Information about the Air Quality Index (AQI)

Excerpts from Georgia EPD's 'Ambient Air Suveillance Report' and information taken from 40CFR58 Appendix G

Click HERE for Excerpts from GA EPD's report and information listed above
NEW in Ozone Season 2016: Smog Alerts will be activated at lower pollution levels to be more protective of public health. EPA has raised the bar by lowering the standard! ( See Fact Sheet for more information).

The Air Quality Index

The Air Quality Index (AQI) is a national air standard rating system developed by the U.S. Environmental Protection Agency. The AQI is used statewide to provide the public, on a daily basis, with an analysis of air pollution levels and possible related health risks. Generally, an index scale of 0 to 500 is used to assess the quality of air, and these numbers are synchronized with a corresponding descriptor word such as: Good, Moderate, Unhealthy for Sensitive Groups, Unhealthy, and Very Unhealthy. To protect public health, the EPA has set an AQI value of 100 to correspond to the National Ambient Air Quality Standard (NAAQS) for the following criteria pollutants: Ozone (O3), Sulfur Dioxide (SO2), Carbon Monoxide (CO), Particulate Matter 10 (PM10), Particulate Matter 2.5 (PM2.5), and Nitrogen Dioxide (NO2). The index value of 100 is associated with the numerical level of the short-term standard (i.e., averaging time of 24-hours or less) for each pollutant. The AQI for a reporting region equates to the highest rating recorded for any pollutant within that region. Therefore, the larger the AQI value, the greater level of air pollution present, and the greater expectation of potential health concerns. However, this system only addresses air pollution in terms of acute health effects over time periods of 24 hours or less and does not provide an indication of chronic pollution exposure over months or years.

The following figure shows how the recorded concentrations correspond to the AQI values, descriptors and health advisories. Each day the AQI values are available for each of Georgia EPD’s site. The AQI figures are to be reported to news media and EPA’s AIRNOW for applicable pollutants in all metropolitan areas of the United States with populations exceeding 350,000.

AQI Value Descriptor EPA Health Advisory
0 to 50 Good
Air quality is considered satisfactory, and air pollution poses little or no risk.
51 to 100 Moderate
Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people. For example, people who are unusually sensitive to the condition of the air may experience respiratory symptoms.
101 to 150 Unhealthy for Sensitive Groups
Members of sensitive groups (people with lung or heart disease) are at greater risk from exposure to particle pollution. Those with lung disease are at risk from exposure to ozone. The general public is not likely to be affected in this range.
151 to 200 Unhealthy
Everyone may begin to experience health effects in this range. Members of sensitive groups may experience more serious health effects.
201 to 300 Very Unhealthy
AQI values in this range trigger a health alert. Everyone may experience more serious health effects. When the AQI is in this range because of ozone, most people should restrict their outdoor exertion to morning or late evening hours to avoid high ozone exposures.
301 to 500 Hazardous
AQI values over 300 trigger health warnings of emergency conditions. The entire population is more likely to be affected.

On days when two or more pollutants exceed the standard (have AQI values greater than 100) in one metropolitan area, the air quality index from the pollutant with the highest concentration is used for that reading. The pollutant responsible for the highest index value is called the ‘critical’ pollutant.

Groups within the general population can be more sensitive to higher concentrations of different pollutants. The following table describes which groups of the general population can be more sensitive with higher concentrations of each pollutant.

When this pollutant has an index value above 100 *  *  * When this pollutant has an index value above 100 *  *  *
Ozone Children and people with asthma are the groups most at risk.
PM2.5 People with respiratory or heart disease, the elderly and children are the groups most at risk.
PM10 People with respiratory disease are the group most at risk.
CO People with heart disease are the group most at risk.
SO2 People with asthma are the group most at risk.
NO2 Children and people with respiratory disease are the groups most at risk.