WASHINGTON, Aug. 27 (Xinhua) -- A new study by scientists at U.S. National Oceanic and Atmospheric Administration (NOAA) found that nitrous oxide has now topped the ozone-depleting emissions and is expected to remain the largest throughout this century, the journal Science website said Thursday.

    The study for the first time evaluated nitrous oxide emissions from human activities in terms of their potential impact on Earth's ozone layer.

    Today, nitrous oxide emissions from human activities are more than twice as high as the next leading ozone-depleting gas, said an article on the website.

    It will remain a significant ozone-destroyer, as Chlorofluorocarbons (CFCs, a class of chemical compounds that deplete the ozone) ebb in the atmosphere, said the article.

    Nitrous oxide is emitted from natural sources and as a byproduct of agricultural fertilization and other industrial processes, the article said.

    NOAA researchers found, based on calculation of the effect on the ozone layer now and in the future, that emissions of nitrous oxide from human activities erode the ozone layer and will continue to do so for many decades, it added.

    "The dramatic reduction in CFCs over the last 20 years is an environmental success story. But manmade nitrous oxide is now the elephant in the room among ozone-depleting substances," said A.R. Ravishankara, leading author of the study and director of NOAA Earth System Research Laboratory's chemical sciences division in Boulder, Colorado.

    The ozone layer serves to shield plants, animals and people from excessive ultraviolet light from the sun. Thinning of the ozone layer allows more ultraviolet light to reach the Earth's surface where it can damage crops and aquatic life and harm human health, the article said.

    Nitrous oxide is also a greenhouse gas, so reducing its emission from manmade sources would be good for both the ozone layer and climate, the scientists said in the study.

    In addition to soil fertilization, nitrous oxide is emitted from livestock manure, sewage treatment, combustion and certain other industrial processes. About one-third of global nitrous oxide emissions are from human activities.