Why are the Subdivided Unit Residents Disproportionately Burdened under Escalating Extreme Weather in Hong Kong?

In its June weather review this year, the Hong Kong Observatory (HKO) mentioned that at the beginning of the month, some areas recorded rainfall reaching “severe rainstorm” levels and described the first half of the year as “abnormally warm.”. Extreme weather conditions have become increasingly frequent in the city. These weather patterns disproportionately impact the residents of subdivided units (SDUs) due to their inadequate living conditions. According to the latest “Long-term Housing Strategy,” a total of 127,500 households or 4.8% of Hong Kong households were classified as living in inadequate private housing by 2022. Clean Air Network continues to place emphasis on indoor air quality, as numerous scientific studies have indicated that long-term residence in spaces with substandard air quality in subdivided units can lead to physical and mental health issues, and local extreme weather events may further exacerbate the situation.

Extreme Heat Poses Health Risks for Subdivided Unit Residents

Hong Kong has experienced escalating temperatures, with the HKO recording an increased number of hot weather days [1]. Some SDUs have very few or even no windows, resulting in limited indoor air circulation, high humidity, and temperatures often exceeding 30°C. Poor ventilation, combined with extreme heat and humidity, can easily increase residents’ heat stress (i.e., the stress caused by heat on the human body), posing significant health risks. This makes them more susceptible to heat-related illnesses such as heatstroke and dehydration, especially among vulnerable groups like the elderly and children. Although air conditioning can alleviate some of the heat, high electricity costs and overcharging by landlords discourage its use, leaving residents to endure unhealthy living conditions.


The inadequate ventilation in SDUs is exacerbated during extreme weather, leading to poor indoor air quality. The lack of windows and proper airflow systems traps pollutants including particulate matters inside the units. Under extreme heat, the accelerated formation of ozone further compounds the already unsafe air quality. Data collected by the Hong Kong Red Cross in 2023 from 33 SDUs revealed that over half of the households had an average indoor temperature of 30°C and a humidity level of 70%. Additionally, PM2.5 levels were four times the WHO standard, and PM10 levels were six times higher. Poor indoor air quality can cause respiratory issues, allergies, and emotional distress among the residents.


SDUs are sometimes poorly constructed, making them susceptible to damage from typhoons and heavy rainfall. Water damage from rainfall and humid living conditions can result in mould growth, which poses severe respiratory health risks, such as asthma and other respiratory conditions, particularly in poorly ventilated SDUs.

Government Action Needed to Set Minimum Standards for Subdivided Unit Livability

The government’s “Task Force on Subdivided Units” is planning to set “Minimum Standards for Subdivided Unit Living Environment”, which proposed to focus on building safety, fire, and sanitation requirements, as well as living areas. CAN welcomes these measures and suggested that the related “standards” should encompass aspects including indoor air quality, and ventilation systems to ensure a hygienic living environment in our recent submission.


As extreme weather events become increasingly frequent and severe, the need for decisive government action to protect the well-being of subdivided unit residents has never been more urgent. Together, we can drive changes to build a healthier, safer, and more resilient living environment in Hong Kong.


Reference
[1] The Hong Kong Observatory. The Weather of June 2024 – A hot and cloudier June. Retrieved from https://www.weather.gov.hk/en/wxinfo/pastwx/mws2024/mws202406.htm
[2] According to HKO, there were 54 very hot days, 56 hot nights, and 4 extremely hot days in 2023. Retrieved from The Hong Kong Observatory. The Year’s Weather – 2023. https://www.hko.gov.hk/en/wxinfo/pastwx/2023/ywx2023.htm