A bird sits on a wire as the sun sets through wildfire smoke last month in Chehalis.
Research has shown wildfires across the Western United States have grown larger and more frequent with time, as a majority of fires in the last 60 years have occurred since 2000.
And while it's documented that wildfire smoke can cause respiratory issues and worsen preexisting conditions, a new theory coauthored by a University of Idaho researcher suggests smoke particulates also may carry potentially harmful microorganisms, including bacteria and fungi.
The research, recently published in Science, explains that wildfire smoke can carry quantities of microbes from sources including disturbed soil and burnt plant matter. Leda Kobziar, an associate professor of wildland fire science at the University of Idaho, said researchers have developed a list of more than 1,000 different microorganisms recovered from smoke plumes that were not found in ambient air conditions.
The health and ecological effects of these microorganisms are among the unanswered questions for researchers, said Kobziar, who coauthored the paper published in Science magazine with Dr. George Thompson III, an associate professor from UC Davis. In light of the research, Kobziar said she believes the precautions people already take in a smoke-inundated area are still appropriate.
"We know that smoke in general has deleterious health impact on people," she said, "but we don't know the connection between infectious diseases and how much people are exposed to smoke."
Kobziar used a drone in September to capture smoke samples from fires in Eastern Washington and Oregon, she told the Los Angeles Times.
It is unclear exactly how far these microbes can travel in smoke. According to the Science paper, some microorganisms and bacteria can potentially travel hundreds of miles — depending on fire behavior and atmospheric conditions — before they are deposited or inhaled downwind.
Research said studying wildfire smoke is becoming more relevant as wildfire seasons get more severe with climate change.
In 2020, more than 58,250 wildfires burned approximately 10.3 million acres nationwide, according to the Congressional Research Service. Federal data shows an average of 70,685 wildfires per year burned an average of 7.1 million acres between 2011 and 2020, more than doubling the 3.3 million average acres burned in the '90s despite a lower average number of wildfires.
"More and more people are becoming interested in this topic, which is exciting," Kobziar said.
While smoke plumes can reach temperatures high enough to kill off some microbial organisms, variables in "fuel, ambient air mixing and fire behavior" can make for environments in which organisms can latch onto smoke particulates, according to the research.
"Smoke emissions from high-intensity, large wildfires have been transported across continents, increasing particulate matter concentrations in distant locations," researchers wrote in Science. "The consequences for more immediate populations, such as firefighters on the front line who often spend up to 14 consecutive days in smoky conditions, are likely greater given that microbial concentration in smoke is higher near the source of a fire."
Kobziar said she and other researchers have evaluated wildfire smoke over several years.
Petri dish samples taken in 2015 from smoke plumes during prescribed burns in the University of Florida's Austin Cary Forest helped form the basis of a 2018 study published in Ecosphere. Seventy aerosolized microbial morphotypes were recovered from that study, which documented pathogenic and nonpathogenic fungal species.
Kobziar said the research methodology has since developed, with researchers employing drones to fly into plumes to sample smoke at various distances. She said researchers used drones to sample smoke plumes at 10,000 feet from Fishlake National Forest in Utah, finding more than 900 different bacteria and over 100 different fungal species.
"Fire has been a natural thing and playing its natural roles at least since the last glaciation in North America, and these types of effects have been happening for a long time," she said. "We just haven't thought of smoke this way before."
Greg Mason can be reached at (509) 459-5047 or gregm@spokesman.com
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