Key Takeaways
- Smoke from wildland-urban interface (WUI) fires is significantly more harmful to human health than smoke from wildfires in remote areas.
- A new study finds that emissions from WUI fires are three times more likely to cause premature deaths due to their proximity to populated areas.
- Scientists used advanced computer modeling and real-world data to analyze fire emissions and their health effects across different continents.
Risk to human health
A new study has revealed that fires burning through the wildland-urban interface (WUI)—where wildland vegetation meets developed areas—pose a far greater risk to human health than wildfires in remote locations. Researchers found that emissions from WUI fires are three times more likely to lead to premature deaths due to their proximity to densely populated areas.
The research, published in Science Advances, was led by scientists from the U.S. National Science Foundation National Center for Atmospheric Research (NSF NCAR). It analyzed global WUI fire emissions using an advanced atmospheric chemistry model.
Their findings highlight the growing public health risks associated with increasing WUI fires, particularly as urban expansion continues to push into fire-prone regions.
“Even though the emissions of WUI fires are relatively small globally, the health impacts are proportionately large because they’re closer to human populations,” said lead author Wenfu Tang, an NSF NCAR scientist.
The Growing Threat of WUI Fires
The wildland-urban interface now makes up 5% of the world’s land area (excluding Antarctica) and continues to expand across all populated continents. With this expansion has come a surge in devastating fires that have resulted in widespread destruction and loss of life.
Some of the deadliest WUI fires in recent history include:
- 2009 Black Saturday bushfires (Australia) – 173 deaths
- 2018 Attica fires (Greece) – 104 deaths
- 2023 Lahaina Fire (Hawaii) – 100 deaths
- 2025 Southern California Fires – Destroyed 16,000 structures, with estimated financial losses of $250 billion or more.
Previous research led by Tang showed that the percentage of wildfires occurring in WUI areas has increased significantly in the 21st century. The latest study builds on this by assessing the long-term health effects of WUI fire smoke, beyond the immediate casualties of the fires themselves.
Why is WUI smoke more dangerous?
WUI fires are particularly harmful because they produce large amounts of fine particulate matter and ozone precursors, which severely impact cardiovascular and respiratory health. Unlike wildfires in remote areas, the smoke from WUI fires affects large numbers of people, leading to more premature deaths.
Using the Multi-Scale Infrastructure for Chemistry and Aerosols (MUSICA) computer model, researchers simulated fire emissions and their impact on air quality. Their findings revealed that while WUI fires made up just 3.1% of global fire emissions in 2020, they accounted for 8.8% of all premature deaths linked to fire smoke exposure.
The impact varied across continents:
- North America: WUI fires represented 6% of total fire emissions, but caused 9.3% of premature deaths.
- Europe: WUI fires made up 11.4% of total emissions but were responsible for 13.7% of premature deaths.
Future research implications
A crucial next step in this research is examining the differences in emissions from burning wildland vegetation versus burning man-made structures. Buildings contain toxic materials such as plastics, treated wood, and synthetic insulation, which may release highly hazardous pollutants when burned.
“It is very important to have an emission inventory that explicitly accounts for the burning of structures,” Tang emphasized. “We need to know what is being burned in order to determine what is going up in smoke.”
As WUI fires continue to rise due to climate change and urban expansion, the study’s findings highlight the need for stricter building regulations, better fire prevention measures, and enhanced air quality monitoring in high-risk areas.