Which of the following refrigerants has been phased out due to its ozone-depleting properties?

The refrigerant identified as R-22 has been phased out primarily because of its detrimental effects on the ozone layer. R-22, a hydrochlorofluorocarbon (HCFC), was commonly used in residential air conditioning systems and refrigeration. However, due to its ozone-depleting potential, it became a target for regulation under the Montreal Protocol, which aims to protect the ozone layer by phasing out substances responsible for its depletion.

The transition away from R-22 aligns with international efforts to reduce the use of ozone-depleting substances and replace them with alternatives that have less environmental impact. In contrast, the other refrigerants listed—R-410A, R-134a, and R-32—are either hydrofluorocarbons (HFCs) or mixtures that do not contribute to ozone depletion. Specifically, R-410A and R-32 are known for having a lower global warming potential compared to older refrigerants, while R-134a has been recognized for its lower ozone depletion potential but still faces scrutiny regarding its climate impact. Therefore, R-22's phase-out is a significant step in environmental protection and marking progress in the transition to more sustainable cooling technologies.