Here's a breakdown:
* Chlorofluorocarbons (CFCs): These were widely used in refrigerators, air conditioners, aerosols, and other applications. They are very stable in the lower atmosphere but when they reach the stratosphere, they are broken down by ultraviolet radiation, releasing chlorine atoms.
* Halons: These are similar to CFCs, but they contain bromine instead of chlorine. They were primarily used in fire extinguishers. Bromine is even more effective at destroying ozone than chlorine.
How these molecules damage the ozone layer:
1. UV Radiation: Ultraviolet (UV) radiation from the sun breaks down these molecules in the stratosphere.
2. Free Radicals: This breakdown releases chlorine (Cl) or bromine (Br) atoms, which are highly reactive free radicals.
3. Ozone Depletion: These free radicals catalytically destroy ozone molecules (O3), converting them to oxygen (O2). One chlorine atom can destroy thousands of ozone molecules.
Other substances that can contribute to ozone depletion:
* Methyl bromide: Used as a fumigant for pest control.
* Hydrochlorofluorocarbons (HCFCs): Similar to CFCs but with a shorter atmospheric lifetime. They were introduced as substitutes for CFCs, but still contribute to ozone depletion.
* Methyl chloroform: Used as a solvent and cleaning agent.
Important note: While CFCs, halons, and other ozone-depleting substances have been phased out in many countries, they can persist in the atmosphere for decades. This means that the ozone layer is still recovering from the damage they caused.
