How Real Is Smoke Brain?

Keith Bein is a storm chaser—or whatever the wildfire equivalent of that is. An air-quality researcher at UC Davis, he drives toward fires, grabbing air samples, analyzing some on the scene and transporting others back to a lab for assessment. He knows what it’s like to inhale wildfire smoke. “I’ve been in situations where the air pollution is just so thick, you just can’t think about anything else except How do I escape this? or How do I get out of this?” he told me. “You really have to kind of force yourself to focus.”

Call it “smoke brain”: that foggy feeling that comes from breathing soot-clogged air. Lots of people can likely relate—particularly Americans across the country who are marinating in smoke from Canadian wildfires right now. Researchers have good reason to believe that smoke brain is a real phenomenon, in part because they can extrapolate the effects of bad air from other air-pollution research. The science on how wildfire smoke in particular affects your cognitive function is in very early stages, though. Experts told me that only a handful of studies have actually looked at what such smoke does to brain processing.

That’s partially because wildfires, although a natural part of our landscape, have become more unruly and started affecting more people. Researchers haven’t been studying the public-health effects of a giant wildfire sending smoke plumes across a population center the size of Manhattan, because we haven’t spent decades anticipating that giant wildfires would regularly send smoke plumes over population centers the size of Manhattan. People didn’t used to breathe in wildfire smoke like this—not this often, or at this scale.

Then a warming climate supercharged fires. In the past, you’d have gotten “exposed to emissions from a large-scale wildfire maybe once in your life—if that,” Bein explained. “And now it’s happening every season.” These fires also expose more people to more smoke for longer, sometimes multiple times in a single season. “These fires are bigger; they’re more severe; they’re pumping out a lot of air pollution over large distances,” Bein said. Meanwhile, scientists are playing catch-up.

[Read: Wildfire masking is just different]

In addition to plenty of anecdotes, a few scattered studies on smoke brain do exist. A 2022 paper published in Nature Sustainability looked at the standardized-test performance of students in more than 11,000 school districts across the United States and found that smoke exposure correlated with lower test scores. Similarly, a group of researchers analyzed cognitive-performance data from a brain-training phone game called Lumosity, mapping users’ scores against wildfire-smoke data. They found that medium and high smoke density were associated with lower scores.

The link between air pollution and a struggling brain is more well established. The Nature study cites previous work looking at the effect of unclean air on all sorts of tasks, like “performance in chess tournaments, stock trading, call centre productivity, umpire decisions, cognitive assessments, and online brain games.” The results all pointed to declining function. Another study showed that particulate levels in the classroom reduced students’ ability to focus on the material being presented.

“I would think those are probably a pretty good guide for what happens during wildfires, though we don’t know for sure,” Marshall Burke, a Stanford University professor and one of the authors of the test-score study, told me. Other studies have found links between pollution and neurodegenerative diseases, including Alzheimer’s and dementia.

Wildfire smoke might even be worse than, say, car exhaust. “In our research, we found it to be even more toxic than some of your standard air-pollution sources,” Bein told me. The haze drifting off fires can contain tiny bits of all sorts of nasty stuff that was incinerated—parts of homes or other things that burned.

But this line of inquiry is all pretty recent. “The entire world of the neurological impacts of air pollution in general is fairly new—we’re talking five years,” Bein explained. Breathing wildfire smoke irritates the body, and can cause inflammation. In the past, researchers have tended to focus on how smoke inhalation affects the lungs or the heart. At least in theory, this inflammation could also affect how our brain functions. As Burke put it: “We—we being the broader scientific community—just hadn’t thought to look at cognitive outcomes until recently.” He pointed out that until we fully understand wildfires’ neurological impacts, we won’t fully understand their economic impacts. If everyone in a city like New York is functioning just slightly less well for a day, or a week, the cost of that could be substantial.

And researchers are only beginning to think about how to untangle the possible effects of stress over the fire itself from any direct cognitive impacts of smoke. “The biggest gap in knowledge that we have is, would this occur even if we were not stressed over the sheer anxiety of a wildfire,” Ana Rappold, a scientist at the EPA and one of the authors of brain-game study, told me.  

[Read: Neuroscientists have discovered a phenomenon they can’t explain]

Smoke brain aside, breathing wildfire smoke is not good for you. There are plenty of well-established, non-smoke-brain reasons that you might want to avoid inhaling as much wildfire smoke as you can. Carlyn Matz, a risk assessor at Health Canada, the country’s health-policy department, told me that wildfires damage people in three ways that meet the group’s scientific threshold for issuing health guidance: Exposure exacerbates asthma, exacerbates chronic obstructive pulmonary disease (COPD), and shortens life expectancy.

Everything else inhalation causes, she puts in the category of “emerging science,” including research on the neurological, as well as mental-health, impacts of smoke inhalation, though she said she’d love to see more work on those subjects. Still, she pointed out that some of the precautions you can take now to avoid inhaling this worrisome mix will likely help should the science evolve: “If I’m limiting my wildfire-smoke exposure to limit asthma, I’m also limiting my wildfire-smoke exposure to limit potentially, like, a neurological [effect], as that evidence grows.” Though we might not fully understand the consequences of what we’re breathing in during weeks like these, we do know we want to keep it out of our body.

That we have such limited research on smoke brain is just another reminder of how much has changed, and how fast. Millions of people have already taken a gulp of smoky air this year—and are wondering what consequences linger for them. It’s not just this era of science that’s behind; we’re still playing catch-up in other areas of major fire planning, such as evacuation policy. These mega-burns are very quickly forcing us into a future we don’t fully understand.