What atmospheric layer does not exist above polar regions?

Polar regions are not actually devoid but have small concentrations of the ozone layer which is a protective layer present in the stratospheric region of earth and which helps in the absorption of the harmful UV radiations coming from the sun. The reason is a pretty obvious one that the CFC's which are used by the mankind for their good are carried towards the poles by polar stratospheric winds which in turn move in the stratospheric region due to the high pressure. These CFC's hinder the rate of formation of ozone thus causing depletion or what we mention as an "ozone hole".