LCQ11: Air Pollution in Hong Kong
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Question:
The Environmental Protection Department (EPD) has indicated earlier that days with high-level air pollution (i.e. the days on which the Air Quality Health Index reaching 8 or above) were observed in 11 months of 2016. Over 80 per cent of such days of high-level air pollution were caused by pollutants brought by tropical cyclones and from the Pearl River Delta Region. Some environmentalists have pointed out that such a remark indicates that the authorities have overlooked the responsibility to reduce the local sources of air pollution. In this connection, will the Government inform this Council:
(1) in respect of the concentrations of sulphur dioxide (SO2) and ozone (O3) in the air as recorded by the 16 air quality monitoring stations (AQMSs) (both roadside and general ones) across the territory in 2015 and 2016, of (i) the respective numbers of days on which such figures exceeded the relevant target limits under the Air Quality Guidelines (AQG) of the World Health Organization (numbers of days of exceedance), and (ii) the extent by which such figures exceeded the annual average concentration target limits (i.e. SO2 being 5.1 μg/m3 and O3 being 23.5 μg/m3) as estimated by some academics on the basis of AQG's targets; if such data are unavailable, of the reasons for that;
(2) of the respective numbers of days of exceedance in each month of 2016 in respect of the following pollutants as recorded by the AQMSs: (i) SO2, (ii) nitrogen dioxide (NO2), (iii) fine suspended particulates (i.e. PM2.5), (iv) respirable suspended particulates (i.e. PM10) and (v) O3, and set out such figures in tables of the same format as Table 1; if such data are unavailable, of the reasons for that;
Table 1 Air pollutant:
| AQMS | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Total no of days | |
| General | Yuen Long | |||||||||||||
| Tuen Mun | ||||||||||||||
| … | ||||||||||||||
| Roadside | Mongkok | |||||||||||||
| … | ||||||||||||||
(3) as a study has pointed out that the use of a "time-based apportionment method" to analyse each day in a year can identify the most likely pollution source or region that influences the air quality of Hong Kong on that day, whether the Government knows, based on that method of analysis, the following information on the air pollutants mentioned in (2), as recorded by various AQMSs in each month of 2016:
(a) the respective numbers of days of exceedance in respect of which the main source of air pollutants was "local" (i.e. "Local Vehicle/Power Plant" and "Local Vehicle/Marine") (L) and Regional All (R), and set out such figures in tables of the same format as Table 2; if such data are unavailable, of the reasons for that;
Table 2 Air pollutant:
| AQMS | Source | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Total no of days | |
| General | Yuen Long |
L | |||||||||||||
| R | |||||||||||||||
| Tuen Mun |
L | ||||||||||||||
| R | |||||||||||||||
| … | |||||||||||||||
| Roadside | Mongkok | L | |||||||||||||
| R | |||||||||||||||
| … | |||||||||||||||
(b) the respective numbers of days of exceedance in respect of which the main source of air pollutants was "Regional East" (E) and "Regional West" (W), and set out such figures in tables of the same format as Table 3; if such data are unavailable, of the reasons for that;
Table 3 Air pollutant:
| AQMS | Source | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Total no of days | |
| General | Yuen Long | E | |||||||||||||
| W | |||||||||||||||
| Tuen Mun | E | ||||||||||||||
| W | |||||||||||||||
| … | |||||||||||||||
| Roadside | Mongkok | E | |||||||||||||
| W | |||||||||||||||
| … | |||||||||||||||
(c) the respective numbers of days of exceedance in respect of which the main source of air pollutants was "Local Vehicle/Power Plant" (P) and "Local Vehicle/Marine" (M), and set out such figures in tables of the same format as Table 4; if such data are unavailable, of the reasons for that; and
Table 4 Air pollutant:
| AQMS | Source | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Total no of days | |
| General | Yuen Long | P | |||||||||||||
| M | |||||||||||||||
| Tuen Mun | P | ||||||||||||||
| M | |||||||||||||||
| … | |||||||||||||||
| Roadside | Mongkok | P | |||||||||||||
| M | |||||||||||||||
| … | |||||||||||||||
(4) how the EPD currently integrates air pollutant concentration data with meteorological data (e.g. wind directions and wind speed) to identify the sources of air pollutants?
Reply:
President,
To improve our air quality and protect public health, the Hong Kong Special Administrative Region (SAR) Government is committed to reducing local emission of pollutants and working closely with the Guangdong Provincial Government to reduce the regional air pollution in the Pearl River Delta (PRD). In recent years, the SAR Government has undertaken enhancement measures with focus on the control of local pollution sources. The key measures include phasing out some 82 000 pre-Euro IV diesel commercial vehicles by the end of 2019; subsidising franchised bus companies to retrofit their eligible Euro II and III buses with selective catalytic reduction devices; strengthening the vehicle emission control regime for petrol and liquefied petroleum gas vehicles; tightening the emissions from power plants; capping the sulphur content of locally supplied marine light diesel at 0.05 per cent; and being the first Asian city to require ocean going vessels to switch to marine fuel with sulphur content not exceeding 0.5 per cent while at berth.
These measures have yielded notable results. Over the past five years (i.e. 2012-2016), roadside concentrations of major air pollutants including respirable suspended particulates (RSP or PM10), fine suspended particulates (FSP or PM2.5), nitrogen dioxide (NO2) and sulphur dioxide (SO2) have decreased by 28 per cent, 28 per cent, 31 per cent and 30 per cent respectively. For the same period, ambient concentrations of RSP, FSP, NO2 and SO2 have dropped by 21 per cent, 21 per cent, 8 per cent and 18 per cent respectively, while the O3 level in general air which is affected by regional air pollution has shown a decline of 3 per cent.
However, we shall not overlook the impact of weather and regional pollution on local air quality as there are occasional episodes of high-level air pollution (i.e. the Air Quality Health Index reaching 8 or above) in Hong Kong. According to the analysis of the Environmental Protection Department (EPD), over 80 per cent of days of high-level air pollution in 2016, for instance, were caused by pollutants brought by tropical cyclones or from the PRD region. Whenever Hong Hong is under the influence of subsiding air of tropical cyclones, the weather within the PRD region is mainly sunny and calm, which is conducive to the accumulation of O3 and FSP (PM2.5) within the region. If tropical cyclones approach Hong Kong from the east, wind direction will change to westerly or north-westerly and this will bring the polluted air in the PRD region to Hong Kong, leading to deterioration in our air quality.
To effectively solve the problem of regional air pollution caused by O3 and suspended particulates, the Hong Kong SAR Government and the Guangdong Provincial Government set in November 2012 the emission reduction targets and ranges for 2015 and 2020 respectively regarding nitrogen oxides, volatile organic compound (VOC), SO2 and RSP respectively. Both sides are now conducting a mid-term review to assess the attainment of the emission reduction targets for 2015 and to finalise the emission reduction targets for 2020. The review will be completed in the first half of this year.
Our replies to the questions are as follows:
(1) and (2) The Air Quality Guidelines (AQG) of the World Health Organization (WHO) has recommended that countries in setting their air quality standards should strike a balance between the needs of public health and local circumstances, and take into account practical circumstances, such as health risk due to air pollution, latest technological developments, as well as economic, political and social considerations. Recognising that its AQG levels are very stringent, the WHO has also recommended interim targets (ITs) so that countries may progressively improve their air quality with a view to achieving the AQG levels in the long run. As far as we know, no country has fully adopted the AQG levels as its air quality standards.
The current Air Quality Objectives (AQO) of Hong Kong have been drawn up in light of the aforementioned WHO recommendations and the practices of environmentally advanced countries. Half of our AQO limits have adopted the WHO AQG levels, with the rest (including O3 (8-hour) and SO2 (24-hour)) pitching at the WHO ITs. The standards of major air pollutants as stipulated in the AQO of Hong Kong and the WHO AQG are set out in Annex 1.
Certain scholars have once derived the mathematical relationship between the short-term and annual air quality limits of SO2 and O3 by way of statistical analysis (Remark). However, the AQO have to be set on the basis of relevant health risks. In this connection, the WHO considers that there is still insufficient health data to support the setting of annual average concentration limits for SO2 and O3. The WHO will review the concentration limits of pollutants in the AQG from time to time and we will keep such reviews in view, taking them as references for our AQO.
In 2015 and 2016, the number of exceedances for SO2 (24-hour) and O3 (8-hour) according to WHO AQG are set out in Annexes 2 to 5. The concentration of SO2 (10-minute) complied with the WHO AQG. For other major air pollutants, the number of exceedances of the WHO AQG in each month of 2016 are set out in Annexes 6 to 8.
Implementation of effective emission reduction measures remains the key to improvement of air quality, regardless of whether our AQO limits are set at the WHO AQG or IT levels. The SAR Government will continue to explore and formulate new practicable measures to further improve the air quality of Hong Kong.
(3) The EPD adopts various scientific methods, including total emission method, source apportionment and time-based apportionment, to measure and analyse emission of pollutants. As Hong Kong is small in area, it is easy for pollutants emitted from various air pollution sources to mix up. Moreover, pollutants will undergo different chemical reactions under varied meteorological conditions. Therefore, the adoption of time-based apportionment cannot accurately identify the sources of pollutants, while the analysis of different pollutants may produce different results. We do not have the requested information.
In addition, the EPD compiles the Hong Kong Air Pollutants Emission Inventory every year to understand and keep abreast of the changes in emission of pollutants from various pollution sources. The EPD will also consider the air quality trends when formulating relevant emission reduction measures.
(4) The EPD currently makes use of the real time monitoring and model forecast meteorological data provided by the Hong Kong Observatory for daily air quality assessment and forecast.
Remark: HK Lai, A.J. Hedley, Thuan-Quoc Thach, CM Wong, A method to derive the relationship between the annual and short-term air quality limits – Analysis using the WHO Air Quality Guidelines for health protection. Environment International 2013; 59:86-91.
Ends/Wednesday, March 22, 2017
Issued at HKT 19:00
Issued at HKT 19:00
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