On the nature and health impacts of BTEX in a populated middle eastern city: Tehran, Iran

This study describes a spatio-temporal characterization of concentrations of BTEX in ambient air of four hot spots (bus terminals) in the megacity of Tehran. Monte Carlo simulations were performed to evaluate cancer risk and non-cancer risk owing to BTEX exposure in three age groups (<6, 6 to <21 and 21 to <81 years). The average toluene to benzene ratios for the four intercity bus terminals were 2.63 (summer) and 2.88 (winter). Furthermore, the mean xylenes to benzene and ethylbenzene to benzene ratios in the two seasons for all stations ranged from 3.33 to 4.40 (summer) and 2.13�2.80 (winter), respectively. There was insignificant difference in BTEX levels between working and non-working days owing to the lack of change in vehicular traffic during the full week. Factors promoting BTEX formation in the study region were fuel evaporation, gas stations, diesel bus emissions, and a lack of hydroxyl radicals (radOH) for reacting with the target compounds. Calculations suggested that cancer risk for benzene and ethylbenzene in three age groups at the four bus terminals exceeded values recommended by U. S. EPA. In addition, the hazard quotient for BTEX in both seasons for different age groups ranged between 1.23 � 10 �5 and 3.58 � 10 �1 , values of which were lower than reference levels. Carcinogenic emissions such as with benzene and ethylbenzene discharged by bus terminals impact the growing population in the study region, which requires additional action to reduce health effects. © 2019 Turkish National Committee for Air Pollution Research and Contro

On the nature and health impacts of BTEX in a populated middle eastern city: Tehran, Iran

This study describes a spatio-temporal characterization of concentrations of BTEX in ambient air of four hot spots (bus terminals) in the megacity of Tehran. Monte Carlo simulations were performed to evaluate cancer risk and non-cancer risk owing to BTEX exposure in three age groups (<6, 6 to <21 and 21 to <81 years). The average toluene to benzene ratios for the four intercity bus terminals were 2.63 (summer) and 2.88 (winter). Furthermore, the mean xylenes to benzene and ethylbenzene to benzene ratios in the two seasons for all stations ranged from 3.33 to 4.40 (summer) and 2.13�2.80 (winter), respectively. There was insignificant difference in BTEX levels between working and non-working days owing to the lack of change in vehicular traffic during the full week. Factors promoting BTEX formation in the study region were fuel evaporation, gas stations, diesel bus emissions, and a lack of hydroxyl radicals (radOH) for reacting with the target compounds. Calculations suggested that cancer risk for benzene and ethylbenzene in three age groups at the four bus terminals exceeded values recommended by U. S. EPA. In addition, the hazard quotient for BTEX in both seasons for different age groups ranged between 1.23 � 10 �5 and 3.58 � 10 �1 , values of which were lower than reference levels. Carcinogenic emissions such as with benzene and ethylbenzene discharged by bus terminals impact the growing population in the study region, which requires additional action to reduce health effects. © 2019 Turkish National Committee for Air Pollution Research and Contro

Characteristics of gaseous and particulate air pollutants at four different urban hotspots in Tehran, Iran

This study reports a characterization of outdoor gaseous and particulate pollutants and their associated health effects in four different urban hotspots in Tehran, Iran during winter and summer. Buses, taxis, and cars are prominent sources of toxic pollutants in Tehran. There is a significant level of exposure to emissions from diesel buses in bus terminals, especially with boarding, disembarking, and waiting. Mean concentrations (μg/m3) in summer and winter, respectively, ranged from 10 to 20.67 and 17�21 for PM1, 52.50�79.19 and 58.33�85.33 for PM2.5, 64.50�102 and 78.83�125.83 for PM7, 130.17�204.67 and 157�231.67 for PM10, 261�409.50 and 305.83�458.83 for TSP, and 372.50�418.33 vs. 351.27�373.47 for CO2 (ppm). Particulate concentrations were higher in winter, especially the first three days of the week, assisted in part by the shallower mixing layer height as compared to summer. Mean hazard quotient (HQ) values for both PM2.5 and PM10 in both seasons for bus terminals in three scenarios ranged between 0.81 and 4.96, which exceeded reference levels (1 < HQ). The results of this study have implications for public health, especially in dense traffic areas. © 2021 Elsevier Lt

A case study of BTEX characteristics and health effects by major point sources of pollution during winter in Iran

This is the first such study investigating BTEX in this understudied, yet largely populated, region in the Middle East with attention geared towards spatial and diurnal trends, health effects of BTEX, and amount of BTEX emissions in gas stations versus CNG stations. © 2019 Elsevier Ltd This study characterized spatio-temporal variations in the concentration of benzene, toluene, ethylbenzene, and xylene (BTEX) compounds in the vicinity of gas and compressed natural gas (CNG) stations in Tehran, Iran. Health risk assessment (HRA) was computed using Monte Carlo simulations (MCS) for evaluating inhalation lifetime cancer risk (LTCR), the hazard quotient (HQ), and sensitivity analysis (SA) for BTEX exposure in different age groups (birth to <81) and as a function of distance (0�250 m) from the center of the stations. For all monitoring stations, the average values of benzene, toluene, ethylbenzene, and xylene in winter were 466.09 ± 132.25, 873.13 ± 233.51, 493.05 ± 141.22, and 910.57 ± 145.40 μg m �3 , respectively. The mean wintertime ratios of T/B for the 12 stations ranged from 1.69 to 2.04. Furthermore, there was no significant relationship between the concentration of BTEX with either the specific month or distance from the center of stations (p > 0.05). Factors promoting BTEX formation in the study region were fuel evaporation and gas/CNG station emissions. The LTCRs for the target compounds in the winter for different age groups and distances from the center of stations was limited to 2.11 � 10 �4 to 1.82 � 10 �3 and 2.30 � 10 �4 to 2.01 � 10 �3 , respectively, which exceeded proposed values by U.S. EPA. Moreover, the HQs for BTEX for three age groups and distances were limited to between 2.89 � 10 �5 and 9.33 � 10 �2 , which were lower than the acceptable limit (HQs < 1). The results of this work are applicable to similar areas that are heavily populated with vehicular traffic. This study motivates a closer look at mitigation strategies to limit the health effects of carcinogenic emissions such as benzene and ethylbenzene from gas/CNG stations. © 2019 Elsevier Lt