Climate-amplified wildland-urban interface disasters create persistent internal metal mixtures associated with pulmonary impairment.

Wildland-urban interface (WUI) wildfires are increasingly important climate-related exposure events because they burn built infrastructure and can mobilize legacy contaminants in addition to generating smoke. Although the acute respiratory effects of wildfire smoke are well described, persistent internal metal mixtures and their association with pulmonary function after WUI disasters remain poorly characterized. Using the August 2023 Maui wildfires as a sentinel model, we evaluated 1,400 adults enrolled 6 to 18 mo after the disaster in a community-engaged cohort. We measured 24 urinary metals and assessed pulmonary function by standardized spirometry at the same visit, enabling paired exposure-response analyses. Compared with US reference levels, participants exhibited elevated internal metal burdens, including antimony (40-fold), manganese (3.8-fold), barium (2.3-fold), and arsenic (2.2-fold), with the highest concentrations clustering in the most affected regions. Across three complementary mixture-modeling approaches, higher cumulative metal burden was consistently associated with greater odds of abnormal spirometry. In weighted quantile sum models, each 1-quantile increase in the positive mixture index, driven primarily by arsenic, cadmium, and copper, was associated with higher odds of FVC, FEV1, FEV1/FVC, and FEF25-75 below the lower limit of normal (odds ratio [OR], 1.71, 1.53, 1.83, and 1.84, respectively). These findings suggest that WUI disasters may generate persistent internal metal mixtures associated with pulmonary impairment months after the event and that air monitoring alone may underestimate the longer-term internal toxic burden following climate-amplified WUI disasters.