Study: Wildfire Smoke May Lead to Thousands More U.S Deaths

A study led by Stony Brook University faculty and published in Nature projects that smoke exposure from wildfires in the coming decades toward 2050 could result in tens of thousands of excess deaths in the United States.

This projection, by a national team of investigators led by Stony Brook's Minghao Qiu, is based on research that assesses wildfire activity in an increasingly dry and warming climate.

Wildfires have significantly increased in recent years, often in the western U.S. but also in other regions. Warmer, drier conditions are increasing the scope, damage, and exposures to people from wildfires. The study details the use of historical data from wildfires and smoke pollution, along with statistical models and machine learning tools to estimate deaths caused by exposure to smoke particulates in climate change scenarios.

Deaths from wildfire smoke result from inhaling a complex mix of chemicals. Wildfires can expose large numbers of people to these toxic pollutants for days or weeks at a time, contributing to deaths up to three years after the initial exposure, according to the study.

Within wildfire smoke pollution, researchers often focus on fine particulate matter, known as PM2.5, which penetrates the lungs and enters the bloodstream. While the health effects of PM2.5 from other sources are well studied, less is known about the specific dangers of PM2.5 from wildfire smoke. Some recent research shows that wildfire smoke can contain a range of toxic chemicals harmful to human health. The research team linked U.S. death records to estimated population exposure to smoke pollution, to assess these additional risks from smoke.

"The link between wildfire exposure and mortality burden can be very high, and what we are seeing is a clear increase in wildfire smoke nationwide, including long-range transport of smoke and dangerous particulates across the nation," said Qiu, lead author and assistant professor in the School of Marine and Atmospheric Sciences (SoMAS), and a core faculty member of the Program in Public Health at Stony Brook Medicine.

The research led to four key findings:

• Using the ensemble of statistical and machine learning models, they found that wildfire smoke is likely to substantially increase under future climate change, with average exposures across the U.S. population increasing two-to-three-fold in 2050 relative to 2011-2020. Qiu explained this large increase is the result of tight coupling between fuel aridity (lack of moisture in vegetation) and wildfire activity.
• Using the historical data, research shows that increases in annual exposure to smoke PM2.5 are associated with higher county-level annual mortality rates across the contiguous U.S., with increases detectable at even very low levels of annual wildfire exposure.
• The study projects that future smoke PM2.5 could result in more than 71,000 excess deaths per year by 2050 under a high warming scenario - a 73 percent increase relative to the 2011-2020 averages from current wildfire smoke.
• When monetized, climate-induced smoke deaths result in annual damages that exceed prior aggregate estimates of all other economic damage due to climate change in the U.S. - meaning wildfire smoke could be the most deadly and damaging climate disasters in US.

"There's a broad understanding that wildfire activity and wildfire smoke exposure are changing quickly. This is a lived experience, unfortunately, for folks on the West Coast over the last decade and folks on the East Coast in the last few years," said senior study author Marshall Burke, a professor of environmental social sciences in the Stanford Doerr School of Sustainability. "Our paper puts some numbers on what that change in exposure means for health outcomes, both now and in the future as the climate warms. And our understanding of who is vulnerable to this exposure is much broader than we thought."

The authors added that "by focusing on mortality alone, our estimated health damages exclude short- and long-term non-fatal health impacts from smoke PM2.5, including morbidity, worsened mental health, and potential long-run cancer risks associated with the carcinogenic constituents of wildfire smoke."

They conclude that their overall findings point to the urgent need for wildfire smoke adaptation if mortality damages are to be avoided. These adaptations could include better land management, such as the use of prescribed fires to regulate fire risks and protecting vulnerable groups from pollution exposure when smoke exposures do occur.

This research was supported by the Keck Foundation, Stanford's Center for Innovation in Global Health, Stony Brook University's SoMAS and the Program in Public Health, the Harvard University Center for the Environment, and the Standford Research Computing Center.