WASHINGTON (AP) _ The leading producer of chemicals that destroy the earth's protective ozone layer has come out in favor of worldwide production limits.

The policy switch by the DuPont Co., which makes chemicals called chlorofluorocarbons, or CFCs, on four continents, was hailed by a major environmental organization, the Natural Resources Defense Council, as ''the biggest breakthrough'' since the U.S. ban on use of the chemicals as aerosol propellants in 1978.

DuPont invented the chemicals in the 1930s. From plants in Japan, Latin America, Europe, Canada and the United States, it still sells, under its Freon trademark, 20 percent to 25 percent of world production it estimates at 2.4 billion pounds a year.

DuPont's new policy statement, distributed to customers last month, said the company believed there was no immediate threat to the ozone layer from current use of chlorofluorocarbons.

But ''the science is not yet sufficiently developed to define with certainty a safe CFC emissions growth rate'' and ''we conclude that it now would be prudent to limit worldwide emissions of CFCs while science continues to work,'' the statement said.

The major trade association of CFC manufacturers and users, the Alliance for Responsible CFC policy, said last month it now supported a ''reasonable global limit on the future rate of growth of ... CFC production capacity.'' Association executives said they would suport production limits, not just limits on production growth, if scientific findings justified them.

By calling for outright production limits, DuPont's statement appeared to go beyond the position of the trade group, but company spokesman Jim Adshead said Thursday in Wilmington, Del.: ''I don't think there's a significant difference. Basically, we support the alliance proposal.''

As to just what the production limit ought to be, ''We don't have a position. It ought to be discussed and analyzed.''

The Environmental Protection Agency should convene an advisory group of users, manufacturers and environmental groups to help the State Department in international negotiations on the problem, DuPont suggested.

Major producing countries are scheduled to meet in Vienna in December to consider further ozone regulations. Countries of the European Economic Community already have agreed to production capacity limits, but well above current production. They declined to join the 1978 U.S. action banning aerosol use.

Until the alliance announcement, DuPont and others had insisted there was plenty of time for scientists to investigate the effects of chlorofluorocarbons on the ozone layer and regulations were not needed.

The company's new position is based on recent findings showing that ''without question that CFCs do destroy the ozone. The big question is how much (the layer) can tolerate,'' Adshead said.

The discovery of the drastic 40 percent drop in ozone over the South Pole each winter ''is another cause of concern,'' he said.

Chloroflurocarbons are valued as refrigeration fluids and foam blowing agents because they are non-toxic, non-flammable and chemically almost inert. Some of them can last more than 100 years in the atmosphere, gradually rising to the ozone layer 15 to 25 miles above the earth where the sun's ultra-violet light helps break them down and liberate their chlorine atoms to attack ozone.

Though ozone at ground level is a pollutant, at high altitudes it makes life on earth possible by blocking ultra-violet. Each percentage point decrease in the amount of ozone above the earth could mean almost 200,000 extra skin cancer cases worldwide each year, EPA has estimated.

DuPont said it believed substitute chemicals could be brought to market in about five years.