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Human Health

Healthy people do not normally notice any effects from air pollution, except when the pollution is very high. However, people sensitive to pollution, such as asthmatics, and those with heart conditions or lung diseases, may experience distress and other health effects, even at lower levels of pollution. The Government uses an air pollution banding system to describe the potential health impacts of poor air quality. Information on pollution across the UK can be obtained by a number of sources.

Particulates may be seen as the most critical of all pollutants, and some estimates have suggested that particulates are responsible for up to 10,000 premature deaths in the UK each year. The extent to which particulates are considered harmful depends largely on their composition. Sea salt, for example, is believed to have a positive effect on health. Man-made sources of particulates, however, are rarely harmless. In towns and cities, these are extensively from diesel vehicle exhausts. The effects of particulate emissions are considered detrimental due to their composition, containing mainly unburned fuel oil and hydrocarbons that are known to be carcinogenic among laboratory animals. Very fine particulates can penetrate deep into the lung and cause more damage, as opposed to larger particles that may be filtered out through the airways’ natural mechanisms.

Ozone differs from most pollutants in that it is created as a secondary pollutant by the action of sunlight on volatile organic compounds (VOCs) and oxides of nitrogen. Ozone is a toxic gas that can bring irreversible damage to the respiratory tract and lung tissue if delivered in high quantities. Asthmatics are known to adopt these symptoms more easily.

Nitrogen oxides consist mainly of nitrogen dioxide (NO2) and nitric oxide (NO). Nitric oxide is more readily emitted to the atmosphere as a primary pollutant, from traffic and power stations, and is often oxidised to nitrogen dioxide following dispersal. The amount of nitrogen dioxide emitted directly to the atmosphere is relatively small. Nitric oxide is relatively non-toxic, but at high concentrations the health effects include changes to lung function. Nitrogen dioxide, however, is damaging to health, due to its toxicity. Health effects of exposure to nitrogen dioxide include shortness of breath and chest pains.

Transport, tobacco smoke and gas appliances are the major sources of carbon monoxide. Its link with haemoglobin, the oxygen carrying component of the blood stream, forms carboxyhaemaglobin (COHb) which can be life-threatening in high doses. The effects of carbon monoxide pollution are more damaging to pregnant women and their foetus. Research into smoking and pregnancy shows that concentrations within the blood stream of unborn infants is as high as 12%, causing retardation of the unborn child’s growth and mental development.

A significant proportion of atmospheric lead comes from traffic emissions, due to the lead content in petrol. This has been significantly reduced in recent years but lead is still a serious air pollutant especially to those living near to areas of dense traffic. Damage to the central nervous system, kidneys and brain can result from high concentrations in the blood. Children, however, exhibit vulnerability to the toxic effects of lead at much lower concentrations than for adults. It has been shown that there is a strong link between high lead exposures and impaired intelligence.

Even moderate concentrations of sulphur dioxide may result in a fall in lung function in asthmatics. Tightness in the chest and coughing may also result at higher levels. Sulphur dioxide pollution is considered more harmful when particulate and other pollution concentrations are high. This is known as the "cocktail effect."

Some VOCs are quite harmful. Benzene, for example, has been linked with an increase susceptibility to leukaemia, if exposure is maintained over a period of time.

  

Air Quality

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• Dept. of Health
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