Investigation of ambient BTEX concentrations along a bus rapid transit route in Tabriz: Spatio-temporal variations and health risk assessment

Abstract

Urgent actions are imperative to assess ambient BTEX concentration in urban areas and increase awareness of the significant health risks linked to exposure to these volatile compounds. This study examines the spatiotemporal variations of BTEX concentration in BRT stations and provides a health risk assessment in Tabriz, located in the northwest of Iran. We collected samples repeatedly from four BRT stations and three areas between stations ( N = 86). The mixture BTEX compounds had average concentrations ranging from 6.7 to 52.9 mu g/m 3 , with the highest concentration belonging to o-xylene. Additionally, the average ratios of toluene/benzene, m-xylene/ benzene, and o-xylene/benzene were 2.4, 2.3, and 3.0, respectively. Total BTEX concentrations were significantly higher in BRT stations than areas between stations. Furthermore, the concentration of total BTEX doubled in the evening compared to the morning. Although the maximum concentrations of BTEX were recorded in winter, there were no significant seasonal differences. The lifetime cancer risk (LCR) of benzene exposure was 1.07 x 10 -7 and 1.52 x 10 -5 for passengers and residents located in the vicinity of the BRT lane, respectively. In conclusion, this study suggests that emissions from BRT buses are one of the main contributors to BTEX in Tabriz.