Wildfire smoke could create health risks for Toronto residents this summer. Here is why doctors say you should be careful

The Toronto skyline is pictured from Polson St. as wildfire smoke rolls into Toronto, on Wednesday, June 28, 2023. THE CANADIAN PRESS/Andrew Lahodynskyj

It’s almost summer in Toronto which means many will be looking to soak up the sun after an unseasonably cool May.

But with wildfires burning across the northern Ontario, the Prairies, and Western Canada, residual smoke threatens to return to the province’s south and could force people indoors due to deteriorating air quality.

The city, and much of the surrounding area, saw smoky skies earlier this month as out-of-control fires burned across Canada, which have already displaced tens of thousands of people. The smoke triggered Environment Canada to issue a special air quality statement for the region as well as five other provinces and one territory.

On June 6, Toronto briefly held the unenviable title of having the worst air quality in the world due to the smoke, according to Swiss air quality tracker IQAir.

“I think we’re already seeing, out of the gate, much higher than our 10-year [wildfire] average. So, it does look like we are in for a tough season,” said Dr. Samir Gupta, a respirologist and associate professor at the University of Toronto, referring to the 183 fires recorded in Ontario so far in 2025. Last year, the province saw 100 forest fires.

The 2025 wildfire season has already burned 3.7 million hectares, six times the area of Prince Edward Island, and is the second worst since 2023.

The Weather Network released its 2025 summer forecast last month and predicted that conditions by the Ontario-Manitoba boundary will be warmer and drier in the months ahead, which could lead to even more fires and drifting smoke.

“We need to be extra vigilant this summer and really hope that we don’t get those fires started because conditions will be more conducive to fire spreading if they do start,” network meteorologist Doug Gillham told The Canadian Press at the time.

So, what should you know about Toronto’s air quality this summer and how can you stay safe on a smoky day? We spoke with Dr. Gupta to find out.

How far reaching can wildfire smoke be?

Although people in Toronto won’t see any flames as fires burn thousands of kilometres away in Alberta, Saskatchewan, Manitoba, northern Ontario and beyond, they will likely smell the smoke this summer -- if they haven’t already.

“It’s not just Toronto, the smoke from the Prairies, at its peak, was affecting three quarters of the continental U.S.,” Gupta said.

On June 4, a U.S. Environmental Protection Agency map showed that the smoke from Canadian wildfires was lingering over skylines from Kansas City to Minneapolis. At the same time, the smoke crossed the Atlantic and reached as far as Europe, according to an EU climate monitor.

“It doesn’t matter where it burns. The wind will carry it. The wind carried it all the way to London,” Gupta said. “So, we will definitely see the effects in Toronto.”

What happens when air quality deteriorates due to wildfire smoke?

Gupta said while there are “lots” of health effects associated with inhaling wildfire smoke, the most measurable are emergency room visits and hospital admissions, both of which he said increase “within hours” of the Air Quality Health Index level rising.

“We see increased emergency room visits for things like asthma exacerbations or flare ups, COPD (chronic obstructive pulmonary disease) flare ups. So, obviously lung diseases, because that’s the first point of entry of that smoke,” he said.

But the health effects aren’t limited to the respiratory system. Gupta said the smoke can also cause cardiovascular issues to spike.

“We start to see more heart attacks. In some studies, they’ve shown more strokes and more heart failure admissions and that’s partly because obviously the irritation happens at the level of the lungs when you’re breathing in the smoke, but the smoke contains these tiny particles that are small enough to get into the bloodstream through the lungs. And when that happens, they go to all the organs, and that includes the heart, and the heart is very sensitive to these particles, and so it starts to affect cardiovascular function as well.”

Headaches, coughs and red eyes

In addition to the more serious health effects listed above, wildfire smoke can also cause headaches, a mild cough, as well as nose, throat, eye and sinus irritation.

However, because the very-fine particles in the air aren’t visible to the human eye, Gupta said by the time you realize you’re having a reaction, “it’s often too late.”

“The problem is that for most people, it’s silent, you know. some people might have some irritation, sore throats and nose after prolonged exposure, but most people won’t know.”

In more serious cases, wildfire smoke can cause dizziness, wheezing and chest pains.

Who’s most at risk?

According to Gupta, the most vulnerable populations include (but aren’t limited to), the elderly, people with chronic diseases, those who are pregnant, and infants and young children.

“Those people have to check the Air Quality Health Index and try to avoid going out on poor air quality days, because you won’t feel it, but it’ll be doing the damage,” he said.

According to the Air Quality Health Index, which can be viewed on most weather apps, level 1 to 3 represents a low risk, 4 to 6 is moderate risk, 7 to 10 is high risk and above 10 is very high risk.

What if I work or exercise outdoors?

In addition to monitoring the air quality in your area, if you need to be outdoors on a smoky day, Gupta advises minimizing your time in the open air as much as you can.

Beyond that, he says an N-95 mask, similar to the ones used during the COVID-19 pandemic, is a good bet.

“We worry about those tiny particles. So if you can get your hands on one of those high-quality masks, that’s the best.”

If you exercise or run outdoors, Gupta said you should plan your workouts around the current air quality reading.

“I run outside and I won’t run on a 7 plus day. I’ll have to do it indoors. I’ll have to find an alternative, because I know that with running, you’re breathing in double the amount of pollution. It really can take a toll, even on a healthy person.”