Burning fossil fuels in air produces nitrogen oxides. 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.
Epping Forest District Council measures the concentration of NO2 using Passive diffusion tube. This is a simple and relatively inexpensive device consisting of a plastic tube, which can be attached to street furniture (e.g. a street light) allowing a sample of air to be collected (over a recorded exposure period) by diffusion into the sampler. The tubes are sealed and then sent off for quantitative analysis. They give a good general indication of average pollutant levels.
Currently the council has 37 diffusion tubes strategically located around the district. The data from this survey is being used in the second review and assessment of the districts air quality.
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