Canadian wildfire smoke has returned to the United States this week, triggering air quality alerts for more than a dozen states from Montana to Vermont. Around 70 million Americans would see decreased visibility and poor air quality, including residents of Chicago, Detroit, New York, St. Louis and Cleveland. Canada is on pace to have its…

Canadian wildfire smoke has returned to the United States this week, triggering air quality alerts for more than a dozen states from Montana to Vermont. Around 70 million Americans would see decreased visibility and poor air quality, including residents of Chicago, Detroit, New York, St. Louis, and Cleveland. Canada is on pace to have its…