Nitrous oxide is top destroyer of ozone layer: study

Nitrous oxide emissions caused by human activity have become the largest contributor to ozone depletion and are likely to remain so for the rest of the 21st century, a US study has concluded.

The study by the National Oceanographic and Atmospheric Agency said efforts to reduce chlorofluorocarbons (CFCs) in the atmosphere over the past two decades were "an environmental success story.

"But manmade nitrous oxide is now the elephant in the room among ozone-depleting substances," said A. R. Ravishankara, lead author of the study, which was published Friday in the journal Science.

While nitrous oxide's role in depleting the ozone layer has been known for decades, the study marks the first time that its impact has been measured using the same methods as CFCs and other ozone depleting substances.

Emissions and production of those substances are regulated under the 1987 Montreal Protocol.

But the treaty excludes nitrous oxides, which are emitted by agricultural fertilizers,livestock

manure, sewage treatment, combustion and certain other industrial processes.

Since nitrous oxide is also a greenhouse gas, the scientists said reducing emissions from manmade sources would be good for the ozone layer and help temper climate change.