Millions Of Residents Exposed To Toxic Metals From LA Fires, Study Shows

As homes ignited and burned down during the 2025 Los Angeles fire, millions of California residents were exposed to a high concentration of airborne toxic metals, a new study discovered.

Almost two years ago, wildfires spread through southern California killing at least 31 people and destroying 16,000 structures — but the extent of the blaze’s far-reaching effects remained unclear. Researchers measured the chemical signatures emitted between urban fires and wildfire smoke to find approximately 7 million Californians inhaled deadly heavy lead poisoning in the air during the first 24 hours of the devastating fires, a study published Wednesday in Science Advances found.

Researchers measured particles present in the smoke every hour during the fires’ blaze and recorded the data in the Atmospheric Science and Chemistry mEasurement NeTwork (ASCENT), according to the study.

ASCENT is the U.S.’s first measurement network able to measure the chemical composition of airborne particles in real time, a researcher told the Associated Press.

The researchers compared the chemical makeup of the smoke from the LA fires with smoke from a 2024 wildfire in Riverside County which mostly burnt vegetation, the study reported. By contrasting the measurements in these two smoke plumes, scientists found the LA fire contained 50 times more lead, three times more arsenic and seven times more halogens. At the peak of the burning, about 7 million people were exposed for a full day to lead levels more than 80 times the typical average, the study found.

“One of the real advantages of this study is that it had the opportunity to make measurements sort of hour-by-hour across the sampling network,” Ed Avol a professor at University of Southern California, who was not involved in the study, told the AP. “And typically we make measurements of airborne particulates and so forth a couple of times a week, at best.”

Thousands of homes burned during the LA fires and toxins from incinerated cars, paint, furniture and chemicals under sinks entered the air the study found. In the aftermath of the fires, researchers also linked this smoke inhalation to tens of thousands of deaths across the United States in a previous study, the AP reported in February.

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