Causal effects of wildfire PM<sub>2.5</sub> on hospital costs and length of stay in Brazil.

Ju, Ke; Xu, Rongbin; Huang, Wenzhong; Zhang, Yiwen; Ye, Tingting; Yu, Wenhua; Yang, Zhengyu; Chen, Gongbo et al. · Nat Commun · 2026

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Abstract

To quantify the hospital burden of short-term wildfire-specific fine particulate matter (PM<sub>2.5</sub>), we linked 184.5 million patient-level hospitalizations across 449 Brazilian regions from 2000-2019 with daily wildfire-specific and non-wildfire PM<sub>2.5</sub> estimates at 0.25° resolution. Using wind-driven variation in wildfire-specific PM<sub>2.5</sub> within a space-time-stratified case-crossover framework, we estimated the effects of exposure on hospitalization costs and length of stay. Each 1 µg/m<sup>3</sup> increase in wildfire-specific PM<sub>2.5</sub> was associated with higher hospitalization costs for all-cause, respiratory, and cardiovascular diseases by 0.36%, 1.59%, and 0.25%, respectively, and longer stays by 0.63%, 1.72%, and 0.68%. Asthma and heart failure showed the largest cost increases, while asthma and pneumonia showed the largest increases in length of stay. Overall, wildfire-specific PM<sub>2.5</sub> accounted for US$755.6 million in hospitalization costs and 30.8 million hospital days, with stronger relative effects among individuals aged 0-19 years and higher burdens in central-west Brazil.