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 were issued in North Jersey Aug. 5 as smoke from Canadian wildfires drifts across the northern United States.

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