U.N. Says Ozone Layer Should Keep Healing

GENEVA - The United Nations marked International Ozone Day on Friday with a cautiously optimistic verdict: the earth's protective ozone layer is healing and could recover to 1980 levels by mid-century — if the world keeps honoring the 1987 Montreal Protocol.

The treaty, which phased out chlorofluorocarbons and other chemicals used in refrigerants, aerosols and solvents, is routinely called the most successful environmental agreement ever written. Some 189 nations have ratified it.

"The protocol is proof that the international community can act together on a global environmental threat," a senior U.N. environment official said in Geneva. "But recovery is not yet assured — the chemicals linger, and illegal trade continues."

Scientists expect the Antarctic ozone hole — which still forms each spring, and which this year again spans an area larger than North America — to keep recurring for decades before shrinking for good.

The progress is not uniform. Customs agents report a thriving black market in banned CFCs smuggled for use in old refrigeration equipment, particularly in Asia and the Middle East.

The treaty's next test is phasing out the substitute chemicals themselves. HCFCs, adopted as transitional replacements, are less destructive but still ozone-depleting and are now scheduled for their own phaseout.

Atmospheric scientists note the same chemicals are also potent greenhouse gases, making the treaty one of the world's most effective climate measures as well — a link gaining attention amid the post-Katrina debate over warming and storms.

The ozone shield blocks ultraviolet radiation that causes skin cancer, cataracts and crop damage. The U.N. estimates the treaty will prevent millions of skin cancer cases by 2060.