Chlorine in refrigerants is associated with which environmental issue?

Chlorine in refrigerants is primarily associated with ozone depletion due to its role in breaking down ozone molecules in the stratosphere. When chlorinated compounds, such as chlorofluorocarbons (CFCs), are released into the atmosphere, they eventually rise to the stratosphere, where ultraviolet (UV) radiation causes them to release chlorine atoms. These chlorine atoms can react with ozone (O3), resulting in the destruction of ozone molecules, which are essential for blocking harmful UV radiation from reaching the Earth's surface. The depletion of the ozone layer contributes to increased UV exposure, leading to various environmental and health issues, including skin cancer and ecological harm.

The other environmental issues mentioned do not directly relate to chlorine in refrigerants. Acid rain is typically associated with sulfur and nitrogen compounds, while the greenhouse effect involves gases like carbon dioxide and methane that trap heat in the atmosphere. Air pollution includes a broad range of pollutants but is not specifically linked to the chlorine compounds used in refrigerants. Thus, the connection of chlorine to ozone depletion is well-established and is the reason why this answer is correct.