Level of Ozone-Depleting Chemicals in Atmosphere Lower, Researchers Find

The level of ozone-depleting chemicals in the atmosphere is falling, mostly because of reductions in one solvent, meaning further cuts can occur only if emissions of other chemicals are lowered, Stephen A. Montzka of the National Oceanic and Atmospheric Administration says in today’s Nature. The researchers monitored levels of the chemicals at remote locations worldwide between 1992 and 1997 and found they declined about 3%. Production of a solvent called methyl chloroform was phased out between 1993 and 1996. Levels of the chemical have dropped almost by half since then.

Other chemicals such as CFC-12, a refrigerant, and CFC-11, used to make foam, are still present at more than twice the peak levels of methyl chloroform. Although CFCs are regulated, CFC-12 levels rose, while CFC-11 declined slightly. Manufacture of the two chemicals is still permitted on a limited basis in developing countries until 2010.

--Compiled by Times medical writer Thomas H. Maugh II