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Nitrous oxide

N2O, nitrous oxide, laughing gas, nitrogen (I) oxide

SPRI Emission Reporting Threshold
10,000 Kg/yr Pollutant Emissions to Air
This sheet is a generic summary, designed to give the reader a basic level of background information about the substance in question. Great care has been taken to represent as effectively and correctly as possible the broad range of (not necessarily consistent) information which is available from a variety of sources. The reader must accept therefore that this sheet has no legal status and cannot be relied upon in any legal proceedings. SEPA disclaims any responsibility or liability whatsoever for errors and omissions in this sheet.
What is it?
Dintrogen oxide occurs naturally and also as a result of man's activities. In environmental conditions it is a colourless, sweet smelling gas. It is only slightly soluble in water and although non-flammable itself it will support combustion. When inhaled it has an anaestheic (sedative) and analgesic (pain relieving) effect - as well as causing amusing effects, hence the name "laughing gas".
What is it used for?
The anasethetic and analgesic properties of nitrous oxide have been used in medicine and dentistry since the late nineteenth century, when it was also used as a recreational drug. Now, it is used in the dairy industry as a mixing and foaming agent, in motor sports to speed engines and by deep sea divers to avoid nitrogen narcosis.
Where does it come from?
Nitrous oxide is released naturally from soils and water bodies as part of the microbial processes of nitrification and de-nitrification. The two major man-made sources are from agriculture (application of fertilisers to soils - and subsequent leaching to water bodies) and the manufacture of acids and nylon. It is also released from power stations and road transport (particularly since the introduction of catalytic convertors).
How might it affect the environment?
Nitrous oxide does not have a local environmental impact. On a global scale however it does contribute to global warming and is the third most important greenhouse gas in the UK. Although relatively small amounts are released, it has a high "global warming potential" (310 times that of carbon dioxide). Nitrous oxide also damages the ozone layer, thus reducing the protection offered from harmful UV sun rays.
How might exposure to it affect human health?
At normal environmental concentrations, nitrous oxide is not harmful to humans. Inhalation of higher concentrations in an enclosed space could however exclude oxygen - causing dizziness, nausea and eventually unconsciousness. Depletion of the stratospheric ozone layer (in which nitrous oxide plays a part) means that humans may be exposed to high doses of UV sunlight which might cause skin cancers.
What steps are being taken to limit the potential impacts?
The United Nations Framework Convention on Climate Change (Kyoto Protocol, 1997) introduced measures designed to achieve reduction of greenhouse gas releases (including nitrogen monoxide). Amongst the other signaturies from around the world, the UK government (including Scotland) is committed to reaching targets of reduced nitrogen monoxide emissions by 2008-2012.