Chlorofluorocarbons (CFCs) are anthropogenic additions to the atmosphere. Invented in 1928, CFCs are non-flammable, non-corrosive, relatively non-reactive and not very toxic. These characteristics made CFCs desirable compounds for use as refrigerants, air conditioning agents, propellants in aerosol cans, blowing agents, solvents and ingredients in some cleaning products for electronics.

In the 1980s, scientists discovered that the presence of CFCs in the atmosphere was depleting the ozone layer. In 1987, international representatives signed the Montreal Protocol in an effort to protect the ozone layer. Since then, the atmospheric concentration of most CFCs has either leveled off or decreased.