This transcript has been edited and condensed for clarity.
At a prescribed burn site in rural Idaho, a team of fire scientists are using a tricked-out drone to hunt for life in the smoke. What they discover could have big implications for our world, and our health.
Inside the cloud of smoke, amid all the dust and ash, are hundreds, or even thousands, of different bacteria and fungi. The scientists studying them are part of an entirely new field of research: Pyroaerobiology, the study of life in smoke.
The field is so new that it didn’t exist just a few years ago. Back then, there was only one published study on this subject. And it came from a high school science fair project.
Sarah Mims lives in San Antonio, Texas. And back in high school, she made an accidental discovery in her backyard. She’d set out microscope slides, trying to find dust that had traveled across the world. But instead, she found something unexpected.
“When I was looking at the slides under the microscope, there were a large number of just solid black particles,” Mims said. “And there were also a substantial number of fungal spores.”
She kept finding ash and, along with it, fungal spores. And it always seemed to happen on days when smoke was drifting in from crop fires in Mexico. Maybe, she thought, the fungal spores were coming from the smoke.
After that, she went all in on this idea — whether microbes could live and travel in smoke. She designed a simple, but clever experiment that Grist video producer Jesse Nichols decided to replicate.
Here’s the idea: Take a petrifilm — it’s a little sheet of paper that microbes like yeast and mold like to grow on — and expose it to smoke from different types of burning yard waste. Then, compare that to another petrifilm that’s exposed to normal air. After a few days, count the number of fungal colonies on each film.
Grist found more than 10 times as many colonies on the films exposed to burning sticks than on the control. And Mims’ results were about the same.
“I was very excited because that was just kind of confirming everything that I had found so far,” she said.
She and her dad published the study in a scientific journal, and her project ended up winning local and national awards. But then, Mims went to college, and chose a different career path.
For years, the study just sat there.
About a decade later, fire scientist Leda Kobziar, now at the University of Idaho, was working on a prescribed burn. She was thinking about a story she’d read the night before, about people adding bacteria to snow machines to help form better snowflakes.
“There’s always time where you’re standing around the fire, just watching the smoke,” Kobziar said. “I just started to think about smoke, kind of like the snow coming out of a snowmaking machine, and wonder if there might be anything living in it.”
After the burn, Leda searched for studies about microbes living in smoke. And all she could find was Mims’ study from 2003. But the lone result made her curious.
“I wasn’t able to find anything else published about the idea, which was really shocking,” Kobziar said. “I guess it just didn’t get seen by enough microbiologists or fire people.”
So Kobziar set out to build on Mims’ findings. Was there really life in the smoke? They tested smoke from prescribed burns on petri dishes, and found microbes. They sampled smoke in different locations and temperatures, and they found microbes. They went to a sterile indoor combustion lab, where there was nothing besides the burning material, and they found microbes!
“We kind of tried all of the ways that we could shoot ourselves down,” Kobziar said. “And the results have been unequivocal.”
Smoke, it turns out, isn’t sterile. It is a whole world full of microbes, fungi, and bacteria.
But that discovery has raised more questions than answers. One of those questions: What this means for human health in a time of more frequent and severe wildfires?
While scientists have a clear picture of the health impacts of smoke itself — how tiny smoke particles harm the lungs or the cardiovascular system — the health risks of bacterial or fungal infections from wildfire smoke remains a total mystery.
“I get emails every couple of weeks from firefighters about their experiences and how they had a strange infection after fire season, and it was a fungal pathogen that grew in their lungs,” Kobziar said. “I think there are a lot of stories like that out there that mean to me that it’s really important to look into this and find out whether there’s a link, because those are my brothers and sisters in fire.”
While plenty of fungi are harmless, some fungal illnesses can be life threatening. Take Valley fever: It’s a disease caused by a fungus that grows in hot, dusty climates in the American West and travels on the wind. Cases have been rising in the past few decades. The fungus travels through the air, and scientists like Kobziar wonder whether wildfires in the West could play a role in its spread.
Now, she’s collaborating with four other labs across the nation, on a major study to try to find answers to those big questions both on a macro level — using epidemiology — and on a micro level (literally).
Kobziar’s lab is chasing wildfires and prescribed burns around the country, flying drones over the smoke plumes and collecting samples on filters. Then, in her DIY microbiology lab that she built out of a plastic tub, she preps the filters to be sent off to a lab in Florida. There, the team will investigate what kind of microbes are in the smoke samples, and they’ll test for harmful microbes, like the kind that causes Valley fever. Finally, another team will see if any microbes within the smoke are actually potent enough to infect a lab animal. At the end of this multi-year study they’re hoping to get some answers to what, until now, has been a bit of a mystery.
Pyroaerobiology is being built by people following their curiosities. For Mims, it was investigating the tiny black particles that showed up on her microscope slide. And for Kobziar, it was building on a decade-old science fair project, with study after study, until it became a whole field of research.
“I think it’s amazing there’s so much more to potentially be discovered,” said Mims. “And I think it’s great that it’s actually being done now.”
“From here going forward, I already know that there are many other groups who are starting to do this work. And that’s just so exciting,” said Kobziar. “It looks to me like a model of a tree that is just creating branches every day. And I think it’s going to be pretty incredible what we discover going forward.”
