Seasonal occurrence, source apportionment, and cancer risk assessment of PAHs in the second largest international holy metropolitan: Mashhad, Iran.

Street dust resuspension is one of the main sources of particulate matter with impacts on air quality, health, and climate. This research was aimed to determine the concentration, source, and health risk of polycyclic aromatic hydrocarbons (PAHs) in street dust of Mashhad city. To this end, USEPA-regulated 16 PAHs were measured in 84 dust samples using gas chromatography coupled to mass spectrometry (GC-MS). The source of Σ16PAHs was identified using diagnostic ratios (DRs), positive matrix factorization (PMF), and principal component analysis (PCA). The measured Σ16PAHs demonstrated different spatial concentrations (from 1,005 to 9,138.96 μg kg) and showed higher levels in summer (1,206.21-9,138.96 μg kg), although 4-ring PAHs exhibited maximum levels in both summer and winter. The findings revealed that the dust-deposited PAHs are predominantly emitted through combustion of fossil fuels (such as diesel and gasoline) and natural gas. The total incremental lifetime cancer risk (ILCR) was assessed by considering three possible exposure routes separately for children and adults and calculated carcinogenic risk values of 2.24E-06 and 2.14E-06, respectively. ILCR is above the baseline value (1.0E-06) for children and adults in both seasons.