These changes incorporated:
· revisions to the primary health-based national ambient AQI (O3 and PM)
· separate values for PM2.5 and for PM10
· a new category “unhealthy for sensitive groups” in the index range of 101–150
· color symbols to represent different ranges of AQI values
· requirements for authorities to supply information to the public on health effects at various index levels
· mandatory requirements for the calculation and reporting of the AQI in metropolitan areas (populations in excess of 350,000).