Air quality at a local level can be an issue of concern for some people. The effects of pollutants on a national and global level are of concern for all of us.

Most healthy people do not normally notice any effects from air pollution, unless levels of pollutants increase as a result of traffic and weather conditions in more urban areas.

Some people may get eye irritation or start to cough and in more serious cases may experience breathing problems.

As pollutant levels increase the adverse effects on health increase.

Main types of air pollutants


A hydrocarbon that comes almost entirely from vehicle exhausts.


Almost exclusively from vehicle exhausts.

Carbon monoxide

The product of incomplete combustion of fossil fuels.

Particles or PM10

Small airborne particles that can penetrate deep into the lung. They come from many sources including sea salt, windblown soil, combustion processes and droplet formation in the atmosphere. However, in town centres and throughout Somerset, the primary source is from combustion processes, especially diesel engines.

Fine particulate matter or PM2.5

These are even finer particles. There has been a recent move towards these parameters as better representing health related issues than PM10 – see above.

However under current UK law there is no absolute requirement to assess these parameters at a local level.

Nitrogen dioxide

This is formed whenever fossil fuels are burnt in air. The main source in Somerset is from motor vehicle exhausts.


Lead was once used as a petrol additive. However, with the phasing out of this fuel in 2000, ambient concentrations have now dropped significantly.


In the upper atmosphere it is essential to protect the earth from harmful ultraviolet light. However, at high levels near the ground this gas can irritate the airways of the lungs. It is formed as a secondary pollutant, that is, by the reaction of other pollutants with each other.

Sulphur dioxide

This is mainly produced during the burning of coal and oil.

Further information on these pollutants can be found in the National Air Quality Strategy that can be downloaded from the DEFRA website

Last reviewed: May 24, 2023 by Paul

Next review due: November 24, 2023

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