New research published in the Proceedings of the National Academy of Sciences reveals that survivors of urban firestorms retain high concentrations of toxic metals in their urine for up to 18 months, exposing a severe health threat from man-made building materials incinerated by wildfires.
Toxic Smoke Aftermath in Maui and Los Angeles
When wildfires sweep into populated areas, they transform into urban conflagrations fueled by hazardous synthetic components. Walls covered in lead paint, insulation containing asbestos, copper-coated wiring, and plastic furniture burn alongside natural vegetation. This lethal combination releases concentrated chemical plumes entirely distinct from standard wilderness fires.
A study of 1,400 survivors of the devastating 2023 Maui blaze tracked biological markers following the disaster, which claimed more than 100 lives according to a federal after-action report. Researchers discovered elevated toxic metals in participants’ urine stretching nearly a year and a half post-fire. Individuals displaying higher metal volumes regularly struggled on breathing tests, pointing toward lasting pulmonary complications.
Atmospheric chemists observed a similar phenomenon closer to the mainland during the 2025 Eaton Fire. Scientists at the University of California at Los Angeles documented lead concentrations in the local smoke plume reaching up to 250 times higher than normal baselines. Additional hazardous substances, including arsenic, copper, and bromine, remained detectable in the air more than 15 miles away from the active blazes.
“A normal [wilderness] wildfire would not have such high concentrations of most of those elements,” said Suzanne Paulson, an atmospheric chemist at UCLA who led the research published last month in the American Chemical Society’s journal ES & T Air. “It’s a really complex and toxic mixture of chemicals we don’t normally see.”
Mapping the Contaminants Across Vulnerable Communities
Researchers investigating the Los Angeles region utilized advanced air-monitoring instruments maintained by the South Coast Air Quality Management District to parse hourly elemental concentrations. This technology isolated toxins originating from the Eaton Fire from standard industrial and vehicular pollution.
The vast quantities of lead detected in Altadena—where roughly 10,000 structures burned—reflect older housing stocks constructed before federal bans on lead paint and asbestos insulation. Yet, monitoring data confirmed that ambient air quality in unaffected zones returned to normal levels within a week of the fire’s containment.
Conversely, biological tracking inside the burn zone on Maui revealed prolonged exposure risks. Months after Lahaina burned, researchers from the University of Hawaii measured urine samples showing antimony concentrations 40 times higher than the overall U.S. population. Concentrations of manganese, barium and arsenic were at least twice as high as in the general public.
| Contaminant Detected | Observed Level in Survivors | Primary Material Source |
|---|---|---|
| Antimony | 40x national average | Pipe metal, textiles, plastics, paints |
| Arsenic | 2.2x national average | Legacy agricultural herbicides, treated wood |
| Lead | Significantly elevated in plume & soil | Pre-ban paint, older housing stock |
Environmental Legacy and the Risk of Remobilization
Many toxins found in survivor samples correspond directly with heavy metal deposits recorded in local ash. Alika Maunakea, co-author of the Maui Wildfire Exposure Study, noted that some contaminants may have spent years lying dormant in the landscape before flames remobilized them. Arsenic levels among study participants were 2.2 times higher than the general population, which may stem from historical use on former sugar plantation lands surrounding Lahaina.
Data showed that patients tested six months post-fire maintained metal concentrations comparable to those evaluated a full year later. This persistence indicates that residents continue inhaling microscopic toxins mixed with household dust or settled on exterior surfaces.
“The national lesson we are seeing from Maui is that we should not assume the disaster is over because the flames are out or the air is clean,” said Ruben Juarez, who co-directs the Maui Wildfire Exposure Study.
