ozone

Air Quality


According to the Environmental Protection Agency (EPA), ozone season in the Dallas/Fort
Worth area begins May and goes through October. What is ozone and what can be done to reduce ozone pollution? Ozone is a gas that occurs in the Earth’s upper atmosphere and at ground level. It can be good or bad, depending on where it is found. For current Ozone Activity visit www.nctcog.org
  • Good Ozone – Occurs naturally in the Earth’s upper atmosphere, 6 to 30 miles above the Earth’s surface. It forms a protective layer that shields the Earth from the sun’s harmful ultraviolet rays. Manmade chemicals are known to destroy this beneficial ozone. An area where the protective “ozone layer” has been significantly depleted—for example, over the North or South pole—is sometimes called “the ozone hole.” The United States, along with more than 180 other countries, recognized the threats posed by ozone depletion and in 1987 adopted a treaty called the Montreal Protocol to phase out the production and use of ozone-depleting substances. The EPA has established regulations to phase out ozone-depleting chemicals in the United States.
  • Bad Ozone – In the Earth’s lower atmosphere, near ground level, ozone is formed when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources react chemically in the presence of sunlight. Ozone at ground level is a harmful air pollutant.

Reduce the “bad ozone” or ozone-forming emissions by:

  • Using mass transit or carpooling.
  • Combining trips and traveling less.
  • Limiting or avoiding idling.
  • Observing the speed limit.
  • Bicycling or walking instead of driving.
  • Considering clean fuels and technology.
  • Reporting smoking vehicles.
  • Avoiding the use of small gas powered engines (such as garden equipment) between 10 a.m. and 6 p.m.
  • Maintaining vehicles by getting them inspected, keeping tires properly inflated and changing filters regularly.

For more information about Air North Texas' Go Green Breathe Clean, a campaign for clean air, visit www.airnorthtexas.org

Where do the pollutants that form ozone come from?
Pollutants that contribute to ground-level ozone formation come from many different types of sources. As you learned, these pollutants are NOxand VOCs. The figure below shows the sources of these pollutants, which include point and area sources such as electrical generation plants, non-road engines such as lawnmowers and airplanes, on-road vehicles including cars and trucks, and miscellaneous sources such as trees and fires. In the DFW region pollution from cars and trucks, or on-road vehicles, contribute approximately 45 percent of the NOxpollution that leads to ozone formation.

Why do we care about the ozone?
The EPA sets federal standards for air pollutants according to health-based criteria. When levels are near or above the National Ambient Air Quality Standards an Ozone Watch or Warning is issued. The EPA has established levels at which ozone is unhealthy for humans. Ozone irritates the lining of the lungs, can aggravate respiratory conditions, and can make breathing more difficult for some people such as young children, seniors, asthma sufferers and those with respiratory diseases.The Watch and Warning system using the Air Quality Index (AQI) colors, was developed to notify citizens that ozone concentrations are close to exceeding or do exceed healthy levels of ozone and that outside activities might be unhealthy for sensitive groups. For most of the population, exposure for long periods of time to higher ozone levels indicated by the color purple on the AQI are unhealthy.

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