Spatial Heterogeneity of Heatwave and Air Pollution Effects on Cause-Specific Mortality Across Greece

Climate change is intensifying heatwaves, wildfire activity, and dust transport in the Mediterranean region, yet their combined impacts on mortality remain poorly characterized. Associations between heatwaves, ambient air pollution, source-specific particulate matter, and cardiovascular and respiratory mortality were investigated across Greece at the NUTS2 regional level. Monthly mortality counts for 2014–2022 were analyzed using generalized linear Poisson regression models adjusted for region, year, age group, sex, relative humidity, and population size. Analyses included conventional pollutants (PM2.5, PM10, and O3), wildfire-related particulate matter, and Saharan dust-related particulate matter, while multiplicative interaction terms were used to evaluate modification of pollution effects during heatwave conditions. All major pollutants were positively associated with cardiovascular and respiratory mortality, with the strongest and most consistent effects observed for wildfire-related particulate matter. Heatwave–pollution interaction terms were generally weak, indicating that the combined effects of heat and air pollution were predominantly additive rather than strongly synergistic at the national scale. Spatial analyses revealed substantial regional heterogeneity, with stronger associations identified in parts of northern mainland Greece and selected urbanized regions. These findings highlight the importance of considering wildfire smoke and desert dust separately from conventional air pollutants and support the development of integrated climate-health adaptation strategies in Greece and other climate-vulnerable Mediterranean regions.