Final answer:
R-22, while non-toxic, is environmentally harmful because it depletes the ozone layer and has been phased out under international environmental legislation.
Step-by-step explanation:
Even though R-22 is considered non-toxic, it is important to recognize that it poses environmental hazards. R-22, also known as Chlorodifluoromethane, was commonly used as a refrigerant but is now being phased out due to its ozone depletion potential. When leaked into the atmosphere, R-22 contributes to the degradation of the ozone layer. Similar to other greenhouse gases, such as HFCs, PFCs, and SF6, R-22 has no natural sources and has been found to have negative environmental consequences despite its non-toxic classification. Its use and emission into the atmosphere has been subject to international environmental legislation under the Montreal Protocol to control and reduce harm to the environment.