The ozone layer is a natural ozone gas belt which lies between 15 and 30 kilometers above the Earth as if it were a shield against harmful ultraviolet B radiation emitted by the sun.
Ozone is a highly reactive molecule that contains three oxygen atoms. It is constantly forming and breaking into the upper atmosphere, at 10-50 kilometers above the Earth, in the area called the stratosphere.
At present, there is widespread concern that the ozone layer is deteriorating due to the release of pollution chemicals containing chlorine and bromine. This deterioration allows large amounts of ultraviolet B rays reach the Earth which can cause skin cancer and cataracts in humans and damaging to animals.
An excess of ultraviolet B radiation to reach the Earth also inhibits the cycle of phytoplankton, single-celled organisms like algae that make up the final link in the food chain. Biologists fear that these reductions cause a phytoplankton population less than other animals. Researchers have also documented changes in reproductive rates of young fish, shrimp and crabs and frogs and salamanders that are exposed to excessive ultraviolet B.
Chlorofluorocarbons (CFCs), chemicals that are found mainly in aerosol spray widely used by industrialized nations for most of the past 50 years, are the main culprits for the deterioration of the ozone layer. When CFCs reach the top of the atmosphere, exposed to ultraviolet rays which causes them to decompose into substances that include chlorine. Chlorine is reactive to oxygen atoms into ozone and destroys the ozone molecule.
A chlorine atom can destroy over one hundred thousand ozone molecules according to the Agency for Environmental Protection US
The ozone layer over Antarctica has suffered a considerable impact since the mid-80s Low temperatures in this area accelerated conversion of CFC chlorine. In the spring and summer in the south, where the sun shines for long periods of the day, chlorine reacts with ultraviolet ozone destroying massively, up to 65%. This is what some people erroneously called “ozone hole”. In other areas, the ozone layer has deteriorated 20%.
Approximately 90% of current CFC in the atmosphere were emitted by industrialized countries in the Northern Hemisphere, including the United States and Europe. These countries banned CFCs in 1996 and the amount of chlorine in the atmosphere is decreasing. However, scientists estimate that it will take another 50 years to return chlorine levels to their natural figure.