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A woman wearing a mask vacuums a room of a house while surrounded by scientific equipment
Researchers gather more evidence of lingering particles and chemicals in a Maryland test house, as part of a Colorado State University-led consortium's look at how long wildfire smoke and other contaminants remain on surfaces. (John Eisele, CSU Photography)

The latest jaw-dropping research on the lingering health impacts of wildfires began with a graduate student waving a cocktail smoker around the living room of a test house in Maryland. 

The methods were just as enlightening as the results, to the researchers from Colorado State University. The cocktail smoker had been proposed by an environmental sciences student who used to be a bartender. 

Turns out the residue from burning wood chips to make a smoked bloody mary is remarkably similar to what lingers inside a home after a wildfire has roared through nearby woods. 

And the study’s upshot, according to CSU’s Delphine Farmer, is that homeowners who have suffered through such a nearby tragedy should reach for a mop before they install new air filters. The smoke-carried volatile organic compounds with potential health hazards linger much longer than expected on surfaces like carpet, drywall and even countertops, Farmer’s research team showed. 

A hand holds onto equipment with a tube that emits wildfire smoke
Researchers on the wildfire smoke study found a common cocktail smoker closely emulated wildfire smoke when the right kind of wood chips were used. (John Eisele, CSU Photography)

That has implications for thousands of homeowners cleaning up after disasters like the 2021 Marshall fire and dozens of other major wildfires in the Colorado wildland-urban interface. Hitting the “on” button on an expensive filtering system is not enough. Scrubbing and wiping to eliminate tiny cling-on particles is just as important. 

As the research coalition watched the cocktail-smoker residue settle inside their test house, for hours and then days, their sensors found “all the surfaces would act as a sort of reservoir,” said Farmer, a professor in CSU’s chemistry department.

“Once the air in the house had cleared, the surfaces started to then release those gases,” which are lingering volatile organic compounds, Farmer said. Those chemicals’ persistence was the biggest surprise. “And these molecules, these gases, never went back down to the levels that we had before the smoke events. No matter what we did.” 

Their research was published in “Science Advances,” and relied on a collaboration with scientists from University of Colorado, University of California San Diego, the National Institutes of Standards and Technology, which runs the Maryland test house, and others. 

Farmer said much of her career has been spent as a chemist looking at components and impacts of outdoor air pollution. But the air pollution field has started to move indoors as researchers focus on how much time modern humans spend inside their homes or workplaces. 

“We should start thinking about the air we’re breathing inside,” Farmer said. 

Previous CSU studies looked at lingering residue from indoor cooking or cleaning chemicals. That’s when researchers added to their knowledge of where chemicals cling. 

“We realized that surfaces were so important in terms of mediating air chemistry, and what people are actually breathing,” Farmer said. 

Thinking about what other chemical influences might find their way into a house, the research team thought back to fly-throughs they had done with the National Science Foundation that helped analyze the chemical components of wildfire smoke out in the open. 

That kind of smoke is pervasive no matter how much homeowners try to defend their properties, Farmer said. 

A woman poses in a room of a house with testing equipment behind her.
CSU Chemistry Professor Delphine Farmer and other researchers crammed a test house with precision measuring equipment as part of a Colorado State University-led consortium’s look at how long wildfire smoke and other contaminants remain on surfaces. (John Eisele, CSU Photography)

“You don’t have to have your windows or doors open for this, with smoke creeping around the edges of your windows or your foundation,” Farmer said. “We call that infiltration. So the smoke will infiltrate the home, even if you don’t want it to.”

They considered more complicated ways to produce the equivalent of wildfire smoke at the Maryland house, until graduate students tossed in more ideas. 

“It turns out that these cocktail smokers, which are designed to make very fancy cocktails, actually produce unbelievably realistic, chemically correct smoke,” Farmer said. Researchers can add in wood chips from the kinds of forests common in the wild.

With rooms full of sensitive instruments, the researchers can watch on monitoring screens the chemicals settling and then lingering on walls, carpet and countertops. They mark intervals at hours and then a couple of days, but then have decomposition models that can predict farther out from there.  

Chemistry and health researchers now need to extend the results to potential human impacts for people living with smoke particles on their home surfaces. There’s much more to be learned about long-term effects of PM 2.5 particulate matter and volatile organic compounds emanating off surfaces, Farmer said. 

“We know that high levels of exposure to these compounds is toxic,” Farmer said. “There are big questions about what happens when someone is exposed to a whole diversity of different VOCs for a long period of time.”

Michael Booth is The Sun’s environment writer, and co-author of The Sun’s weekly climate and health newsletter The Temperature. He and John Ingold host the weekly Sun-Up podcast on The Temperature topics every Thursday. He is co-author with...