Sensitivity of BTEX pollution and health effects to traffic restrictions: A case study in an urban center of Tehran, Iran

•Major sources of BTEX are traffic, bus, and stationary point source emissions.•Mean level of BTEX on non-working days significantly exceeds that of working-days.•Toluene to benzene ratios in bus cabins and stations ranged from 2.84 to 5.55.•Lifetime cancer risk for benzene in this study ranged from 3.08 × 10−5 to 7.07×10−5.•Hazard quotient of all studied pollutants in bus cabins/stations is less than 1. This study reports a spatiotemporal characterization of BTEX concentrations in urban air of hotspots in Iran, specifically at the Bus Rapid Transit system in Tehran Traffic Zone. The average concentrations ± (SD) of benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene in bus cabins versus bus stations were 8.75±4.21 vs. 8.74±2.61, 24.33±19.19 vs. 32.77 ± 13.59, 25.90 ± 10.63 vs. 28.74 ± 6.41, 43.71 ± 21.88 vs. 45.19 ± 15.60, and 33.46 ± 14.88 vs. 39.46 ± 10.57 μg/m3, respectively. The toluene to benzene ratios in bus cabins and bus stations ranged from 2.84 to 2.95 and from 2.20 to 5.55, respectively, indicating that traffic, bus, and stationary point source emissions were the primary source of BTEX. The average lifetime cancer risks (LTCRs) of benzene for bus cabins and bus stations along various routes ranged from 3.08 × 10−5 to 7.07×10−5 and from 4.58 × 10−5 to 5.42 × 10−5, respectively, surpassing guideline values by EPA and WHO. Target pollutant concentrations increased on non-working days due to fewer traffic restrictions imposed by the city allowing people to travel without restrictions with their own vehicles. Hence, enforcing traffic restrictions on working and non-working days could reduce BTEX pollution, with implications for better public health as a result of reduced exposure to BTEX and associated non-carcinogenic and carcinogenic effects.