Smoke from the Wildland-Urban Interface is a more fatal fire than a remote wildfire, research finds

Smoke from fires that burn the Wildland-urban Interface (WUI) has far greater health effects than smoke from remote wildfires, new research finds.

The study, published in Science Advances, estimates Wui fire emissions are about three times more likely to lead to early deaths per year than typical wildfire emissions. This is because fires and associated emissions are much closer to densely populated areas.

The work was carried out by an international team of researchers led by scientists at the National Center for Atmospheric Research (NSF NCAR). This study was based on a database of WUI fires and advanced computer modeling techniques.

“WUI fire emissions are relatively low worldwide, but close to human populations, so the health impact is proportionally large,” said NSF NCAR scientist Wenfu Tang. “The contaminants released by a vine fire, such as particulate matter and precursors to ozone, are more harmful because they are not dispersed for hundreds or thousands of miles.”

Spreading of the Wie Fire

The Wildland-urban interface is a geographical area where wild vegetation and developed land come together or mix. The WUI region is expanding across all population areas and currently accounts for around 5% of the world’s land areas except Antarctica.

This expansion caused a catastrophic fire. Some of the most deadly Wui flames of recent years include the 2009 Black Saturday Bush Fire in Australia, which killed 173 people directly, the 2018 Attica fire in Greece, which killed 104 people, and the 2023 Lahaina fire in Hawaii, which killed 100 people.

Earlier in 2025, the tragic outbreak of a fire in Southern California burned an estimated 16,000 homes, businesses and other structures, with financial losses up to more than $250 billion.

Previous research led by Tang used satellite observation and machine learning technology to show that the proportion of global fires that occur in the WUI region has increased significantly over the century.

Based on that work, Tang and her colleagues wanted to estimate the health effects of fire emissions beyond immediate death. Certain pollutants associated with smoke, such as particulate matter and ground level ozone, are particularly harmful to the cardiovascular and respiratory systems.

Researchers have turned to advanced NSF NCAR-based computer models, a multi-scale infrastructure for chemistry and aerosols (Musica) to simulate contaminants from fires. Their modelling included carbon monoxide chemical tracers, which allowed them to estimate emission sources and distinguish between wild and wheat fires.

They have also used Wui Fires datasets over the past 20 years around the world. This was developed by Tang and her colleagues last year.

To compare Wui Fire emissions with those from Wildland Fires, researchers simulated four scenarios: These are: The fire consisted of both wui and wild fires, wui fires alone, wild fires alone. The difference between all fires and wild fires indicates the impact of fire emissions in the wil.

The results showed that WUI fire emissions constituted 3.1% of all fire emissions on all six population continents in 2020, but the partial contribution of WUI fire emissions to premature deaths was 8.8% of all fire extinguishing emissions, due to the number of people affected by smoke from Wui fires.

Numbers vary by continent depending on what is close to the dense group wui fire. In North America, for example, Wui fires accounted for 6% of all fires and 9.3% of premature births due to emissions. However, in Europe these figures were 11.4% and 13.7%, respectively.

The next important factor that Tang wants to look into is the difference in emissions from wild fires that consume trees and other vegetation, as opposed to the vine fires that burn structures containing additional toxic substances. Smoke from different combustion materials can have a very different effect on human health.

“It’s very important to have an emission inventory that explicitly describes the combustion of the structure,” Tang said. “To determine what’s going on with the smoke, you need to know what’s burning.”