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The U of T Engineering team is embarking on two large-scale urban air quality studies

U of T Engineering researchers have launched two major air quality studies to assess non-ventilation emissions and winter air pollutants. The research included data collection at Toronto landmarks, including the CN Tower, two U of T campuses, Toronto Pearson International Airport and High Park. Future findings may inform future work aimed at understanding potential links between air pollutants and adverse health effects.

For the Improved Assessment and Characterization of Traffic Emissions (IMPACT) study, Profs Greg Evans (ChemE, ISTEP), Marianna Hatzopoulo (CivMin) and Arthur Chan (ChemE) examines changes in concentrations of non-use emissions, such as those resulting from brake, tire and road wear, across Toronto.

“The good news is that vehicle technology has improved and tailpipe emissions from cars have dropped significantly. “Unfortunately, at the same time, we're seeing a steady increase in non-tailpipe emissions,” says Evans.

“More and more Canadian drivers are choosing to buy heavier vehicles, such as pickup trucks and SUVs, where they need more brake and tire wear to slow them down. As brake pads and tires wear, they shed a lot of water and airborne particles. It's important to understand our exposure to these emissions.”

Evans, Hatzopoulou and Chan contribute to a separate study conducted alongside the IMPACT project. Toronto Winter Air Pollution Study (SWAPIT)A study of air pollution during the colder months, led by Environment and Climate Change Canada.

Notably, the SWAPIT project is one of the few air quality studies completed in winter, and it is the largest wintertime urban air quality study conducted globally in terms of the number of pollutants measured.

“Most air quality studies have been conducted in the summer, when smog and wildfires are most common, but air pollution remains a problem in the colder months,” says Evans. “And some pollutants are found in higher concentrations in the winter.”

Evans points out that some vehicle emissions treatment systems designed to operate in warmer weather, such as those designed to treat exhaust gases for diesel vehicles, are less effective at removing nitrogen oxides when temperatures drop.

In addition, stagnant winter air confuses the issue.

“On summer days, when we have more wind, the vehicle emissions are dispersed and diluted more quickly, and we don't see them in such high concentrations when we're away from the highways,” Evans says. “However, in winter, stagnant air is common, which causes pollutants to become trapped around those roads, creating high concentrations that can persist for a kilometer or more from the road.

“If we find that pollutant levels and chemistry vary seasonally, we need to consider what that means. This might raise questions about whether we should be pushing for better exhaust treatment systems, for example, or better ways to keep our windshields frost-free without drawing in potentially polluted outside air. Of course, the electrification of our vehicles in the next decade will help a lot to solve these problems.”

Research will install an air monitoring system in the attic.
Cheol-Heon Jeong, senior scientist at ChemE, investigates the air quality measurement system installed for the IMPACT and SWAPIT projects. (Photo credit: Ye Ka Wong)

To answer the questions of the IMPACT and SWAPIT projects, researchers installed air quality measurement systems across Toronto, including 40 roadside poles and the roof of the CN Tower. Sites equipped with heavy equipment will also be set up at the St George's and Scarborough campuses, High Park and Evergreen Brick Works. The U of T Engineering team also uses mobile labs—vehicles equipped with measurement systems—to collect samples while navigating specific routes around the city.

Over a six-week period, from the end of January to the beginning of March, the measurement systems collect air samples at regular intervals. The team will analyze the samples for particulate matter in the air, including metals. Using AirSENCE monitoring technology developed at U of T, researchers also measure gases such as carbon monoxide, carbon dioxide, nitrogen oxides and ozone.

To better understand how pollutant concentrations change, U of T Engineering researchers will set up systems at different distances from major roads, including the 401 freeway. And the team will use access to the CN Tower to set up test stations in various locations. altitudes to estimate pollutant concentrations at different altitudes.

Results from the IMPACT and SWAPIT projects add to U of T Engineering's comprehensive body of knowledge to improve understanding of urban air pollution. and its effects on human health and the environment.

There are researchers in the past Assessed air quality in the Toronto metro system, UrbanScanner collected air quality data across the city using a mobile lab and launched initiative to decarbonize transportation, among other activities. And by recognizing their research contributions theSouthern Ontario Center for Atmospheric Aerosol Research (SOCAAR), Evans, Hatzopoulo, Chan and their colleagues were honored NSERC 2021 Blockhouse Award for Interdisciplinary Research in Science and Engineering.

Evans hopes the IMPACT and SWAPIT initiatives will give researchers a clearer picture of air pollution in the city.

“We hope that what we learn will help future epidemiology ask health-related questions,” he says. “For example, what are the health impacts in areas where emissions outside the tailpipe are high?” Are there links between off-pipe emissions and various health effects? What is the effect of stagnant air on exposure to moving pollutants?

“We can use the data we collect to frame new questions and think about larger implications, particularly what health benefits we can expect over the next decade if we reduce emissions from burning fossil fuels.”

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