What is Ozone?

Ozone is a gas that is formed in the atmosphere when three atoms of oxygen combine. Naturally occurring ozone is found high in the stratosphere surrounding the earth and in ground-level ambient air. Stratospheric ozone forms high in the atmosphere when intense sunlight causes oxygen molecules (O2) to break up and re-form as ozone molecules (O3). Popularly called "good ozone," it shields people, trees, crops, property, and microorganisms from the harmful effects of the sun's ultraviolet light. Ozone also forms low in the atmosphere at ground level. If ground-level ozone were produced only from natural sources of emissions, it would be of no concern.  But many human activities result in emissions of additional chemical compounds that react in the air to form ozone or "bad ozone."

Tips for Reducing Air Pollution
 

How Does Ozone Occur?

Ozone pollution is a key component of smog. It is mainly a daytime problem during the summer months. Strong sunlight and hot weather causes ground level ozone to form in harmful concentrations in the air. Ozone is not emitted directly into the air. Instead it is formed in sunlight, which initiates a series of complex atmospheric chemical reactions. These reactions primarily involve nitrogen oxide (NOx) and volatile organic compound (VOC) emissions, called precursors.

Common sources of NOx include:
 

• automobiles, trucks and marine vessels
• construction equipment
• power generation
• industrial processes
• natural gas furnaces

VOCs include many organic chemicals that vaporize easily, such as those found in gasoline and solvents. They are emitted from many sources, including:
 

• gasoline stations
• petroleum storage tanks
• oil refineries
• motor vehicles, airplanes, trains, boats
   

In addition, biogenic, or natural emissions from trees and plants, are a major source of VOCs.
 

Why are People Concerned?

Ozone pollution near the ground is the most wide-spread air quality problem in the United States. In Texas, four urban areas do not meet federal standards for ozone. These areas are home to nearly 50 percent of our state's population:
 

• Houston-Galveston
• Dallas-Fort Worth
• Beaumont-Port Arthur
• El Paso
   

The biggest concern with high ozone concentrations is the damage it causes to human health and vegetation. High concentrations of ozone can cause shortness of breath, coughing or wheezing, headaches, nausea, throat and lung irritation. There are numerous people that can be affected by ozone pollution.
 

Children often play outside for long periods during the summer. Their lungs are still developing, and they breathe more rapidly and inhale more air pollution per pound of body weight than adults. On days when ozone levels are high, these factors put children at increased risk for respiratory problems.
 

People who suffer from lung diseases like bronchitis, pneumonia, emphysema, asthma, and colds have even more trouble breathing when the air is polluted. The effects can be worse for anyone who spends significant periods of time exercising or working outdoors.  During exercise or strenuous work we breathe more often and draw air more deeply into the lungs. When we exercise heavily, we may increase our intake of air by as much as 10 times our level at rest. The interaction between air pollution and exercise is so strong that health scientists typically use exercising volunteers in their research.

How Do I Know When the Ozone Reaches an Unsafe Level?

For real time ozone levels in the DFW metroplex, click here.
 

For more information on "Go Green, Breathe Clean" click here.

For more information on Air Quality, click here.