How polluted is our air?

If there were such a thing as a ranking table of air pollution for major cities in the world, Hong Kong's overall air pollution would rank somewhere near the middle of the scale.

As a result of our various control programmes, concentrations of some of our air pollutants, like lead, carbon monoxide and sulphur dioxide, are not at all high by world standards. On the other hand, we do have very high levels of fine dust particles (respirable suspended particulates) similar to those found in Tokyo, Seoul and Kuala Lumpur.

Vehicle emissions are now our major air pollution problem, especially in the urban areas. Because of our high diesel vehicle usage, we have higher levels of air pollution associated with diesel emissions, i.e. particulates and nitrogen dioxide. For years, most of our monitoring stations have been recording particulate levels violating our annual Air Quality Objectives. The situation is worst at busy roadsides in the urban areas.

Ozone is another air pollutant that merits attention. Ozone is the major component of photochemical smog. It is not produced directly from pollution sources but is formed in the atmosphere under sunlight. Nitrogen oxides and volatile organic compounds (VOC), which are mostly emitted by motor vehicles, are the main source pollutants. Calm and sunny weather is more favourable for the formation of ozone.