2017 No https://www.sciencedirect.com/science/article/abs/pii/S100107421730966X?via%3Dihub Rogula-Kozlowska, Wioletta Europe Exposure Study Particulate Matter (PM) Indoor air Submicrometer particles Health hazard Polycyclic aromatic hydrocarbons (PAHS) Benzo(a)pyrene The indoor and outdoor concentrations of individual PAH in Gliwice were correlated, in Warsaw - they were not. Most probably, the lack of the correlations in Warsaw was due to the existence of an unidentified indoor source of gaseous PAH enriching PM1 in phenanthrene, fluorene, and pyrene. Although the ambient concentrations of PM1-bound PAH were low compared to the ones observed earlier at both sites, they were much higher than in other urbanized European areas. However, because of low mass share of heavy PAH in ΣPAH, the various indicators of the health hazard from the 16 PAH mixture were low compared to other regions.