No joke: Scientists call for stricter controls on emissions of laughing gas

Nitrous oxide could soon pose a bigger threat to ozone than CFC chemicals, says atmospheric chemist
David Adam, environment correspondent
guardian.co.uk, Thursday 27 August 2009 19.00 BST
Scientists have called for stricter controls on emissions of laughing gas, after discovering the common chemical poses a new threat to the recovering ozone layer. The gas, properly known as nitrous oxide, could soon pose a bigger threat to ozone than CFC chemicals, the use of which has been restricted since the 1980s.
Akkihebbal Ravishankara, an atmospheric chemist with the US National Oceanic and Atmospheric Administration, who led the research, said: "The dramatic reduction in CFCs over the last 20 years is an environmental success story. But man-made nitrous oxide is now the elephant in the room among ozone-depleting substances."
The gas, which is not covered by existing regulations to protect ozone, is now the largest ozone-depleting substance produced by human activity, the research shows. It is expected to remain the largest over the next few decades.
About a third of global nitrous oxide emissions are from human activity. The gas is produced as a byproduct of fertiliser use in agriculture and other industrial processes. It is also a common anaesthetic, used by dentists and in maternity wards.
Nitrous oxide is stable at ground level but breaks down in the upper atmosphere to form compounds that trigger chemical reactions that destroy ozone. Its ability to destroy ozone has been known for decades, but the new research is the first to quantify the danger and compare it to other gases.
Although the gas is 60-times less damaging to ozone than CFCs, around 10m tonnes of nitrous oxide are produced by human activity each year, compared with slightly more than a million tonnes from all CFCs at the peak of their emissions.
Nitrous oxide is also a potent greenhouse gas, which contributes to global warming, so efforts to restrict emissions could tackle climate change as well as ozone loss, the scientists say. The study is published in the journal Science.