Ozone Depletion

Agency

www.epa.gov/sunwise

1EPA

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 accumulating evidence that the ozone layer was being depleted. Depletion of the

ozone layer results in increased UV radiation reaching the 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 troposphere 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

life.

Other ozone-depleting substances include pesticides such as methyl bromide,

halons used in fire extinguishers, and methyl chloroform used in industrial

processes.

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 ozonedepleting 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.
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.

Program

In response to the serious public

health threat posed by exposure to

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 <www.epa.gov/sunwise>.

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