An ozone hole five times the size of California opened over the Arctic this spring, matching ozone loss over Antarctica for the first time on record, scientists say.

Formed by a deep chill over the North Pole, the unprecedented hole at one point shifted over eastern Europe, Russia and Mongolia, exposing populations to higher, but unsustained, levels of ultraviolet light.

A NASA image shows an ozone hole five times the size of California which opened over the Arctic this (Northern hemisphere) spring that has opened over the Artic. [The red colors represent large ozone concentrations.] Credit:AFP/NASA/JPL

Ozone, a molecule of oxygen, forms in the stratosphere, filtering out ultraviolet rays that damage vegetation and can cause skin cancer and cataracts.

The shield comes under seasonal attack in both polar regions in the local winter-spring.