Abstract
Abstract Exposure to extreme heat and air pollution brings significant risks to human health and well-being. Urbanization can increase local exposure to high temperature and air pollution through the urban heat and air pollution islands (UHI and UPI), respectively. Previous studies have mainly focused on heat or air pollution separately, with limited consideration of the combined impacts on health in global cities. In this study, we investigate the daily 1 km compound patterns of UHI and UPI using the satellite-based air temperature and PM2.5 datasets and their combined impacts on mortality among 327 global cities from 2003 to 2020 with the exposure–response functions and structural equation modeling. Global South cities experienced 1.4 times higher compound frequency of UHI and UPI compared to Global North cities, whereas Global North exhibited greater compound intensity. Global South cities experienced 625 times, well over two orders of magnitude, higher compound exposure to extreme heat and air pollution. By contrast, Global North cities showed the higher relative risks to high temperature-related mortality linked to elevated compound frequency/intensity of UHI and UPI levels. These findings underscore the urgent need for region-specific urban heat mitigation strategies, i.e., reducing absolute background exposures in the Global South and managing relative UHI and UPI amplification in the Global North, as tailored interventions that are critical for lowering mortality risks and fostering healthier, more equitable cities worldwide.