Facing the upper-tail risks for health due to exposure to heat and air pollution under a warming climate

Climate change is fundamentally reshaping environmental health risks in cities worldwide. Heat and air pollution are increasingly coupled, creating compound exposures whose health impacts exceed those of individual stressors. These coupled conditions have shifted health risks towards the upper tail of the distribution, producing sharp increases in short-term mortality and acute morbidity that are often overlooked by assessments centered on average exposures. Such tail risks for environmental health are unevenly distributed across populations and urban settings, reflecting structural inequalities in vulnerability, environmental exposure and adaptive capacity. Conventional frameworks that treat heat and air pollution independently are therefore insufficient for capturing the full scope of climate-sensitive health burdens. Addressing these emerging risks requires a reframing of health risk perception, greater emphasis on extreme events and compound exposures, and more integrated public health and urban governance approaches. Recognizing and characterizing upper tail risks for health is essential for improving preparedness, reducing inequalities and safeguarding public wellbeing under a warming climate.