What is it?
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.
Where does it come from?
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.
Ground Level Ozone - regularly referred to as “bad ozone” forms when emission sources including, but not limited to, transportation, industrial and commercial operations, and vegetation emit oxides of nitrogen (NOx) and/or volatile organic compounds (VOC) which react in the presence of sunlight.
How is it harmful?
Breathing ozone can trigger a variety of health problems including chest pain, coughing, throat irritation, and congestion. It can worsen bronchitis, emphysema, and asthma. Ground level ozone also can reduce lung function and inflame the linings of the lungs. Repeated exposure may permanently scar lung tissue. People with lung disease, children, older adults, and
people who are active outdoors may be particularly sensitive to ozone.
What's being done to help?
The Environmental Protection Agency (EPA) currently has a primary and secondary 2008 8-hour standard for ozone set at less than or equal to 75 parts per billion (annual forth-highest daily maximum 8-hour concentration, averaged over three years). These standards are subject to change as updated scientific
information is obtained on the effects of this pollutant on human health.
There are various programs in place to help decrease ground-level ozone in the North Central Texas region. To learn more about these programs, click on the following links:
The 10-county region of
North Central Texas is currently designated as moderate nonattainment for the 2008 8-hour ozone standard. Previously, the nine-county region was designated as serious nonattianment for the 1997 8-hour standard; however, the EPA revoked this standard on April 6, 2015. Although the 1997 8-hour standard is revoked, the nine-county region, per the Clean Air Act continues to be held to anti-backsliding requirements, There are currently 20 monitors
throughout the region that measure ozone.
For detailed information on ozone nonattainment designations and rule implementation, visit the EPA's Ozone web page.