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More About Ozone...

On April 15, 2004, Anderson, Blount, Jefferson, Knox, Loudon and Sevier Counties and the portion of Cocke County within the Great Smoky Mountains National Park were designated in non-attainment of the US Environmental Protection Agency’s (EPA) standard for 8-hour ground level ozone. These counties must show attainment by 2009.

Ground level ozone is an invisible gas that is created when sunlight, heat and certain pollutants mix in the atmosphere. Ozone causing pollutants Nitrogen Oxide (NOx) and Volatile Organic Compounds (VOC) come from vehicles, factories, burning, and natural sources. High ground level ozone is typically seen in summer months when sunlight is at its greatest intensity and temperatures are warmer.

The Regional Clean Air Coalition (RCAC) website includes a two day forecast for ground level ozone for both the valley and mountains from March 1 through October 31. The forecast format uses the US Environmental Protection Agency’s (EPA) Air Quality Index (AQI). The AQI has a five color air quality scale as follows:

  • Green: The forecasted air quality is good- No health impacts are expected
  • Yellow: The forecasted air quality is moderate- Unusually sensitive people should consider limiting prolonged outdoor exposure.
  • Orange: Unhealthy for sensitive people- Active children and adults, and people with lung disease, such as asthma, should reduce prolonged or heavy exertion outdoors.
  • Red: Unhealthy- Active children and adults, and people with lung disease, such as asthma, should avoid prolonged or heavy exertion outdoors. Everyone else, especially children, should reduce prolonged or heavy exertion outdoors.
  • Purple: Very unhealthy- Active children and adults, and people with lung disease, such as asthma, should avoid all outdoor exertion. Everyone else, especially children, should avoid prolonged or heavy exertion outdoors.

When either the forecasted ozone or particulate matter (PM2.5) is a color scale orange or higher, an Air Quality Action Day will be in effect in which people should takes measures to reduce their outdoor exposure to the pollutant and take measures to reduce the emissions they may create.