United States
                           Environmental Protection
                        Air and Radiation
Ozone  Depletion
September 1999
                           The ozone layer forms a thin shield in the upper atmosphere, protecting life on
                           Earth from the sun's ultraviolet (UV) rays. In the 1980s, scientists began accu-
                           mulating evidence that the ozone layer was being depleted. Depletion of the
                           ozone layer results in increased UV radiation reaching die Earth's surface, which
                           in turn can lead to a greater chance of overexposure to UV radiation and the
                           related health effects of skin cancer, cataracts, and immune suppression.

                           What  Is Stratospheric Ozone?
                           Ozone is a naturally occurring gas that is found in two layers of the atmosphere.
                           In the layer surrounding the Earth's surface—the troposphere—ground-level or
                           "bad" ozone is an air pollutant that is a key ingredient of urban smog. The tro-
                           posphere extends up to the stratosphere, which is where "good" ozone protects
                           life on Earth  by absorbing some of the sun's UV rays. Stratospheric ozone is
                           most concentrated between 6 to 30 miles above the Earth's surface.

                           Ozone Depletion
                           Until recently, chlorofluorocarbons (CFCs) were used widely in industry and
                           elsewhere as refrigerants, insulating foams, and solvents. Strong winds carry
                           CFCs into the stratosphere in a process that can take as long as 2 to 5 years.
                           When CFCs  break down in the stratosphere, they release chlorine, which
                           attacks ozone. Each chlorine atom acts as a catalyst, repeatedly combining with
                           and breaking apart as many as  100,000 ozone molecules during its stratospheric
                           Other ozone-depleting substances include pesticides such as methyl bromide,
                           halons used in fire extinguishers,  and methyl chloroform used in industrial

                           What  Is Being  Done?
                           Countries around the world, including the United States, have recognized the
                           threats posed by ozone depletion  and adopted a treaty called the Montreal
                           Protocol to phase out the production and use of ozone-depleting substances.

                           How Ozone  Depletion Affects UV Levels
                           Scientists predict that ozone depletion should peak between 2000 and 2010. As
                           international  control measures  reduce the release of CFCs and other ozone-
                           depleting substances, natural atmospheric processes will repair the ozone layer
                           around the middle of the 21st  century. Until that time, we can expect increased
                           levels of UV radiation at the Earth's surface. These increased UV levels can  lead
                           to a greater risk of overexposure to UV radiation and related health effects.

                                                    EPA's SunWise School
                                                    Program                       ^
                                                    In response to the serious public
                                                    health threat posed by exposure to     °1' PV° '
                                                    increased UV levels, the U.S. Environmental
                                                    Protection Agency (EPA) is working with schools
                                                    and communities across the nation through the
                                                    SunWise School Program. SunWise aims to teach
                                                    children in elementary school and their caregivers
                                                    about ozone depletion, UV radiation, and how to
                                                    protect themselves from overexposure to the sun.

                                                    For More Information
                                                    To learn more about the ozone layer, the SunWise
                                                    School Program, and actions being taken to prevent
                                                    ozone depletion, call EPA's Stratospheric Ozone
                                                    Information Hotline at 800 296-1996 or visit our
                                                    Web site at .
 The use and emission of ozone-depleting substances
 damages the stratospheric ozone layer, which allows
 more UV rays to reach the Earth's surface and cause
 adverse human health effects.
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