Scientists race to untangle complex links between exposure and mortality as fire weather grows more prevalent

A thousand kilometres from the infernos gorging on northern Ontario’s boreal forests, Erin O’Connor watched the sky above Canada’s biggest city turn an “almost post-apocalyptic” orange as it filled with light-scattering particles of soot and ash. Stepping outside the halls of Toronto General hospital, where air filters were keeping patients safe from the worst of the fumes, she was struck by a smell so strong it felt like standing by a campfire.

“It really hit you in the face as soon as you walked outside,” said O’Connor, who runs University Health Network’s emergency department and saw a rise in patients presenting with allergies and shortness of breath. “As the days progressed, it was like that everywhere. It seemed even inside you could smell that burning.”