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Following is a question by the Dr Hon HO Chung-tai and a written reply by the Secretary for the Environment, Transport and Works, Dr Sarah Liao, at the Legislative Council meeting today (February 25):

Question:

Regarding the level of ozone concentration in the air exceeding the prescribed standard and the impact of chemical substances containing ozone on human health, will the Government inform this Council:

(a) of the numbers of days in the past year on which the ozone concentration in the air in various districts of Hong Kong exceeded the standard in the air quality objectives;

(b) whether it has measures to control the level of ozone concentration in the outdoor and indoor air; if so, of the details; if not, whether the authorities will formulate measures in this regard; and

(c) whether it has made publicity efforts to alert the public to the impact of ozone on human health, so that they will cautiously use chemical substances containing ozone; if not, whether it will strengthen the relevant publicity efforts?

Reply:

Madam President,

(a) There are 11 general air quality monitoring stations in Hong Kong. These stations that are located in different areas monitor the concentrations of air pollutants (including ozone). Over the past year, only the monitoring stations at Tap Mun and Tung Chung had records of incidents of ozone concentrations exceeding the Air Quality Objective (AQO): the ozone concentrations recorded at the Tap Mun station and the Tung Chung station exceeded the AQO in 13 hours and 26 hours respectively.

(b) Ozone in the ambient air is not directly emitted from any source but is formed under photochemical reaction between nitrogen oxides (NOx) and volatile organic compounds (VOC) under sunlight. When a temperature inversion is formed in the Pearl River Delta (PRD) Region, or when a weak northerly or northwesterly wind prevails, ambient air pollutants (including NOx and VOC) in the region will be trapped easily in the lower atmosphere and cannot be dispersed effectively. The above factors, if coupled with strong sunlight, will favour the building up of ozone concentrations. To control ozone concentrations, we have to reduce the emissions of NOx and VOC in the whole of the PRD Region. In this connection, the Hong Kong Special Administrative Region Government and the Guangdong Provincial Government have jointly drawn up a "Regional Air Quality Management Plan" to reduce the emissions of four major air pollutants, including NOx and VOC that are to be reduced by 20% and 55% respectively. When the targets are achieved, the ambient ozone concentrations in Hong Kong and in the whole of the PRD Region will fall significantly and air quality will also improve. Under the Regional Air Quality Management Plan, the two Governments will implement enhanced air pollution control measures, including those for reducing NOx and VOC emissions. The details of those measures are set out at the Annex.

Office equipment, such as photocopying machines, laser printers, fax machines, computer terminals, air purifiers operating on electrostatic precipitation and ultraviolet equipment, are the main sources of indoor ozone. Since ozone is highly reactive, its concentration will only build up near the sources. Generally speaking, ozone will not affect indoor air quality as long as good ventilation is maintained. At present, the Occupational Safety and Health Ordinance enforced by the Labour Department requires employers to ensure the safety and health of their employees by providing or maintaining a working environment that is safe and free of health hazards. The Labour Department has published the "Code of Practice on Control of Air Impurities (Chemical Substances) in the Workplace" and "A Simple Guide to Health Risk Assessment - Office Environment Series" that set out recommendations for employers on how to control ozone concentrations and the ozone concentration standards for the workplace. Moreover, the Environmental Protection Department (EPD) has compiled "Guidance Notes for the Management of Indoor Air Quality in Offices and Public Places" to guide members of the public on how to improve the indoor air quality in those premises, including how to select office equipment with low ozone emission and how to lower indoor ozone concentrations.

(c) EPD disseminates information on the health impacts of major air pollutants through its website, Air Pollution Index Hotline, annual reports and pamphlets. To educate the public about the importance of good indoor air quality, the Department has also published a series of pamphlets and booklets, set up an Indoor Air Quality Information Centre and a related website, and organised exhibitions and educational activities on environmental protection. By publicising and providing relevant information through different channels, EPD endeavours to reduce the negative impact of ozone and other air pollutants on indoor air quality and public health.

Ends/Wednesday, February 25, 2004

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