Each day, concentrations of various air pollutants are measured in areas across Idaho. A federal standard, or limit, has been estabished for each air pollutant. These limits are based on the health effects of the pollution and vary by type of pollutant.

After the amount of pollution is measured, it is compared to the federal standard. To make it easy to compare the various pollutants and determine the air quality, the U.S. Environmental Protection Agency (EPA) developed the Air Quality Index, or AQI.

You can think of the AQI as a measuring stick that runs from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health danger. For example, an AQI value of 50 represents good air quality and little potential to affect public health, while an AQI value over 300 represents hazardous air quality with potentially serious health impacts.

An AQI value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level EPA has set to protect public health. So, AQI values below 100 are considered healthful. 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.

• Good: The AQI is between 0 and 50. Air quality is considered satisfactory and air pollution poses little or no risk.  Color: Green. r: Green.

   

• Moderate: The AQI is between 51 and 100. Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of individuals. For example, people who are unusually sensitive to ozone may experience respiratory symptoms if ozone levels fall into this range.  Color: Yellow.

   

• Unhealthy for Sensitive Groups: The AQI is between 101 and 150.  Sensitive* people may experience health effects. For example, children and adults who are active outdoors and people with respiratory disease are at greater risk from exposure to ozone, while people with heart disease are at greater risk from carbon monoxide. Some people may be sensitive to more than one pollutant. Color: Orange.

• Unhealthy: AQI values are between 151 and 200. Everyone may begin to experience health effects. Sensitive people* may experience more serious health effects. Color: Red.

• Very Unhealthy: AQI values are between 201 and 300.  This trigger a health alert, meaning everyone may experience more serious health effects. Color: Purple.

• Hazardous: The AQI is over 300.  This triggers health warnings of emergency conditions. The entire population is more likely to be affected. Color: Maroon.

Air quality in Idaho is measured by monitors that record the concentrations of various pollutants throughout the state each day. The raw measurements are then converted into AQI values using standard formulas developed by EPA.

An AQI value is calculated for each of the pollutants in an area (ground-level ozone, two forms of particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide). Finally, the highest AQI value for an individual pollutant becomes the AQI value for that day. For example, if on one day a certain area had AQI values of 90 for ozone and 88 for sulfur dioxide, the AQI value would be 90 for the pollutant ozone on that day.

DEQ is required to publish the AQI for areas with populations over 350,000 on working days and at least once per day. DEQ publishes this information for certain areas with lower populations as well.

When the AQI is above 100, DEQ also must report which groups (such as children, the elderly, and people with asthma or heart disease) may be sensitive to the specific pollutant. If two or more pollutants have AQI values above 100 on a given day, DEQ reports all the groups that are sensitive to those pollutants.

Because the AQI is a national index, the values and colors used to show local air quality and the associated level of health concern are the same everywhere in the U.S. Look for a report on the AQI in your local newspaper, on television and radio, on the Internet, and on state and local telephone hotlines.

Locate the nearest Air Quality Monitoring Locations in Idaho and link to real-time local air quality data and AQI scores on DEQ's Web site.

Link to these DEQ Web pages:

Air Quality Monitoring Locations in Idaho: Link to real-time local air quality data.

Air Quality and Your Health: Discusses the health impacts of exposure to various pollutants.

More Links:

EPA's Air Quality Index Web Site

EPA's AIRNow Publications