Ozone depletion is caused by the discharge of hydrofluorocarbons, chlorofluorocarbons and other ozone-depleting substances that were once commonly used as solvents, refrigerants and insulating foams. The chemicals methyl chloroform, methyl bromide and halons also cause damage to the ozone layer and are used in commercial products such as industrial solvents, pesticides and fire extinguishers. When these ozone depleting chemicals enter the stratosphere, they are exposed to ultraviolet radiation from the sun and release chlorine atoms that begin a destructive cycle of the ozone layer.
A single chlorine atom is capable of separating over 100,000 ozone molecules. The bromine atoms released by halons and methyl bromide are 60 times more harmful to ozone molecules than chlorine atoms. The resulting damage to the ozone from harmful ozone-depleting substances causes Earth's surface to be exposed to higher levels of ultraviolet radiation.
The increased levels of radiation from the sun can increase the risk of people developing weakened immune systems, cancer and cataracts. Higher levels of ultraviolet radiation can negatively effect the marine food chain, reduce the amount of food that crops produce and can also have other disastrous effects.
The ozone layer contains about 90 percent of Earth's ozone and is a concentration of ozone molecules within Earth's stratosphere. The stratosphere stretches for about 6 to 30 miles above Earth's surface and is responsible for filtering ultraviolet radiation emitted from the sun.