Air quality in Tehran, Iran: Spatio-temporal characteristics, human health effects, economic costs and recommendations for good practice

Air pollution is one of the most important environmental problems in world cities. The main aims of this study were to characterize the spatio-temporal changes in the concentration of air pollutants in Tehran metropolis, Iran, in the last 6 years, identify the major sources of pollution, estimate the human health effects and economic costs, and recommendations for good practice. Hourly concentrations of standard air pollutants including PM₁₀, PM_2.5, NO₂, SO₂, CO and O₃ were collected from 21 air quality monitoring stations in Tehran from 2016 to 2021 and then, the air quality index (AQI) was calculated monthly and annually. The reached results indicated that AQI is relatively high in Tehran city and is above 100 (unhealthy for sensitive groups/unhealthy) on average on more than 20% (16.99–33.43%) of the days per year. According to the data, the highest and lowest percentages of clean days were observed in 2019 and 2021, respectively, with only 8.49% and 1.10%. Specifically, the highest concentrations of pollutants were observed in the autumn and winter seasons and during the months (by decreasing order) of December, November, and January. The produced annual emission rate of pollutants in Tehran city showed that approximately 84% are due to mobile sources while stationary sources correspond only to about 16%. The economic costs of the effects of air pollution on health were investigated and data showed that cardiovascular diseases > diabetes > lung cancer impose the highest costs to the health care system. Cardiovascular diseases accounted for the largest share of all premature deaths (26.28%) followed by stroke (10.46%), diabetes (3.77%), chronic obstructive pulmonary diseases (COPD) (3.21%), and lung, pharynx and bronchial cancer (2.28%). In addition, the share of air pollution in COPD was 34.2%, which is 31.98–39.2% more than the other ailments under investigation. Implementation of mitigation strategies in Tehran is urgently needed.