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Ozone Layer

Illustration: the sun's rays stream toward earth. The ozone layer high in the atmosphere absorbs and reflects some UV rays, but some pass through. The ozone layer forms a thin shield high up in the sky. It protects life on Earth from the sun's ultraviolet (UV) rays. In the 1980s, scientists began finding clues that the ozone layer was going away or being depleted. This allows more UV radiation to reach the Earth's surface. This can cause people to have a greater chance of getting too much UV radiation. Too much UV can cause bad health effects like skin cancer and eye damage.

What Is Stratospheric Ozone?

Ozone is a natural gas that is found in two different layers of the atmosphere. One layer, called the troposphere, is at the Earth's surface where we live. Ozone in the troposphere is "bad" because it dirties the air and helps make smog, which is unhealthful to breathe. The other layer, called the stratosphere, is miles above the Earth's surface. Ozone in the stratosphere is "good" because it protects life on Earth by absorbing some of the sun's harmful UV rays. Stratospheric ozone is found most often between six and 30 miles above the Earth's surface.

Ozone Depletion

Recently, chlorofluorocarbons (CFCs) were used a lot in industry and elsewhere to keep things cold and to make foam and soaps. Strong winds carry CFCs up into the stratosphere where UV radiation breaks them apart, releasing chlorine atoms. Each chlorine atom can attack and break apart (destroy) as many as 100,000 ozone molecules during the time it is in the stratosphere. The chlorine from CFCs reduces (depletes) the amount of ozone in the stratosphere.

Other ozone-eating chemicals are pesticides such as methyl bromide, halons used in fire extinguishers, and methyl chloroform used in businesses.

What Is Being Done?

Countries around the world, including the United States, have seen the threats created by ozone depletion and agreed to a treaty called the Montreal Protocol. This Protocol will help humans to stop making and using ozone-eating chemicals.

How Ozone Depletion Affects UV Levels

Scientists predict that ozone depletion should peak around year 2010. As world-wide controls reduce the release of CFCs and other ozone-eating substances, nature will repair the ozone layer. By year 2065 stratospheric ozone should return to the amount present in 1980. Until then, we can expect higher levels of UV radiation at the Earth's surface. We need to take care to avoid the bad health effects that could result from too much UV radiation.