July 15, 2025

Wildfire smoke poses a serious hazard to hemodialysis patients

A study following the 2023 Canadian wildfires shows that exposure to high concentrations of wildfire smoke was associated with an increased risk of mortality and hospitalization among hemodialysis patients in the eastern and midwestern United States. 

The year 2023 marked a record-breaking wildfire season in Canada, with more than 6,500 fires burning an estimated 18.5 million hectares of land. Significant portions of the resulting smoke were blown south of the border. Wildfire smoke contains high concentrations of numerous air pollutants that are known to exacerbate chronic disease.  

Climate scientist Hyeonjin Song and colleagues were interested in exploring the effects of the 2023 wildfires on hemodialysis patients. They analyzed data of nearly 53,000 patients receiving dialysis from Fresenius Kidney Care clinics between June and July 2023, in 22 heavily impacted states in the eastern and midwestern U.S. They cross-referenced the data with local air quality measurements and satellite data of smoke plumes to estimate peoples’ exposure to smoke.  

The results show that wildfire smoke plume significantly worsened air quality in the eastern and midwestern U.S. When air quality was at its worst, the level of harmful fine particles in the air (called PM2.5) was more than seven times higher than what is considered safe. When wildfire smoke was present, the risk of dying from any cause on that same day went up by 18 per cent, and hospitalizations increased by 3 per cent. For every small increase in smoke particles (10 micrograms per cubic metre), the researchers observed a 139 per cent increase in same day all-cause deaths and a 33 per cent increase in hospitalizations. 

The researchers found that the health risks linked to wildfire smoke varied based on race and sociodemographic factors.  For instance, people aged 65 to 75 did not face the same increased risk of death or hospitalization as those in other age groups. The researchers suggest this could be due to several reasons, such as limited data for this age group or possibly protective behaviours—like following medical advice more closely, managing health conditions effectively, or staying indoors during poor air quality events—that reduce their exposure to wildfire smoke.