Ozone hole largest yet

The ozone layer protects Earth from harmful radiation

The hole in the ozone layer over Antarctica has grown to its greatest size yet, the US space agency says.

These observations reinforce concerns about the frailty of Earth's ozone layer

Dr Michael Kurylo

Nasa says this year's hole in the ozone layer - an annual event around September and October - measures 28.3 million square kilometres (11 million square miles).

That is three times the size of the United States. The previous record was 27.2 million square kilometres (10.5 million square miles), two years ago.

Scientists who have been studying the ozone layer since the early 1970s were shocked by the hole's size.

The hole in the ozone beats records two years ago

Dr Michael Kurylo, manager of Nasa's Upper Atmosphere Research Programme, said: "These observations reinforce concerns about the frailty of Earth's ozone layer."

The ozone layer protects our planet from harmful ultraviolet radiation and ozone depletion is believed to contribute to high rates of skin cancer in countries like Australia.

It was hoped that the Montreal Protocol in 1987, which restricted the release of man-made pollutants such as chlorofluorocarbons (CFCs) would lead to a recovery of the ozone layer by 2050.

Chief culprit

But recent investigations suggest the problem may be on a much larger scale than previously thought.

Ozone

Scientific name: (O3), triatomic allotrope of oxygen

Occurs naturally in small amounts in stratosphere

Irritating, pale blue gas, explosive, toxic

Absorbs solar ultraviolet radiation

Dr Kurylo said: "Although production of ozone-destroying gases has been curtailed under international agreements, concentration of the gases in the stratosphere are only now reaching their peak."

The chief culprit in ozone depletion is a family of man-made gases, notably CFCs, which were widely used in aerosols and refrigeration.

Others, like halons, are used in fire extinguishers, while methyl bromide is a soil fumigant.

The ozone hole is now closely monitored by satellites and ground-based instruments after it was first spotted by British Antarctic scientists in the 1970s.