What does Toronto’s air-quality score mean for you? A local built a tool to make sense of it

Toronto’s smoky skies are expected to improve significantly on Sunday, but one local air-quality advocate says residents should not have to decode government data to determine whether it is safe to step outside.

Toronto remained under a yellow air-quality warning Saturday morning as smoke from wildfires continued to cause poor air quality and reduced visibility.

Environment Canada forecast a maximum Air Quality Health Index (AQHI) of 10+, or very high risk, for Saturday. The index is expected to fall to six, or moderate risk, Saturday night before reaching two, or low risk, on Sunday.

The agency said conditions would gradually improve Saturday morning before smoke potentially returns in the evening and lasts into Sunday morning. A “major improvement” is expected Sunday.

The warning comes after smoke from northwestern Ontario blanketed Toronto earlier in the week. On Wednesday, Toronto’s air quality was ranked the worst among major global cities, while the AQHI reached 10+.  

With Torontonians trying to determine whether they should exercise, walk their dogs or take their children outside, Toronto resident Amrit Sharma created toronteau.com/air, a website that translates air-quality readings, forecasts, and advisories into plain language.

“Torontonians are struggling to interpret AQHI numbers and have been left guessing to make sense of it. Is it safe to go outside? Is the AQHI getting better? When might the smoke clear?” Sharma wrote in an email to Now Toronto.

Sharma serves on the board of OpenAQ, a non-profit focused on making global air-quality data more accessible, and works at ecobee designing utility grid-resiliency programs.

“What does this mean for me? Like, should I go for my run today? Should I walk my dog? Should I keep my kids home?” Sharma told Now Toronto on Friday, describing some of the questions coming from friends, coworkers and people around the city.

“Toronto typically has clean air, which is why I think we haven’t really had to understand what the air quality index really, really means.”

However, as wildfire smoke becomes a more frequent part of Toronto summers, Sharma believes residents need information that clearly connects an AQHI number with the actions they should take.

“So it doesn’t make up answers, and I don’t have my own advisories,” Sharma said about the website.

Instead, the site takes air-quality information from Environment and Climate Change Canada and the Ontario government and presents it in a format resembling an iMessage conversation.

“It acts like a smart friend of yours who understands air quality, who answers the common question that you’ll ask,” Sharma said.

Sharma stressed that “everything on my website is official government data, so I’m not measuring air quality myself.”

What the AQHI numbers mean

Canada’s AQHI runs from one to 10+, with the numbers divided into four health-risk categories. 

Readings between one and three are considered low risk, four to six are moderate risk, seven to 10 are high risk and anything above 10 is considered very high risk.

At seven, Sharma said people in the general population should monitor how they are feeling and consider reducing outdoor activities if they develop symptoms.

“For folks who are at risk, they should not wait for symptoms. They should reduce and reschedule their activities outdoors proactively,” Sharma said.

When the index reaches 10+, everyone faces an elevated risk of health effects from the air they are breathing.

Environment Canada currently advises people who are more vulnerable to smoke—including adults 65 and older, pregnant people, infants, young children, outdoor workers and people with existing illnesses or chronic conditions—to reduce or reschedule strenuous outdoor activities.

The agency recommends limiting time outside, keeping windows and doors closed when possible and using a high-quality air filter or portable air cleaner indoors. A properly fitted N95 or equivalent respirator can help reduce exposure to fine smoke particles when someone must be outside, although it does not eliminate all health risks.

Sharma also cautioned against viewing wildfire smoke as only a temporary inconvenience.

“The health effects aren’t short-term; they accumulate over time,” Sharma said.

Despite the risks, Sharma said residents are not powerless. Air-quality forecasts can help people plan outdoor activities, arrange indoor alternatives, and prepare masks or air purifiers before conditions deteriorate.

“One thing I want them to remember is you’re not powerless,” Sharma said. “You can access today and tomorrow’s air quality for up to 36 hours, and that data is readily available on the internet.”

For now, Environment Canada advises residents to continue monitoring Toronto’s air-quality warning throughout Saturday, with clearer and healthier conditions forecast to arrive Sunday.