Evaluation of temporal and spatial variations of BTEX and styrene in Tabriz urban air and health risk assessment

Abstract

Volatile organic compounds (VOCs) are common air pollutants that are primarily emitted by motor vehicles and through industrial activity and can have a significant impact on air quality and adversely affect human health. The aim of this study was to characterize benzene, toluene, xylenes and styrene (BTXS) in the ambient air of Tabriz, a city in northwestern Iran, and describe their spatiotemporal variations, ozone formation potential (OFP) and provide a health risk assessment. The measured concentrations of BTXS ranged from 0.46 to 69.32 µg/m3. Diurnal variation showed a significant difference between the morning and evening concentrations, in which the evening values were primarily higher. Spatial analysis showed that the maximum levels of BTXS occurred in the industrial zone. The estimated OFP values ranged from 26 to 418 µg/m3 and 16 to 725 µg/m3 in winter and summer, respectively. In addition, the mean T/B ratio was 1.84, indicating the combustion of fuel in motor vehicles as the main source of VOCs. The hazard ratio of target pollutants was lower than the limits recommended by the USEPA and WHO; however, the estimated lifetime cancer risk for benzene was 7.82 × 10-6, which exceeds the threshold of 1 × 10-6.