The seven main pollutants of concern
Nitrogen dioxide is one of a group of gases called nitrogen oxides
Particulate matter in the atmosphere can be from a whole range of sources
Term often used when discussing traffic pollution
Carbon monoxide is a colourless, odourless poisonous gas
Carbon dioxide is produced by 'complete' fossil fuel combustion
Sulphur dioxide is produced when a material, or fuel, containing sulphur is burned
While naturally occurring ozone in the upper atmosphere, 'the ozone layer', protects the Earth, ground level ozone is harmful to health
The main source of lead in the atmosphere was from the combustion of petrol
