Smoke from LA fires exposed millions of people to high levels of toxic heavy metals, study says
At the height of the Los Angeles fires in 2025, millions of residents were exposed in a 24-hour period to toxic lead levels from smoke that were 80 times higher than the typical background level, according to a new study.
In 2025, the Los Angeles fires released toxic heavy metals into the air, exposing millions of residents to dangerous levels of lead, arsenic and halogens. Researchers from the California Institute of Technology analyzed smoke samples from the Eaton Fire and compared them to a different wildfire, discovering that the urban plume contained significantly higher levels of these metals.
Lead levels were 80 times higher than usual, while arsenic and halogens were 50 times and seven times higher, respectively. The main takeaway is that wildfire smoke is chemically distinct from urban smoke, according to study author Nga Lee Sally Ng. This new technology allowed researchers to detail the components of particulate matter in the air, providing crucial insights into the health impacts.
Co-author Haroula Baliaka emphasized that understanding these differences in smoke composition is vital as wildfires become more frequent and intense due to climate change. While the study's findings are not surprising to experts like Ed Avol, they highlight the urgent need for improved monitoring, public alerts and preventative measures to protect public health during these extreme events.
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