The haze hanging over Chicago, Toronto, and Washington, D.C., this week is not an inconvenience. It is a public health emergency measured in emergency room visits, hospital admissions, and — when exposure is prolonged — deaths. As smoke from more than 900 active Canadian wildfires continues to stream across North America, doctors and researchers are warning that the health consequences are already being felt, and that the populations most at risk may not fully recognize the danger they are in.
