Dirty air in subdivided flats Study: bacteria count is six times the acceptable limit

RESIDENTS of subdivided flats in Mong Kok (旺角) and Kwai Chung (葵涌) are exposed to six times the local standard bacterial count, a study shows.

The joint study was carried out by Hong Kong Baptist University (香港浸會大學) and the World Green Organization (世界綠色組織).

Air samples were taken from 20 subdivided units in four districts from July to September last year. They included Mong Kok, Kwun Tong (觀塘), Tsuen Wan (荃灣) and Kwai Chung.

According to the Hong Kong Indoor Air Quality Index (香港室內空氣質素指標), an indoor bacterial count of less than 1,000 colony-forming units (CFU) is considered acceptable.

But the survey showed that the highest unit of bacteria measured in fl ats in Mong Kok and Kwai Chung exceeded 6,500 CFU. It is three times higher than recorded in a similar survey done in 2002. Two flats in Tsuen Wan recorded 2,600 CFU and 2,150 CFU.

The two flats recording high CFU are located on the first floor with poor air ventilation. The hygiene quality of the surrounding environment and building conditions are also poor.

“We recommend residents keep their windows closed if sanitary conditions outside are worse,” said Lai Ka-man (賴嘉雯), an associate professor from HKBU Department of Biology (生物系). She said bacteria may come from street alleys outside the windows.