Investigating and evaluating the emission and distribution of benzene pollutant in gas stations in the 4th district of Tehran using the AERMOD model and determining the dangerous and safe points using the WISER model

Background and Benzene is one of the primary volatile organic compounds in urban air pollution. Beside its environmental implications, benzene poses various health risks to urban inhabitants. This study aimed to measure benzene levels at fuel stations (petrol pumps) in a specific area of Tehran and model its dispersion to determine safe distances from the release point.  The study, assessed benzene pollutant concentrations at 11 selected gas stations in Tehran’s 4th district over one-year using gas chromatography with a GC-FID flame ionization detector. Additionally, pollution dispersion modeling was conducted using the AEROMOD model, while the WISER software determined safe distances to aid emergency responses to chemical releases exceeding standard limits.  Benzene measurements at the selected stations indicated average emissions of 3.07 µg/  in spring, 3.50 µg/   in summer, 2.95 µg/  in autumn, and 2.35 µg/  in winter. Notably, levels surpassed standards at three locations, posing environmental and health risks to residents’ station 53 and the Takhti sampling area exhibited the highest and lowest benzene emissions, respectively, at 4.24 µg/  and 1.62 µg/ . The dispersion model revealed a maximum annual benzene concentration of approximately 7.89 µg/ , exceeding the standard limit. Safe distances determined by the WISER model ranged from 0.5 to 0.7 µg/ , extending between 50 and 300 meters from the sampling area.  The study concludes that benzene emissions are higher in summer and lower in winter at the sampled locations. Distance from emission sources correlates with reduced benzene concentrations, thus minimizing population exposure. Safe areas were identified based on these findings. Given the health risks posed benzene emissions from gas stations, particularly in locations exceeding standard levels, targeted monitoring and control programs are imperative municipal areas and fuel stations.