What substance is mainly responsible for the depletion of the ozone layer?

Chlorofluorocarbons (CFCs) are the primary substances responsible for the depletion of the ozone layer. CFCs are man-made compounds that were widely used in refrigeration, air conditioning, and aerosol propellants. When released into the atmosphere, CFCs rise up to the stratosphere, where they are broken down by ultraviolet (UV) radiation, releasing chlorine atoms. These chlorine atoms are highly reactive with ozone (O3) molecules, leading to the destruction of ozone and consequently contributing to the thinning of the ozone layer.

The ozone layer is crucial for life on Earth as it absorbs the majority of the sun's harmful UV radiation. The depletion of this layer increases UV exposure at ground level, which can lead to higher incidences of skin cancer, cataracts, and effects on ecosystems.

In contrast, substances like carbon dioxide and sulfur dioxide have different roles. Carbon dioxide is mainly a greenhouse gas contributing to climate change, while sulfur dioxide can lead to air pollution and acid rain but does not have the same direct effects on the ozone layer. Ozone itself, while it is vital in the stratosphere, is the very substance that is being depleted by CFCs and is not a cause of depletion.