Air Quality Forecasting

Like the weather, air quality conditions can be forecast. The APCD works with the Indiana Department of Environmental Management (IDEM) to forecast levels of ground-level ozone (O3) and fine particle pollution (PM2.5) in Louisville and Southern Indiana. The forecast is generated using meteorological expertise and computer models, as well as local air monitoring and meteorological data.

The goal of forecasting air quality is to let the public, particularly those in sensitive populations, know what the air quality is going to be like so they can plan their day accordingly. You can find Louisville's daily forecast on EPA's AirNow, as well as the APCD's Twitter and Facebook pages.

For Ozone

  • Forecast peak 8-hour average concentrations for one to three days ahead.
  • Concentrations are forecast from March through October.

For PM2.5

  • Forecast peak 24-hour average concentrations for a three- or four-day period.
  • Concentrations are forecast year-round.
Air Quality Index

The Air Quality Index (AQI) is used to convey the risks that local air quality may have on individual health. 

To do this the AQI represents local air pollution levels on a scale from 0-500. The higher the value the greater the level of pollution and potential health risk. The values are sorted into six color-coded categories ranging from "Good" (1-50) to "Hazardous" (301-500). While there is no "healthy" amount of air pollution, any AQI value below 100 is considered to be acceptable for public health. 

0 to 50

Good (Green): Air quality is satisfactory, and air pollution poses little or no risk to public health.

51 to 100

Moderate (Yellow): Air quality is considered acceptable. However, there may be a risk for some
people, particularly those who are unusually sensitive to air pollution.

101 to 150

Unhealthy for Sensitive Groups (Orange): Members of sensitive groups may experience health
effects. The general public is less likely to be affected.

151 to 200

Unhealthy (Red): Some members of the general public may experience health effects; members
of sensitive groups may experience more serious health effects

201 to 300

Very Unhealthy (Purple): Health alert. The risk of health effects is increased for everyone.

301 to 500

Hazardous (Maroon): Health warning of emergency conditions. Everyone is more likely to be affected.

Air Quality Alerts

If the AQI is expected to be above 100, an air quality alert will be issued. Alerts are used to help residents avoid air pollution related health impacts; and encourage businesses and individuals to take action to reduce polluting activities. Here are some general recommendations considerations for days that are considered Unhealthy for Sensitive Groups (USG) on the scale (101-150):

  • Those in populations that are more susceptible to air pollution, including children, elderly adults, and those with preexisting conditions of the heart or lungs, should consider limiting outdoor activity. The higher the AQI, the more people should consider limiting their activity. 
  • As the AQI gets higher, all people should consider limiting strenuous activity outdoors. 
  • Reduce vehicle usage, attempt to carpool, work from home. 
  • Don't use gas-powered lawn equipment, wait a day or two to do the yard work. 

It is uncommon for Louisville to experience days higher than USG, but as the AQI increases the alert will affect more groups and have the potential to cause greater health issues.

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