Air Pollution


Sources of air pollution

Local authorities, health and environment
Sources of air pollution

This section summarises the main sources of air pollution today. The contribution of each source to local pollution will vary according to the type and number of local industrial processes, density and age of road transport and local weather conditions. Other pamphlets in this series will describe the problems in more detail and offer solutions for improvement.

top of pageIndustrial SourcesThe figures used describing the respective production of pollutants by each sector are taken from “Air pollution in Europe” (EEA, 1997). Data relates to the year 1994 and to 28 countries in Europe(3).

top of pagePower Generation
NMVOC=Non Methane Volatile Organic Compounds

Siting fossil fuel power stations in mainly rural areas and distributing the pollution produced more evenly via tall chimneys has resulted in improved urban air quality, though they still remain a major source of pollution, mainly sulphur dioxide and nitrogen oxides.

Better dispersion of pollutants emitted by tall chimneys leads to better dilution in the air and thus lower local concentrations of pollutants. This has however led to pollution being dispersed more widely and to transboundary air pollution.

Stricter operating practices and the use of modern abatement techniques have resulted in a considerable reduction in the amount of pollutants emitted from power stations; high concentrations do however occur in many eastern European countries, particularly from older power stations and from the use of high sulphur lignite or brown coal. Exceptional concentrations may also occur on a very local basis if a plume of smoke from, for example, an industrial chimney falls to the ground due to local atmospheric conditions.

The countries of the European Union and those which are a party to the UNECE Convention on the Long Range Transport of Air Pollution, Second Sulphur Protocol, are committed to major reductions in sulphur dioxide emissions. Power generation is, however, likely to remain an important source of pollution for some time to come, particularly as some countries are reconsidering their programmes of nuclear power generation.

top of pageOther Industry and waste disposalNMVOC=Non Methane Volatile Organic Compounds

Although fossil fuel power plants are the major source of industrial air pollution in many countries, all industry and many businesses, large and small, can be significant local sources of a wide range of air pollutants. The use of both regulatory and planning controls will help to minimise their effect on local air quality.

All waste has the potential to affect the environment adversely by contaminating the air, soil or water. Poorly managed waste disposal sites (landfill or incineration) can also pose a danger to public health, through all these routes.

Landfill and incineration are the two most common methods of waste disposal. If not properly managed landfill sites can cause a number of problems; these include the production of potentially explosive levels of methane gas (65%), dangerous levels of carbon dioxide (35%), plus trace concentrations of a range of organic gases and vapours. Landfill sites also have the potential to cause major odour when badly managed.

Uncontrolled or poorly managed burning of waste (incineration) can result in the production of poisonous chemicals such as hydrochloric acid, dioxins, furans and heavy metals. Hydrochloric acid contributes locally to acid rain and is given off by the burning of plastics. If organic matter and plastics are burnt at low temperatures, dioxins and furans may be emitted. Modern, properly operated incinerators produce fumes which respect the strictest existing legislation.

top of pageRoad TransportNMVOC=Non Methane Volatile Organic Compounds

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.

Traffic pollutionThe 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.

Measures for inclusion in a Local Transport Strategy
  • adequate and affordable public transport;
  • provision of safe cycling and pedestrian routes;
  • regular emissions testing of private and public transport vehicles;
  • encouraging local business to use car pooling or car sharing schemes;
  • encouraging less use of motor cars during weather conditions likely to lead to an episode of pollution.
  • encouraging better fuel quality
  • better planning of the built environment aimed at reduced mobility and improved access to shops, jobs, etc.

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).

Average emission factors of different fuels
Emission factor Environmental third class diesel Environmental first class diesel Ethanol
Regulated pollutants:
Carbon monoxide, g/km 3.3 1.9 0.25
Hydrocarbons, g/km 1.3 0.72 0.13
NOX, g/km 13.2 9.7 9.5
Particulates, mg/km 510 200 53
Unregulated pollutants:
Carbon dioxide, kg/km 1.2 1.1 1.2
Formaldehyde, mg/km 70 29 18
Acetaldehyde, mg/km 19 20 72
Sum, particle-bound PAH
(> 3 aromatic rings) mg/km 220 39 6.0
All emission factors from emission tests performed using the Braunschweig transient bus cycle. (From:Westerholm, R. and Wijk, A., “Vehicle exhausts”, Swedish Environmental Protection Agency, Report 4528, Stockholm, 1996).

top of pageDomestic SourcesNMVOC=Non Methane Volatile Organic Compounds

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.

top of pageAgricultureNMVOC=Non Methane Volatile Organic Compounds

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.

(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.