The National Academy of Sciences will issue a report later this month warning that the ozone layer, which shields the Earth from the sun's ultraviolet light, is breaking down at twice the rate scientist thought is was. u

The report will say that fresh and exhaustive calculations on the amount of fluorocarbon chemicals being discharged from the Earth into the upper atmosphere suggest they are enough to break apart a little more than 14 percent of the ozone layer in the next 50 to 100 years.

This is twice what the National Academy of Sciences predicted in 1976 would be stripped from the ozone layer, which lies 23 miles above the Earth where it blocks most of the sun's searing untraviolet light.

Scientists worldwide have been concerned that the fluorocarbon gases -- that serve as propollants in spray cans -- rise and accumulate in the upper atmosphere. There, they are broken down by the sun's ultraviolet light and release free chlorine that destroys the ozone.

Scientists have sorried that if the Earth's inhabitants continue to use spray cans containing fluorocarbon propellants as they did in 1975, about 7 percent of the ozone layer would be stripped away in as little as 50 years. This would have allowed 14 percent of the ultraviolet light from the sun to penetrate the atmosphere, reach the Earth's surface and trigger a world-wide increase in skin cancer.

The newest report of the National Academy of Sciences, which is scheduled to be turned over to the Environmental Protection Agency on Nov. 10, is expected to say that the use has increased and the gases are rising into the atmosphere faster than in 1975.

This increase has occurred even in the face of a ban last April by the United States on all aerosol products containing fluorocarbons.

Most of the increased usage of fluorocarbons, the National Academy report will state, has come from a higher rate in Japan, Western Europe, the Middle East and Asia.