According to a recent study by the US National Oceanic and Atmospheric Administration, the leading man-made substance leading to the depletion of the Earth's protective ozone layer is Nitrous oxide or "laughing gas," which will most likely continue having damaging effects on the ozone throughout the century.

The study, published in the journal Science, Friday edition, noted that for a "win-win" situation for both ozone as well as the climate, it is essential that tighter limits should be imposed on emissions of nitrous oxide.

The study assumes greater significance in the wake of the fact that way back in 1989 - when the use of chlorofluorocarbons (CFCs) was depleting the ozone layer over Antarctica, and exposing humans to harmful ultraviolet radiation - over 190 countries signed the Montreal Protocol, to phase out the use of CFCs, and successfully so.

Though the Montreal Protocol did not regulate nitrous oxide, it still is among the greenhouse gases covered by the United Nations' Kyoto Protocol, which obligates developed countries to reduce in its emissions by 2008-12 such that it falls 5 percent below the 1990 levels.

About the need to restrict nitrous oxide emissions, the study went thus: "Nitrous oxide emission currently is the single most important ozone-depleting substance emission. Limiting future nitrous oxide emissions would enhance the recovery of the ozone layer from its depleted state."