The trend of air quality index (AQI) in Tehran during (2011-2016)

Introduction: Tehran city with the most population, about 4 million cars, million liters of fuels consumption, the presence of polluting industries such as petrochemicals and refineries, thermal power plants, and surrounding industrial towns is considered as one of the most populous and most polluted cities in the world . This study aims to investigate the trend of variation in air quality index in Tehran. Materials and methods: In this descriptive and evaluative study, the air quality data of 7 monitoring stations in 2012 were taken from the Tehran Department of Environment and Tehran Air Quality Control Company(AQCC). The calculation of AQI was done according to the EPA guidelines. Results: According to the results of this study, highest AQI averaging for 2016 (208.49±42.13) and the lowest for 2011 (134.13±46.80). Also observed that during the study period PM2.5 particles with an average of 71.59% is the most important factor in increasing the air quality index. Conclusion: It was observed that in the cold seasons of the year, due to the temperature inversion phenomenon in Tehran and the increase in the concentration of pollutants, air quality in most regions of Tehran is in unhealthy conditions, but in other season of the year the air quality is in moderate condition. Among the index pollutants, particulates are the major cause of Tehran’s air quality decline.