Ozone hole is largest ever.

• Author: Mastny, Lisa

The seasonal hole in the ozone layer over Antarctica reached record proportions in September, according to a report by the World Meteorological Organization (WMO). Covering an area of 25 million square kilometers, or about 2.5 times the area of Europe, this year's hole surpassed the previous record - set in 1993 - by about 3 million square kilometers. The rift was also the "deepest" and fastest-growing ever, said WMO expert Rumen Bojkov. It involved the destruction of more than 85 percent of ozone in the lower stratosphere over an area of more than 10 million square kilometers.

Since the mid-1980s, the appearance of the ozone hole has become an annual occurrence during the Antarctic spring months, when cooler temperatures in the whirlpool-like polar vortex over the South Pole create conditions for accelerated ozone destruction. If these temperatures are unusually low, as they were in September, the depletion of the ozone layer caused by the release of chlorofluorocarbons (CFCs), halons, and other man-made chemicals into the atmosphere can cause the hole to expand even faster. "The hole was worse this year because the stratosphere was cooler," said David Hofmann of the U.S. National Oceanic and Atmospheric Association. "We experienced greater ozone loss around the edges and a large nibble from the top."

Without the protection of the ozone layer, humans and animals risk excessive exposure to UV-B radiation, which has been shown to cause skin cancer, eye abnormalities such as cataracts, and changes in the immune system that can make people more susceptible to cancer or infectious disease. Plants and marine life are also sensitive to UV-B radiation, which can damage marine ecosystems and reduce plant and fish yields.

Scientists predict that ozone depletion will reach its worst point during the next few years. The layer should then begin to heal and - according to the standard projections - return to normal...