Smoke from hundreds of Canadian wildfires continued to cast a haze over populous areas of the eastern U.S., and could last for days, as polluted air sent people with asthma to their doctors, disrupted air travel and altered school schedules.
Millions of people in North America have been advised to wear N95 masks outdoors due to poor air quality levels sparked by intense wildfires in Canada.
Millions of Americans in the Midwest and the Northeast are under air-quality alerts as smoke moves south from more than 400 active Canadian wildfires.