A recent study revealed that during the devastating Los Angeles fire in 2025, millions of California residents were exposed to high levels of airborne toxic metals. As the flames engulfed homes, the full impact of the wildfire, which claimed at least 31 lives and destroyed around 16,000 structures, wasn’t immediately clear.
The research indicated that approximately 7 million Californians inhaled significant amounts of lead and other hazardous metals in the air within the first day of the fires. This information comes from a study released on Wednesday in Science Advances, where researchers compared the emissions from urban fires and wildfire smoke.
The scientists collected data every hour during the fire using the Atmospheric Science and Chemistry Measurement Network (ASCENT). This network is noted as the first in the U.S. capable of real-time analysis of the chemical composition of airborne particles, as mentioned by a researcher speaking with the Associated Press.
By analyzing the differences in smoke from the LA fires compared to a 2024 wildfire in Riverside County, which primarily affected vegetation, the researchers established that the LA fire produced 50 times more lead, three times more arsenic, and seven times more halogens. Alarmingly, at the height of the fire, about 7 million people were exposed to lead levels over 80 times higher than the typical average.
Ed Avol, a professor at the University of Southern California who wasn’t part of the study, noted the study’s strength lay in its ability to provide hour-by-hour measurements. “Typically, we only manage to collect data on airborne particulates a couple of times a week,” he remarked.
As thousands of homes were consumed by the flames, toxic substances from burnt materials like cars, furniture, and household chemicals also filled the air. Previous research has linked this smoke inhalation to tens of thousands of deaths across the U.S., as reported by the AP earlier this year.
