Introduction Ozone is a gas that exists both in the Earth's upper atmosphere and at ground level. Depending on where it is in the atmosphere, ozone can be "good" or "bad" for ones health and the environment. Ozone can be found in two layers of the atmosphere. Ground level or "bad" ozone is an air pollutant that is hazardous to one's health and harms crops, trees, and other vegetation. It is a major contributor to urban smog. The stratospheric, or "good" ozone layer, extends u