Phase distribution and risk assessment of PAHs in ambient air of Hamadan, Iran.

In the present study, both gaseous and particulate (PM with dae <2.5 µm) phases of polycyclic aromatic hydrocarbons (PAHs) were measured in the ambient air of Hamadan city, Iran. For this reason, two low-volume samplers equipped with glass fiber filters were used for sampling of particulate phase (N = 30) and XAD-2 sorbent tubes were applied for sampling gaseous phase of PAHs (N = 30). The sampling was conducted during warm and cold seasons in 2019. The average of cold/warm season ratios for ΣPAH and PM concentrations were 1.14 and 0.62, respectively. Summed PAHs concentration were determined to be in the range 0.008-59.46 (mean: 11.61) ng/m and 0.05-40.83 (mean: 10.22) ng/m for the cold and warm seasons, respectively. A negative Pearson correlation coefficient was obtained for wind speed and relative humidity. The average Benzo (a) Pyrene equivalent carcinogenic (BaP) levels in the cold season were lower than the maximum permissible risk level of 1 ng/m for BaP. The BaP toxicity equivalency (ΣBaP) and BaP mutagenicity equivalency (ΣBaP) appeared to be significantly higher in the cold season (averaging 0.35 and 1.65 ng/m, respectively) than those in warm season. Health risk assessment was performed for children and adults based on BaP, inhalation cancer risk. The diagnostic ratios of individual PAHs concentration showed that the significant sources of PAH emissions may be related to light duty vehicles (LDVs) in Hamadan. Although, some other sources such as pyrogenic source and petrol combustion were also suggested.