Atmospheric Pollutants in an Iranian Industrial Metropolis: Spatiotemporal Analyses Associated with Health Risks and Photochemical Pollutions

The present research addressed the spatiotemporal variations in such pollutants as benzene, toluene, ethylbenzene, and xylene (BTEX) in the atmosphere of Arak, a city in central Iran. Also, the health risk evaluation and ozone formation potential (OFP) were assessed.

The air samples were collected and evaluated through gas chromatography-mass spectrometry (GC-MS) over a one-year period.

The overall BTEX levels ranged between 2.7-256 µgr/m3. The seasonal levels showed considerable variations among benzene, toluene, ethylbenzene, and xylene, and the levels of total BTEX. Comparison of the air samples between morning and evening for the concentrations of BTEX components revealed that the values were higher in the evening; however, there were no significant differences observed among them. The spatial map indicated that the maximal concentration of BTEX components occurred in high-traffic zones of the city. The maximal and minimal OFP levels were recorded in the summer (254.8 µgr/m3) and autumn (64.9 µgr/m3), respectively. The average toluene/benzene (T/B) ratio found to be 4.3, indicating the fuel combustion was the major source of atmospheric BTEX from vehicles.

The measured cancer risk value for benzene (6.68×10-5) was higher than those recommended by the WHO and U.S. Environmental Protection Agency. Therefore, exposure to atmospheric benzene had a carcinogenic risk for Arak inhabitants.  This needs further investigation in future studies. The acceptable hazard quotients (<1) for all BTEX species posed minimal risks of non-cancer diseases for the population.