NASA scientists will unveil firm scientific evidence supporting the belief that man-made chlorine is causing the ozone hole above Antarctica, space agency officials said Friday.

Details will not be released until Monday, but NASA spokesmen said the data gathered by the Upper Atmospheric Research Satellite makes clear chlorine, an ingredient in chlorofluorocarbons (CFCs), is responsible.CFCs, used in antifreeze, refrigerants and insulation products, are being phased out under international agreements, but scientists fear decades will pass before there is significant improvement in the ozone layer.

Ozone is a form of oxygen that provides a natural, high-altitude shield for the Earth against the sun's harmful untraviolet rays.

Without that protection, ultraviolet radiation is believed to cause skin cancer, cataracts and crop damage. It also harms the marine organisms that are the starting point for much of the world's food chain.

Its depletion is seen most clearly in the hole, roughly the size of North America and first noticed in the 1970s, that opens each year over the South Pole.

Despite a plan to halt production of the most ozone destructive chemicals as of Jan. 1, 1996, many related chemicals will still be made.

The banned products, though no longer manufactured, will still be in use for years in existing refrigerators, air conditioners and cooling systems.