Los Angeles Fire Smoke: New Data Reveal Extreme Lead Exposure
A study in Science Advances found that urban fire smoke contained heavy metal levels 80 times higher than background norms during the 2025 Eaton Fire.
By Harper Foster ·
Researchers from the California Institute of Technology report that millions of Los Angeles residents breathed smoke containing toxic lead levels 80 times higher than typical background concentrations during a single 24-hour period in January 2025. The findings, published Wednesday in the journal Science Advances, detail the chemical makeup of the Eaton Fire plume and distinguish it sharply from standard wildfire smoke.
Nga Lee Ng, an author of the study, explained that urban smoke is fundamentally different from wildland smoke. Using the Atmospheric Science and Chemistry mEasurement NeTwork, or ASCENT, the team measured trace elements in fine particulate matter every hour. This allowed them to identify specific chemicals released as the fire burned through structures, vehicles, and electronics. Ng noted that this new technology enabled them to see the detailed components of the particles people were breathing.
The Eaton Fire ignited on Jan. 7, 2025, alongside the Pacific Palisades fire. Together, the two infernos killed at least 31 people and destroyed more than 16,000 structures. The urban setting meant the fire consumed paint, furniture, and stored chemicals. Compared to a 2024 wildfire in Riverside County that burned mostly vegetation, the Eaton Fire plume contained 50 times more lead, three times more arsenic, and seven times more halogens.
Haroula Baliaka, a co-author, said understanding this chemical gap is necessary as urban growth and climate change push more fires into cities. Wildfires are growing larger and more frequent due to drier and warmer weather. Baliaka argued that emergency response and monitoring systems must adapt to these changing conditions.
Ed Avol, a professor emeritus at the Keck School of Medicine at the University of Southern California, called the exposure levels surprising because such data had not been documented before. He highlighted that the study’s ability to measure airborne particulates hourly provided a level of detail rarely seen in air quality research, which typically relies on measurements taken only a few times a week.
Lead is a neurotoxin that can stunt development in children and raise blood pressure in adults. While scientists still study the long-term effects of short-term high exposure, arsenic is associated with various cancers. Yaguang Wei, an assistant professor at the Icahn School of Medicine at Mount Sinai, said the findings align with his own research showing that wildfire smoke particulates are often more toxic than those from other sources.
Wei stated that burning properties releases toxic materials like wall paint, plastics, and electronics. He suggested that governments should invest in stronger monitoring and public alerts to protect residents during future events. Avol added that while we will continue using metal-containing materials in homes, the study serves as a reminder to think about how to minimize human exposure to these elements.
