Where Calgary's worst air quality is, and how that changes with the seasons

People who spend time outdoors south of the Bow River in Calgary are breathing in some of the worst winter air in the city, according to a new study by the University of Calgary.

Don't panic; the city's worst air is only 'moderate risk' by Environment Canada's standards, says researcher

New research from the University of Calgary reveals surprising variation in air quality across Calgary, not just by neighbourhood but according to the time of year. (Genevieve Normand/CBC Radio-Canada)

People who spend time south of the Bow River in Calgary are probably breathing in some of the worst winter air in the city, suggests a new study by the University of Calgary.

Researchers Stefania Bertazzon and Rizwan Shahid from the geography department used data from 2010 and 2011 to map out where the city's most polluted air is.

They measured by levels of ozone, nitrogen dioxide and fine particulate matter, which can include dust, fumes, smoke and pollen that are 2.5 microns in diameter and smaller.

Both Bertazzon and Shahid were surprised to see how air quality varies not only across the city's neighbourhoods, but also depending on the season.

The darker the orange colour, the worse the air quality in that area. The data used to create these maps was gathered in 2010 and 2011, but the researchers say early findings from 2015 and 2016 confirm these patterns. (Rizwan Shahid)

A quick glance at the summer map above shows that pollution levels tend to be higher in the downtown core, along major corridors, like Crowchild Trail and Deerfoot, and in the northeast quadrant.

That makes sense, considering traffic emissions degrade air quality, and knowing that the northeast is home to many industrial emitters and a major airport.

But when it comes to winter air quality, Shahid and Bertazzon were surprised to see a more diffused pattern settling in over the city's south end. Note the large, dark orange swath covering much of the area below the Bow River in the map below.

The researchers say more analysis is required to explain what causes the seasonal variation in air pollution across the city. (Rizwan Shahid)

The researchers believe the seasonal variations owe in part to wind patterns, which blow from the southwest in the summer and from the north in the winter.

But Shahid and Bertazzon say further analysis is needed to fully explain what is happening. For the moment, they suspect it may have something to do with topography or elevation.

In the meantime, they've shared their findings with Alberta Health Services and the Calgary Region Airshed Zone, which monitors, analyzes and provides information on air quality and develops strategies to manage air quality issues within the city.

Overall air quality still safe

The air pollution levels are all relative, so Calgarians shouldn't be too concerned about any health impacts, Shahid said.

"There is no need to panic. Overall, Calgary air pollution levels are in [the] safe zone. They only vary in different areas, and even then, they are not bad," said Shahid.

The city's worst air quality would correspond to the low end of "moderate risk" on Environment Canada's Air Quality Health Index, he said.

Calgary: The Road Ahead is CBC Calgary's special focus on our city as it passes through the crucible of the downturn: the challenges we face, and the possible solutions as we explore what kind of Calgary we want to create. Have an idea? Email us at

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With files from Dave Gilson