Maui wildfire survivors show elevated metals tied to poorer lung function, study finds

Residue left behind by the 2023 Maui wildfires carried metal mixtures that were associated with weakened lung health in nearby residents long after the flames died down, according to new research published in the Proceedings of the National Academy of Sciences.

The study, led by researchers at the University of Hawaii, examined urine samples from about 1,400 adults and found substantially elevated concentrations of metals including arsenic, cadmium, copper and antimony — detected as much as a year and a half after the fires. The researchers suggest these metals may have come from burned buildings, vehicles, electronics and other materials destroyed in the blaze, producing a different kind of exposure than the burned vegetation typically studied after large fires.

Participants with higher combined metal mixtures were more likely to show abnormal results on standard breathing tests, including reduced breathing capacity and difficulty moving air in and out of the lungs. The lung effects followed the geographic spread of smoke and ash, with residents closest to Lahaina, Wailuku and Kahului showing a different pattern from those near Kula.

Alika Maunakea, a professor at the University of Hawaii at Manoa, said the findings point to persistent heavy metal burdens among exposed individuals that could be contributing to poor health outcomes. He cautioned that the study cannot determine how much of a person's exposure came specifically from the fire, nor can it prove that the metals caused the lung function findings. Still, he said, the results implicate environmental exposures that may linger over time.

Ruben Juarez, an economist at the university, said the Maui Wildfire Exposure Study was designed to follow people over time because the health consequences of such a disaster can continue long after the immediate emergency. The research examines a broad picture, including lung health, biological exposure, mental health and housing displacement.

Juarez said climate-related disasters can alter the environment in ways that outlast the emergency itself, disturbing soil, debris, buildings and legacy contaminants, and creating pathways for exposure. He said the broader lesson is that disaster response should not end when the visible danger is gone.

The wildfires, which spread from a brushfire driven by downed power lines and strong winds in August 2023, destroyed the town of Lahaina and killed more than 100 people, making them among the deadliest in U.S. history. The study's authors say post-wildfire air quality needs longer-term monitoring, and that recovery efforts should account for what may remain in contaminated soot, residue and dirt well after burning stops.

Wildfires are becoming larger, more intense, faster-moving and more frequent in parts of the world, experts say, driven in part by warming and drier conditions linked to climate change.