Air quality impacts of open-plan cooking in tiny substandard homes in Hong Kong

Abstract

This study investigated the air quality impacts of open-plan cooking in subdivided units (SDUs), which is a type of substandard housing in Hong Kong. About 210,000 persons (2.9% of the population) currently live in such tiny and poorly ventilated dwellings. With a median floor area of merely 9.3 m2 (100 ft2), most SDUs do not have space for a partitioned kitchen to contain the air pollutants generated by cooking, posing a serious indoor air quality issue that affects all members living in the SDU. The CO, CO2, PM10, PM2.5 and VOC concentrations in seven SDUs were monitored for 72 h to capture the emissions from their routine cooking activities. All SDUs used induction or electric cookers and 32 cooking events were recorded. Under natural ventilation, the mean PM10 and PM2.5 concentrations during cooking were 36 and 20 μg/m3, which were 136% and 82% higher than the pre-cooking levels respectively. Their mean maximum concentrations reached 1644 and 749 μg/m3 respectively. The mean PM10 concentration exceeded the local guideline (excellent class) by 1.82 times. However, cooking activities did not contribute to substantial changes in CO, CO2 and VOC concentrations. When the air conditioner was turned on to relieve the heat from cooking, it took 90 min for air pollution to return to pre-cooking levels after a cooking event because of poor ventilation, which significantly increased the occupants’ exposure to the cloistered air pollutants. Lacking a partitioned kitchen and effective ventilation in SDUs may pose chronic health threats to their occupants, particularly children.