Acknowledging an "alarming" new study, the head of the Environmental Protection Agency has reversed himself in calling for a complete phase-out of chemicals linked to depletion of Earth's protective ozone layer.

EPA Administrator Lee Thomas, in a major policy shift Monday, for the first time said the United States and other nations must go beyond the requirements of the Montreal Protocol, an international agreement to reduce the industrial emissions believed to be breaking down the ozone layer.The protocol, which takes effect in January, requires its 45 signatory nations to halve their use of chlorofluorocarbons, or CFCs, a chemical widely employed as a refrigerant, industrial cleaner and in the production of foam.

The EPA has issued regulations to achieve the 50 percent reduction in the United States, but Thomas and other agency officials until now have avoided any statements suggesting an immediate need to go beyond those measures.

Monday, Thomas said a report by the Ozone Trends Panel, an international group of scientists, did more than previous studies to show greater efforts are needed to protect the ozone layer, which screens harmful levels of the sun's ultraviolet radiation.

Thomas said using ground-based instruments, the panel found higher levels of stratospheric ozone depletion than predicted by any computer model.

"The Ozone Trends Panel's report and the new analysis we are releasing today paint an alarming picture of present and future global ozone levels," Thomas warned. "The depletion that already has occurred calls into question our earlier projections of future damage.

"Regretfully, our new analysis predicts an even worse scenario than anticipated. We must go further than a 50-percent reduction in these chemicals in order to stabilize ozone levels."

Thomas noted the Montreal Protocol contains specific provisions requiring signatory nations to take into account new scientific information.

"It is increasingly clear that we, as a global environmental community, must use the protocol to go even further to eliminate these chemicals which damage the stratospheric ozone layer and threaten our future," he declared.

In addition to the complete phase-out of CFCs, Thomas also recommended efforts to eliminate the use of halons, a fire-extinguishing agent, and a worldwide freeze on the use of methyl chloroform, a solvent employed in a broad variety of industrial cleaning processes.

Only last week, the Environmental Policy Institute issued a report calling for reductions in the use of methyl chloroform, saying its contribution to ozone depletion had been largely unrecognized.