Why the Sask. Roughriders postponed, but other sports played on: how air quality indexes work

Saskatchewan Roughriders fans who headed to Regina's Mosaic stadium Friday had a rough night, sitting through rounds of delays and ultimately the postponement of the game more than three hours after the scheduled kick-off time.

While the Riders postponed, other sports in Saskatchewan played on, despite much of the province being blanketed in wildfire smoke last weekend.

Experts say there is no single rule for making decisions to postpone or cancel sporting events due to air quality, and specific leagues have different health guidelines.

"Different sports require different amounts of huffing and puffing and exposure time," said Madeline Orr, an assistant professor of sport ecology at the University of Toronto whose research focuses on how climate change impacts sports. 

"Depending on the sport, depending on the exposure time, depending on how old the people are, these are all factors that should be considered. There is no one standard policy," Orr said.

She said the Canadian Football League has air pollution guidelines, but no rules.

Sports should be stopped as soon as the air becomes unsafe for people with sensitive conditions and wildfire smoke is particularly dangerous, Orr said.

With various air quality indexes available, and as wildfire smoke becomes an increasingly common health risk, here's what often goes into the decision to play or not — and how to make sense of air quality indexes when making your own decisions.

The Air Quality Health Index (AQHI) is run by Environment and Climate Change Canada (ECCC) and used widely across the country. It is meant to rate the health risk of three types of dangerous contaminants in the air on a one-to-10 scale — the higher the number, the greater the risk.

"It helps individuals make a judgment call around the air quality that they are breathing," said Céline Audette, manager of health and air quality forecast services at ECCC. 

Any rating of five or higher means at-risk people and those with pre-existing conditions should consider heading inside, she said. At seven, the general population should take precautions. At 10, everyone is at risk and exposure could cause health effects, Audette said. 

While other air quality indexes measure the concentration of specific pollutants in the air, the AQHI is based on epidemiologists' estimation of "the likely impact of that level of the pollution on the population," said Amir Hakami, an environmental engineering professor at Carleton University in Ottawa.

He works on air quality models similar to the one ECCC uses to create the AQHI.

The ECCC's national air pollution surveillance program uses more than 130 stations across Canada to measure air pollutants every hour. A model is then used to predict what the air quality and the corresponding health rating would be at areas not being tested.