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  |
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Nitrogen oxides |
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 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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Click other pollutant below to view more: |
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