We investigate the multi-year trends in aerosol pollution over Poland. We show that, while the local sources might have dominated in the past decades, there are no statistically important trends observed in the last twenty years which it difficult to unambiguously determine the types and sources of the currently observed aerosols. We propose an innovative method for determination of dominant source regions from which the identified aerosol types originated based on statistical analysis of air-mass backward trajectories. The method is then expanded with an additional analysis focused on the study of changes in the aerosol optical parameters observed during transport that allows for the determination of additional source regions.