Ozone

Ozone is a gas composed of three atoms of oxygen. Ozone occurs both in the
Earth’s upper atmosphere and at ground level. Ozone can be good or bad,
depending on where it is found:

• Good Ozone. Ozone occurs naturally in the Earth’s upper
  atmosphere-6 to 30 miles above the Earth’s surface-where it forms a protective
  layer that shields us from the sun’s harmful ultraviolet rays. This beneficial
  ozone is gradually being destroyed by manmade chemicals. 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."

• 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.

   

  

For more information on ozone please visit:

• Ozone: Good
  Up High, Bad Nearby
• Ozone and
  Your Health
• Smog – Who Does
  it Hurt

For more information on other common air pollutants please visit:

• EPA’s six common air
  pollutants.
• Air Quality
  Index – A Guide to Air Quality and our Health