Ozone repair.

Ozone Repair: The effort to heal the atmosphere's ozone layer recently received an important political boost, as well as some constructive criticism. Last October, the Nobel Prize in chemistry was awarded to the three scientists whose work explained why the layer is thinning and allowing more dangerous ultraviolet (UV) radiation to reach the Earth's surface. This was the first Nobel prize ever awarded for work in an environmental science, and it adds momentum to the process begun by the Montreal Protocol, the international agreement signed in 1987 to phase out production of ozone-destroying chemicals. In the same month, the Massachusetts Institute of Technology Press published Mending the Ozone Hole, by Arjun Makhijani and Kevin Gurney, which argues that the list of targeted chemicals should be expanded, and that they should be phased out more rapidly. Makhijani is president of the Institute for Energy and Environmental Research in Takoma Park, Maryland; Gurney is a scientist at the Institute.

The protocol has already achieved substantial success in reducing the production of chlorofluorocarbons (CFCs), a class of ozone-destroying chemicals used primarily for refrigeration. CFC production has fallen more than 75 percent from its 1988 peak of 1,260,000 tons to 295 tons in 1994. But although the rate of ozone depletion is slowing, the ozone layer is still deteriorating. The most marked drop in ozone levels occurs in the "ozone hole" that forms over Antarctica during September and October. Ozone levels in the hole now drop to less than half those observed during the 1970s. Last year's hole was three times the size of China - a record dimension. To a lesser degree, the layer appears to be thinning everywhere except over the tropics. Over Europe and North America, ozone levels have dropped nearly 10 percent since the 1950s, and larger losses have been observed over the Arctic. Strict adherence to the protocol would allow the ozone layer to heal, but there is a considerable lag between chemical production and ozone damage, so the process would not be complete until around 2050.

The protocol, which underwent a ministerial review in Vienna last December, would phase out CFC production in developed countries this year, except for relatively small amounts destined for export to developing countries. CFC production would be phased out entirely by 2006. Production of hydrochloroflourocarbons or HCFCs - the chemicals initially developed as substitutes for CFCs - would not be phased out entirely until 2030. But Makhijani and Gurney argue that this timetable should be shortened. HCFCs were introduced because they do less total damage to the ozone layer than CFCs, but because HCFCs break down more rapidly, some of them are about as harmful as CFCs over the short term (5 to 20 years after emission). Reliance on HCFCs, the authors argue, puts an unnecessary additional stress on the ozone layer at precisely the time when it is likely to be most vulnerable. According to the authors, safe alternatives to HCFCs already exist for virtually all applications. They also argue that the protocol does not effectively regulate a number of other important ozone-destroying chemicals, such as methyl bromide, a chemical used as a pesticide and a byproduct of the combustion of leaded gasoline.

Such regulatory problems are important because rising UV radiation presents a wide spectrum of threats. Human health effects include increases in the incidence of skin cancers and cataracts, as well as immune system damage. Crop yields could be affected, and ecological damage is also forecast. Increased UV radiation may already be contributing to the widespread decline of amphibian populations, for example. According to one study, UV damage to plankton in the oceans around Antarctica may already have occurred. Plankton are the basis of the ocean food chain and a principal means of removing carbon dioxide, the main greenhouse gas, from the atmosphere. Plankton declines could therefore accelerate climate change. Given the dangers, the authors' recommendations merit attention; Makhijani and Gurney argue that it is technically possible to heal the ozone layer in about 35 years.