Nitrogen Oxides

Fuels are burnt in air containing approximately 78% nitrogen it is therefore no surprise that nitrogen oxides are also formed during this process, sources include the electricity generating industry and of course transport. The three oxides of nitrogen commonly encountered in the atmosphere are, Nitrous oxide N2O, Nitrogen Oxide NO, and nitrogen dioxide NO2. Nitrogen oxides combine with water to form nitric acid that is a major component of atmospheric acidification with sulphur. There is a strong link between exposure to nitrogen oxides and asthma. Acute exposure to NO2, i.e. 50 to 100 parts per million (ppm) for one hour causes inflammation of lung tissue. However, exposure to 150 to 200 ppm causes a condition fatal within 3 - 5 weeks, and exposure to air containing greater than 500 ppm results in death generally within 2 - 10 days. In addition nitrogen oxides are major contributors to the formation of ground level ozone. (ozone and its local and global implications are discussed in unit 5)