What is Air Pollution?Air pollution is anything that causes the air to become contaminated with pollutants at levels harmful to our health or the environment.

The main cause of air pollution in past years has been high levels of sulphur dioxide and smoke resulting from the burning of fossil fuels for both industrial and domestic purposes.

However, today, the main threat to our health additionally comes from vehicle emissions which, although less visible, are making our air more toxic than ever.

The World Health Organisation

The World Health Organisation (WHO) takes air pollution very seriously. They regard it as a major environmental health risk and have been operating air quality assessments since 1987, providing up-to-date and widely accepted statistics and recommending global targets for reducing pollutants and increasing human health.

In their most recent global report, the WHO estimates that each year, air pollution causes two million premature deaths. Most of these deaths occur in the developing countries of the world where air quality is much poorer. However, over 300,000 people in Europe die early from air pollution and of these, 32,000 occur in the UK.

Calculations taken from a study by the European Commission suggest that polluted air also reduces life expectancy by about nine months in Europe.

Key Pollutants

Although there are hundreds of different pollutants in the air, the four of main concern today are:

  • Particulate matter (particularly PM10s)
  • Nitrogen dioxide
  • Sulphur dioxide
  • Ozone

Particulate Matter

Particulates are tiny particles made up of a solid/liquid mix of carbon, mineral dust, water, sodium chloride, ammonia, nitrates and sulphate which suspend in the air. They are formed from combustion and burning processes.

In their most lethal state particulates are less than 10 micrometres in diameter (i.e. PM10s) and thus easily able to enter the body. Particles even smaller than PM10’s (PM25s) can be absorbed directly into the blood stream and could also interfere with gas exchange in the lungs as they settle deep into the lung tissue.

Particulates have been known to be harmful to health for some time and levels are closely monitored. Health risks include respiratory disease, cardiovascular disease, and lung cancer. The WHO would like to see the incidence of particulate matter in the air drastically reduced and so help immediately cut related deaths by an estimated 15%.

Nitrogen Dioxide

Nitrogen Dioxide (NO2) is a toxic gas which also plays a significant part in the production of particulates, and in the presence of sunlight, the formation of ozone.

NO2 will affect the airways, triggering asthma attacks, bronchitis, reduce lung function growth, and causing general breathing difficulties.

Sulphur Dioxide

Sulphur Dioxide (SO2) is a sharp-smelling, colourless gas produced from burning coal, oil and other fossil fuels, including for domestic heating uses.

Detrimental health effects include respiratory problems and impaired lung function, irritable, itchy eyes, and coughs. It has been found that when SO2 levels are high, hospital admissions for heart-related problems also rise and the two sets of statistics are now being linked.

An additional environmental hazard of sulphur dioxide is that when mixed with water, sulphuric acid is formed which is the main constituent of acid rain.


Ozone in the upper atmosphere provides a much-needed protective layer against the harmful effects of sunlight. However at ground level, it is highly damaging.

Ozone is produced by a photochemical reaction when emissions from vehicle exhaust, industrial processes, and solvents react with sunlight. At times of still, hot weather, ozone levels rise, generating photochemical smog, which can have a fast and detrimental effect on lung function – even in very fit people.

Improving Air Quality

Although most governments do follow national clean air targets, many countries are not as stringent as the World Health Organisation would like them to be. Even taking into consideration interim levels for developing countries, the WHO are calling for governments to target city blackspots and clean up. In particular, they would like to see the allowable levels of PM10s in the air dramatically lowered in order to save lives.