The Air Quality Index is designed to help you determine how clean or polluted the air is, and focuses on the associated health effects you may experience within a few hours or days after breathing polluted air.


In March 2008, the U.S. EPA revised the National Ambient Air Quality Standard for ozone from an eight–hour average of 84 parts per billion (ppb) to an eight-hour average of 75 ppb. Simultaneously, the U.S. EPA revised the Air Quality Index (AQI) used for ozone. Ozone Alerts are now issued when we forecast ozone levels to reach 76 parts per billion (ppb) averaged over 8 hours.

Most importantly, the new, lower levels are more protective of public health. The new levels will also mean that the Evansville EPA will be issuing more Ozone or Ozone / Particulate Alerts. Based on past years' data, the Evansville EPA believes it will issue Ozone Alerts four to six times more frequently than under the previous standard. The increase in the number of alerts does not necessarily mean a decrease in air quality.

The table below compares the new AQI to previous AQI levels for ozone:

Air Quality Index

New 2008
Ozone Levels

(8 hr. avg.)

Previous 1999
Ozone Levels

(8 hr. avg.)


0 - 59 ppb

0 - 64 ppb


60 - 75 ppb

65 - 84 ppb

Unhealthy for Sensitive Groups

76 - 95 ppb

85 - 104 ppb


96 - 115 ppb

105 - 124 ppb

Very Unhealthy

116 - 374 ppb

125 - 374 ppb

Higher levels of ozone can cause lung and throat irritation, shortness of breath, increase the frequency of asthma attacks and aggravate respiratory diseases such as asthma, emphysema and bronchitis. Children, active adults, and people with respiratory diseases should limit prolonged outdoor exertion especially between 12:00 p.m. to 6:00 p.m. when ozone levels are highest.

No open burning is allowed during Ozone Alerts. The use of gas and charcoal grills is permitted, but postponing grilling until air quality improves is encouraged.


In September 2006, U.S. EPA revised the 24-hour National Ambient Air Quality Standard for Particulate Matter 2.5 micrometers in diameter (PM2.5) from 65 micrograms per cubic meter (µg/m3) to 35µg/m3. However, U.S. EPA did not revise the Air Quality Index. U.S.EPA’s Air Quality Index uses 40µg/m3 averaged over 24 hours as the “Unhealthy for Sensitive Groups” level. The Vanderburgh County Health Department and Evansville EPA, to be more protective of public health and to be consistent with the National Ambient Air Quality Standard, issue Particulate Alerts when we forecast particulate levels to reach a twenty-four hour average of 35µg/m3. When you receive a notice for a Particulate Alert from EnviroFlash, that notice will reflect our policy of calling Particulate Alerts at the more protective 35µg/m3 averaged over 24 hours.

Air Quality Index

PM2.5 levels
(Averaged over 24 hours)


 0 - 15.4 µg/m3

Moderate (51 - 100)

15.5 - 40.4 µg/m3*

Unhealthy for Sensitive Groups

40.5 - 65.4 µg/m3


65.5 - 150.4 µg/m3

Very Unhealthy

 150.5 - 250.4 µg/m3

* NOTE:  Evansville Alerts issued at 35 µg/m3

To do your share to protect air quality and reduce pollution levels:

  • CONSERVE ENERGY – turn off lights, reduce air conditioner use, etc.
  • Limit your driving. Avoid unnecessary vehicle idling.
  • Park and go inside instead of using drive-through windows, especially if there are long lines.
  • Postpone fueling your vehicle until after 6:00 p.m. Don’t ‘top-off’ your tank when filling up.
  • Consider using electric or manually operated lawn equipment. If you use gasoline-powered lawn and garden equipment, stop working at 10:00 a.m. and/or postpone work until after 6:00 p.m.
  • Limit the use of solvents, parts cleaning fluids, paint thinners and chemicals. Replace lids when finished.
  • Postpone painting or use water-based paints instead of oil-based paints.

Real-time pollution levels, forecasts and more information can be found at: and

Have a question or comment about Mayor Weinzapfel's sustainability initiatives? Want to get involved? Contact us.

Last updated: 8/26/2008 9:21:13 AM