Introduction:Smoke plumes from the 2023 Canadian wildfires severely impacted air quality across the Eastern and Midwestern USA. However, a comprehensive health impact assessment is lacking in this large region. We investigated the association between wildfire-related air pollutants and the risk of mortality and hospitalization among hemodialysis patients in 22 heavily impacted states in the Eastern and Midwestern USA.
Methods:We conducted a retrospective observational study using a time-stratified case-crossover analysis with a conditional quasi-Poisson model. The study included 52,995 patients with end-stage kidney disease (ESKD) receiving hemodialysis at Fresenius Kidney Care clinics during June and July 2023. The presence of wildfire smoke and fine particulate matter (with aerodynamic diameter < 2.5 microns, PM2.5) concentrations were assessed using satellite-derived smoke polygons and ground-based monitors. Daily number of all-cause deaths, all-cause hospitalizations, respiratory disease hospitalizations, and cardiovascular disease hospitalizations were counted for each hemodialysis clinic.
Results:The highest daily wildfire-related PM2.5 concentration observed (251.1 μg/m3) far exceeded the National Ambient Air Quality Standard (35 μg/m3). The presence of wildfire smoke plume was associated with an 18% increase in risk of same day (lag0) all-cause mortality (rate ratio [RR]:1.18; 95% confidence interval [CI], 1.13-1.24) and a 3% increase in risk of all-cause hospitalization (RR:1.03; 95% CI: 1.00-1.07). A 10 μg/m3 increase in wildfire-related PM2.5 was associated with a 139% increase in same day all-cause mortality (RR: 2.39; 95% CI: 1.79-3.18), and a 33% increase in all-cause hospitalization (RR:1.33; 95% CI: 1.10-1.62).
Conclusion:Our findings suggest that air pollution from the 2023 Canadian wildfires resulted in increased risk of mortality and hospitalization among hemodialysis patients in Eastern and Midwestern USA.