A wildfire burns near Chance Harbour, N.L., on July 14.Dawn Gough/The Canadian Press

Even thousands of kilometres from the flames, Canadians were coughing, wheezing and red-eyed. As wildfires raged, smoke and haze spread last week across the country, sparking health warnings for millions of people. For a few hours, Toronto had the second worst air in the world. On a scale of 1 to 10, the city’s air quality was off the chart, officially clocked at 10 .

The smoke was a reminder that the threat of fires is bigger than the immediate danger posed to those nearby. As climate change causes hotter and drier conditions – which leads to more frequent and more fierce blazes – Canadians have to start taking seriously the toxic stew carried on the wind.

A century ago, professional cyclists believed that smoking cigarettes on the bike would “open up the lungs” during difficult races in the mountains. We now know that all smoke contains particulate matter that can damage the lungs, leading to cardiovascular problems, and even get into the bloodstream. The Canadian Lung Association warns bluntly that “there is no safe........

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