Thermal exposure across age groups: Social, spatial, and temporal inequalities in Nanjing, China

Abstract

As climate change and urban expansion intensify, unequal thermal exposure among different age groups has emerged as a significant health concern. Existing studies on age groups' thermal exposures have notable gaps: (1) the lack of comparison between summer and winter seasons; and (2) insufficient understanding of how metropolitan location (e.g., inner-city, suburban) and built environment characteristics (e.g., land cover, morphology) influence thermal exposure. To bridge these gaps, this study analyzes Land Surface Temperature (LST) exposure of children (0–14 years), adults (15–59 years), and senior citizens (60+ years) across Nanjing's neighborhoods during the summer and winter of 2020. The study shows that variations in metropolitan locations correspond to demographic differences and built environment characteristics such as impervious surfaces, vegetation, and building heights, leading to social, spatial and temporal LST inequalities among age groups. For instance, inner-city areas exhibited higher thermal exposure risk in both summer and winter, particularly affecting senior citizens. In contrast, adults experienced relatively moderate LST exposure, likely due to their suburban residence. Random forest model results indicate that built environment characteristics significantly and seasonally influence LST. In summer, higher proportions of impervious surfaces and lower levels of vegetation contribute to elevated LST in inner-city areas. Conversely, in winter, greater impervious surface areas, taller buildings, and greater distance from industrial zones correlate with lower temperatures in these regions. This study ultimately highlights the need for policy interventions to mitigate thermal exposure inequities among different age groups.