Final answer:
CFCs harm the ozone layer through the release of chlorine atoms, which act as catalysts in destroying ozone molecules over an extended period. The Montreal Protocol has helped phase out CFC production, yet challenges remain in completely stopping emissions.
Step-by-step explanation:
The main reason why chlorofluorocarbons (CFCs) are the most harmful to the ozone layer is due to the presence of stable chlorine atoms in their molecular structure. These atoms are released when CFCs are broken down by ultraviolet (UV) radiation in the stratosphere. The chlorine atoms act as a catalyst in a destructive cycle, repeatedly destroying ozone molecules, which results in a significant depletion of the ozone layer, thus reducing its ability to absorb harmful UV radiation.
Montreal Protocol was established in 1987 to phase out the production of CFCs globally, following the discovery of their damaging effects. While the protocol has been largely successful, continued efforts to fully eliminate CFC emissions are vital as some regions still have CFC banks where old equipment can release detectable amounts of CFCs into the atmosphere.
One chloride atom can destroy ozone molecules for up to two years before settling back to the surface, and because CFCs are stable, they can contribute to ozone depletion for many years. Alternatives to CFCs, such as hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs), do not contain chlorine or bromine, thereby posing much less risk to the ozone layer.