Pollutants - what you need to know

Choose from the list of pollutants related to air pollution below, the image will update to illustrate the causes of each.

Landscape showing pollution sources in Kent and Medway
Factcard - Nitrogen Dioxide

Nitrogen Dioxide (NO2)

Nitrogen dioxide is a red/brown coloured gas with a sharp, unpleasant smell. NO2 is made up of one nitrogen atom and two oxygen atoms as shown in the diagram. It is a secondary pollutant and is created when nitric oxide (NO) – formed in the combustion process – reacts with oxygen in the atmosphere.

Definition: A primary pollutant is an air pollutant emitted directly from a source. A secondary pollutant is not directly emitted in large quantities, but forms when other pollutants (primary pollutants) react in the atmosphere.

The major sources of NO2 in the UK are through the burning of fossil fuels (coal, oil, gas, petrol and diesel) for domestic heating, power generation and road transport. In Kent and Medway, transport emissions are thought to be the largest contributor to NO2 air concentrations which are highest near busy and congested roads.

NO2 can be formed naturally in the atmosphere by lightning and can also be produced by plants; although naturally formed NO2 only represents fraction of the total NO2 found in the atmosphere.