office" /><o:p></o:p>[/COLOR][/font][/center][/TD][/TR][/TABLE][/CENTER][font=Comic Sans MS]What is ozone?[/font]<o:p></o:p>
[font=Comic Sans MS]Ozone is a gas that occurs both in the Earth's upper atmosphere and at ground level. Ozone can be "good" or "bad" for your health and the environment, depending on its location in the atmosphere.<o:p></o:p>[/font]
[font=Comic Sans MS]How Can Ozone Be Both Good and Bad?[/font]<o:p></o:p>
[font=Comic Sans MS]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 extends upward from about 6 to 30 miles. The stratospheric or "good" ozone protects life on Earth from the sun's harmful ultraviolet (UV) rays.<o:p></o:p>[/font]
[font=Comic Sans MS]What is Happening to the "Good" Ozone Layer?[/font]<o:p></o:p>
[font=Comic Sans MS]Ozone is produced naturally in the stratosphere. But this "good" ozone is gradually being destroyed by man-made chemicals referred to as ozone-depleting substances (ODS), including chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), halons, methyl bromide, carbon tetrachloride, and methyl chloroform. These substances were formerly used and sometimes still are used in coolants, foaming agents, fire extinguishers, solvents, pesticides, and aerosol propellants. Once released into the air these ozone-depleting substances degrade very slowly. In fact, they can remain intact for years as they move through the troposphere until they reach the stratosphere. There they are broken down by the intensity of the sun's UV rays and release chlorine and bromine molecules, which destroy the "good" ozone. Scientists estimate that one chlorine atom can destroy 100,000 "good" ozone molecules.<o:p></o:p>[/font]
[font=Comic Sans MS]Even though we have reduced or eliminated the use of many ODSs, their use in the past can still affect the protective ozone layer. Research indicates that depletion of the "good" ozone layer is being reduced worldwide. Thinning of the protective ozone layer can be observed using satellite measurements, particularly over the Polar Regions.<o:p></o:p>[/font]
[font=Comic Sans MS]How Does the Depletion of "Good" Ozone Affect Human Health and the Environment?[/font]<o:p></o:p>
[font=Comic Sans MS]Ozone depletion can cause increased amounts of UV radiation to reach the Earth which can lead to more cases of skin cancer, cataracts, and impaired immune systems. Overexposure to UV is believed to be contributing to the increase in melanoma, the most fatal of all skin cancers. Since 1990, the risk of developing melanoma has more than doubled.<o:p></o:p>[/font]
[font=Times New Roman][FONT=Comic Sans MS]UV can also damage sensitive crops, such as soybeans, and reduce crop yields. Some scientists suggest that marine phytoplankton, which are the base of the ocean food chain, are already under stress from UV radiation. This stress could have adverse consequences for human food supplies from the oceans[/font].<o:p></o:p>[/FONT]