Air quality indexes indicate how polluted the air is, or forecast how polluted it could become, based on levels of five ...

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 ...

Government agencies use these indexes to measure public health risks and ... but allergens like pollen and ragweed aren't counted on the Air Quality Index as those particles are too large.