Ozone Action Days

What you should know about
Ground-level Ozone

Air Division
Planning & Air Quality Analysis Branch

Tony Davis, Branch Manager - (501) 682-0728

Ozone Action Days

What is ground-level ozone?

Ground-level ozone is the main ingredient in smog.  When the temperature heats up in the summer sun, pollutants in the air react and produce ozone smog.  Air pollutants can come from cars, trucks, buses and industrial smoke stacks.  Those are the obvious culprits.  But they can also come from gas stations, outboard motors, oil-based paints, cleaning solvents, lawn mowers, and farm and construction equipment.

Isn't the ozone supposed to protect us from the sun?

Yes, and that's the confusing part.  This invisible gas can be found in both the upper and lower atmospheres.  The ozone layer in the upper atmosphere is essential because it filters out harmful ultraviolet radiation from the sun.  But at ground level it can cause all sorts of problems.  An easy way to remember the difference is this little rhyme "Good up high, bad nearby."

Then why is ozone hazardous to my health?

High concentrations of ozone near ground level can be harmful to people, animals and crops.  As it builds up, it becomes toxic, causing shortness of breath, coughing, wheezing, headaches, nausea, and eye and throat irritation.  People who suffer from lung diseases like emphysema, pneumonia, asthma and colds have even more trouble breathing when the air is polluted.  And it can be worse in children, the elderly, and those of us who exercise outdoors.

Can what I do really make a difference?

And how!  Even the smallest actions taken by individuals can add up to a big difference.  Every summer day in the Little Rock Metro area, gasoline-powered lawn and garden equipment releases more pollutants into the air than a typical large industrial plant.  By not mowing your lawn on critical Ozone Action Days, you and your neighbors can really make an impact.

Why are children so vulnerable?

Children like to play outside, and on steamy summer afternoons this could spell danger.  Their lungs are still developing, and they breathe more rapidly and inhale more air pollution per pound than adults.  On days when ozone levels are high, these factors put children at increased risk for respiratory problems.

What if I like to exercise outdoors?

An adult breathes about 20,000 times each day.  During exercise or strenuous work, we breathe more often and draw air more deeply into our lungs.  When we exercise heavily, we may increase our intake of air by as much as 10 times our level at rest.  When ozone levels are high, exercising outdoors greatly increases the chances that we will suffer the symptoms of ozone exposure.

How will I know when to protect myself and my family?

During summer months, meteorologists forecast a day ahead weather conditions that will be conducive to ozone formation.  A notice is sent to newspapers, television and radio stations, which get the word out to you.  So keep your eyes and ears open during ozone season.  Not everyone is sensitive to ground-level ozone.  You are the best judge of whether you notice any of the symptoms described here.  If you do, try to stay indoors, especially in the late afternoon.  And keep an eye on your children and other folks, like the elderly, who are sensitive.  If they show symptoms, they should stay inside.  Symptoms usually disappear within a few hours.

Watch for Ozone Action Days and follow these do's and don'ts.

Things to Do
  • Limit driving.  Share a ride, carpool, walk or ride the bus.
  • Combine errands.
  • Keep your car well tuned, avoid jackrabbit starts and excessive idling.
  • Stay indoors as much as possible.
Things to Don't
  • Don't do lawn and gardening chores that use gasoline powered equipment.
  • Don't use oil-based paints and solvents.
  • Don't use products that release fumes or evaporate easily.  If it smells strong, it's probably wrong.  Things like paint strippers and varnish... even things like fingernail polish remover.
  • Don't refuel.  If you must, do it after dark and don't fill the tank completely.
  • Don't exercise outdoors.


The AQI colors illustrated below can help people to rapidly determine whether air pollutants are reaching unhealthy levels. Today's AQI and tomorrow's ozone forecast will be posted daily on the ADEQ web site. These colors will also be displayed when the AQI is reported in the newspaper or on television.

Air Quality Index (AQI): Ozone
Index Values
Levels of Health Concern
Cautionary Statements
0-50  0.000 - 0.059  Good  No health impacts are expected in this range.
51-100*  0.060 - 0.075  Moderate  Unusually sensitive people should consider limiting prolonged outdoor exertion.
101-150  0.076 - 0.095  Unhealthy for
Sensitive Groups 
Active children and adults, and people with respiratory disease, such as asthma, should limit prolonged outdoor exertion.
151-200  0.096 - 0.115  Unhealthy  Active children and adults, and people with respiratory disease, such as asthma, should avoid prolonged outdoor exertion; everyone else, especially children, should limit prolonged outdoor exertion.
201-300  0.116 - 0.374  Very Unhealthy  Active children and adults, and people with respiratory disease, such as asthma, should avoid all outdoor exertion; everyone else, especially children, should limit outdoor exertion.
301-500  0.375 & above  Hazardous  Everyone should avoid all outdoor exertion.

* Generally, an AQI of 100 for ozone corresponds to an ozone level of 0.075 parts per million (averaged over 8 hours).

Newspapers may use different formats to report the AQI. Here is one example.


A Q I Logo Newspaper Sample Pollutant:
Today's Forecast:
Unhealthy for Sensitive
Groups. Children and
people with asthma are
the groups most at risk.