Ozone-depleting chemicals are most efficient at the poles, both for Arctic and Antarctic regions. The major reason for this is:

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Ozone-depleting chemicals, such as chlorofluorocarbons (CFCs), break down ozone in the presence of sunlight. In the polar regions, very cold temperatures combine with high-altitude clouds to create a chemical reaction that releases chlorine and bromine atoms, which then break apart ozone molecules at a high rate. This phenomenon is known as the "ozone hole." Thus, the very cold winters at the poles allow for a more efficient breakdown of ozone-depleting chemicals and a faster destruction of the ozone layer.

Ozone-Depleting Chemicals Are Most Efficient at the Poles, Both for Arctic