A multidisciplinary team reported that residents near the August 2023 Maui wildfires had persistently elevated concentrations of several toxic metals in urine well after the fires ended. The work, published in Proceedings of the National Academy of Sciences, analyzed biomonitoring data collected as part of the Maui Wildfire Exposure Study (MauiWES) and found metal mixtures associated with respiratory harm up to a year and a half after the event. The fires destroyed the town of Lāhainā and killed more than 100 people.
University of Hawai‘i researchers conducted one of the largest postfire investigations in the U.S. and analyzed urine from approximately 1,400 adults. The study aimed to assess internal exposure to metals and evaluate potential links to respiratory outcomes. The research compared measured concentrations with U.S. biomonitoring data to identify elevations in specific metals.
The investigators reported substantially elevated levels of several metals. Notable findings included antimony at nearly 40 times the levels in U.S. biomonitoring comparisons. Other metals were elevated as well: manganese about 3.8 times higher, barium about 2.3 times higher, and arsenic about 2.2 times higher. The study links these elevated internal burdens to potential respiratory harm in the affected population.
Researchers attribute the detected metals to combustion of nonvegetation materials consumed in the fires — including buildings, vehicles, electronics, and other manufactured goods. These materials can release different chemical mixtures compared with fires that involve primarily vegetation, producing soot, residue, and contaminated dust that can remain in the environment after visible burning stops.
The study found that higher internal metal concentrations were associated with abnormal results on standard breathing tests, including reduced lung capacity and impaired airflow. Those lung function effects aligned spatially with the distribution of smoke and ash: residents closest to Lāhainā and to areas such as Wailuku and Kahului experienced different impacts than those farther away, for example near Kula. The investigators emphasized that what remains on land and in the environment can influence exposures people inhale or ingest over time.
The authors noted an important limitation: there were no comparable biomonitoring data from before August 2023 to establish individual baselines. Consequently, the study cannot precisely quantify how much of the measured metal burden was directly attributable to the wildfires versus other chronic or background exposures. Potential alternative sources cited include Hawai‘i’s local geology, dietary patterns, historic agricultural and industrial activity, and other environmental contributors.
The findings suggest that postfire air quality and environmental contamination require longer-term monitoring than is often practiced. Recovery and remediation efforts should consider residual contamination in soot, dust, soil, and debris as potential sources of ongoing exposure. Co-principal investigators on MauiWES argued that disaster response should extend beyond the visible emergency to identify and mitigate pathways for re-exposure that could contribute to sustained health effects.
The report situates its findings within broader trends: wildfires in many regions are becoming larger, faster-moving, and more frequent in association with warming and drier conditions. Experts quoted in the coverage and the study team warned that as climate-related disasters increase in frequency and intensity, similar prolonged environmental and health consequences may occur elsewhere. They recommended incorporating assessments of lingering contaminants into public health, recovery planning, and efforts to build community and health system resilience.
The MauiWES biomonitoring study documents elevated levels of multiple metals in residents up to roughly 18 months after the August 2023 Maui wildfires, links those elevated levels to impaired lung function, and highlights the need for extended environmental monitoring and remediation after major fires. The work also acknowledges constraints due to absence of prefire baseline data and recognizes other possible local sources of metals that the study could not fully disentangle.