Smoke from wildfires in Canada is once again shrouding parts of the United States — cities like Chicago and Milwaukee — with unhealthy air, according to the US Environmental Protection Agency. Parts of the plume have reached as far as Europe. The bulk of the smoke is forecasted to drift eastward across North America and thin out.
As of Thursday afternoon, Canada was battling more than 200 blazes, the majority in western provinces like British Columbia and Alberta, according to the Canadian Interagency Forest Fire Centre. In Canada, the fires forced more than 27,000 people to evacuate, but the smoke is “impacting aerial operations for both suppression and evacuation flights.”
This is all too familiar. Canada faced a massive spate of wildfires in 2023 and in 2024 that similarly sent clouds of ash and dust across North America, reaching places like New York City. The burned area this year is a fraction of the size of the regions scorched in 2023, a record-breaking year for wildfires in Canada, but it’s still early in the fire season. Canadian fire officials warn that the “potential for emerging significant wildland fires is high to extreme” and lightning may lead to more ignitions in the next few days.
These blazes remind us that the dangers of wildfires reach far beyond their flames, and the threat is growing.
Wildfire smoke contains a melange of gases like carbon monoxide, particles of soot, and hazardous chemicals like polycyclic aromatic hydrocarbons that can cause cancer. The tiniest particles in smoke can penetrate deep into the lungs, and even reach the bloodstream, leading to a variety of health problems. When it drifts over a community, it often causes a surge in emergency room visits as people who breathe the smoke suffer strokes, heart attacks, and asthma attacks. There’s also evidence that long-term exposure to smoke can lead to a higher likelihood of death from heart, lung, kidney, and digestive diseases.
And experts believe the true health burden from wildfires is likely much more extensive than we realize.
The harms to health will increase as wildfires become more destructive. Though wildfires are a natural, regular, and vital phenomenon across many landscapes, more people are now living in fire-prone areas, increasing the risk to lives and homes. That increases the odds of starting a fire and means more people and property are in harm’s way when one ignites. Decades of fire suppression have allowed fuels like trees and grasses to build up to dangerous levels. And as humanity continues to burn fossil fuels, emitting greenhouse gases and heating up the planet, the climate is changing in ways that enhance fire conditions.
On top of wildfires, the summer season can cause other problems. The hot, sunny weather can trigger the formation of ozone, a compound that can cause lung trouble. Dry air can lead to more airborne dust. This week, there’s also a huge cloud of dust from the Saharan Desert making its way westward across the Atlantic Ocean. Such clouds can also fill the air with tiny irritating particles and carry pathogens and heavy metals.
So smoke isn’t the only pollutant to worry about, and as average temperatures continue to rise, these factors are undoing hard-fought progress in improving air quality across much of the world.
However, there are ways to clear the air and avoid some of the worst harms. One tactic is to pay attention to the Air Quality Index in your area and avoid being outdoors when pollution reaches high levels. Wearing a high-quality KN95 or N95 mask can help reduce the damage from polluted air. Blocking air from getting indoors and filtering the air in living areas reduces smoke exposure as well.
It’s also important to mitigate wildfires where possible. On a bigger scale, that means smarter planning: limiting development in areas likely to ignite, building defensible perimeters around structures, and reducing fuels with controlled burns. And we can’t get around the fact that reducing our risk will also require limiting climate change. Otherwise, more smoky, dusty, and dirty summers lie ahead.
