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Air Pollution

In both developed and rapidly industrialising countries, the major historic air pollution problem has typically been high levels of smoke and sulphur dioixide arising from the combustion of sulphur-containing fossil fuels such as coal for domestic and industrial purpose. The major threat to clean air is now posed by traffic emissions. Petrol and diesel-engined motor vehicles emit a wide variety of pollutants, principally carbon monoxide (CO), oxides of nitrogen (NOx), volatile organic compounds (VOCs) and particulates (PM10), which have an increasing impact on urban air quality. In addition, photochemical reactions resulting from the action of sunlight on nitrogen dioxide (NO2) and VOCs from vehicles leads to the formation of ozone, a secondary long-range pollutant, which impacts in rural areas often far from the original emission site. Acid rain is another long-range pollutant influenced by vehicle NOx emissions. In all except worst-case situations, industrial and domestic pollutant sources, together with their impact on air quality, tend to be steady-state or improving over time. However, traffic pollution problems are worsening world-wide. Below is an introduction to the principal pollutants produced by industrial, domestic and traffic sources: Click here for a glossary of terms used in air pollution.

To find out more about air pollution visit the Enviropedia

Nitrogen oxides

Nitric oxide (NO) is mainly derived from road transport emissions and other combustion processes such as the electricity supply industry. NO is not considered to be harmful to health. However, once released to the atmosphere, NO is usually very rapidly oxidised to nitrogen dioxide (NO2), which is harmful to health. NO2 and NO are both oxides of nitrogen and together are referred to as nitrogen oxides (NOx).

Nitrogen dioxide can irritate the lungs and lower resistance to respiratory infections such as influenza. Continued or frequent exposure to concentrations that are typically much higher than those normally found in the ambient air may cause increased incidence of acute respiratory illness in children.

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