Antarctica in 2006 suffered its highest recorded single-year loss in ozone, the atmospheric molecule that protects against dangerous ultraviolet light, the European Space Agency (ESA) said.

A view of the stratosphere above Australia's Mawson staion, Antarctica, in July 2006. Antarctica in 2006 suffered its highest recorded single-year loss in ozone, the atmospheric molecule that protects against dangerous ultraviolet light, the European Space Agency (ESA) said.(AFP/HO/File/Renae Baker)

Ozone measurements made by the agency's Envisat satellite showed a loss of 40 million tonnes in October, exceeding the previous record of 39 million tonnes set in 2000, it said in a press release.

Ozone loss is calculated by measuring the area and depth of the so-called ozone hole in the stratosphere, about 25 kilometers (15 miles) above Earth's surface

This year's ozone hole measures 28 million square kilometers (10.81 million square miles), which is nearly as large as in 2000, and the depth of the ozone hole is 100 Dobson units, a measurement of the thickness of the layer, which rivals a record set in 1990, ESA said.

Ozone, a molecule of oxygen, filters out dangerous ultraviolet rays from the Sun that damage vegetation and can cause skin cancer and cataracts.

The layer has been badly damaged by man-made chemicals, especially chlorine and chlorofluorocarbons (CFCs), according to scientists.

The chemical reaction that thins ozone reaches its peak with colder high altitude temperatures in the southern hemisphere winter, normally in late August to October.

"Such significant ozone loss requires very low temperatures in the stratosphere combined with sunlight," ESA Atmospheric Engineer Claus Zehner said.

"This year's extreme loss of ozone can be explained by the temperatures above Antarctica reaching the lowest recorded in the area since 1979."

Last Friday, the World Meteorological Organisation (WMO) gave notice that the seasonal ozone hole in 2006 was heading for a record.

The ozone level globally has lowered by 0.3 percent a year over the past decade.

CFCs -- mainly aerosol gases and refrigerants -- and other ozone destroyers were belatedly controlled by an international treaty, the Montreal Protocol signed on September 16, 1987.

But there is already so much of the pollution stored in the atmosphere that large ozone holes are expected to persist for the next couple of decades, the WMO says.

The ozone layer over the Antarctic will only be completely replenished 15 years later than predicted, by 2065, WMO and the UN Environment Programme (UNEP) said in August.

Ozone in the stratosphere is protective. At ground level, though, ozone, as a chemical reaction between exhaust fumes and sunlight, is a pollutant that can be dangerous for people with bad respiratory or heart problems.

Copyright © 2006 Agence France Presse

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