Air Quality Forecast

As a driving force in the fight for cleaner air in the St. Louis region, The Clean Air Partnership is best known for its daily air quality forecasting. The forecasts take place over the summer months and utilize a color-coded system designed to keep area residents informed about ozone pollution levels in the region, and how those levels can affect their health.

 
 

What is the forecast based on?

The daily air quality forecast is based on the Air Quality Index or AQI. The EPA and local officials use the AQI to provide information about local air quality, which is designed to inform individuals about how unhealthy the air is and what health effects may be a concern due to air quality.

 

The AQI is calculated for four major air pollutants regulated by the Clean Air Act: ground level ozone, particle pollution, carbon monoxide, and sulfur dioxide. For each of these pollutants, EPA has established national air quality standards to protect public health.

 

AQI values can range from 0-500. As the level of air pollution rises, so do health concerns. 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. AQI values at or below 100 are generally thought of as healthy. But, when AQI values rise above 100, air quality is considered to be unhealthy.

 

The AQI is divided into five color-coded levels as follows:

AQI ValueActions to Protect Your Health From OzoneActions to Protect Your Health From Particle Pollution
Good (0-50)NoneNone
Moderate (51-100*)Unusually sensitive people should consider reducing prolonged or heavy outdoor exertion.Unusually sensitive people should consider reducing prolonged or heavy exertion.
Unhealthy for Sensitive Groups (101-150)The following groups should reduce prolonged or heavy outdoor exertion:
- People with lung disease, such as asthma
- Children and older adults
- People who are active outdoors
The following groups should reduce prolonged or heavy outdoor exertion:
- People with heart or lung disease
- Children and older adults
Unhealthy (151-200)The following groups should avoid prolonged or heavy outdoor exertion:
- People with lung disease, such as asthma
- Children and older adults
- People who are active outdoors
Everyone else should limit prolonged outdoor exertion.
The following groups should avoid prolonged or heavy exertion:
- People with heart or lung disease
- Children and older adults
Everyone else should reduce prolonged or heavy exertion.
Very Unhealthy (201-300)The following groups should avoid all outdoor exertion:
- People with lung disease, such as asthma
- Children and older adults
- People who are active outdoors
Everyone else should limit outdoor exertion.
The following groups should avoid all physical activity outdoors:
- People with heart or lung disease
- Children and older adults
Everyone else should avoid prolonged or heavy exertion.

* An AQI of 100 for ozone corresponds to an ozone level of 0.070 parts per million (averaged over 8 hours).

* For particles up to 2.5 micrometers in diameter: An AQI of 100 corresponds to 35 micrograms per cubic meter (averaged over 24 hours).

* For particles up to 10 micrometers in diameter: An AQI of 100 corresponds to 150 micrograms per cubic meter (averaged over 24 hours).

 

Each AQI category corresponds to a different level of health concern:

  • Good. The AQI value for your community is between 0 and 50. Air quality is satisfactory and poses little or no health risk.
  • Moderate. The AQI is between 51 and 100. Air quality is acceptable; however, pollution in this range may pose a moderate health concern for a very small number of individuals. People who are unusually sensitive to ozone or particle pollution may experience respiratory symptoms.
  • Unhealthy for Sensitive Groups. When AQI values are between 101 and 150, members of sensitive groups may experience health effects, but the general public is unlikely to be affected.
    • Ozone: People with lung disease, children, older adults, and people who are active outdoors are considered sensitive and therefore at greater risk.
    • Particle pollution: People with heart or lung disease, older adults1, and children are considered sensitive and therefore at greater risk.
  • Unhealthy. Everyone may begin to experience health effects when AQI values are between 151 and 200. Members of sensitive groups may experience more serious health effects.
  • Very Unhealthy. AQI values between 201 and 300 trigger a health alert, meaning everyone may experience more serious health effects.
  • Hazardous. AQI values over 300 trigger health warnings of emergency conditions. The entire population is even more likely to be affected by serious health effects.

*Source: airnow.gov

To view St. Louis area AQI data from previous years, click here:

http://www.ewgateway.org/environment/aq/AQICalendar/aqicalendar.htm