The hole in the ozone layer over Antarctica, one of the signs of global environmental destruction, is back with a vengeance.

Preliminary satellite data from the U.S. National Aeronautics and Space Administration indicate that the depletion of ozone matches the worst levels ever observed, in 1987 and 1989."Not only has the 1990 ozone hole matched the lowest levels previously observed, but ozone levels throughout the Southern Hemisphere have been as low as any previously recorded year," NASA said.

Data continue to be collected and final results on this year's depletion are expected to be released within the next month.

The hole is a large area of intense ozone depletion that develops over Antarctica during its winter in late August until early October. Ozone, a molecule made up of three oxygen atoms, forms a thin layer in the atmosphere that helps to shield the earth from harmful ultraviolet radiation from the sun.

The depletion this year "is very bad news and indicates the ozone crisis is far from over," said Robert Hornung, an Ottawa expert on ozone for the Friends of the Earth environment group.

Ozone is destroyed by chlorofluorocarbons or CFCs, used mainly for refrigerants and cleaning agents, and several other industrial chemicals. In June, major governments agreed to phase out the use of ozone-destroying CFCs by the year 2000.