Fire Season Is Back – and It’s Everyone’s Problem

Why Wildfire Smoke Could Be One of the Biggest Threats to Brain Health in North America

Wildfire season is back, and it’s already living up to the warnings. With record-setting temperatures and early-season blazes, in Canada, massive swaths of forest are again, from British Columbia to Quebec. But what happens in Canada isn’t staying in Canada. Wildfire smoke is drifting southward and blanketing U.S. cities in an eerie haze. From New York to Chicago to Denver, millions of Americans are already breathing air that’s laced with PM2.5—tiny particles with outsized health consequences.

Below is an image from one of the Apps I use to track wildfire smoke, FireSmoke Canada, from June 11, 2025.

This isn’t just a nuisance. It’s a public health emergency in slow motion, and it’s time we treated it that way.

The Real Danger Is Microscopic

The haze that turns your sky orange and makes your throat scratchy carries something far more dangerous than an unpleasant odor. At the center of this threat are PM2.5 particles—microscopic bits of soot and debris less than 2.5 microns in diameter. To put that in perspective, they’re about 30 times smaller than the width of a human hair. Because of their size, they bypass the body’s natural defenses, slipping past nasal filters and burrowing deep into the lungs, and from there, entering the bloodstream.

Decades of research have linked PM2.5 exposure to heart attacks, asthma, and strokes. But the latest science is sounding the alarm about an even more insidious consequence: damage to the brain.

A New Frontier in Air Pollution Research: Your Brain

Emerging studies show that PM2.5 doesn’t stop at the lungs. These particles can reach the brain directly via the olfactory nerve or indirectly through systemic inflammation once they enter circulation. The result? Chronic exposure is now being linked to cognitive decline, depression, anxiety, and even increased risk for Alzheimer’s disease.

A 2022 review in Nature Aging concluded that long-term exposure to PM2.5 may accelerate neurodegeneration by activating the brain’s immune cells—microglia—which respond to airborne toxins with a storm of inflammation. Once switched on, these microglia can damage neurons and disrupt brain circuits responsible for memory, attention, and emotional regulation. In short, wildfire smoke doesn’t just choke the sky—it scrambles the brain.

This is especially alarming for children, whose brains are still developing, and older adults, whose brains may already be vulnerable. But let’s be clear: no age group is immune.

Smoke Has No Borders—So Neither Can Our Concern

Wildfire smoke is uncontainable. Once airborne, PM2.5 can travel thousands of miles. In 2023, smoke from Quebec’s fires triggered air quality alerts in over 20 U.S. states, caused school closures in New York City, and pushed AQI (Air Quality Index) numbers to “hazardous” levels across the Midwest and East Coast. The same is already happening in 2025, just weeks into the Canadian fire season.

And with hotter, drier summers becoming the norm thanks to climate change, this is no longer a once-a-decade event—it’s an annual threat. If you’re anywhere in North America, this affects you.

What You Can Do to Protect Yourself

While we can’t stop the wind—or the fires—there are meaningful steps you can take to minimize your exposure and protect your brain and body:

1. Track the Air Quality Daily – Use reliable sources like AirNow.gov or apps like IQAir and PurpleAir to monitor real-time AQI in your area. When levels are “unhealthy,” take it seriously. Limit outdoor activity, especially strenuous exercise.
2. Upgrade Your Indoor Air – If you haven’t already, invest in a HEPA air purifier. These devices can dramatically reduce indoor PM2.5 levels, especially when kept in the rooms you use most. At home we use the Lichen air purifier because it has the highest HEPA rating (14) as well as thenhighest clean air delivery rate (CADR)
3. Create a Clean Room – Designate one room in your home as a “clean air zone.” Close the windows, run an air purifier continuously, and seal any drafts. If wildfires worsen, this becomes your safe zone.
4. Use High-Quality Masks Outdoors – Not all masks are created equally. Cloth and surgical masks do little to block PM2.5. If you must go outside during smoky days, wear a well-fitted N95 or KN95 mask.

This Is the New Normal—Unless We Change Course

The era of thinking wildfire smoke is just “a Canadian problem” is over. The atmosphere doesn’t recognize borders, and neither do airborne toxins. As smoke rolls across the continent again this summer, the question isn’t whether the air will look hazy—it’s whether we’ll act in time to protect our health.

The research is clear. PM2.5 pollution isn’t just a respiratory issue. It’s a brain threat. And the more we understand that, the more urgently we’ll treat this as the health crisis it truly is.

To learn more about this important health threat, I recommend reading a recent Psychology Today article entitled: Wildfire Smoke: The Impact on Your Brain and Body, by Austin Perlmutter, MD