What is ‘smoke brain’? How air pollution can harm our cognition and mental health

As air quality across Canada continues to fluctuate in response to ongoing wildfires, scientists warn that even brief exposure to smoke or air pollution could harm your brain function.

While it’s unknown exactly how smoke particles impact the brain, experts tell the Star there is a litany of evidence around its health harms, both in the short-term and years down the line.

“I have no doubt that wildfire smoke is affecting our brains when it is occurring,” said Sarah Henderson, the scientific director of Environmental Health Services at British Columbia’s Centre for Disease Control, to the Star.

As carbon emissions continue to climb and the climate warms, wildfires are only expected to grow more prevalent and longer in duration. Experts say now is the time to prepare.

Short-term wildfire smoke exposure and impact on the brain

In the short-term, studies have shown exposure to wildfire smoke generally lowers brain performance, Henderson said. While its impacts may be too subtle to notice yourself, research has found people who breathe in more air pollution consistently perform worse on cognitive tests.

“We did a study using data from the brain training platform, Lumosity,” said Henderson, whose paper was published last year. “What we found is when it was smoky, people didn’t do as well (on the platform). That was particularly true for younger adults … and it was true for older adults.”

Her results are corroborated by numerous other papers, including a longitudinal 2022 U.S. study of over 10,000 adults that found drops in test performance in regions where wildfire smoke was present. A similar study on California’s 2018 fires found brain function was still lowered even six to 12 months after the event.

Additionally, a study earlier this year found just two hours of exposure to traffic pollution can impair brain function. Its lead author, Chris Carlsten, told the Star he believes his findings also apply to wildfire smoke, given its similarities in composition.

Anecdotally speaking, Henderson has encountered “so many” people asking about their senior parents with dementia, “who seemed more confused on smoky days.”

“For individuals who are already in cognitive decline, they may experience more confusion and more decline on those days when it’s smoky,” she continued.

Long-term effects of smoke inhalation on the mind

While fewer studies have been done on long-term smoke exposure, Dr. Samantha Green, a physician at Toronto’s Unity Health and incoming president of the Canadian Association of Physicians for the Environment, says we can extrapolate from what we already know about air pollution.

“We know that particulate matter and other components of air pollution can cause long-term neurological harm,” Green said. “For example, there’s growing evidence associating long-term exposure to air pollution and an increased risk of dementia

“There is also similarly an increased risk of Parkinson’s disease from long term exposure to air pollution, and increased risk even of ALS,” Green continued.

These diseases are often associated with seniors, but air pollution harms young children too, Green continued. “Even in the prenatal and early life, exposure is associated with an increased prevalence of ADHD, lower IQ scores, increased need for academic support and other neurobehavioral harms.”

Jeff Brook, an associate professor at the University of Toronto’s Dalla Lana School of Public Health and Department of Chemical Engineering and Applied Chemistry, agrees and adds that studies have also shown “strong correlations” between air quality and the development of autism.

For example, a Harvard study linked particles in air pollution to a significantly increased risk of autism in children, especially when exposed during the third trimester of pregnancy or early childhood.

Although we’ll likely spend less time exposed to wildfire smoke than general air pollution, Green says, towns could be enveloped in smoke for months at a time during intense fire seasons — “enough time to see an effect.” As climate change worsens fires across the globe, Green expects these incidents to become more prevalent.

How to protect yourself from air pollution

The main thing people can do is monitor their local air quality, according to Green. “Really pay attention to the air quality health index because it can shift over hours and between municipalities and regions.”

If the air quality level is at seven or above, Green advises you to “not go outside and exert yourself,” and to “keep the windows closed inside.” It’s also helpful to invest in an air purifier and place it in the room where you spend the most time — like a bedroom or office, she said.

If air purifiers are too expensive, Brook says you can always build your own, adding that one of his students did so when they were surveying forest fires earlier in the year.

“It was $75 to order furnace filters and a fan,” he said. “When she turned it on in the hotel room, it cleaned the air by 90 per cent very quickly.” Here’s how you can build the design for yourself.

If you have to go out, Henderson advises wearing a fitted respirator or N95 mask: “If they are fitted well to your face, they can be very effective for reducing those exposures.”

Finally, if you’re more vulnerable to the effects of air pollution, Green says you should consider staying indoors even when air quality dips below seven.

“People who are more vulnerable with underlying chronic conditions or pregnant women, young children, the elderly, they should take precautions even when the air quality is in the moderate range.”

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