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Protecting the Stratospheric Ozone Layer
Did you know?
Ozone-destroying chemicals escape into the air and reach the stratosphere. Over time they reduce the layer of stratospheric ozone that protects us.
When the protective ozone layer is damaged, there is an increase in harmful rays from the sun reaching the Earth. These rays can harm both health and the environment.
Service stations must have special equipment that prevents release of refrigerant chemicals to the air when they are recharging car air conditioning systems.
Ozone can be good or bad depending on where it is located. Close to the Earth's surface, ground-level ozone is a harmful air pollutant. Ozone in the stratosphere, high above the Earth, protects human health and the environment from the sun's harmful ultraviolet radiation. This natural shield has been gradually depleted by manmade chemicals. So in 1990, Congress added provisions to the Clean Air Act for protecting the stratospheric ozone layer.
Ozone in the stratosphere, a layer of the atmosphere located 10 to 30 miles above the Earth, serves as a shield, protecting people and the environment from the sun's harmful ultraviolet radiation. The stratospheric ozone layer filters out harmful sun rays, including a type of sunlight called ultraviolet B. Exposure to ultraviolet B (UVB) has been linked to cataracts (eye damage) and skin cancer. Scientists have also linked increased UVB exposures to crop injury and damage to ocean plant life.
In the mid-1970s, scientists became concerned that chlorofluorocarbons (CFCs) could destroy stratospheric ozone. At that time, CFCs were widely used as aerosol propellants in consumer products such as hairsprays and deodorants, and as coolants in refrigerators and air conditioners. In 1978, the U.S. government banned CFCs as propellants in most aerosol uses.
Scientists have been monitoring the stratospheric ozone layer since the 1970s. In the 1980s, scientists began accumulating evidence that the ozone layer was being depleted. The ozone hole in the region of the South Pole, which has appeared each year during the Antarctic winter (our summer), often is bigger than the continental United States. Between 1978 and 1997, scientists have measured a 5 percent loss of stratospheric ozone-a significant amount.
Over 190 countries, including the major industrialized nations such as the United States, have signed the 1987 Montreal Protocol, which calls for elimination of chemicals that destroy stratospheric ozone. Countries that signed the Protocol are committed to limiting the production and use of those chemicals.
The 1990 Clean Air Act required EPA to set up a program for phasing out production and use of ozone-destroying chemicals. In 1996, U.S. production ended for many of the chemicals capable of doing the most serious harm such as CFCs, halons, and methyl chloroform.
Unfortunately, it will be about 60 years before the stratospheric ozone layer heals. Because of the ozone-destroying chemicals already in the stratosphere and those that will arrive within the next few years, stratospheric ozone destruction will likely continue throughout the decade. September 24, 2006, tied for the largest ozone hole on record at 29 million square kilometers (11.4 million square miles). The year 2006 also saw the second largest sustained ozone hole.
The Clean Air Act includes other steps to protect the ozone layer. The Act encourages the development of "ozone-friendly" substitutes for ozone-destroying chemicals. Many products and processes have been reformulated to be more "ozone-friendly." For instance, refrigerators no longer use CFCs.
Sometimes it isn't easy to phase out an ozone-destroying chemical. For instance, substitutes have not been found for CFCs used in certain medical applications. The limit on the production of methyl bromide, a pesticide, was extended because farmers did not yet have an effective alternative. Despite the inevitable delays because of technical and economic concerns, ozone-destroying chemicals are being phased out, and, with continued work, over time the protective ozone layer will be repaired.
For more information about stratospheric ozone, visit www.epa.gov/ozone.