The recent economic crisis in Greece resulted in a serious wintertime air pollution episode in Thessaloniki. This air quality deterioration was mostly due to the increased price of fuel oil, conventionally used as a source of energy for domestic heating, which encouraged the residents to burn the less expensive wood/biomass during the cold season. A wintertime sampling campaign for fine particles (PM2.5) was conducted in Thessaloniki during the winters of 2012 and 2013 in an effort to quantify the extent to which the ambient air was impacted by the increased wood smoke emissions. The results indicated a 30% increase in the PM2.5 mass concentration as well as a 2-5-fold increase in the concentration of wood smoke tracers, including potassium, levoglucosan, mannosan, and galactosan. The concentrations of fuel oil tracers (e.g., Ni and V), on the other hand, declined by 20-30% during 2013 compared with 2012. Moreover, a distinct diurnal variation was observed for wood smoke tracers, with significantly higher concentrations in the evening period compared with the morning. Correlation analysis indicated a strong association between reactive oxygen species (ROS) activity and the concentrations of levoglucosan, galactosan, and potassium, underscoring the potential impact of wood smoke on PM-induced toxicity during the winter months in Thessaloniki.

Thirteen particle-phase PAHs, including nine >4-ring congeners [Benz[a]anthracene (BaAn), Chrysene (Chry), Benzo[b]fluoranthene (BbF), Benzo[k]fluoranthene (BkF), Benzo[e]pyrene (BeP), Benzo[a]pyrene (BaP), Dibenzo[a,h]anthracene (dBaAn), Benzo[g,h,i]perylene (BghiPe), Indeno(1,2,3-c,d)pyrene (IP)], listed by IARC (International Agency for Research on Cancer) as class 1, class 2A, and 2B carcinogens, plus four ≤ 4-ring congeners [Phenanthrene (Ph), Anthracene (An), Fluoranthene (Fl), Pyrene (Py)], were concurrently measured in inhalable and respirable particle fractions (PM10 and PM2.5) at a heavy-traffic and an urban background site in Thessaloniki, northern Greece, during the warm and the cold period of the year. Carcinogenic and mutagenic potencies of the PAH-bearing particles were calculated, and the inhalation cancer risk (ICR) for local population was estimated. Finally, Chemical Mass Balance (CMB) modeling was employed for the source apportionment of ambient PAH levels and the estimated lung cancer risk. Resulted inhalation cancer risk during winter was found to be equivalent in the city center and the urban background area suggesting that residential wood burning may offset the benefits from minor traffic emissions.