In response to new evidence that Earth's protective ozone shield may be weakening over parts of the United States, President Bush directed American manufacturers on Tuesday to end by Dec. 31, 1995, virtually all production of chemicals that destroy ozone.
The policy, authorized under a provision of the 1990 Clean Air Act, takes effect immediately. On Friday the Bush administration reversed its previous opposition to such a plan and backed a Senate proposal to phase out the production of the chemicals as soon as possible, rather than by 2000.
The president's order affects a family of chlorine- and bromine-based chemicals, widely used in American industry as solvents, refrigerants, fire retardants and as feedstocks for other chemicals. These chemicals are chlorofluorocarbons or CFCs, halons, methyl chloroform and carbon tetrachloride.
The action not only affects a dozen chemical companies and thousands of manufacturing workers across the country, but also puts enormous pressure on makers of automobile air conditioners, computer equipment, fire prevention systems and refrigerators and other industrial users of the chemicals to redesign their equipment.
"It's a substantial step, one that we believed was warranted by the scientific evidence, but nevertheless still a big job for us," said Kevin Fay, the executive director of the Alliance for Responsible CFC Policy, a coalition of users and producers of the chemicals.
"There is a scientific consensus that these chemicals are destructive to ozone in the atmosphere," William Reilly, administrator of the Environmental Protection Agency, said Tuesday in an interview, "and this administration has a record of responding quickly to that threat."
Michael Deland, chairman of the President's Council on Environmental Quality, added: "It's a substantial step forward. President Bush is unilaterally accelerating the phaseout of ozone-depleting substances. It is another step in a consistent posture of leadership by this president on this issue."
Earth's ozone layer protects against harmful ultraviolet radiation, which can cause skin cancer and eye problems in humans and various disorders in animals.
The EPA has estimated that ozone depletion could cause 200,000 additional skin cancer deaths in the United States over the next 50 years.
Experts with several of the nation's prominent environmental groups praised Bush's action Tuesday but said that even more aggressive steps were necessary to halt the deterioration of the ozone.
"This is a modest step in the right direction but not all that is required to protect the ozone layer," said David Doniger, a lawyer at the Natural Resources Defense Council in Washington.
"What we've asked the Environmental Protection Agency to do under the Clean Air Act is to phase out one chemical, halons, immediately. We asked that methyl chloroform be eliminated by beginning of next year. And we want CFC production to be eliminated by the end of 1994."
Bush's directive came as an environmental group said that about two-thirds of the United States' ozone-destroying chemicals are released by the military.
The Boston-based National Toxics Campaign Fund said the Pentagon and its contractors were responsible for most of the nation's dangerous emissions of an ozone-eating chemical known as chlorofluorocarbon-113.
CFC-113, a solvent used to clean metal and electronic components, breaks down in the stratosphere and attacks the ozone molecules that block harmful sun rays.
"What we found is that the private sector is starting to to make strides at getting rid of this stuff yet the military still requires these things under military specifications when there are safe substitutes available," said John O'Connor, the fund's chairman.
Pentagon spokesman Bob Hall said Tuesday he had no figures on actual emissions by the U.S. mili%% WARNING %%tary and defense industry. He said the military purchased 4,255 metric tons of CFCs in 1989, the most recent figure available, for use ranging from air conditioners to cleaning solvents.
Hall said that represented only about 1 percent of the total CFCs procured in the country in 1989.
_ Information from the New York Times, Reuters was used in this report.