Chlorofluorocarbons (CFCs) were commonly used as aerosol spray can propellants. They could also be found in refrigerants in air conditioners and refrigerators.
It was discovered that there was a link to the use of CFCs and ozone layer depletion. In 1995, the scientists who made this discovery were given a Nobel Prize.
The ozone layer over Antarctica usually thins for a short time naturally. However, there was excessive ozone thinning that couldn't be explained by natural causes. This ozone "hole" became gradually larger through the end of the 20th century. There is additional thinning in the ozone layer over the Arctic.
When CFCs are released into the atmosphere, they rise to the stratosphere where UV radiation breaks them down and chlorine is released. Chlorine then adheres to the clouds and can react with ozone (O3) causing it to break down into oxygen (O2).
The ozone layer at the top of the stratosphere forms a protective layer that shields the Earth's surface from ultraviolet radiation. Because of the holes in the ozone layer, more dangerous UV radiation is entering the Earth's lower atmosphere and affecting life on the surface.
Excessive UV radiation has been linked to skin cancer, cataracts and lowered immunity to diseases. The rate of skin cancer has been increasing in recent years.
Antarctic phytoplankton are diminishing and these are the producers of the ocean food chains in that region of the world which can have devastating affects on higher trophic levels that depend on these organisms.
UV radiation can act as a mutagenic agent and many cold--adapted Antarctic fish species have increased incidences of mutations in their eggs and young. Crops, forests, and organisms in ecosystems around the world are showing effects of excessive UV exposure.
The Montreal Protocol in 1987 was an agreement signed by many countries to reduce CFC production by 1998. Substitutes for CFCs were developed that don't destroy ozone. Many countries around the world have since stopped producing and using CFCs. Evidence based on satellite imaging has found that the ozone layer is recovering due to these efforts.