A man-made ozone hole has formed above the Arctic comparable in size to the ozone hole above Antarctica, researchers reported Monday.

The unprecedented hole was the largest ever recorded and caused residents in parts of northern Russia, Greenland and Norway to become exposed to high levels of UV radiation, an international team of researchers reported in the journal Nature.

The ozone layer lies in the upper stratosphere and acts as a layer of protection against harmful ultraviolet radiation from the sun that causes cancer and cataracts.

The chemical ozone destruction over the Arctic in early 2011 was, for the first time in the observational record, comparable to that in the Antarctic ozone hole, the scientists, led by Gloria Manney of the Jet Propulsion Laboratory in Pasadena, California, told The Guardian.

The hole in the Arctic was known before, but was always much smaller, scientists said, until March when a powerful winds and cold temperatures high in the atmosphere caused further damage from ozone-eating chlorine chemicals that already existed in the ozone layer.

Man-made chemicals, such as chlorofluorocarbons (CFCs), break down ozone in the presence of light, scientists said.