EPA's Air Quality Index

The U.S. Environmental Protection Agency has developed the Air Quality Index, or AQI (exit DNR), (formerly known as the Pollutant Standards Index) for reporting monitored levels of ozone and other common air pollutants. The index makes it easier for the public to understand the health significance of air pollution levels.

Air quality is measured by a nationwide monitoring system that records concentrations of ozone and several other air pollutants at more than 1,000 locations across the country. EPA "translates" the pollutant concentrations to the [standard] AQI index, which ranges from 0 to 500. The higher the AQI value for a pollutant, the greater the health concern. An AQI value of 100 usually corresponds to the national ambient air quality standard (NAAQS) for the pollutant, meaning that pollutant concentrations have reached unhealthy levels. These standards are established by EPA under the Clean Air Act to protect public health and the environment.

To make it easier for the public to quickly determine the air quality in their communities, EPA has assigned a specific color to each AQI category. You will see the AQI for ozone reported in your newspaper, local television news, radio station, on EPA's AIRNOW website and on the DNR's AQI Hotline. This color scheme can help you quickly determine whether air pollutants are reaching unhealthy levels in your area. The chart below explains the AQI color system.

Good
Moderate
Unhealthy for Sensitive Groups
Unhealthy
Very Unhealthy

For the latest air monitoring levels, visit the Department of Natural Resources' Air Monitoring web page, or call the DNR's Air Quality Index Hotline at 1-866-DAILY AIR (1-866-324-5924) for daily air quality readings for these counties:

For more information

• New standards, new Air Quality Index
• Additional information on AQI changes

The links below exit DNR:

• American Lung Association (phone 1-800-LUNG-USA, or 1-800-586-4872)
• EPA's AIRNOW website - for information on ozone and particle pollution mapping, the AQI, and more.