As wildfires continue to rage in Canada, millions of Americans are affected by its smoke, which can have devastating impacts on the brain.
Canada is facing the worst wildfire season ever, as drought has sparked more than 400 fires across the country, already burning over four million hectares. Wildfire smoke also reached the Midwest and Northeast, raising air pollution to hazardous levels.
Small air pollutants known as PM 2.5 particles produced by wildfires may get into one’s lungs and cause short-term health problems, such as throat and lung irritation or coughing. Whereas long-term exposure to PM 2.5 is associated with asthma, lung cancer, and increased mortality from heart disease.
"We now have evidence that air pollution, such as wildfire smoke, poses a hazard to the brain as well," says Domenico Praticò, M.D., Professor and Director of the Alzheimer’s Center at Temple.
A recent analysis of 16 different observational studies suggests that there is strong evidence for a biological relationship between PM 2.5 exposure and the onset of dementia. In particular, the incidence of dementia increases by 17% for every 2 microgram increase in annual PM 2.5 exposure per cubic meter of air.
A 2021 study reports that when inhaled, microscopic particles from burning wood smoke burrow into lung tissue, they trigger the release of inflammatory immune molecules into the bloodstream, which carries them into the brain. Once there, they start to degrade the blood-brain barrier, triggering the response from the protective cells in the brain that normally help with learning, memory, and other functions.
Therefore, exposure to such particles may put people at risk for neurological problems, including premature aging, dementia, depression, and psychosis.
A study published in the journal Nature investigated how wildfire smoke exposure affects learning outcomes. Using data from nearly 11,700 school districts in the United States, researchers found that average smoke-attributable PM2.5 exposure of 35 micrograms per cubic meter of air during the school year reduced standardized test scores by about 0.15%, with more significant decreases among younger students. The study authors projected that smoke PM2.5 exposure in 2016 reduced discounted future earnings by nearly $1.7 billion.
In a 2022 study, the researchers analyzed data from over 10,000 players of Lost in Migration, a phone game that challenges a player’s focus, who live in areas affiliated with wildfire events. The study found that PM 2.5 exposure can reduce attention in adults within just hours of exposure. Another research discovered that prolonged exposure to particulate pollution shortens attention spans, specifically in younger populations aged 18 to 29 years.
Climate change, which some scientists call the greatest threat to global public health, increases drought and, as a result, the risk of wildfires. As rising temperatures are estimated to set a new global record in 2024, wildfires and health risks associated with its smoke are here to stay.
- British Medical Journal. Ambient air pollution and clinical dementia: systematic review and meta-analysis.
- NewsWise. Air Quality from Wildfires Also Bad for the Brain, Expert Says.
- New York State Department of Health. Fine Particles (PM 2.5) Questions and Answers.
- The University of New Mexico. Particulate Peril.
- United States Environmental Protection Agency. Fighting the Haze: Effects of Wildfire Smoke and Particulate Matter on Brain Function.
- The New England Journal of Medicine. Call for Emergency Action to Limit Global Temperature Increases, Restore Biodiversity, and Protect Health.