Landscape Fire-Sourced PM2.5 and Cause-Specific Renal Hospitalizations: A Multicountry Two-Stage Time-Series Analysis of 12.5 Million Admissions

Landscape fire-sourced PM2.5 (LFS PM2.5) is increasingly recognized as an important air pollutant, but its short-term contribution to renal hospitalizations remains unclear. Here, we assessed the associations between LFS PM2.5 and renal hospitalizations across 1020 locations in Australia, Brazil, Canada, Chile, New Zealand, and Thailand during 2000–2019 using a two-stage time-series design and estimated the attributable hospitalizations. LFS PM2.5 was associated with increased renal hospitalization risk, with the strongest associations observed for acute kidney injury. A 10 μg/m3 increase in cumulative LFS PM2.5 exposure over lag 0–5 was associated with a 1.1% increase in renal hospitalizations (RR = 1.011, 95% CI: 1.007–1.015). Associations were stronger in warmer areas and differed across levels of GDP per capita. Associations were consistently stronger for LFS PM2.5 than for non-LFS PM2.5. We estimated that LFS PM2.5 contributed to 1.38 renal hospitalizations per 100,000 population annually across the study regions. These findings highlight renal disease as an underrecognized health consequence of landscape fire smoke and support strengthened strategies to reduce wildfire smoke exposure under a changing climate.