XN000022-1995-05-15 — Page 12

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Air quality report for April

The Environmental Protection Department today (Monday) released air quality information for April.

The purpose of the announcement was to keep the public informed of the air quality levels in the territory and to explain the measurements.

The

announcement contains monitoring results from Mong Kok, Central/Western and Kwai Chung, which represent three important land use types in the territory:

locations close to road traffic in built-up urban areas; combined commercial and residential districts; and districts close to industrial areas.

The department currently monitors air quality continuously at eight stations, including the three mentioned. Short-term measurement exercises are also undertaken as and where the need arises.

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.

High levels of dust and NO2 were recorded on April 6. Levels of TSP and RSP also exceeded the respective 24-hour air quality objectives at the street-level site in Mong Kok on that day. The high levels of pollutants were caused by low wind speeds which prevented the dispersion of locally emitted pollutants.

Sulphur dioxide levels remained low at all sites throughout the month.

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.