The Air Quality Health Index combines ozone, fine particles (PM2.5) and nitrogen dioxide into one number for the short-term health risk of the air. Wildfire smoke can push it above 10 even hundreds of kilometres from the fires, so check it before a long run or hike in summer.
Most of Quebec reports air quality through the province's own IQA index; Montréal, Gatineau and Québec City also have the AQHI.