US AQI: US Air Quality Index is the EPA index for reporting air quality. Less than 50 is good; over 300 is hazardous.
PM2.5 µg/m3: Measure of fine Particulate Matter less than 2.5 micrometers over a 24-hour period (e.g, forest and grass fires, vehicle exhausts, burning of fuels, power plants). Levels at or below 12 μg/m3 are healthy; over 35 μg/m3 is unhealthy.
