Our air quality is communicated using the Air Quality Index (AQI). It tells us how clean or polluted our air is, and what associated health effects might be a concern.
The Environmental Protection Agency (EPA) calculates the AQI for five major air pollutants regulated by the Clean Air Act: ground-level ozone (O3), particle pollution (also known as particulate matter or PM), carbon monoxide (CO), sulfur dioxide (SO2), and nitrogen dioxide (NO2).
For each of these pollutants, EPA has established National Ambient Air Quality Standards to protect public health. AQI values range from 0-500. A higher AQI value means more air pollution and greater health impacts. AQI values below 100 are generally thought of as satisfactory. When AQI values are above 100, air quality is considered to be unhealthy—at first for certain sensitive groups of people, then for everyone as AQI values get higher.