LA Wildfire Smoke Exposed 7 Million to Dangerous Toxic Metals

A catastrophic 2025 Los Angeles firestorm exposed some 7 million people to high levels of airborne lead and other toxic metals released from burning homes and vehicles, according to a new study.

Scientists for the first time were able to quantify in real time the chemical composition of wildfire smoke thanks to a sensor network that went online months before the January 2025 Eaton conflagration that destroyed more than 9,400 buildings, killing 19 people.

Related: Will California’s New Smoke Claims Law Create a Recovery Bottleneck?

As climate change triggers urban firestorms like the inferno in the LA suburb of Altadena, the paper published Wednesday in the journal Science Advances offers the first indication of how the incineration of homes, electronics, cars and infrastructure could affect even people who live far from the burn zone due to wind-blown toxic smoke.

The researchers determined that over a 24-hour period, smoke from the fire contained 80 times the concentration of lead normally found in the atmosphere. Lead is a neurotoxin linked to an array of health effects and is particularly harmful to children. Sensors also detected highly elevated levels of arsenic and other toxins. The smoke plume covered eastern LA and the San Gabriel Valley and affected about 70% of the county’s population.

Nga Lee (Sally) Ng, a co-author of the study and a professor of environmental science and engineering at the California Institute of Technology, said that while chronic exposure to metals like lead is well-studied, the health effects from short-term exposure to highly concentrated airborne toxins remains largely unknown.

“The hope is that with these real-time measurements, we can better understand and characterize the health impacts of these short-term exposures,” she said.

The data on Eaton was collected by a Los Angeles monitoring site that happened to be downwind of the fire. It’s part of the Atmospheric Science and Chemistry Measurement Network (ASCENT) that has established stations across the country. Ng, who is a principal investigator for the National Science Foundation-funded project, said the LA site wasn’t able to collect data on the Palisades fire, which ignited 34 miles away from the Eaton site hours earlier, due to the wind direction.

Related: Edison Drops on Willful Misconduct Allegations in Eaton Fire Case

ASCENT also allowed the researchers to track how the toxic composition of the smoke plume changed over time as the fire burned, according to Haroula Baliaka, the study’s lead author who was a PhD candidate at Caltech at the time. That could help health researchers pinpoint health impacts from urban firestorms.

She said the study results should encourage policymakers to rethink strategies for evacuating residents from urban wildfires, given toxic smoke exposure can occur far from the burn zone. “I can envision that in the future we have these evacuation zones for smoke exposure as well,” said Baliaka. “Unfortunately, this is not a one-time event. It’s a new reality and we need to adapt to it and we need to do it sooner rather than later.”

Top photo: A fallen street light on the road during the Eaton Fire in Altadena, California, on Wednesday, Jan. 8, 2025. Bloomberg.