What substance has a long atmospheric life that is harmful to the ozone layer?

The substance that has a long atmospheric life and is harmful to the ozone layer is chlorofluorocarbons, commonly known as CFCs. CFCs are synthetic compounds that were widely used in refrigeration, air conditioning, foam-blowing agents, and aerosol propellants.

CFCs are particularly harmful to the ozone layer because they release chlorine atoms when they are broken down by ultraviolet (UV) radiation in the upper atmosphere. These chlorine atoms then participate in chemical reactions that deplete ozone, which is crucial for protecting life on Earth from harmful UV radiation.

The long atmospheric lifetime of CFCs means that they can remain in the atmosphere for many years, allowing them to slowly rise to the stratosphere where they impact the ozone layer. In contrast, substances like HFCs, while they have a long atmospheric life, do not significantly affect the ozone layer, and CO2 and SO2 do not affect ozone depletion at all. Thus, CFCs are specifically noted for their detrimental effects on ozone, making them the correct answer in this context.