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The air quality and air quality objectives of Hong Kong

8 June 2011

Hong Kong (HKSAR) – Following is a question by the Hon Lee Wing-tat and a written reply by the Acting Secretary for the Environment, Dr Kitty Poon, at the Legislative Council meeting today (June 8):


Regarding the air quality and air quality objectives (AQOs) of Hong Kong, will the Government inform this Council:

(a) given that according to the 2010 Environmental Performance Report of the Environment Bureau and the Environmental Protection Department (EPD), the 2010 targets included: to “finalise the proposed new Air Quality Objectives and the long-term air quality management strategy” and “submit the final set of recommendations for consideration to the Legislative Council”, of the reasons why EPD failed to achieve the aforesaid two targets within 2010;

(b) given that some environmental groups consider that the statistics of Air Pollution Index (API) of each month broken down by number of hours which are compiled by EPD cannot clearly indicate the situation of air pollution in Hong Kong, and they instead recommend compiling statistics on the number of days on which API exceeds the prescribed standards in each month for indicative purpose, or on whether the average daily API for that month has exceeded such standards, so as to enable the public to better understand the actual situation of air pollution, whether the Government will consider such recommendations; and based on the data recorded in the past three years and using such recommended methods of compilation, of the statistical outcome for each of the past three years;

(c) given that an environmental group analysed and compared the data collected from 11 general air monitoring stations in Hong Kong and found that the Sham Shui Po District has the worst air quality, whether the Government had conducted similar analyses and comparisons in the past five years; if it had, of the details; if not, the reasons for that; whether it had introduced any targeted measure to improve air quality in districts with poorer air quality, such as Sham Shui Po and Kwai Chung, etc.; if it had, of the details of the efforts made in various districts each year;

(d) as it has been reported that the diesel particulate filters and diesel oxidation catalysts which were installed in vehicles with government subsidies using public money will increase primary nitrogen dioxide emissions from vehicles, whether it knows, when taking forward the subsidy scheme, that such devices would increase nitrogen dioxide emissions; if so, of the increase in the quantity of nitrogen dioxide and other air pollutants thus caused and the impact on public health, and whether it has made public such information;

(e) given that in the 2010-2011 Policy Address, the Government indicated that it would collaborate with franchised bus companies to conduct a trial on retrofitting Euro II and Euro III buses with catalytic reduction devices, and subject to satisfactory trial results, the Government would fully fund the retrofit of the devices on Euro II and Euro III buses on a full scale, of the amount of fund required, the timetable and other details (e.g. the origin and service life, etc. of the catalytic reduction devices) for retrofitting the devices on a full scale; whether it knows if the catalytic reduction devices will increase the emissions of other air pollutants; if it knows, of the details, and the Government’s counter measures if the emissions of other air pollutants will be increased; and

(f) given that in reply to a question of a Member of this Council on March 16 this year, the Secretary for the Environment indicated that “the Government needs to analyse in detail the different views collected and assess their impacts on the relevant policy issues in order to fully consider and coordinate the implementation of the recommended measures”, and in reply to a question of a Member at the Question and Answer Session of this Council on May 19, 2011, the Chief Executive indicated that announcement on AQOs will be made within this year, of the current progress of the efforts with respect to opinion analysis, impact assessment and consultation with different stakeholders, etc.?



(a) Taking effective air quality improvement measures to reduce the emission of air pollutants is necessary to improve air quality.In updating the AQOs, we need to formulate additional air quality improvement measures for achieving the proposed new AQOs.

The two are closely connected and equally important as part of the air quality management strategy.

The proposed air quality improvement measures encompass a wide range of issues and cut across a number of policy areas. Many of them are controversial and complicated. These include, for instance, updating the fuel mix for the power sector, rationalising bus routes, setting up low emission zones, etc.

The public are also concerned that some air quality improvement measures would increase their financial burden such as causing electricity tariffs, bus fares and operating costs of the business sector to increase. The Government needs to analyse in detail the different views collected and assess their implications for the relevant policies in order to fully consider and coordinate the implementation of the recommended measures. When the work is completed, we will submit the finalised recommendations to the Legislative Council for deliberation.

(b) To provide the public with updated air quality information as soon as possible, the Environmental Protection Department (EPD) releases hourly the latest APIs of every air monitoring station.

This is also a common international practice. Therefore, the EPD provides in its “Air Pollution Index Monthly Summary (the Summary)” the hourly statistics at different pollution levels in the month. This approach gives more details than the suggestions – “compiling statistics on the number of days on which API exceeds the prescribed standards in the month, or on whether the average daily API for that month has exceeded such standards”.

In the Summary, the public can also understand the distribution of different levels of pollution recorded for each monitoring station in the month. If we adopt “the number of days on which API exceeds the prescribed standards in the month”, the public will not know the actual exceedance because each “exceedance day” can be caused by one or more hours exceeding the limit. If we use “the number of days in a month that the average daily API has exceeded the standards”, the Summary cannot provide comprehensive data accurately reflecting low and high air pollution.

As such, we consider there is insufficient scientific justification for adopting the two suggestions for compiling the “Air Pollution Index Monthly Summary” statistics.

(c)Over the past five years from 2006 to 2010, the concentrations of sulphur dioxide (SO2) and respirable suspended particulate (RSP) recorded at the Sham Shui Po general air quality monitoring station dropped by 10 £gg/m3 and 7 £gg/m3, representing a reduction of 42% and 13% respectively. The annual averages of nitrogen dioxide (NO2), and ozone (O3) increased slightly by 2 £gg/m3 and 3 £gg/m3 respectively. The situation was similar to that in urban areas from Tsuen Wan to Kowloon Peninsula (including Tsuen Wan, Kwai Chung and Kwun Tong).

Please refer to the attached Table for details.

Air pollution in different districts in Hong Kong is caused by common air pollutant emission sources such as power plants, vehicles, etc. Therefore, the Government has been implementing territory-wide measures to cut down local emissions as well as joining hands with the Guangdong Provincial Government to reduce emissions from the Pearl River Delta (PRD) region so as to improve air quality in all districts, including Sham Shui Po and Kwai Chung.

We implemented the following key measures in the past five years to reduce local emissions:

(i) imposed emission caps on power plants since August 2005. We have recently further tightened the emission caps of the power plants by about 34% to 50%, as compared with the 2010 level. The new caps will start from 2015 and their compliance requires maximising the utilisation of existing natural gas-fired generation equipment, and prioritising the use of coal-fired generation units that have been retrofitted with additional emission control equipment;

(ii) introduced Euro IV vehicle emission standards to newly registered vehicles from January 2006 in tandem with the European Union;

(iii) implemented between April 1, 2007 to March 31, 2010 a grant to encourage the early replacement of pre-Euro and Euro I diesel commercial vehicles;

(iv) introduced on April 1, 2007 a first registration tax concession scheme for environment-friendly petrol private cars, and introduced in April 2008 a similar scheme for environment-friendly commercial vehicles;

(v) mandated the use of ultra-low sulphur diesel for industrial and commercial processes from October 2008;

(vi)amended the Air Pollution Control (Volatile Organic Compounds) Regulation in October 2009 to cover adhesives, sealants, vehicle refinishing paints, marine vessel paints, pleasure craft paints, etc ., so as to limit their VOC contents in phases from January 2010;

(vii) mandated motor vehicle fuels to comply with Euro V standard from July 1, 2010; and

(viii) introduced on July 1, 2010 a 36-month one-off grant to encourage the early replacement of Euro II diesel commercial vehicles with new commercial vehicles.

(d) Roadside air pollution problem is mainly caused by RSP and NO2, both of which have adverse impacts on health.

RSP mainly comes from diesel vehicles and much of the RSP are fine particulates (i.e. PM2.5). To minimise the adverse impacts of these particulates on public health, the Government, making reference to the successful experiences of technologically advanced places such as the European Union and the United States, funded the retrofit of pre-Euro diesel commercial vehicles with diesel oxidation catalysts (DOC).

Roadside NO2 is mainly formed by further photochemical oxidation of nitric oxide (NO) emitted by vehicles in the presence of volatile organic compounds (VOCs) and O3.

When implementing the subsidy programme for installing DOC for pre Euro diesel commercial vehicles, we appointed an expert team that comprised local and international experts to advise us on the programme. As for the potential increase in the emission of NO2 by DOC, they recommended to stipulate in the technical specifications that the DOC should not increase vehicle emissions of nitrogen oxides (NOx) (including NO and NO2) and other air pollutants (including carbon monoxide (CO) and hydrocarbons (HC)), thereby reducing the impacts to other roadside pollutants (including NO2). This recommendation was consistent with the common practice adopted by the major vehicle manufacturing economies (including the European Union, the United States and Japan), i.e.

reducing NOx emissions from vehicles as a means to reduce roadside NO2 pollution.

Under the above retrofit programme, test reports submitted by the DOC manufacturer and audited by the aforementioned expert team, DOC could reduce particulate emissions by about 35% without affecting the NOx emissions. It could also reduce the CO and HC emissions by about 40% while reduction of HC emission could correspondingly reduce the oxidation of NO to NO2 and the emission of carcinogenic substances in the HC to the atmosphere. When briefing the Legislative Council about the effectiveness of retrofitting DOC to pre-Euro diesel commercial vehicles, we had provided the above emission data.

(e) Selective catalytic reduction devices (SCRs) are well proven to be effective in reducing the emission of NOx (including NO and NO2).

They have been applied to Euro IV and Euro V diesel commercial vehicles (including buses). Based on our understanding, SCRs will continue to be a key NOx emission reduction device for Euro VI diesel commercial vehicles. As long as their design is in good order, SCRs will not increase the emission of other air pollutants from the vehicles.

We are now making preparation with the franchised bus companies to launch a trial of retrofitting Euro II and III buses with SCRs.We anticipate that the trial could commence in the third quarter of this year.

We will review the initial results after the first six months of the trial to understand as soon as possible the feasibility of retrofitting Euro II and III buses with SCRs on a large-scale. Subject to satisfactory trial results, we will discuss with the franchised bus companies the details of the SCR retrofit programme, including the timetable, type and quantity of buses, and specifications of the SCRs, etc.

Regarding the cost of the retrofit, according to the preliminary information provided by suppliers, the cost of a large-scale retrofit of SCRs to Euro II and Euro III franchised buses is about HK$150,000 per bus.The actual cost of the retrofit will depend on the complexity of the retrofit, exchange rate and the trial results.

(f) The Chief Executive explained at the Question and Answer Session on May 19, 2011 that the new AQOs would be put forward in this year for deliberation by Members. After completing the proposal, we shall consult the Panel on Environmental Affairs of this Council.

Source: HKSAR Government

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