but the Eaton and Palisades fires were unique in their size, scope, and the sheer volume of materials that burned,” explained Dr. Joseph Ebinger, a cardiologist at Cedars-Sinai and the study’s lead author.
Interestingly, the research team did not find a significant increase in the overall number of emergency department visits during the period between January 7, when the fires began, and April 7. Dr. Susan Cheng, director of public health research at Cedars-Sinai and senior author of the study, noted that the department saw fewer in-person visits for mental health emergencies and chronic conditions compared to the same timeframe in previous years.
This decrease was offset by the increase in visits for acute cardiovascular issues and other serious, sudden-onset illnesses. The team also analyzed blood test results from patients visiting the emergency department with unexplained physical symptoms, such as dizziness or chest pain not related to heart attacks.
These blood tests revealed abnormal results at more than double the rate observed in previous years. According to Cheng, these atypical findings spanned a range of blood panel markers, including electrolyte imbalances, protein level changes, and alterations in kidney or liver function tests.
The persistence of these abnormal test results over the three-month period led the team to conclude that exposure to wildfire smoke induced a “kind of biochemical metabolic stress on the body that likely affects not just one organ system, but many,” Cheng said. “This resulted in a constellation of different types of symptoms affecting different people.”
Joan Casey, an environmental epidemiologist at the University of Washington who was not involved in the Cedars-Sinai study, pointed out that the research identified health effects lasting longer than those observed in similar studies. “Three months is a very long period to monitor elevated visits, as most studies focusing on acute care use after wildfire smoke exposure have found increases in visits over roughly a one-week period,” Casey said. Previous research found a 27% increase in respiratory visits for Kaiser Permanente outpatients in Southern California living within 12.4 miles of burn areas in the week following the fires.
“The Los Angeles fires were a very severe event, involving not only smoke but also evacuations and significant stress on the population, and the effects may have persisted longer ” Casey added.
While 31 deaths have been directly attributed to injuries sustained in the fires, researchers believe the actual death toll is likely much higher when considering fatalities resulting from health conditions exacerbated by the smoke. A research letter published earlier this year in the Journal of the American Medical Association estimated 440 excess deaths in Los Angeles County between January 5 and February 1, accounting for deaths caused by factors ranging from air pollution exposure to disruptions in healthcare access due to closures and evacuations.
A team from Stanford University recently projected that exposure to wildfire smoke, specifically, contributed to 14 additional deaths.
Wildfires are a major source of fine particulate matter pollution, with particles 2.5 micrometers in diameter or smaller small enough to cross the blood-brain barrier and reach the outer branches of the lungs. Compared to other sources, wildfire smoke contains a higher proportion of ultrafine particles small enough to penetrate the brain after inhalation, according to Casey. The smoke has been linked to a range of health problems, including dementia, cancer, and cardiovascular failure.
Over the past decade, an increasing number of wildfires have erupted in Western states, generating enough fine particulate matter pollution to reverse years of improvements made under the Clean Air Act and other pollution control measures.
