The level of ozone-depleting chemicals in the atmosphere is dropping, primarily because of reductions of one solvent, methyl chloroform, which was phased out between 1996 and 1997, according to a report published in today’s issue of the journal Nature. The study indicates that the Montreal Protocol, the 1994 treaty to protect the ozone layer, is working, says lead author Steven Montzka, a chemist with the National Oceanic and Atmospheric Administration. Further cuts in ozone-depleting substances will now need to come from other chemicals, particularly CFCs, which are permitted to be manufactured in developing countries until 2010.