This study examines the population exposure to multiple air pollutants and their compound episodes in Europe from 2003 to 2019. Using Quantile LightGBM (QLG) machine learning models, the researchers analyzed daily ambient concentrations of PM2.5, PM10, NO2, and O3 at a 0.1-degree resolution across 1426 contiguous regions in 35 European countries, representing 543 million people. The findings show that PM10 levels declined by 2.72% annually, followed by NO2 (2.45%) and PM2.5 (1.72%). In contrast, O3 levels increased by 0.58% in southern Europe, leading to more unclean air days. Despite improvements in air quality, 86.3% of Europeans still experience at least one compound event day per year, particularly for PM2.5-NO2 and PM2.5-O3. The study highlights the need for targeted measures to address specific pollutants and their compound events, especially in the context of rising temperatures. The results provide valuable insights for environmental health assessments and policymaking to mitigate the health risks associated with air pollution in Europe.This study examines the population exposure to multiple air pollutants and their compound episodes in Europe from 2003 to 2019. Using Quantile LightGBM (QLG) machine learning models, the researchers analyzed daily ambient concentrations of PM2.5, PM10, NO2, and O3 at a 0.1-degree resolution across 1426 contiguous regions in 35 European countries, representing 543 million people. The findings show that PM10 levels declined by 2.72% annually, followed by NO2 (2.45%) and PM2.5 (1.72%). In contrast, O3 levels increased by 0.58% in southern Europe, leading to more unclean air days. Despite improvements in air quality, 86.3% of Europeans still experience at least one compound event day per year, particularly for PM2.5-NO2 and PM2.5-O3. The study highlights the need for targeted measures to address specific pollutants and their compound events, especially in the context of rising temperatures. The results provide valuable insights for environmental health assessments and policymaking to mitigate the health risks associated with air pollution in Europe.