Smoke from Canadian wildfires is causing air quality concerns for millions of Americans in the Midwest and Northeast.  Air quality alerts were in effect Tuesday in several states, including Michigan and New York.

Massachusetts can expect hazy skies on Wednesday as smoke from Canadian wildfires continues to drift down the East Coast, prompting an Air Quality Alert for the western part of the state.

The smoke drifting across the border contains fine particulates, pollution so small that it’s basically invisible to the naked eye.