Dr Lai Ka-man of HKBU (left) and Dr William Yu of WGO share the results of their survey and analysis of the environmental hygiene in subdivided units in Hong Kong.


浸會大學賴嘉雯博士(左)及世界綠色組織余遠騁博士介紹劏房戶環境衛生的研究結果。

Samples of Airborne fungi


空氣中的真菌樣本

Date: 21 May 2014 (Wednesday)

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Sub-divided Flat Study: Sanitation concern as indoor bacterial concentration is off the chart

基層住屋研究: 室內細菌含量「爆錶」 劏房戶環境衛生響警號

Many underprivileged households in Hong Kong are living in a harsh environment. Dr Lai Ka-man, Associate Professor of the Department of Biology of HKBU, together with a team led by Dr William Yu, CEO of World Green Organisation (WGO), completed a survey and analysis of the indoor air quality and environmental hygiene in subdivided units in Hong Kong. The study indicates that the total indoor bacterial count can reach more than 6,535 CFU/m3, which is three times higher than the bacterial count recorded in similar past research. High airborne bacterial counts pose potential environmental hygiene hazards to residents and increase the risk of transmission of communicable diseases. In addition, the indoor bacterial endotoxin concentrations recorded were generally higher than in previous studies in Hong Kong. This concentration level may affect the respiratory system and thus the health of residents, especially children with asthma.

The research team concludes that poor air quality could have arisen from the following factors:
1.    Overcrowded living environment could lead to inadequate air ventilation. This enhances the growth of bacterial and fungal colonies originating from the residential environment, which causes an accumulation of bacteria.
2.    Poor building conditions such as water seepage, spilt water and sewage that could have microbial contamination and result in the release in bacterial toxins.
3.    Poor hygienic quality of the surrounding environment such as garbage or sewage accumulation in canopies and patio.

The research team visited 41 sub-divided units from July to September 2013 and conducted surveys in different districts. Meanwhile 20 households in Tsuen Wan, Mong Kok, Kwun Tong and Kwai Chung were randomly selected for the collection of bacteria, fungi, air and dust samples for further analysis. The questionnaires focus on the residential building environment, indoor air quality and health conditions. The study indicates that the living area per capita in these sub-divided flats is 41.4 ft2 on average, which is even smaller than the Housing Authority standard of 59.2 ft2. Over half of the households felt that indoor air ventilation and sanitation conditions in common areas of the buildings are poor. Mosquitoes, fleas, cockroaches, rodents and other pests are often found inside the sub-divided units.

Seven out of the 20 studied sub-divided units did not meet the Air Quality Index in Hong Kong. The total bacterial counts in the sub-divided flats were measured as between 133 to 6,535 CFU/m3. The worst indoor air quality was recorded in sub-divided flats in Kwai Chung, Mong Kok and Tsuen Wan. The total bacterial counts in the cases of Mong Kok and Kwai Chung were even more than 6,535 CFU/m3 (reached the limit of measuring apparatus). This result is three times higher than in similar past studies which recorded bacterial counts of 2,100 CFU/m3. In the Kwai Chung case, three adults live in a poorly ventilated, crowded flat with lots of household items.

Dr Lai Ka-man concludes that household cleaning is important to improve environmental quality but more urgently needs to be done to improve the building and outside environment. Landlords should take responsibility for providing tentants with basic environmental hygiene by conducting regular cleaning and maintenance of the building walls in order to avoid water seepage and subsequent microbial growth. Occupants of sub-divided units should avoid opening the windows directly facing rubbish sites, and hanging clothes and bedsheets in this area may bring dust into the living space and increase hazard exposure levels. Households should also take care of personal hygiene in order to minimise the transmission of communicable diseases.

Next, the research team will study possible remedial measure to reduce environmental endotoxins and glucans, and the relationship between prolonged exposure to endotoxins and respiratory health of sub-divided unit households.

Dr William Yu of WGO says that the sub-divided flat issue has increasingly aroused concern in Hong Kong. He believes that the overcrowded environment not only increases fire safety concerns, but also causes poor air ventilation and thus is a potential health threat. On the positive correlation between carbon dioxide concentration and the indoor bacterial count, he speculates that because sub-divided flats have few or no windows, this affects the air circulation and causes carbon dioxide accumulation. Moisture accumulation, cooking and other activities would also induce the increase in bacterial content. WGO is now collecting different designs to improve the living environment of sub-divided flats.



本港不少基層住屋環境惡劣,浸會大學生物系副教授賴嘉雯博士,聯同世界綠色組織行政總裁余遠騁博士的團隊,完成一項有關劏房的基層住屋環境研究。結果發現,有居所內的空氣總細菌含量超過每立方米6,535個單位(CFU),是過往類似住屋研究的3倍。細菌含量高意味著潛在環境衛生危機,例如增加環境與人,或人和人之間疾病傳播的風險,研究亦發現單位內「細菌內毒素」(Endotoxin)濃度普遍較過往報告中香港普通住宅中含量為高。如此濃度的細菌毒素可能影響居民呼吸道健康,尤其是患有哮喘的兒童。

研究團隊總結出可能使空氣生物性質素惡化的原因:
1.    居住環境擠迫,空氣流通不足導致來自居民自身的正常菌群以及起居環境滋生的細菌積聚;
2.    惡劣的建築物狀況,例如滲漏、溢出的水及污水可能隱藏微生物以及它們釋放的細菌毒素;
3.    惡劣的周邊環境質素,例如垃圾或污水淤積在簷篷及天井。

研究團隊於2013年7月至9月進行家訪,以問卷訪問41個劏房戶,並在荃灣、旺角、觀塘及葵涌等4個地區中20個住戶抽取相關細菌、真菌、空氣及灰塵樣本。問卷問題環繞居住大廈的環境、室內空氣質素及衛生情況。研究發現受訪劏房戶的人均居住面積是41.4平方呎,較房委會擠迫戶標準每人59.2平方呎還差。逾半住戶覺得室內空氣不流通和大廈公共地方衛生環境惡劣,單位內不難發現蚊、跳蚤、蟑螂等害蟲及老鼠出沒。

在20個研究的劏房戶中,有7個未能符合香港空氣質素指標。單位內的空氣細菌總含量介乎每立方米133至6,535個單位(CFU)。數據以葵涌,旺角及荃灣三間劏房內空氣最為惡劣,尤其是旺角及葵涌個案,總細菌含量「爆錶」,錄得超過每立方米6,535個單位(已達儀器上限值),是過往類似研究錄得2,100個單位含菌量的3倍。究其原因,葵涌個案中室內有三名成年住戶及大量雜物,擠迫的環境加上空氣流通不足造成細菌積聚。這不僅是單一案例,連同其他個案的分析,二氧化碳濃度與室內細菌數目呈正比關係;而室內二氧化碳濃度與細菌數目,均是室內環境質素的重要指標。

賴嘉雯博士表示,家居清潔固然重要,但應同等重視改善建築物及室外的環境衛生。為了改善整體的衛生情況,除了經常清理大廈垃圾外,業主亦應定期維修滲水的牆壁,減少細菌滋生。在預防措施方面,住戶應避免打開面向垃圾堆的窗戶及在垃圾堆積的環境晾曬衣物,從而減少受生物污染的粉塵進入室內,同時注意個人衛生,減低細菌傳染的風險。她又稱,未來會研究如何有效減少環境中的微生物與內毒素,以及人體長期暴露在內毒素中與呼吸系統健康的關係。

余遠騁博士表示,近年社會日趨關注劏房的問題,過往普遍認為擠迫環境不僅帶來消防安全的顧慮,亦影響空氣流通,帶來焗促的環境,而今次研究更帶出劏房潛在的健康危機。對於二氧化碳濃度與室內細菌數目呈正比關係,他估計是劏房窗戶不足,影響空氣的對流,令室內二氧化碳積聚;而室內的濕氣、以至煮食等其他活動更令細菌滋生,令室內環境空氣質素變得惡劣。他又稱,世界綠色組織現正徵集不同的設計方案,改善劏房的居住環境。