Air quality alerts are in effect on Tuesday in 10 states as toxic smoke from hundreds of wildfires burning in Canada continues to waft into the United States, creating hazy, gray skies over major metropolitan areas,

Canada is battling more than 700 active wildfires across the country, roughly two-thirds of which are burning out of control, according to the Canadian Interagency Forest Fire Center (CIFFC). Smoke billowing from the blazes has blanketed central Canada and the northern U.S., prompting widespread air quality alerts.

Breathing in polluted air for extended periods of time can pose a serious health risk for people, especially for vulnerable populations.