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.

Wildfires in Canada are sending heavy smoke across the northern U.S., and New Jersey is experiencing some unhealthy air pollution. The air quality has some Northeasterners wondering, what is the AQI, or Air Quality Index? AQI, or Air Quality Index, is the measure of how healthy or unhealthy the air is.

Air quality alerts are in place for portions of 10 states from Minnesota to Delaware as officials warn the smoke may become dangerous for sensitive groups.There are two U.S. cities in the top 10 globally for worst air pollution among major cities worldwide Wednesday morning: Chicago and Detroit.