Answer:
The ozone layer is depleted primarily by the action of human-made chemicals called chlorofluorocarbons (CFCs), halons, and other ozone-depleting substances (ODSs). When these chemicals are released into the atmosphere, they rise into the stratosphere, where they are broken down by the intense ultraviolet radiation from the sun. The resulting chemical reactions release chlorine and bromine atoms, which react with ozone (O3) to form oxygen (O2) and chlorine monoxide (ClO) or bromine monoxide (BrO) molecules. These reactions can be represented as follows:
O3 + Cl → ClO + O2
O3 + Br → BrO + O2
The chlorine and bromine atoms are then free to react with more ozone molecules, repeating the cycle and depleting the ozone layer.
These reactions occur naturally to a limited extent, but the introduction of human-made ODSs into the atmosphere has dramatically increased the rate of ozone depletion. The ozone hole, a severe depletion of ozone over Antarctica that occurs each year, is directly linked to the presence of ODSs in the atmosphere.