The main pollutants related to air quality are described below.
Sulphur dioxide (SO2) is produced when a fuel or other material containing sulphur is burned. Globally, much of the sulphur dioxide in the atmosphere comes from natural sources but, in the UK, the major source is power stations burning fossil fuels - principally coal and heavy oils. Widespread domestic use of coal can also lead to higher local concentrations of SO2. SO2 is a respiratory irritant that can cause the airways to constrict: people with asthma are likely to be particularly sensitive to it. SO2 is considered more harmful when concentrations of particles and other pollutants are also high. This is a good example of combined or synergistic effects of air pollutants.