THE REAGAN administration deserves enormous credit for the part it played in achieving the world ozone treaty signed this week. On most environmental issues the administration has been more laggard than leader. On this the reverse has been true. Environmental administrator Lee Thomas and Secretary of State George Shultz were able to brush aside the minority of objecting ideologues within the administration and produce a sound position.

The treaty signed in Montreal under U.N. auspices must still be ratified, but that is thought likely. It deals with chlorofluorocarbons, or CFCs, compounds widely used -- in air conditioning, refrigeration, the manufacture of a wide variety of foam products and as solvents -- because, among their other attributes, they are cheap, durable and neither flammable nor toxic. But when released into the atmosphere, as almost all eventually are, these compounds rise to mix with and dilute the ozone layer that shields the Earth from ultraviolet radiation. A thinning of the ozone layer is thought likely to lead to more skin cancer, crop and other plant damage and serious climatic changes.

The treaty would freeze CFC production in 1990 at 1986 levels, then cut it in half by 1999. By itself this might not be enough to stop attenuation of the ozone layer. But the 50 percent cut is thought likely to stimulate development of alternate compounds, which will then supplant the offending CFCs. The chemical industry feels confident that it can produce such compounds. That may have helped to make this an easier treaty to negotiate; the affected interest group had less to lose. But the industry has behaved in exemplary fashion even so.

Some people hope the ozone treaty will become the example for other such agreements. We don't know if it can, but it is an extraordinary achievement on its own terms, the more so because of how quietly it was brought about. A major environmental threat has apparently been deflected with very little of the shouting that usually accompanies such problems -- maybe because there was so little shouting. Good for everyone involved.