香港貧困人口是否吸入更多污染空氣？
「港大劍橋清潔能源與環境研究平台」  揭示空氣污染引致環境不公

惡劣的空氣質素極其損害個人身體健康，能引起如癌症、中風、哮喘或者心臟病等疾病 [1, 2]。由香港大學(港大)及英國劍橋大學(劍橋)合作成立的「港大劍橋清潔能源與環境研究平台」， 最近一項跨學科研究發現，空氣中PM_2.5（直徑2.5微米或以下的微細懸浮粒子）平均濃度與香港社會剝奪指數統計上存在顯著的正相關。 這表示香港各選區間，存在由空氣污染引起的環境不公。相關論文近期在國際學術期刊《環境科學與政策》發表。（Li, V.O.K., Han, Y., Lam, J.C.K., Zhu, Y., and Bacon-Shone, J., 2018, Air pollution and environmental injustice: Are the socially deprived exposed to more PM2.5 pollution in Hong Kong? 80, 2018, 53-61.）

此項研究的起點是：香港貧困人口是否吸入較多污染空氣？香港市民有否因吸入不同空氣污染濃度而面對環境不公？由於本港境內僅有少數污染監測站（僅16個，包括1個近期新增）， 有關本港空氣污染所致的環境不公研究，過去只能基於稀疏的空氣污染數據。這使得想在更細緻的地理尺度下，研究空氣污染與社會剝奪的關係，及相關的環境公平議題，變得十分困難。

最近，身兼「港大劍橋清潔能源與環境研究平台」總監的港大電機電子工程系系主任李安國教授和「港大劍橋清潔能源與環境研究平台」共同總監、港大工程學院電機電子工程系副教授林哲奇博士帶領的一項創新性跨學科研究，使得這個問題得到了解決。研究團隊構建了一個格蘭傑因果模型，利用與空氣污染密切相關的現有城市動態數據作為替代數據，為全香港提供細緻度達100米乘100米的精準空氣污染估計, 將16個政府監測站轉化成11萬個虛擬站。這些替代數據包括空氣污染物濃度，車流量信息，氣象數據和城市型態數據（包括城市佈局和街道地圖），可從香港的環境保護署、運輸署、天文台，以及百度地圖獲得。細緻的估算使研究人員能夠更準確鎖定污染物濃度最高的地區，為香港的環境決策提供有力憑據。

圖一： 建立110,000虛擬監測站為全港空氣質量作精密估量

研究的核心，是分析 412個具有不同社會剝奪程度的選區，其PM_2.5 的濃度分佈是否有差異？由於PM_2.5能導致嚴重健康問題，我們瞄準這個污染物，對其在412個選區的濃度分佈及各選區的社會經濟地位指數進行相關分析。

社會剝奪的程度是透過「社會剝奪指數」（SDI）來量度。「社會剝奪指數」使用「主成分分析方法」，選取和結合了四個反映社會經濟地位的因素，包括：低收入、低教育水平、非專業職位，以及非業主住戶。這些數據乃從2011年人口普查數據中獲得。

基於412個選區的「社會剝奪指數」和平均PM_2.5污染程度，研究團隊發現，香港的空氣PM_2.5濃度與社會剝奪指數統計上存在顯著的正相關; 即是説，「社會剝奪指數」越高，平均PM_2.5污染程度越高。換句話說，香港各選區間存在空氣污染引起的環境不公。

圖二： 香港各選區PM_2.5污染濃度估量與社會剝奪指數
(較深顏色代表較高平均PM_2.5污染濃度及較高社會剝奪指數)

圖三：紅色區域同時具有最高平均PM_2.5污染濃度及最高社會剝奪指數

此項跨學科研究結果顯示，香港迫切需要建立更加統一、以民為本、因地制宜及公平公正的環境政策，以科學實證為本的決策機制，合理應對空氣污染導致的環境不公。

此項結合估量空氣污染及政策研究的跨學科研究方法，可以應用到其他地區，尤其像北京這些本地生產總值增長迅速、人口密集、污染嚴重（包括懸浮顆粒子污染），並且貧富差距在不斷擴大的城市。

相關論文可按此下載瀏覽(只有英文) : https://www.sciencedirect.com/science/article/pii/S1462901117306020

傳媒查詢:
「港大劍橋清潔能源與環境研究平台」總監李安國教授 (電話： +852 2857 8425 ; 電郵：vli@eee.hku.hk )
「港大劍橋清潔能源與環境研究平台」共同總監 林哲奇博士 (電郵：jcklam@eee.hku.hk )
傳訊及公共事務處 梁菁栘女士（電話：+852 2857 8555/ +852 9022 7446；電郵：rhea.leung@hku.hk）
工程學院 曾寶怡女士（電話：+852 3917 1924；電郵：bonniepy@hku.hk)

[1] Pope III, C.A., Dockery, D.W., 2006. Health effects of fine particulate air pollution: lines that connect. J. Air Waste Manage. Assoc. 56, 709-742.
[2] Pui, D.Y., Chen, S.-C., Zuo, Z., 2014. PM _2.5 in China: measurements, sources, visibility and health effects and mitigation. Particuology 13, 1-126.

Are the Socially Deprived Exposed to More Air Pollution in Hong Kong? HKU-Cambridge CEERP reveals air pollution-induced environmental injustice

Poor air quality can result in extremely detrimental health consequences, such as cancer, stroke, asthma or heart disease [1, 2]. Interdisciplinary research conducted by the HKU-Cambridge Clean Energy and Environment Research Platform (HKU-Cambridge CEERP) revealed that there is a statistically significant, positive relationship between ambient PM_2.5 (Particulate Matter of width 2.5 microns or less) concentration and the Social Deprivation Index in Hong Kong, and showed the existence of air pollution-induced environmental injustice at the constituency area level in the territory. The paper was recently published in the journal Environmental Science and Policy (Li, V.O.K., Han, Y., Lam, J.C.K., Zhu, Y., and Bacon-Shone, J., 2018, Air pollution and environmental injustice: Are the socially deprived exposed to more PM_2.5 pollution in Hong Kong?, 80, 2018, 53-61).

The starting point for the research was: Are the socially deprived exposed to a higher level of air pollution in Hong Kong? Can this exposure to air pollution therefore be seen as environmental injustice? Existing research on air pollution-induced environmental injustice in Hong Kong was based on sparse air pollution data due to the limited number of government pollution monitoring stations (only 16, one added recently) in the territory, rendering it difficult to study the relationship between air pollution exposure and social deprivation (SD), and hence the study of environmental injustice, at finer geographical scales.

This challenge was recently overcome by a breakthrough research led by Professor Victor Li On-kwok, Director of HKU-Cambridge CEERP and Head of Department of Electrical and Electronic Engineering (EEE), Faculty of Engineering, HKU and Dr Jacqueline Lam Chi-kei, Co-Director of CEERP and Associate Professor at the HKU Department of EEE, through the development of a Granger Causality Model. This model utilised readily available urban dynamics data closely related with air pollution as proxy data, including ambient pollutants concentration, traffic, meteorology and urban morphology to provide a fine-grained (100m × 100m) estimation of air pollution in Hong Kong, transforming the measurements of 16 government monitoring stations to 110,000 virtual stations. Ambient pollutants concentrations are available from Hong Kong Environmental Protection Department, vehicular traffic data from Hong Kong Transport Department, meteorology data from Hong Kong Observatory, and urban morphology data including urban layout and roadmap from Baidu Map. The fine-grained estimation allows us to identify the areas with the highest level of pollutants concentration, thus providing important inputs for policy-making.

Figure 1
Air quality estimation based on 110,000 virtual stations.

Our investigation focuses on whether there was any differential distribution in PM_2.5 pollution across the 412 constituency areas with different levels of SD. Our study focuses specifically on the ambient PM_2.5 concentration, given its serious health consequences and the potential differential PM_2.5 distribution across groups of different socio-economic status (SES) in Hong Kong.

SD is measured by the Social Deprivation Index (SDI), which is a composite indicator comprising four SES variables, namely, low-income, low-education, non-professional occupation, and non-owner occupier, selected and combined via Principal Component Analysis. SES data are available from the 2011 Population Census.

The team found that there is a statistically significant, positive relationship between ambient PM_2.5 concentration and SDI in Hong Kong, based on the SDI and mean PM_2.5 exposure values derived from 412 constituency areas. The higher the SDI, the higher the mean PM_2.5 exposure. In other words, the postulation of air pollution-induced environmental injustice at the constituency area level in Hong Kong is justified.

Figure 2
Visualization of PM_2.5 pollution estimates and Social Deprivation Index at the constituency area level in Hong Kong. (Darker colours correspond to higher values of air pollution and SDI.)

Figure 3
Constituency areas with both the highest level of PM_2.5 pollution concentration and the highest level of Social Deprivation Index.

This study highlights an emerging need for Hong Kong to develop more integrated, human-centric, location- and justice-based environmental policies, and the need for evidence-based policy-decision-making to properly address air pollution-induced environmental injustice.

The policy implications and recommendations can be extended to the rest of the world, particularly cities like Beijing, where the growth of Gross Domestic Product is rapid, population density and pollution concentrations (including particulate pollution) are high, and the income gap between the rich and the poor is widening.

The journal paper can be viewed and downloaded here:
https://www.sciencedirect.com/science/article/pii/S1462901117306020

Media enquiries:
Professor Victor Li On-kwok, Director, HKU-CEERP (Tel: +852 2857 8425; Email: vli@eee.hku.hk)
Dr Jacqueline Lam Chi-kei, Co-Director, HKU-CEERP (jcklam@eee.hku.hk)
Ms Rhea Leung, Communication and Public Affairs Office (Tel: +852 2857 8555/ +852 9022 7446; Email: rhea.leung@hku.hk)
Ms Bonnie Tsang, Faculty of Engineering (Tel: +852 3917 1924; Email: bonniepy@hku.hk)

[1] Pope III, C.A., Dockery, D.W., 2006. Health effects of fine particulate air pollution: lines that connect. J. Air Waste Manage. Assoc. 56, 709-742.
[2] Pui, D.Y., Chen, S.-C., Zuo, Z., 2014. PM _2.5 in China: measurements, sources, visibility and health effects and mitigation. Particuology 13, 1-126.