Ozone Action Forecasts – What Are They?

Weather Knowledge

LITTLE ROCK, Ark. – During the late spring and summertime months, the state of Arkansas is most likely to experience significant levels of ozone concentrations at ground level, which can impact the environment and people living in it.

The Environmental Protection Agency (EPA) regulates six pollutants including particle pollution, ground-level ozone, carbon monoxide, sulfur oxides, nitrogen oxides and lead. While the EPA uses the Air Quality Index (AQI) to notify the public of local air quality, the Arkansas Department of Environmental Quality (ADEQ) issues Ozone Action Forecasts.

What is ozone?

According to the EPA, ozone is a gas composed of three atoms of oxygen (O3) located in both Earth’s upper atmosphere and at ground-level.

Ozone found in the upper atmosphere occurs naturally, forming a layer that protects us from the sun’s harmful ultraviolet rays.

Ozone found at the ground-level is considered a harmful air pollutant because of its effects on the environment and the general population.

Ground-level ozone forms on hot, windless days when volatile organic compounds (VOCs) react chemically with oxides of nitrogen (NOx) in sunlight. Examples of VOCs include gasoline and paint fumes, while NOx may be found in emissions from motor vehicles, gasoline powered lawn mowers, and other sources that produce combustion.

Ground-level ozone formation info-graphic.
Credit: United States Environmental Protection Agency

What are Ozone Action Forecasts?

Air quality is dependent upon a number of factors including sunlight, temperature, wind speed and direction. Daily ozone action forecasts are likely to vary.

There are five categories used for the Ozone Action Forecast to alert the public of potential health impacts due to higher levels of ozone.

GOOD – CODE GREEN: no health impacts expected.

MODERATE – CODE YELLOW: unusually sensitive people should consider limiting prolonged outdoor exertion.

UNHEALTHY FOR SOME – CODE ORANGE: active children and adults, people with respirator disease like asthma should limit prolonged outdoor exertion.

UNHEALTHY – CODE RED: active children and adults, people with respirator disease like asthma should avoid prolonged outdoor exertion. Everyone else should limit prolonged outdoor exertion, especially children.

VERY UNHEALTHY – CODE PURPLE: active children and adults, people with respiratory disease such as asthma should avoid all outdoor exertion. everyone else should limit outdoor exertion especially children.

What are Ozone Action Days?

When high ozone concentrations are forecast, Ozone Action Days are issued by the ADEQ.

According to the ADEQ, Ozone Action Days is a local, central Arkansas program coordinated through Metroplan and the Central Arkansas Clean Cities Coalition with the Department of Health, Arkansas Department of Environmental Quality and the State Highway and Transportation Department.

Six counties participate in the program including Faulkner, Grant, Lonoke, Pulaski, Saline and Perry county.

When there are high concentrations of ozone in the forecast, the ADEQ issues one of two basic types of Ozone Action Days.

  • An Ozone Action Advisory is declared when the forecast is Code Orange, indicating unhealthy conditions for sensitive groups.
  • An Ozone Action Alert is declared when the forecast is Code Red, indicating unhealthy conditions for everyone.

What activities increase or decrease ozone levels in the lower atmosphere?

Highly pollutant based activities that increase ozone levels:

  • lawn and garden chores that require gas powered equipment
  • using oil based paints
  • using products that release fumes or evaporate easily
  • refueling vehicles during the day
  • exercising outdoors

Activities that will reduce ozone levels:

  • limiting driving – carpool instead, walk or take the bus
  • combining errands to one trip vs. several trips
  • keeping your car well tuned, avoiding multiple restarts
  • staying indoors

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