Any chemical compound containing chlorine (Cl), the 17th element in the periodic table. There are a number of chlorine-containing compounds found in the atmosphere, which are emitted from a variety of sources. Organic compounds containing chlorine are produced either via natural oceanic processes (e.g., methyl chloride) or for industrial purposes (e.g., chlorofluorocarbons). Some of these organic compounds are sufficiently long-lived to allow their transport to the stratosphere, where they are destroyed by photolysis. This process liberates chlorine atoms, which are active in the catalytic destruction of stratospheric ozone.