Air Quality Index

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The U.S. AQI is the Environmental Protection Agency’s (EPA) index for reporting air quality for five major air pollutants regulated by the Clean Air Act. Each of these pollutants has a National Ambient Air Quality Standard set by EPA to protect public health: ground-level ozone, particle pollution (also known as PM2.5 or PM10), carbon monoxide, sulfur dioxide and nitrogen dioxide. When ambient air data is collected, the numbers are converted from their concentration levels into numbers on a scale that corresponds to a certain level of health risk. The EPA developed the AQI to make reading ambient air quality data more understandable to the public, and to relate ambient air pollution concentrations to their associated health risks.