The most common sources of chlorofluorocarbons are aerosols and leakages from refrigeration equipment, according to the Scottish Environment Protection Agency. Other CFCs are released into the atmosphere by the industries that produce and use them and products containing them. CFCs do not have any known natural sources in the environment.
Chlorofluorocarbons and halons are man-made chemicals that occur as liquids or gases. They contain carbon, fluorine and chlorine. CFCs do not occur naturally and are always manufactured, according to the Clean Air Strategic Alliance. They are not toxic or flammable, although they have considerable impact on the atmosphere. They are typically used as a foaming agent, coolants in refrigeration and air conditioning, and cleaning solvents. They were often used as propellants in aerosol cans in the past.
Chlorofluorocarbons have two major effects on the atmosphere. The first one is the greenhouse effect, in which CFCs and halons act as greenhouse gases. The second one is the ozone-depletion effect, wherein CFCs and halos travel slowly from the lower atmosphere toward the stratosphere and break down. The chlorine or bromine atoms released in the breakdown have the ability to destroy tens of thousands of ozone molecules, thereby causing the protective ozone layer to become thinner.