LA Wildfire Smoke May Have Exposed Millions to Toxic Lead and Metals
WHO:
ABC News - Researchers from the California Institute of Technology studied the chemical composition of smoke from the Eaton Fire.
ABC News - Nga Lee “Sally” Ng, a study author, said, “The main, key finding is really that wildfire smoke is very different fundamentally from the urban smoke.”
ABC News - Haroula Baliaka, a study co-author, said comparing urban-fire and wildland-fire smoke composition helps address a gap in research.
ABC News - Ed Avol, professor emeritus at the University of Southern California’s Keck School of Medicine, commented on the study and was not involved in it.
ABC News - Yaguang Wei, an assistant professor at the Icahn School of Medicine at Mount Sinai, said the findings were not surprising and had policy implications; he was not involved in the study.
Phys.org - Caltech scientists published a detailed analysis of atmospheric particles in the Eaton Fire smoke plume.
WHAT:
ABC News - Nga Lee “Sally” Ng said the measurement technology let researchers “actually see the very detailed component of these particles that we are breathing.”
ABC News - Ng said ASCENT is the first U.S. measurement network able to measure the chemical composition of airborne particles in real time.
ABC News - A recent study found that metal mixtures in smoke, ash and debris from the 2023 Maui wildfires harmed the lung health of people living nearby long after the fires.
ABC News - Smoke exposure across the United States has been linked to tens of thousands of deaths annually.
ABC News - Yaguang Wei said his findings reinforced a study he co-authored that found PM2.5 from wildfire smoke was more toxic than particulates from other sources.
ABC News - Ed Avol called the study a reminder of a “strange and increasingly dangerous new world” where urban and wildland areas intersect and increasingly catch fire.
Phys.org - A national study found that American children are increasingly exposed to air pollution as wildfire smoke becomes more common, while some schools and child care centers struggle to maintain clean indoor air.
ABC News - At the fires’ peak, about 7 million people were exposed over 24 hours to airborne lead levels more than 80 times the typical background level.
ABC News - The Eaton Fire plume contained 50 times more lead, three times more arsenic, and seven times more halogens than smoke from a 2024 Riverside County fire that mainly burned vegetation.
ABC News - The fires killed at least 31 people and destroyed more than 16,000 structures, mostly homes.
ABC News - Lead can harm children’s development, lower IQ scores, and raise adults’ blood pressure; arsenic exposure is associated with cancers. Researchers said the effects of short-term, high lead exposure remain unknown.
ABC News - Avol said the study recorded measurements hour by hour across a sampling network, whereas airborne-particle measurements are typically made only a couple of times a week at best.
ABC News - Wei said burning homes can release metals from wall paint, plastics, and electronics. He advocated stronger public-health protections, more wildfire monitoring and public alerts, and more prescribed fires.
Phys.org - The Eaton Fire devastated much of Altadena and surrounding areas.
WHERE:
ABC News - The fires burned in Altadena and the Pacific Palisades, in Los Angeles.
Phys.org - Altadena is in Southern California’s San Gabriel Valley.
WHEN:
ABC News - The fires began on Jan. 7, 2025.
ABC News - The study was published in Science Advances.
WHY:
ABC News - Researchers linked higher concentrations of lead, arsenic, and halogens in urban-fire smoke to burning vehicles, building materials, and electronics.
ABC News - Researchers said drier, warmer conditions associated with human-caused climate change contribute to larger, more intense, faster-moving, and more frequent wildfires; urban growth and climate change are bringing more fires into cities.
HOW:
ABC News - Researchers used the Atmospheric Science and Chemistry mEasurement NeTwork (ASCENT), whose instruments measured fine particulate matter (PM2.5) and trace elements hourly in real time.
ABC News - Researchers tracked smoke chemistry over the fires’ course, distinguished emissions from burning structures, and estimated the number of people exposed to heavy metals.
ABC News - The study compared the Eaton Fire plume with pre-fire lead levels and smoke from a 2024 vegetation fire in Riverside County.
Phys.org - Caltech scientists conducted a detailed analysis of atmospheric particles in the Eaton Fire plume.
(UPDATED October 28, 2026 22:04 UTC)
A Caltech study found that smoke from the Eaton Fire in Los Angeles contained far higher levels of toxic elements than smoke from a fire that mainly burned vegetation, including 50 times more lead, three times more arsenic and seven times more halogens. Using a national network that measures airborne particles hourly, researchers estimated that about 7 million people were exposed to lead levels more than 80 times the typical background level at the fires’ peak, while noting the health effects of short-term exposure remain unknown. The researchers linked the metals to burning buildings, vehicles and electronics, and said the findings highlight the need for stronger public-health protections and wildfire monitoring.
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(UPDATED October 28, 2026 20:03 UTC)
A Caltech study found that smoke from the Eaton Fire contained far more toxic metals than smoke from a fire that mainly burned vegetation, with about seven million people exposed to airborne lead levels more than 80 times typical background levels at the fires’ peak. Researchers traced the elevated lead, arsenic and halogens to burning homes, vehicles and electronics, and said the study’s hourly measurements reveal a key difference between urban and wildland fire smoke. The fires killed at least 31 people and destroyed more than 16,000 structures, while researchers said the health effects of short-term exposure to high lead levels remain unknown.