This measure, based on data from the Environmental Protection Agency, evaluates states on the number of days the Air Quality Index in counties was not rated “good.” U.S. News calculated a ...

The Air Quality Index (AQI) is an index for reporting daily air quality. It tells you how clean or polluted your air is, and what associated health effects might be a concern for you. For more ...

It comprises two measures: the number of days with an air quality index below a certain threshold and the number of violation points against drinking water systems in each state. Learn more about ...