Abstract
Extreme heat events are becoming more frequent, intense, and prolonged under global climate change, with urban areas particularly affected by the urban heat island effect. Rapid urbanisation has transformed city environments through three interrelated features—high-rise morphology, dense building clusters with overcrowded housing, and socioeconomic disparities—compounding heat-health risks. While previous studies have examined these factors individually, few have assessed their combined influence at the building level. This study developed a heat-health risk index for a deprived Hong Kong neighbourhood, integrating hazard, exposure, and vulnerability. Heat hazard was estimated using complete urban surface temperature (CST), the aggregated thermal load across all building surfaces, capturing three-dimensional heat exchange in dense urban environments, derived from Landsat 8 imagery; while the latter two domains were derived from local data from the District Office and population census. Among 1277 buildings analyzed, the heat health risk index ranged from 0.163 to 0.661 during the day and 0.152 to 0.845 at night, with the highest risk concentrated in urban cores where overcrowdedness exceeded 400% and >25% of households were low-income. Our findings enable targeted adaptation measures such as prioritising cooling access and outreach for high-risk buildings, supporting resilience planning in high-density cities.
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Data availability
The complete urban surface temperature (CST) estimates used in this study are available from the corresponding author upon reasonable request. Due to privacy and security considerations, raw building-level data cannot be shared openly, but aggregated data necessary to interpret and replicate the findings will be provided upon request. Data on the socioeconomic characteristics at the TPU level are publicly available on the website of the Census and Statistics Department at https://www.census2021.gov.hk/en/index.html.
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Acknowledgements
The authors thank District Office of the Sham Shui Po district for their effort in collecting the overcrowdedness data. The authors also acknowledge the partial support by the CUHK Vice-Chancellor's One-off Discretionary Fund (grant number: 136604080) and Start-up Grant, City University of Hong Kong (Project: Estimations of Urban Compactness and Neighbourhood-level Health Burdens in High-density Cities, Code: 7200792).
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E.T.C.L. and H.C.H. conceived the study design. H.C.H. performed data collection and analyses. E.T.C.L. interpreted results from analyses. P.W. provided professional comments on GIS applications. K.L. provided professional comments on climatic implications. J.W. provided professional comments on health implications. E.T.C.L. wrote the draft of manuscript. E.T.C.L. and H.C.H. revised the manuscript. All authors comments on the revised manuscript and approved the final manuscript for submission.
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Lai, E.TC., Ho, H.C., Wong, P.PY. et al. Building level heat-health risk assessment in a three-dimensional and deprived built environment in Hong Kong. npj Urban Sustain (2026). https://doi.org/10.1038/s42949-025-00332-7
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DOI: https://doi.org/10.1038/s42949-025-00332-7
