At the height of the Los Angeles County wildfires, atmospheric concentrations of lead, a neurotoxin, reached 100 times average levels even miles from the flames, according to early detailed measurements obtained by The New York Times. Levels of chlorine, which is also toxic at low concentrations, reached 40 times the average. The spiking levels underscore the added danger from wildfires when cars, homes, and other structures burn, researchers said. Lead is often present in paint and pipes used in older homes, while chlorine and other chemicals are generated when plastic melts or combusts.

These fires were "a wake-up call," said Haroula Baliaka, a Ph.D. candidate in atmospheric chemistry at the California Institute of Technology, who is part of a new nationwide effort to monitor airborne chemicals in real time. They are "no longer just about burning trees and grass," she said. "They are urban wildfires, fueled by the very materials that make up our homes and cities."

As climate change, combined with new development, increases the chances that wildfires strike more densely populated parts of the world, concerns over toxic releases are likely to grow. For Los Angeles, the toxic smoke means that the eventual death toll from the fires, as well as longer-term health burdens, is likely to grow. Breathing in lead can damage the brain and nervous system, particularly in children. Levels of lead in the air during the fires briefly but dramatically exceeded the long-term safety levels set by the Environmental Protection Agency. Chlorine can damage the lungs and respiratory tract.

Overall, high levels of particle pollution in wildfire smoke have been linked to increased risk of cardiovascular and respiratory illnesses and death. A study published last year found that wildfire smoke may have killed as many as 12,000 Californians prematurely in 2018, when the Camp fire burned the town of Paradise and other communities in Northern California. Wildfire smoke is starting to erode the world's progress in cleaning up pollution from tailpipes and smokestacks, as climate change supercharges fires, scientists have said.

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https://www.nytimes.com/2025/01/20/climate/los-angeles-wildfires-lead-chlorine-air-quality.html