How Can Ozone Be Both Good and Bad?
Ozone (O3) is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic O2. Ozone can be: Harmful: Ground-level ozone is an air pollutant with harmful effects on the respiratory systems of animals. Ozone therapy is a controversial alternative medicine practice; mainstream scientific medicine has found ozone to be harmful to humans, and equipment intended to be used for ozone therapy is banned in the United States. And beneficial: Ozone in the upper atmosphere filters potentially damaging ultraviolet light from reaching the Earth’s surface. It is present in low concentrations throughout the Earth’s atmosphere. It has many industrial and consumer applications. More here: http://en.wikiped
Ozone occurs in two layers of the atmosphere. The layer closest to the Earth’s surface is the troposphere. Here, ground-level or “bad” ozone is an air pollutant that is harmful to breathe and it damages crops, trees and other vegetation. It is a main ingredient of urban smog. The troposphere generally extends to a level about 6 miles up, where it meets the second layer, the stratosphere. The stratosphere or “good” ozone layer extends upward from about 6 to 30 miles and protects life on Earth from the sun’s harmful ultraviolet (UV) rays.
The thing that determines whether ozone is good or bad is its location. Ozone is “good” when it is in the stratosphere. The stratosphere is a layer of the atmosphere starting at the level of about 6 miles (about 10 kilometers) above sea level. The stratosphere naturally contains about six parts per million of ozone, and this ozone is very beneficial because it absorbs UV radiation and prevents it from reaching us (see How Sunburns and Sun Tans Work for a description of the damage that UV radiation can cause to skin). Check out this page for a good description of the chemical reaction that allows ozone to absorb UV light. Ozone is “bad” when it is at ground level. Ozone is a very reactive gas that is hard on lung tissue. It also damages plants and buildings. Any ozone at ground level is a problem. Unfor
Ozone occurs in two layers of the atmosphere. The layer surrounding the earth’s surface is the troposphere. Here, ground-level or “bad” ozone is an air pollutant that damages human health, vegetation, and many common materials. It is a key ingredient of urban smog. The troposphere extends to a level about 10 miles up, where it meets the second layer, the stratosphere. The stratospheric or “good” ozone layer extends upward from about 10 to 30 miles and protects life on earth from the sun’s harmful ultraviolet rays (UV).
