Here's why:
* Ozone Depletion Mechanism: When these compounds reach the stratosphere (where the ozone layer resides), they are broken down by ultraviolet (UV) radiation. This process releases chlorine and bromine atoms, which act as catalysts in a chain reaction that destroys ozone molecules.
* CFCs and Halons: CFCs and halons are very stable and long-lived in the atmosphere, allowing them to reach the stratosphere and persist for decades. This means they can cause significant ozone depletion over time.
* Other Ozone Depleting Substances: Other compounds like methyl bromide, methyl chloroform, and hydrochlorofluorocarbons (HCFCs) also contribute to ozone depletion, although to a lesser extent than CFCs and halons.
It's important to note: While the Montreal Protocol has phased out the production and use of many ozone-depleting substances, some of these chemicals remain in the atmosphere. Therefore, the ozone layer is still recovering, but it is expected to return to pre-1980 levels by the middle of the century.
