As smoke from wildfires increasingly crosses state and international borders, tracking and studying them becomes increasingly important for shaping air quality and health responses around the world.
An upcoming study from researchers at Stanford University offers a new way to trace widespread smoke and pollution back to individual wildfires.
What burns in a wildfire determines what kind of pollution is in the smoke. A forest fire burns differently than a fire in a swamp, or a fire that burns buildings. As smoke moves, its chemical composition can change over time and distance.
The findings could help officials determine which wildfires are likely to have the greatest health impact on the greatest number of people, and allocate firefighting resources accordingly.
“We don’t find that firefighting resources are often spent on the fires that are most damaging from a health perspective,” said Jeff Wen, a Ph.D. candidate in Earth system science at Stanford and the study’s lead author.
Others have done similar research before, but on a much smaller scale. The new study, which has not yet been peer-reviewed, would be the first to cover the entire contiguous United States, according to the authors.
“Historically, we haven’t really been able to study those kinds of questions on a broad spatial, temporal scale,” Mr Wen said.
Clearly, wildfires have become more frequent and intense in recent years, fueled in part by the role of climate change in drying out many landscapes. Less clear to scientists is how the smoke from these fires has changed over time. The new study shows that as fires have gotten worse, their smoke has also gotten worse: From 2016 to 2020, the U.S. population experienced twice as much smoke pollution as it did 10 years earlier, from 2006 to 2010. While the study focused on historical data, its methods can can also be used to predict where smoke from a new fire will travel.
The researchers focused on a pollutant called particulate matter, made of very small solid particles suspended in the air, that can enter people’s lungs and blood and lead to problems such as difficulty breathing, inflammation and damaged immune cells.
Using their new method, Mr. Wen and his team ranked all wildfires observed in the United States from April 2006 to December 2020 based on the resulting smoke exposure. They found that the worst fire from smoke exposure during this period was the 2007 Bugaboo Fire, which burned more than 130,000 acres in and around the Okefenokee Swamp, which spanned Georgia and Florida.
This surprised the researchers at first, as Western states have more large fires. But the east coast is more densely populated, so the smoke from the Bugaboo Fire didn’t have to travel far to affect many millions of people. Peatlands like the Okefenokee Swamp also tend to burn slowly, Mr. Wen said, releasing more particulate matter into the air.
The worst fires in their rankings didn’t quite match the worst fires in traditional rankings, such as acres burned or lost buildings and infrastructure. Even the smokiest fires did not necessarily require more firefighting equipment.
“We often suppress fires, mainly because of structures and direct threats to life,” said Bonne Ford, an atmospheric scientist at Colorado State University who was not involved in this research. While it’s important to save lives and help rural communities in immediate danger, the “short-term thinking” is to focus only on those immediately dangerous fires and ignore others that could harm many people further afield from smoke exposure.
Dr. Ford and others have studied the smoke patterns of wildfires, as well as the resulting exposure to particulate pollution. But the Stanford researchers have come up with something new by putting the two together, she said, especially over so many years and so much land area.
One aspect of the study that Dr. Ford disagreed was to treat all human exposure to particulate matter in smoke the same regardless of where it happened. Some people are more vulnerable to air pollution, she said, depending on their age, pre-existing health conditions, other environmental factors and whether they can take precautions such as wearing face masks outdoors and using air filters indoors. Future research could combine Mr. Wen’s methods with existing vulnerability indexes, said Dr. Ford.
According to John Lin, an atmospheric scientist at the University of Utah who was not involved in the study, there are also more accurate ways to track and predict where smoke is going. Aside from that, Dr. Lin said the Stanford study would be very helpful in figuring out the real human toll of wildfire smoke.
Smoke traveling long distances is “the new normal,” he said. This reality challenges the way governments have historically addressed air quality, through regulations such as the Clean Air Act. As pollution continues to cross borders, Dr. Lin, the way people manage air quality should evolve accordingly.
