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The reported air pollutants include sulphur dioxide (SO2), nitrogen dioxide (NO2), total suspended particulates (TSP) which comprise all sizes of dust particles, and the respirable fraction of the dust (RSP). All these pollutants can affect respiratory health in sufficient concentration..
In October, there were no exceedances of the 24-hour Air Quality Objective (AQO) values at any of the three sites while sulphur dioxide levels were also very low.
Dust levels were lower than for the same month last year because of above average rainfall. The heavier rainfall in October washed out airborne dust and wetted surfaces.
The gases and particles described originated from various sources. SO2 is mostly produced when fuels that contain sulphur are burned. NO2 is formed during combustion by the combination of nitrogen and oxygen, and by the atmospheric oxidation of nitric oxide (NO), also a product of combustion.
Vehicle exhaust is an important, source of NO and NO2 in terms of impact on local air quality. It is also a major source of airborne particulate matter, especially the smaller respirable particles.
Diesel-engined vehicles such as taxis, public light buses, passenger coaches, franchised buses and light and heavy goods vehicles are the greatest contributor of particulate matter. Other sources include industry, furnaces and boilers, construction activities, the sea and the soil.
It is worth noting that while the weather and climate always affect the concentrations of pollutants in the air, the only sure way of reducing the levels is to reduce emissions from the man-made sources.
End/Monday, November 13, 1995
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