Health and Environmental Effects
Reducing Ozone
Ozone Monitoring
Eight-Hour Ozone Info

Depending on the location of ozone in our atmosphere, it can be harmful or helpful. Ozone occurs naturally in the upper atmosphere, where it protects Earth from the sun's harmful ultraviolet rays. However, in Earth's lower atmosphere, ground-level ozone can hurt the environment and harm people and animals. At this level, ozone is not naturally occurring; in fact, it is created when pollutants emitted by cars, power plants, factories, and other sources react chemically in the presence of sunlight. Specifically, heat and sunlight mix with volatile organic compounds, or VOCs, and nitrogen oxides, or NOx, to produce ground-level ozone. Typically, ozone pollution is worse during hot, dry summers because sunlight and warm temperatures speed up the formation of ground-level ozone.

Health and Environmental Effects

Exposure to ground-level ozone can contribute to health and environmental problems. Ground-level ozone is an irritant that damages lung tissue and aggravates respiratory disease. Those most susceptible to ozone include elderly people and individuals with pre-existing respiratory conditions, such as asthma or emphysema. Children also are at increased risk from exposure to ground-level ozone because their lungs still are developing. In addition, healthy adults can experience problems breathing, especially if they exercise or work outdoors.

Ground-level ozone may harm sensitive plants and ecosystems, too. Plants vary in their sensitivity to ozone, and some have shown no sensitivity. Depending on the ozone levels, sensitive plants may show stunted growth and/or experience yellowing. They also may die. Research is ongoing concerning the effects of ground-level ozone on humans and the environment.

Reducing Ozone

Simple everyday steps can help reduce ground-level ozone. These steps primarily limit the emission of harmful pollutants from vehicles and coal-fired power plants.

Ways to decrease ground-level atmosphere include the following:

  • Stopping at the first click when getting gasoline. Do not top off your gas tank. This practice will ensure that your vehicle emits lower levels of gasoline vapors.
  • Using mass transit, carpools, and bicycles. Walking is a great alternative to using your personal vehicle, too.
  • Avoiding the use of gas-powered lawn equipment on hot, sunny days with little or no wind. Wait until early evening to mow your lawn.
  • Conserving energy by turning off lights and appliances when leaving a room to reduce emissions from power plants. Purchase Energy Star® appliances.
  • Reducing utility bills by two percent. This can save money and protect air quality.
  • Keeping tires properly inflated, which makes vehicles run more efficiently and burn less gasoline.
  • Avoiding drive-through lines, which encourage idling and wasteful burning of gasoline.

For more tips, visit

Ozone Monitoring

The Missouri Department of Natural Resources maintains and collects data from air monitors to determine whether our air quality meets standards set by the Environmental Protection Agency (EPA.) Please see the Missouri Air Quality Monitoring Network. The 2015 EPA standard is 0.070 parts per million (ppm), or 70 parts per billion (ppb). The department works with areas that have difficulty meeting the standard to develop the most effective and economical measures for reducing ozone levels. During the last several decades, Missouri has made tremendous strides in reducing ground-level ozone; however, the EPA has lowered the standard several times since the passage of the Clean Air Act in the 1970s, a practice that continues to challenge government, industry, and the public.

Ozone Monitoring Data

The department provides access to the data it collects from air-monitoring sites.

The U.S. Environmental Protection Agency tracks ozone data recorded by state monitors. Go to The charts, below, give an idea of the information available.




Eight-Hour Ozone Information

EPA's sets standards for ozone and other pollutants. Called the National Ambient Air Quality Standards, these standards provide guidance for state and federal regulations. In 2015, EPA tightened the ozone standard to 70 parts per billion (ppb). For more information, see EPA regulatory actions related to ground-level ozone. When the EPA lowered the standard in 2015, the department's Air Pollution Control Program began working on its efforts to meet the new standard.

To learn about Missouri's efforts to attain these standards, you may read about boundary designations as well as Missouri's implementation plan.

Other Ozone Links

Air Quality
APCP Calendar of Events
The Darker Side of Ozone
EPA Ozone webpage
Help fight ozone this summer!
Kansas City AirQ - Kansas City Air Quality Forecast
Other Environmental Links
Ozone - Something you can easily reduce!
St. Louis Regional Clean Air Partnership - St. Louis Air Quality Forecast