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What is Ozone?

Ozone is a gas that forms in the atmosphere when 3 atoms of oxygen are combined (03). It is not emitted directly into the air, but at ground level is created by a chemical reaction between oxides of nitrogen (NOx), and volatile organic compounds (VOC) in the presence of sunlight. Ozone has the same chemical structure whether it occurs high above the earth or at ground level and can be “good” or “bad,” depending on its location in the atmosphere.

How Can Ozone Be Both Good and Bad?

Ozone occurs in two layers of the atmosphere. The layer surrounding the earth’s surface is the troposphere. Here, ground-level or “bad” ozone is an air pollutant that damages human health, vegetation, and many common materials. It is a key ingredient of urban smog. The troposphere extends to a level about 10 miles up, where it meets the second layer, the stratosphere. The stratospheric or “good” ozone layer extends upward from about mile10 to 30 and protects life on earth from the sun’s harmful ultraviolet rays (UV-b).


Health Effects of Ground Level Ozone Exposure

  • Difficulty breathing or shortness of breath
  • Coughing and sore throat
  • Aggravation of lung diseases such as asthma, emphysema, and chronic bronchitis.
  • Inflammation and damage to the airways
  • Increase asthma attacks
  • Cause lungs to be more susceptible to infection

People with asthma are at a greater risk of experiencing health effects of ground level Ozone.

Preventing Ground-Level Ozone Exposure

Look at the Air Quality Index in your area before going outside. Air Now shows the air quality in your area. Try to avoid going outside often if there is a lot of ozone in your area on certain days. To prevent the release of Ozone, try to use your car less and carpool, walk or use public transportation, conserve energy, try to compost, keep your tires properly inflated. For more information on how to reduce your ozone pollution visit the EPA- Actions you can take to reduce pollution.

Stratospheric Ozone

For more information on the stratospheric ozone layer click here.