Toilet flushing can potentially spread bacteria via aerosol droplets

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Description

According to a study revealed by Professor Alvin Lai Chi-keung, Associate Head of the Department of Architecture and Civil Engineering in the College of Engineering at City University of Hong Kong (CityU), and his research team, toilet users’ health can be affected by pathogens embedded in airborne aerosol droplets that may rise as high as one metre from the toilet seat during flushing and spread in the air. Toilets must be kept clean to prevent the transmission of bacteria and pathogens during the outbreak of the novel coronavirus epidemic.

Professor Lai and Dr Iris Li Wai-sum, a member of the research team and a specialist in infectious disease, remind the public that covering the toilet lid before flushing cannot completely prevent pathogens from spreading. They suggested using 1 in 49 diluted household bleach to regularly clean the toilet bowl and 1 in 99 diluted household bleach to clean all areas of the washroom.

Dr Eric Lee Wai-ming, Associate Professor from CityU’s Department of Architecture and Civil Engineering, provided supplementary information on the relationship between sewage systems and hygiene conditions in indoor habitats.

Period13 Feb 2020 → 17 Feb 2020

Media coverage

Title【武漢肺炎】廁所防疫單靠蓋廁板沖廁仲未夠 城大專家團隊教你正確如廁8件事
Description香港城市大學工學院建築學及土木工程學系副系主任賴志強教授的團隊日前發表研究，指出沖廁時傳播病毒的潛在風險，沖廁時可濺高水珠至離廁所板一米的位置，即使蓋上廁板沖板，原來亦不足以杜絕病菌散播。
Persons
Media name/outletU Lifestyle
PlaceHong Kong
Media typeWeb
Producer/AuthorTC Wong
Date17/02/20
Linkhttps://hk.ulifestyle.com.hk/topic/detail/209981/%E6%AD%A6%E6%BC%A2%E8%82%BA%E7%82%8E-%E5%BB%81%E6%89%80%E9%98%B2%E7%96%AB%E5%96%AE%E9%9D%A0%E8%93%8B%E5%BB%81%E6%9D%BF%E6%B2%96%E5%BB%81%E4%BB%B2%E6%9C%AA%E5%A4%A0-%E5%9F%8E%E5%A4%A7%E5%B0%88%E5%AE%B6%E5%9C%98%E9%9A%8A%E6%95%99%E4%BD%A0%E6%AD%A3%E7%A2%BA%E5%A6%82%E5%BB%818%E4%BB%B6%E4%BA%8B/2
Title沖廁令細菌霧化 吸入或損健康
Description城市大學工學院建築學及土木工程學系副系主任賴志強教授團隊發現，沖廁產生的水珠最高可濺起至離廁板一米的位置，細菌會隨氣流擴散，有機會影響如廁者健康。
Persons
Media name/outlet信報財經新聞
PlaceHong Kong
Media typeWeb
Producer/Author紀曉風
Date14/02/20
Linkhttps://www1.hkej.com/dailynews/views/article/2377848/%E6%B2%96%E5%BB%81%E4%BB%A4%E7%B4%B0%E8%8F%8C%E9%9C%A7%E5%8C%96+%E5%90%B8%E5%85%A5%E6%88%96%E6%90%8D%E5%81%A5%E5%BA%B7
TitleToilet flushing can potentially spread bacteria via aerosol droplets
DescriptionProfessor Lai and his team have studied the relationship between airborne aerosol droplets and the transmission of pathogens for years. They have found that each toilet flush can produce approximately 14,000 to 80,000 aerosol droplets, which can rise higher if the water tank is installed on a high position or a valve type flushing system is used. The droplets may rise as high as one metre. Their study revealed that pathogens can be spread in the air by aerosol droplets emitted from toilet flushing, thus contaminating the washroom. Also, the smaller the size of the pathogens, the higher the concentration of distribution in the air after flushing.
Persons
Media name/outletCityU NewsCentre
PlaceHong Kong
Media typeWeb
Producer/AuthorMICHELLE LIU; CHOI YIU
Date14/02/20
Title研究指沖廁可釋八萬顆帶菌水珠
Description城大工學院建築學及土木工程學系副系主任賴志強研究發現，每次沖廁可產生一點四萬至八萬顆帶菌水珠污染洗手間環境，最高更可濺至離廁板一米位置；廁所水壓愈大，會生成愈多水珠，而體積愈小的細菌，在空氣中逗留時間愈長，且濃度愈高，更容易透過氣溶膠傳播，「估計體積遠比細菌細小的病毒，飄留時間及濃度會較細菌高。」
Persons
Media name/outlet星島日報
PlaceHong Kong
Media typeWeb
Date14/02/20
Title【抗擊新冠肺炎】冚廁板沖水 無阻病毒飄散
Description城大工學院建築學及土木工程學系副系主任賴志強，從事病原體藉水珠和氣溶膠散播的研究多年。其團隊模擬家居廁所沖廁情況進行測試，發現每次沖廁可產生1.4萬顆至8萬顆水珠。若水箱位置相對廁板較高，或採用閥門裝置的沖水系統，水珠均會濺起至較高位置，最高可至距離廁所板一米。
Persons
Media name/outlet文匯報
PlaceHong Kong
Media typeWeb
Date14/02/20
Linkpaper.wenweipo.com/2020/02/14/HS2002140029.htm
Title學者：開30分鐘抽氣扇 可減氣溶膠98%
Description城大建築學及土木工程系主任賴志強建議，長期開動廁所的抽氣扇。若在實驗室理想環境下，開動抽氣扇15分鐘，可減少87%氣溶膠，開動30分鐘，可減少98%氣溶膠。
Persons
Media name/outlet大公報
PlaceHong Kong
Media typeWeb
Date14/02/20
Linkwww.takungpao.com.hk/news/232109/2020/0214/415679.html
Title專家：蓋廁板沖廁 仍有細菌漂浮
Description城市大學一項研究發現，沖廁產生的水珠最高可濺起至離廁板一米的位置；即使蓋上廁板沖廁，細菌仍然會離開廁缸，漂浮於空氣之中。
Persons
Media name/outlet香港經濟日報
PlaceHong Kong
Media typeWeb
Date14/02/20
Linkhttps://paper.hket.com/article/2564254/%E5%B0%88%E5%AE%B6%EF%BC%9A%E8%93%8B%E5%BB%81%E6%9D%BF%E6%B2%96%E5%BB%81%20%E4%BB%8D%E6%9C%89%E7%B4%B0%E8%8F%8C%E6%BC%82%E6%B5%AE
Title學者籲冲廁蓋板 關門窗開抽氣扇
Description城大工學院建築學及土木工程學系副系主任賴志強指出，一般而言，病毒的體積比細菌更加細，若根據研究結果，相信冲廁後病毒在空氣的濃度會更高。
Persons
Media name/outlet明報新聞網
PlaceHong Kong
Media typeWeb
Date14/02/20
Linkhttps://news.mingpao.com/pns/%E6%B8%AF%E8%81%9E/article/20200214/s00002/1581618835530/%E5%AD%B8%E8%80%85%E7%B1%B2%E5%86%B2%E5%BB%81%E8%93%8B%E6%9D%BF-%E9%97%9C%E9%96%80%E7%AA%97%E9%96%8B%E6%8A%BD%E6%B0%A3%E6%89%87
Title沖廁8萬水珠藏菌 宜長開抽氣扇
Description香港城市大學建築學及土木工程學系昨日發表研究報告，指沖廁可產生多達八萬顆藏菌水珠，並濺到一米高，排泄物的細菌和病毒會隨氣流擴散，即使蓋上廁板亦未能杜絕細菌散播。
Persons
Media name/outlet東方日報
PlaceHong Kong
Media typeWeb
Date14/02/20
Linkhttps://orientaldaily.on.cc/cnt/news/20200214/00176_031.html
Title蓋廁板沖水難阻氣霧播毒
Description負責研究的城大建築學及土木工程學系副系主任賴志強表示，今次研究採用細菌作實驗對象，結果發現細菌體積與沖廁後在空氣的細菌濃度成反比，即細菌越小，沖廁後在經氣霧傳播的能力越高。他指今次武漢肺炎由病毒引起，病毒體積比細菌更小，相信實際傳播能力會比研究結果更高。
Persons
Media name/outlet蘋果日報
PlaceHong Kong
Media typeWeb
Producer/Author何家朗
Date14/02/20
Title保持衛生 沖廁可產氣溶膠 學者：馬桶冚蓋非萬無一失
Description城市大學工學院建築學及土木工程學系副主任賴志強及其團隊，進行有關常見座廁款式的直沖式(Wash Down)座廁沖廁實驗，發現低水缸座廁(水缸距馬桶49cm)及高水缸座廁(水缸距馬桶98cm)每次沖廁均可產生約1.4萬顆氣溶膠，而實驗中發現愈多氣溶膠或水珠，細菌釋出量愈多，同時體積愈小的細菌釋出量也愈多。

建築學及土木工程學系副教授李偉明建議，如座廁有弱水壓沖廁掣可多使用，減少水壓沖擊以減少氣溶膠產生；抽氣扇也應經常清潔，避免塵埃積累，減低抽氣效能。
Persons
Media name/outletam730
PlaceHong Kong
Media typeWeb
Date14/02/20
Linkhttps://www.am730.com.hk/news/%E6%96%B0%E8%81%9E/%E4%BF%9D%E6%8C%81%E8%A1%9B%E7%94%9F-%E6%B2%96%E5%BB%81%E5%8F%AF%E7%94%A2%E6%B0%A3%E6%BA%B6%E8%86%A0-%E5%AD%B8%E8%80%85%EF%BC%9A%E9%A6%AC%E6%A1%B6%E5%86%9A%E8%93%8B%E9%9D%9E%E8%90%AC%E7%84%A1%E4%B8%80%E5%A4%B1-207408
Title七點半新聞報道
DescriptionAmid the coronavirus scare, researchers at City University of Hong Kong are warning that bacteria and viruses can be spread even when the toilet lid is closed during flushing.
Persons
Media name/outletTVB News
Media typeWeb
Date13/02/20
TitleHK News | Study found long-time operating ventilation fan could reduce the spread of virus
DescriptionDr. Alvin Lai, Deputy Dean of CityU’s Department of Architecture and Civil Engineering said, even if you closed the toilet lid, there would still be the tiniest virus going through the slightest gap, forming highly contagious aerosol in the air. However, in an ideal lab environment, 15-minute of ventilation fan operation is able to reduce at least 87% aerosol.
Persons
Media name/outletdotdotnews.com
PlaceHong Kong
Media typeWeb
Date13/02/20
Title城大研究倡開抽氣扇減播毒 蓋廁板後仍有細菌飄浮
Description內地專家發現新冠肺炎能透過氣溶膠傳播，城市大學工學院建築學及土木工程學系副系主任賴志強，多年來從事有關病原體藉水珠和氣溶膠散播的研究，最新實驗室測試發現，每次沖廁可產生1.4萬至8萬顆水珠，從人體排出的細菌便會隨水珠飛濺，污染洗手間環境，最高更可濺至離廁板一米的位置。
Persons
Media name/outlet星島日報
PlaceHong Kong
Media typeWeb
Date13/02/20
Linkhttps://std.stheadline.com/instant/articles/detail/1200380/%E5%8D%B3%E6%99%82-%E9%A6%99%E6%B8%AF-%E5%9F%8E%E5%A4%A7%E7%A0%94%E7%A9%B6%E5%80%A1%E9%96%8B%E6%8A%BD%E6%B0%A3%E6%89%87%E6%B8%9B%E6%92%AD%E6%AF%92-%E8%93%8B%E5%BB%81%E6%9D%BF%E5%BE%8C%E4%BB%8D%E6%9C%89%E7%B4%B0%E8%8F%8C%E9%A3%84%E6%B5%AE
Title城大研究倡開抽氣扇減播毒 蓋廁板後仍有細菌飄浮
Description內地專家發現新冠肺炎能透過氣溶膠傳播，城市大學工學院建築學及土木工程學系副系主任賴志強，多年來從事有關病原體藉水珠和氣溶膠散播的研究，最新實驗室測試發現，每次沖廁可產生1.4萬至8萬顆水珠，從人體排出的細菌便會隨水珠飛濺，污染洗手間環境，最高更可濺至離廁板一米的位置。
Persons
Media name/outlet頭條日報
PlaceHong Kong
Media typeWeb
Date13/02/20
Title城大研究：多開抽氣扇減病毒散播 蓋廁板後仍有細菌飄浮
Description城大建築學及土木工程學系副系主任賴志強表示，雖然廁板沖廁有助減少細菌和氣溶膠污染空氣，不過在實驗室測試中發現，沖廁時細菌會透過廁板和廁缸的數毫米縫隙，霧化飄浮於空氣中。體積愈細的細菌，沖廁後在空氣中的濃度愈高，比細菌體積更細小的病毒，更易殘留在空氣中。
Persons
Media name/outlet巴士的報
PlaceHong Kong
Media typeWeb
Date13/02/20
Linkhttps://www.bastillepost.com/hongkong/article/5904574-%E5%9F%8E%E5%A4%A7%E7%A0%94%E7%A9%B6%E5%80%A1%E5%A4%9A%E9%96%8B%E6%8A%BD%E6%B0%A3%E6%89%87%E6%B8%9B%E7%97%85%E6%AF%92%E6%95%A3%E6%92%AD-%E8%93%8B%E5%BB%81%E6%9D%BF%E5%BE%8C%E4%BB%8D%E6%9C%89%E7%B4%B0
Title 【防疫攻略】專家：蓋廁板沖廁未杜絕細菌散播
Description城大工學院建築學及土木工程學系副系主任賴志強解釋，沖廁過程中，細菌會隨水珠飛濺污染洗手間及隨霧化過程飄浮於空氣中，形成「氣溶膠」。他指，有國際文獻顯示，由於廁板與廁缸之間有數毫米的縫隙，即使蓋上廁板沖廁，細菌亦有機會透過霧化過程離開廁缸及飄浮於空氣中。
Persons
Media name/outletam730
PlaceHong Kong
Media typeWeb
Date13/02/20
Linkhttps://www.am730.com.hk/news/%E6%96%B0%E8%81%9E/%E3%80%90%E9%98%B2%E7%96%AB%E6%94%BB%E7%95%A5%E3%80%91%E5%B0%88%E5%AE%B6%EF%BC%9A%E8%93%8B%E5%BB%81%E6%9D%BF%E6%B2%96%E5%BB%81%E6%9C%AA%E8%83%BD%E6%9D%9C%E7%B5%95%E7%B4%B0%E8%8F%8C%E6%95%A3%E6%92%AD-207271
Title學者：沖廁時細菌透過氣溶膠傳播　應蓋廁板及定期洗刷
Description城大工學院建築學及土木工程學系副系主任賴志強說，在沖廁過程中細菌會透過氣溶膠傳播，沖廁時蓋上廁板不足以阻隔，市民必須定期刷洗廁缸。
Persons
Media name/outlet新浪香港
PlaceHong Kong
Media typeWeb
Date13/02/20
Linkhttps://sina.com.hk/news/article/20200213/1/10/84/%E5%AD%B8%E8%80%85-%E6%B2%96%E5%BB%81%E6%99%82%E7%B4%B0%E8%8F%8C%E9%80%8F%E9%81%8E%E6%B0%A3%E6%BA%B6%E8%86%A0%E5%82%B3%E6%92%AD-%E6%87%89%E8%93%8B%E5%BB%81%E6%9D%BF%E5%8F%8A%E5%AE%9A%E6%9C%9F%E6%B4%97%E5%88%B7-11198849.html
Title學者：沖廁時細菌透過氣溶膠傳播　應蓋廁板及定期洗刷
Description城大工學院建築學及土木工程學系副系主任賴志強說，在沖廁過程中細菌會透過氣溶膠傳播，沖廁時蓋上廁板不足以阻隔，市民必須定期刷洗廁缸。
Persons
Media name/outlet香港電台
PlaceHong Kong
Media typeWeb
Date13/02/20
Linkhttps://news.rthk.hk/rthk/ch/component/k2/1508329-20200213.htm
Title城大研究建議開動廁所抽氣扇減細菌散播
Description城大建築學及土木工程學系副系主任賴志強表示，在實驗室測試中發現，沖廁時細菌會透過廁板和廁缸的數毫米縫隙，霧化飄浮於空氣中，體積愈細的細菌，沖廁後在空氣中的濃度愈高，比細菌體積更細小的病毒，更易殘留在空氣中，建議開動廁所抽氣扇。
Persons
Media name/outlet881903.com
PlaceHong Kong
Media typeWeb
Date13/02/20
Title【武漢肺炎】城大：廁板與廁缸間存在縫隙　蓋廁板難杜絕細菌散播
Description城大工學院建築學及土木工程學系副系主任賴志強帶領的團隊，於研究中發現沖廁產生的水珠，最高可濺至離廁板一米的位置，而每次沖廁可產生1.4萬至8萬顆水珠。若水箱相對廁板位置較高，或以閥門沖水系統，水珠會濺至較高位置。
Persons
Media name/outlet香港01
PlaceHong Kong
Media typeWeb
Producer/Author張嘉敏
Date13/02/20
Linkhttps://www.hk01.com/%E7%A4%BE%E6%9C%83%E6%96%B0%E8%81%9E/434152/%E6%AD%A6%E6%BC%A2%E8%82%BA%E7%82%8E-%E5%9F%8E%E5%A4%A7-%E5%BB%81%E6%9D%BF%E8%88%87%E5%BB%81%E7%BC%B8%E9%96%93%E5%AD%98%E5%9C%A8%E7%B8%AB%E9%9A%99-%E8%93%8B%E5%BB%81%E6%9D%BF%E9%9B%A3%E6%9D%9C%E7%B5%95%E7%B4%B0%E8%8F%8C%E6%95%A3%E6%92%AD
Title【糞便播毒】每次沖廁水珠可濺起1米高　專科醫生：沖廁時蓋上廁板並不足夠
Description香港城市大學工學院建築學及土木工程學系副系主任賴志強及其團體發研究指，沖廁產生的水珠最高可濺起至離廁板版一米的位置，呼籲市民必須定期刷洗廁缸。
城大工學院建築學及土木工程學系副教授李偉明補充，現時本港家居的洗手間主要使用水箱沖廁或旋渦式沖廁，僅有極少數使用閥門裝置沖廁系統。他又提到，不少市民家中的沖廁模式為兩段式設計，建議可按一邊「小水掣」沖廁，減低水珠濺起數量，若仍未清潔好，可相隔數分鐘再按；並應定時清潔洗手間的抽氣扇。
Persons
Media name/outlettopick.hket.com
PlaceHong Kong
Media typeWeb
Producer/Author陳子謙、郭詩詩
Date13/02/20
Linkhttps://topick.hket.com/article/2563537/%E3%80%90%E7%B3%9E%E4%BE%BF%E6%92%AD%E6%AF%92%E3%80%91%E6%AF%8F%E6%AC%A1%E6%B2%96%E5%BB%81%E6%B0%B4%E7%8F%A0%E5%8F%AF%E6%BF%BA%E8%B5%B71%E7%B1%B3%E9%AB%98%E3%80%80%E5%B0%88%E7%A7%91%E9%86%AB%E7%94%9F%EF%BC%9A%E6%B2%96%E5%BB%81%E6%99%82%E8%93%8B%E4%B8%8A%E5%BB%81%E6%9D%BF%E4%B8%A6%E4%B8%8D%E8%B6%B3%E5%A4%A0
Title城大團隊提醒市民定期清洗座廁 保持洗手間空氣流通
Description城大工學院建築學及土木工程學系副系主任賴志強稱：「(病毒)體積越小，飄浮得越久。如果開風扇十五分鐘，大約可減少氣溶膠(霧化)濃度百分之八十六，剩下百分之十四，再等十五分鐘，一共三十分鐘，只剩下百分之二。」
Persons
Media name/outletTVB News
PlaceHong Kong
Media typeWeb
Date13/02/20
Linknews.tvb.com/local/5e45417a34b031e6393ef63f/%E5%9F%8E%E5%A4%A7%E5%9C%98%E9%9A%8A%E6%8F%90%E9%86%92%E5%B8%82%E6%B0%91%E5%AE%9A%E6%9C%9F%E6%B8%85%E6%B4%97%E5%BA%A7%E5%BB%81-%E4%BF%9D%E6%8C%81%E6%B4%97%E6%89%8B%E9%96%93%E7%A9%BA%E6%B0%A3%E6%B5%81%E9%80%9A
Title[Wuhan Pneumonia] City University: Flushing water drops splash up to one meter from the toilet board
DescriptionA team led by Lai Zhiqiang, deputy head of the Department of Architecture and Civil Engineering of CityU Institute of Technology, found in the study that water droplets generated from flushing can splash up to one meter away from the toilet board, and each flush can generate 14,000 To 80,000 drops of water. The team reminded that covering the toilet board when flushing alone is not enough to prevent spreading of bacteria.
Persons
Media name/outletThe Limited Times
Media typeWeb
Producer/AuthorZhang Jiamin
Date13/02/20
Linkhttps://newsrnd.com/news/2020-02-13--%5Bwuhan-pneumonia%5D-city-university--flushing-water-drops-splash-up-to-one-meter-from-the-toilet-board.SktFhwMXL.html
Title【武漢肺炎】城大：沖廁水珠可濺一米高　 蓋廁板不足防疫　須定期刷洗廁缸
Description城大工學院建築學及士木工程學系團隊今日（13日）表示，經研究發現，沖廁過程中，細菌會隨水珠濺起至最高離廁板一米位置，亦會隨氣流擴散。團隊提醒，單靠沖廁時蓋上廁板不足杜絕細菌散播，必須定期以1:49的稀釋家用漂白水刷洗廁缸，及以1:99的稀釋家用漂白水清潔洗手間各處。
Persons
Media name/outletthestandnews.com
PlaceHong Kong
Media typeWeb
Date13/02/20
Title【防疫攻略】專家：蓋廁板沖廁未杜絕細菌散播
Description城大工學院建築學及土木工程學系副系主任賴志強解釋，沖廁過程中，細菌會隨水珠飛濺污染洗手間及隨霧化過程飄浮於空氣中，形成「氣溶膠」。
Persons
Media name/outletam730
PlaceHong Kong
Date13/02/20
Linkhttps://www.am730.com.hk/news/%E6%96%B0%E8%81%9E/%E3%80%90%E9%98%B2%E7%96%AB%E6%94%BB%E7%95%A5%E3%80%91%E5%B0%88%E5%AE%B6%EF%BC%9A%E8%93%8B%E5%BB%81%E6%9D%BF%E6%B2%96%E5%BB%81%E6%9C%AA%E8%83%BD%E6%9D%9C%E7%B5%95%E7%B4%B0%E8%8F%8C%E6%95%A3%E6%92%AD-207271
Title新冠肺炎|港專家：沖廁水珠可濺起1米高或播菌 市民須定期刷洗廁缸
Description香港城市大學工學院建築學及土木工程學系副主任賴志強表示，沖廁產生的水珠最高可濺起至離廁板一米的位置，令細菌或病毒有機會隨氣流擴散，市民必須定期刷洗廁缸。
Persons
Media name/outlet文匯快訊
PlaceHong Kong
Media typeWeb
Date13/02/20
Linknews.wenweipo.com/2020/02/13/IN2002130047.htm
Title新冠肺炎｜港專家：沖廁水珠可濺起1米高或播菌 市民須定期刷洗廁缸
Description新型冠狀病毒疫情持續擴散，保持洗手間衛生是預防細菌和病毒擴散的重要一環。香港城市大學工學院建築學及土木工程學系副主任賴志強表示，沖廁產生的水珠最高可濺起至離廁板一米的位置，令細菌或病毒有機會隨氣流擴散，市民必須定期刷洗廁缸。
Persons
Media name/outletTakungpao
PlaceHong Kong
Media typeWeb
Date13/02/20
Linkwww.takungpao.com.hk/hongkong/text/2020/0213/415596.html

Media contributions

Title‘Pathogens linger in toilet for hours’
DescriptionAlvin Lai Chi-keung, associate head of the department who led the year-long study, said while water droplets created in flushing might rise up to a metre if the toilet was not covered, international studies suggested polluted particles may still sneak through the gaps between the toilet and its lid, even if it was lowered before flushing. Eric Lee Wai-ming, an associate professor at the department, suggested applying a half flush if possible to reduce the amount of droplets produced in flushing.
Persons
Media name/outletInter News Cast US
PlaceHong Kong
Media typeWeb
Producer/AuthorK.Y. Cheng
Date16/02/20