The mechanism by which chlorofluorocarbons CFCs cause depletion of the ozone layer involves a series of chemical reactions that occur in the stratosphere. The ozone layer is a region of the Earth's stratosphere that contains a high concentration of ozone O3 molecules, which protect life on Earth by absorbing harmful ultraviolet UV radiation from the Sun.When CFCs are released into the atmosphere, they eventually rise into the stratosphere, where they are exposed to UV radiation. This radiation causes the CFC molecules to break apart, releasing highly reactive chlorine atoms:CFCl3 + UV CFCl2 + ClThe released chlorine atoms then react with ozone molecules, initiating a catalytic cycle that destroys ozone:1. Cl + O3 ClO + O22. ClO + O Cl + O2In these reactions, a single chlorine atom can destroy many ozone molecules, as it is regenerated in the second step and can continue to participate in the cycle. This process significantly reduces the concentration of ozone in the stratosphere, leading to the depletion of the ozone layer.The concentration of CFCs in the atmosphere directly affects the rate of ozone depletion. Higher concentrations of CFCs lead to a greater number of chlorine atoms being released in the stratosphere, which in turn increases the rate of ozone destruction. This relationship has been supported by scientific evidence, such as the correlation between increased CFC emissions and the observed depletion of the ozone layer, particularly over the Antarctic region the ozone hole .The discovery of the ozone depletion mechanism and its link to CFCs was made by chemists F. Sherwood Rowland and Mario J. Molina in the 1970s. Their work, along with that of other researchers, led to the adoption of the Montreal Protocol in 1987, an international agreement to phase out the production and use of CFCs and other ozone-depleting substances. Since the implementation of the Montreal Protocol, the concentration of CFCs in the atmosphere has been decreasing, and there are signs of recovery in the ozone layer.