Air quality concerns in southern Ontario due to drifting wildfire smoke

The Kitchener, Ont. skyline was partially obscured by smoke in this image from June 5, 2025.

Environment Canada advised people living in southern Ontario to stay indoors Monday as air quality dropped to unhealthy levels.

The agency uses a scale ranging from one to 10 to determine air quality risk.

It rose to seven on Monday, indicating a ‘high risk,’ as wildfire smoke drifted south from northern Ontario and western provinces.

“I definitely canceled a cycling trip this morning,” said Ze’ev Gedalof, a professor in the Geography, Environment and Geomatics department at the University of Guelph.

IQAir, a Swiss air quality company, backed up Environment Canada’s findings. At one point on Monday, Kitchener was ranked 4th in the province for poor air quality. The company said the ‘Auditorium Neighbourhood’ had the worst of it at 9:45 a.m., with an air quality index of 188 out of 210, which is considered “unhealthy.”

“When you compound this with the heat, you’re just asking for a respiratory emergency,” said Gedalof. “If you don’t have to go outdoors, don’t do it.”

According to Region of Waterloo Public Health, residents with preexisting health conditions and older people are most affected by poor air quality and should reconsider outdoor activities. Anyone who develops a cough or irritated throat may also want to head indoors.

While conditions have improved since Monday morning, experts said it’s still important to check air quality reports throughout the day.

“Most important thing when it comes to poor air quality and to wildfire smoke, is that it can change throughout the day,” said Brandie Bevis, a health promotion and research analyst at Region of Waterloo Public Health. “You want to make sure you go to the Air Quality Health Index tool for the Kitchener-Waterloo Region.”

That section reflects the latest data for the entire region.

“From there you’ll be able to monitor whether or not you want to be changing your plans for the day or whether or not you are taking a little bit more concern about how you are feeling, how is your body managing right now with the heat and with the poor air quality,” Bevis continued. “So, really listening to your body and your symptoms, if you need to take a break, if you’re finding that it’s impacting how you’re breathing maybe reduce your activity, stay in an air-conditioned space.”

The region has also identified 57 “clean air” locations around the community. They are the same spaces used as warming centres in the winter and cooling centres in the summer.

“Anyone can go during regular business hours to get relief from the heat and the poor air quality. It’s really important to take breaks from both,” Bevis said.

She also urged people to check in on family, friends and neighbours who don’t have air conditioning, live alone or are at-risk for developing complications.

Gedalof said if you do need to work outside, a properly fitted N95 mask can help filter out some of the toxins.

“There is no safe level of wildfire smoke, it’s full of all kinds of toxic compounds,” he explained. “The haze is mostly PM10. It’s 10 microns in size and our noses are actually pretty good at filtering that out. It’s what we can’t see that’s dangerous, so PM2.5, up to two-and-a-half microns across. It’s effectively invisible. And when you breathe that in, it’s a bit like asbestos. It goes deep into your lungs, and it just stays there forever.”

Health risks

Environment Canada said people with heart and lung conditions are most affected by poor air quality.

Other vulnerable groups include seniors, pregnant people, infants, children, outdoor workers and those with chronic illnesses.

Air pollution can cause symptoms such as mild eye, nose and throat irritation, headaches or a mild cough. In more severe cases, people may experience wheezing, tightness in the chest or a persistent cough.

Anyone experiencing severe symptoms should seek medical attention immediately.