XN000022-1996-08-15 — Page 12

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Air quality report for July

The Environmental Protection Department today (Thursday) released air quality information for July.

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

The

announcement contains monitoring results from Mongkok, 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 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.

Air quality was poor on July 26. The Mongkok station recorded the highest TSP and RSP levels of the month. On the same day, the air pollution index (API) for the industrial area reached 118 and those for the urban and new development areas approached the unhealthy limit of 100.

The elevated API level was due to a high level of ozone, which was formed by the reaction of vehicle emissions, such as nitrogen oxides and hydrocarbons, in the presence of strong sunlight.

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.