Kids Research Express

CFCs damage the ozone layer when they escape from sources such as leaky car air conditioners, discarded plastic-foam egg cartons, and old home air conditioners crushed in a landfill. The CFCs drift up to the stratosphere, an upper layer of the atmosphere where strong ultraviolet radiation from the Sun breaks them down. As they break down, they release chlorine, which depletes the protective ozone layer. A single chlorine atom can destroy over 100,000 ozone molecules. Ozone absorbs ultraviolet radiation. When the ozone layer thins, more of a harmful type of ultraviolet radiation called UVB reaches Earth’s surface. Studies show that UVB radiation can cause skin cancer. UVB has also been linked to cataracts of the eye and to suppression of the immune system. Fish, shrimp, crabs, amphibians, and other animals that live in or around water—including phytoplankton, microscopic organisms that form the foundation of aquatic food webs—are all at risk from UVB radiation.

Despite these important steps, previously released CFCs continue to damage the ozone layer because they can remain in the atmosphere for more than 100 years. Ozone depletion is particularly bad over the Antarctic, seasonally producing an ozone hole, a large area of the atmosphere that contains extremely low amounts of ozone. Low levels of ozone have also been observed over the United States, Canada, Japan, Russia, and Europe. Scientists predict that the highest levels of CFCs in the atmosphere will occur during the first decade of the 21st century. If international agreements hold, the ozone layer is expected to recover around 2050.

To combat the problem of ozone thinning, in 1978 the U.S. Congress banned CFCs used in aerosols in the United States. In 1987, 27 nations signed an international agreement called the Montréal Protocol, calling for a 50 percent reduction in CFC production by 1998 and an eventual end to all manufacture of CFCs. Later amendments accelerated the timetable for eliminating CFC production. The Montréal Protocol has been remarkably successful in curtailing production of CFCs. More than 175 nations have ratified the protocol. Scientists have worked hard to find alternatives to CFCs that spare the ozone layer. Alternative refrigerants have completely replaced CFCs in the United States and substantial progress has been made finding alternatives for foam products and air conditioning. Many of the alternatives have the added bonus of being highly energy efficient, helping the United States and other countries meet goals of reduced global warming emissions.