The present paper introduces a novel approach for investigating the synergistic effect of thermal stress (maximum apparent temperature, Tapp_max) and air pollutant concentrations (PM₁₀, NO₂, and O₃) on daily mortality in Thessaloniki, Greece. We examine Tapp_max effects on all-cause mortality, analyzing variations at low, medium, and high levels of pollutants using a prototype modeling framework capable of accounting for multiple lagged exposures. We find J-shaped Tapp_max–mortality relationships with increasing pollutant levels, indicating that high thermal stress levels (Tapp_max > 33 °C) favor pollution build-up, subsequently increasing mortality. Heat effects surpass cold effects, with PM₁₀, NO₂, and O₃ associated with 47.7%, 38.7%, and 32% increases in heat-related mortality, respectively, compared to 13.6%, 19.2%, and 2.1% increases in cold-related mortality. Detailed temporal lag structure analysis, conceptualized and conducted for the first time in the present study, unravels different dose-response patterns for the various predictors. PM₁₀ shows the highest mortality risk on the exposure day, whereas NO₂ risk is more pronounced a week after exposure. The temporal pattern of O₃ differs significantly, as the risk increases with lag until a threshold, followed by decrease. These outcomes underline the importance of holistic planning for public health mitigation and adaptation measures, especially in cities.

Parliari D., T. Economou, C. Giannaros, J. Kushta, D. Melas, A. Matzarakis, J. Lelieveld

Urban Climate 56 (2024): 102088,2024