Smoke from ongoing Canadian wildfires has led to some of the worst air quality in the world across parts of the U.S.

Smoke from Canadian wildfires is causing air quality concerns for millions of Americans in the Midwest and Northeast.

Canadian wildfires may be posing “serious health risks’’ to people in New York — prompting an air-quality alert for the state through Monday and a warning for some regions into Tuesday. The metro area’s current ailing air quality and hazy skies are hampering the five boroughs,