Ozone destruction, leading to the ozone hole, becomes faster as temperature falls and the area gets isolated.
Ozone in the stratosphere absorbs dangerous UV radiation to protect us, while ozone in the troposphere is poisonous substance.
Elevated ozone levels can be harmful for health and vegetation. Tropospheric ozone is not directly emitted, but produced by chemical reactions.
Since our natural protection against UV was threatened, the use of ozone destructing chemical substances is regulated in international agreements.