Characterisation of PM2.5 – bound PAHs in outdoor air of Karaj megacity: the effect of meteorological factors

Urbanization and industrialization of cities have resulted in elevated concentration of particulate matters and the compounds contained in them in the air. From among the compounds present in the air, polycyclic aromatic hydrocarbons are very important because of their carcinogenicity and potential hazardous effects on the environment. In this research, through active air sampling in 17 points of the air of the most industrial city of Iran, we dealt with the analysis, source identification, and risk assessment of PAHs within a one-year period. The air samples were taken using PTFE filter based on NIOSH and EPA-TO/13A guidelines and SKC pump that average of flow rate of 3 L/min on the PMI2.5 was performed. In order to achieve a logical outcome for decision-making on the policies of the studied metropolis to mitigate air pollution, meteorological parameters were also measured, and the effect of each of them was tested on PAHs using SPSS software. The results indicated that the concentration of PM2.5 particles within the one-year period was higher than the value set by WHO and EPA guidelines. On the other hand, across all of the measurement stations, PAHs compounds were observed, suggesting that PAHs are a common pollutant across the city of Karaj. The sigma PAHs concentration within one year was 8.72-16.11 ng/m3. Benzo (a) pyrene (BaP), one of the dangerous hydrocarbons to the human health, claimed an above standard concentration among the other compounds. It was also found that factors such as transport fleet, car fule, diesel car, burning of biomass and coal are sources of PAHs. Also, PAHs had a direct relationship with temperature and pressure. Humidity and wind speed had a negative and poor correlation with PAHs. Finally, the results of incremental lifetime cancer risk (ILCR) estimations indicated that the carcinogenicity risk values in the studied region are acceptable.