LA Wildfires Increased Number of Reported Heart Attacks, Other Illnesses: Study

Researchers examined the unseen side effects of the Los Angeles wildfires, which hit Southern California in January 2025, and killed nearly 30 people.

According to the findings of new research, Los Angeles saw a 50% increase in heart attacks during the three months following major wildfires that burned throughout the area in early 2025.

The study was published last month in the Journal of the American College of Cardiology (JACC), suggesting that wildfire smoke may be much more harmful than previously thought. Researchers warn that L.A. residents suffered an increase in the number of health conditions, like heart attacks and lung problems, following wildfires compared to the seven years prior.

Spurred by strong Santa Ana winds and dry conditions, the January 2025 L.A. fires burned nearly 40,000 acres and destroyed thousands of homes, displacing tens of thousands of residents.

Following the destruction, a number of Los Angeles wildfire lawsuits were filed against Southern California Edison and other entities for their alleged role in failing to properly maintain and manage electrical equipment during extreme red-flag fire conditions, which plaintiffs claim contributed to the outbreaks and rapid spread of the blazes.

For the new study, researchers from Harvard, University of California Los Angeles, the University of Southern California and other institutions studied emergency room data from Cedars-Sinai Medical Center, the largest adult acute care medical center in Los Angeles County.

Led by Dr. Joseph Ebinger, the team focused on ER visits involving residents from zip codes directly affected by L.A. fires or adjacent to fire-affected zip codes. Cedars-Sinai is located 10 miles from where the Palisades fire occurred and 18 miles from the Eaton fire. They examined data for particulate matter, a type of tiny air pollution smaller than the width of a human hair that easily enters the respiratory system.

The data indicates levels of air pollution were significantly raised due to the fires. The average outdoor concentration of particulate matter with a diameter of less than 2.5 micrometers during the week after the fires started was 86.2 μg/m³. Comparatively, the average concentration during the week before the fires started was 14 μg/m³.

The research team identified the diagnoses that were most frequently discharged in the ER for visits within 90 days of the fires from January 7 to April 7, 2025, and compared the data with prior years from 2018 to 2024.

The data showed an immediate impact on human health, researchers concluded. While the average number of monthly ER visits were the same across all time periods, visits for some diagnoses were more common in the 90 days after the fires, including:

• 46% increase in heart attack visits
• 24% increase in visits for lung conditions
• 118% increase in other systemic illnesses needing emergency medical attention, such as visits for lower respiratory illnesses, dysrhythmia, high blood pressure conditions, head injuries and sepsis

Additionally, abnormal blood test results more than doubled in the 90 days after the fire began compared to the previous two years.

According to the researchers, wildland-urban interface (WUI) fires can be more harmful than typical wildfires because they spread quickly and consume a greater mixture of both biomass and industrial fuels than wildfires. WUI fires also spread easily into urban areas, not just wild areas, putting residents at risk.

The team said it is important to find ways to reduce the risks that wildfire air pollution poses to those in residential areas and help protect people from health side effects in the future.

They concluded more studies are needed to better determine the long-term risks of air pollution from wildfire smoke. Moreover, research is needed to explore ways to help reduce the health impacts during fires, they determined.

Wildfire Health Risks

Prior findings have also warned of the negative health impacts wildfire smoke may have on human health. Harvard research published in May 2025 suggested exposure to wildfire smoke increases a person’s risk of being hospitalized for several types of respiratory conditions. Another study published in July 2025 linked air pollution from wildfire smoke to a greater risk of suffering from heart failure.

An international study published in August 2025 warned that exposure to wildfire smoke is more harmful than exposure to smoke from vehicle emissions, increasing a person’s risk of death, especially from cardiovascular disease and respiratory conditions.

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