Nitrogen Oxides (outdoor)

These oxides are produced by burning fossil fuels in air. Both nitric oxide (NO) and nitrogen dioxide (NO2) are produced, with nitric oxide being the major primary pollutant. This is the first point in a complex series of chemical reactions, involving a range of other pollutants, including ozone. Together the two oxides are referred to as NOx. The concentration of the different elements of NOx will depend on the oxidising capacity of the local atmosphere.

Road Vehicles are responsible for over 50% of the emissions of nitrogen oxides in the UK.

Nitrogen dioxide has been identified as having a number or adverse health effects, focused around the respiratory system, in both asthmatic and non asthmatic subjects. Short-term exposures can increase reactivity to allergens, such as pollen. In some individuals high levels of nitrogen dioxide can precipitate or exacerbate episodes of asthma. Exposure of children to nitrogen dioxide may increase the risk of respiratory infections and possibly lead to poorer lung function in later life. There is some evidence that use may be linked with impaired lung function.

The Government have set an annual mean objective of 40 ug/m3 to be met by 31.12.2005 and a 1 hour mean objective of 200 ug/m3 not to be exceeded more than 18 times a year by 31.12.2005.