Sources of air pollution

Air pollution from motor vehicles has, in many countries, replaced coal smoke as the major cause for concern; and the continuing growth in vehicle use means that efforts to reduce emissions from individual vehicles are in danger of being overtaken by increases in the volume of traffic. In much of eastern Europe the continued use of rather old cars, which are unable to meet modern pollution control requirements, means that efforts to control pollution from this source are going to be increasingly difficult.

The air pollutants produced as a result of the use of motor vehicles present a two-stage problem: primary and secondary pollutants. Primary pollutants produced by petrol-powered vehicles include carbon monoxide, nitric oxide, benzene, particulate matter and lead. Much of the lead emitted by vehicles burning leaded petrol emerges as particles. Diesel engines burn fuel in excess of air and so produce little carbon monoxide but, instead large quantities of carbon dioxide, (see table). Secondary pollutants produced as a result of the use of petrol-engined vehicles include nitrogen dioxide and ozone.

In those countries which have required the removal of lead from petrol, concentrations of lead in air from this source have been reduced to a level at which they are no longer a problem. Lead-free petrol has also made the use of "catalytic converters" possible. Catalysts substantially reduce emissions of hydrocarbons, NOx and carbon monoxide; they do however increase emissions of carbon dioxide, an important greenhouse gas, and have no effect on emissions of particles. Since 1993 all new petrol-engined cars in the European Union have to be fitted with catalytic converters.

Prior to the introduction of cars fitted with catalytic converters, diesel-powered vehicles were considered "cleaner" than petrol-powered cars. EU legislation requires that they meet the same limits for hydrocarbons, NOx and CO as petrol-driven cars. Diesel fuel contains no lead but is a considerable source of particulate matter, PAHs and SO2. The introduction of lower sulphur diesel fuels throughout the EU will reduce emissions from this source (see table).

In many countries, there has been a policy of progressively tightening emission standards for cars and lorries in line with EU directives and UNECE standards. However, much more will need to be done to ensure that reductions in vehicle emissions are not offset by the rapid increase in vehicle ownership and use.

This is an area in which action by local authorities can make a significant impact on local air quality and indeed benefit the local community in terms both of their health and of local amenities. Each local authority will need to consider how it can best tackle the problem, bearing in mind the resources available and other priorities for cutting pollution. Improved public transport, "park and ride" schemes, traffic restrictions, planning guidelines and encouragement to cycle and walk are some of the measures that local authorities can take. Requiring vehicle owners (and businesses) to maintain their vehicles regularly will ensure that fuel is burnt efficiently and economically, and will therefore be less polluting; and fuel consumption is more efficient at lower speeds (60 - 90 km/h).

Domestic Sources

Before about 1960, the domestic use of coal was the major source of particles. Concentrations of airborne particles in many European cities frequently exceeded 1000 µg/m3 and annual average concentrations of several hundred µg/m3 were commonplace. Today, annual average concentrations in most European cities have fallen to less than 30 µg/m3. In eastern Europe much higher concentrations still occur as, to a lesser extent, they do in southern European cities such as Athens. Brown coal (lignite) is a key source of particles in many parts of eastern Europe.

Coal varies in composition and calorific value from mine to mine. Lignite is probably the poorest quality in terms of calorific value and generates most pollutants when used for domestic heating. Lignite contains 67% carbon (compared with the 95% in anthracite) and burns easily, though inefficiently, on an open fire. Special devices with carefully controlled air supplies are needed to burn anthracite but combustion is efficient and far less black smoke is produced.

Conversion of open fires to stoves suitable for burning anthracite (or other smokeless fuel) should be considered by any local authority where coal smoke is a problem. The greater efficiency of controlled anthracite burning leads to a saving in overall fuel costs, though an initial investment in the necessary equipment must be made. Conversion to stoves which ensure complete combustion are also a possibility as are district heating schemes, using combined heat and power plants. The greater use of renewable energy (wind, solar, tidal, wave, etc.) and enhanced energy efficiency measures in homes and offices also helps improve air quality.

Other important domestic sources of air pollution are:

• gas and paraffin heaters, stoves and cookers produce carbon monoxide. If ventilation is inadequate or appliances poorly maintained, CO may accumulate in dangerous concentrations. Nitrogen dioxide is also generated and concentrations in kitchens will usually exceed those outdoors when cookers are in use. Ventilators can help reduce this pollution;
• bonfires, garden incinerators and barbecues can be a significant local smoke and odour nuisance. Burning garden waste produces smoke, especially if it is damp and smouldering rather than dry and blazing. The smoke contains CO and other noxious and irritating compounds. Problems may be caused for asthmatics, bronchitis sufferers or those with heart conditions. Even if the immediate health risk is small, bonfires add to the general background level of air pollution.

Agriculture

Agricultural practices can also be a significant source of nuisance, contributing both to local levels of air pollution and causing odour problems. The main sources of pollution are the burning of agricultural waste, or of crops in the field and large intensive livestock units. Depending on soil type and fertilisation, the nitrogen in the dung and urine of grazing cattle contributes 20-40% of nitrous oxide emissions from agricultural land; methane is also emitted by cattle and other ruminants; nitrous oxide and methane are of course both greenhouse gases.

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(3) The 28 countries are: the 15 countries belonging to the EU plus Norway, Switzerland, Bulgaria, Poland, Czech Republic, Romania, Hungary, Slvakia, Estonia, Lithuania, Latvia, Slovenia and Malta.