Profiling aerosol Polycyclic Aromatic Compounds (PACs) in a severely polluted European city: A comprehensive assessment of the residential biomass burning impact on atmospheric toxicity.

Fine aerosol Polycyclic Aromatic Hydrocarbons (PAHs), Oxygenated Polycyclic Aromatic Hydrocarbons (OPAHs) and other PM2.5 components were quantified in Ioannina, a Southeastern European city facing severe air quality degradation due to residential biomass burning (BB). Polycyclic Aromatic Compound (PAC) seasonal means were extremely enhanced in winter compared to summer (by 98 and 88 times for PAHs and OPAHs, respectively). Benzo(a)pyrene (BaP) registered a 347-fold winter increase, and its estimated annual mean was 2.4 times higher than the EU standard. Medium- and high-molecular weight PAC species correlated well with PM2.5 DTTv activity (R2: 0.48 and 0.54, respectively), suggesting also their significant non-carcinogenic potential. These PAC groups were strongly associated with methanol- and water-soluble Brown Carbon absorption (R2 > 0.7). Source apportionment by Positive Matrix Factorization (PMF) on the speciation dataset indicated BB as the major aerosol source, contributing > 80 % to average Σ-PAC concentrations and their carcinogenic potential during the study period. The PAC carcinogenic risk assessment highlighted the importance of considering the inclusion of not only legacy PAHs but also emerging species with very high estimated toxicity, such as Benzo(c)fluorene and Dibenzo-pyrenes. Observed concentrations were alarming, posing substantial short- and especially long-term risks. Therefore, there is an urgent need to regulate residential BB in Ioannina and similar urban environments in SE Europe.