PMB's new air quality station

2008-10-24 00:00

See Julia Denny-Dimitriou and Ryan Calder's visit to the new station monitor below.

The new air quality monitoring station that the Municipality has installed in Edendale is a real-time monitoring station which measures volatile organic compounds (VOCs). VOCs such as Benzene, Toluene, Ethyl Benzene and Xylene (BTEX) are a class of organic compounds. Combined with oxides of Nitrogen (NOx) and sunlight, VOCs lead to the formation of the secondary pollutant Ozone (O3) and other compounds of photochemical smog.

The BTX group can have severe health effects:

• Benzene is extremely toxic, a known carcinogen, causing leukemia, and is chiefly emitted by motor vehicles as a result of combustion of fuel. Also emitted from certain industrial processes and biomass burning.

• Toluene affects the brain and can cause tiredness, confusion, nausea, memory and hearing loss. It can affect the kidneys and sources are almost entirely man made, including petrol combustion, petroleum refining and biomass burning.

• Xylene also affects the brain and can cause headaches, lack of muscle coordination, dizziness, confusion and sources include petrol, lacquers and glues.

1. Gaseous Sulphur compounds

These compounds include Sulphur Dioxide (SO2) and reduced compounds such as sulphides, mainly Hydrogen Sulphide (H2S). Sulphur Dioxide is a colourless, irritating and reactive gas that smells like burning matches. It can be detected by taste at very low levels (0.3ppm). Above 0.5ppm (odour threshold) it leaves a burning acrid sensation in the nose. It has both natural and man-made sources, the latter coming from coal, and to a lesser extent oil. SO2 is absorbed in the mucous membrane of the nose and respiratory tract because it is soluble. It can have a range of health effects depending on S02 concentrations and exposure times. The major health concerns associated with exposure to high concentrations of SO2 include effects on breathing, respiratory illness, alteration in pulmonary defenses and aggravation of existing cardiovascular disease. Children, the elderly, and people with asthma, cardiovascular disease and chronic lung disease (such as bronchitis or emphysema), are most susceptible to adverse health effects associated with exposure to SO2.

2. Hydrogen Sulphide is the most important of the sulphides as it has both man-made and natural sources. It is colourless, toxic, and has a strong unpleasant odour like rotten egg, and can be detected at concentrations as low as 0.5ppb. Natural emissions sources include emissions produced by decomposing organic matter and the bacterial reduction of sulphate in anaerobic conditions on land, like water-logged soils or wetlands. Man-made sources include sewage plants, oil refineries, and tanneries. Apart from its strong odour which is a nuisance factor, H2S blackens lead-based paints.

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