Air and hygiene quality in crowded housing environments – a case study of subdivided units in Hong Kong

The purpose of this study is to explore the environmental quality and hygiene in crowded living environments, subdivided units in Hong Kong. Subdivided units are an emerging form of housing environment for the urban poor. It is hypothesised that subdivided unit residents have a higher risk of exposure to poor hygiene conditions but no measurement has ever been taken to test this hypothesis. Twenty questionnaires and environmental assessments were conducted. Dominant bacterial species were identified as Micrococcus luteus and Staphylococcus spp., and the microbial counts were correlated with building, occupants and environmental parameters. Driven by the high bacterial counts and poor hygiene observation, eight subdivided units were selected for endotoxin, glucan and allergen analysis in bed and floor dust. Total airborne bacterial counts and endotoxin and glucan in dust were found at very high levels in some subdivided units, while unexpectedly, the allergen and mould levels were low. In crowded environments the skin bacteria may mislead the environmental and atmospheric bacterial contamination. Outdoor microbial pollution and deteriorated building conditions can be the main source of indoor contamination. ‘Good’ or ‘Excellent’ class of bacterial counts satisfying the Indoor Air Quality Objective does not guarantee a low endotoxin and glucan level.