Maui wildfire study links residents’ metal exposure with abnormal lung tests

University of Hawaiʻi researchers reported on September 28 that higher combined metal exposure was associated with abnormal lung-function measures in 1,400 Maui adults tested six to 18 months after the August 2023 wildfires. The findings, reported as published in the Proceedings of the National Academy of Sciences, raise a question for communities recovering from the Lahaina disaster: what exposures remain after the smoke clears? The measurements do not establish that the fires caused the metal levels or that the metals caused any participant’s breathing difficulty.

The fires devastated Lahaina and killed more than 100 people. Researchers measured 24 metals in participants’ urine and assessed lung function at the same visit. That pairing lets them examine whether metal concentrations and breathing-test results varied together. It cannot show what an individual’s levels or lung function were before the disaster, a gap that matters when trying to separate fire-related exposure from other possible causes.

What the Maui metal and lung tests found

The university reported that participants’ antimony concentrations were nearly 40 times a U.S. biomonitoring reference level. It reported manganese at 3.8 times, barium at 2.3 times and arsenic at 2.2 times the respective national references. Those comparisons describe the group against reference data; they do not measure how much any participant’s concentration changed after the fires or establish an individual health risk.

Across three statistical approaches, the researchers found an association between higher combined metal exposure and abnormal lung-function measures, according to the university’s report. Arsenic, cadmium, copper and antimony contributed strongly to the reported patterns. Because the metal and breathing measurements were taken after the disaster at the same visit, the result identifies a relationship to investigate, rather than a sequence proving that one caused the other.

Why the fires cannot yet be identified as the source

The research team had no comparable measurements of participants’ metal concentrations before the fires. It therefore could not calculate how much of the measured burden came directly from burned homes or other wildfire debris. The team identified geology, diet, historic agricultural and industrial activity, and continuing environmental sources as possible contributors, alongside material generated or stirred up by fire. The absence of a baseline also limits what the breathing tests can say about change since 2023.

Study co-author Alika Maunakea told Inside Climate News that the metal profiles found in wildfire ash and residents overlapped. He also acknowledged that the team could not pinpoint the fires as the source. The outlet reported that transportation infrastructure and Maui’s main airport are other possible pollution sources around Wailuku and Kahului. Those possibilities help explain why the geographic patterns are informative without resolving where each participant’s exposure originated.

The uncertainty matters to patients as well as researchers. Study co-author and family doctor Martina L. Kamaka told Inside Climate News that physicians working with participants were unfamiliar with some of the metals’ health effects and struggled to explain test results. A raised measurement can prompt further investigation, but these findings alone cannot tell a person whether a particular breathing problem was caused by a particular metal or by the wildfire.

What longer-term monitoring could answer

The university says repeated biological testing and environmental sampling are needed to distinguish exposure pathways. Following the same people over time could show whether measured concentrations and breathing results persist or change; sampling soil, ash and dust could help test possible sources. The current findings do not establish that a monitoring or screening program has already reduced exposure or improved health. They provide a reason to investigate those questions over a longer period.

A separate University of Hawaiʻi announcement on September 14 described a planned five-year, $3.6 million project funded by the National Institutes of Health. It is intended to follow 1,000 Hawaiʻi residents using environmental and biological samples and heart and lung assessments, with a focus on legacy contamination and disaster-related exposure. That project may help examine how older pollutants and later disasters interact, but it has not yet supplied an answer to the source question raised by the new Maui measurements.

U.S. Rep. Jill Tokuda told Inside Climate News that elevated metals among survivors warrant more research regardless of their source. For now, the strongest conclusion is narrower: researchers observed unusually high concentrations of several metals relative to national references and a link between combined metal exposure and abnormal breathing tests in the people they assessed. Whether those exposures came from the fires, remain elevated today or explain later lung problems is still unresolved.