Air pollution is a leading environmental risk factor on health and it is the major cause of death and disease at global level. Air pollution has been shown to have a significant share in the non-communicable diseases (NCDs) burden. After smoking, it is the second cause of deaths due to NCDs, associated with an increased risk of developing acute and chronic diseases and mortality.

Results regarding temporal variations of air quality in Tehran that is performed by the Institute for Environmental Research (IER) of Tehran University of Medical Sciences (TUMS), indicated that PM concentration had an increasing trend from 2006 to 2011. The maximum mean concentration of PM_2.5 over the past 12 years has occurred in 2011, which was 38 μg/m³. The PM concentration had a decreasing trend from 2012 to 2015, reaching about 30 μg/m³. However, in the years 2016 and 2017, the annual mean PM_2.5 concentration in Tehran was increased compared to its corresponding value in 2015. Furthermore, results of this study demonstrated that, in Tehran, not even one day was classified as "good” (AQI=0-50) from 2011 to 2017 based on the air quality index (AQI), but the number of days in which AQI was “moderate” (AQI=51-100) was increased from 2011 to 2015, and the number of days with the AQI of “moderate” reached 80 in 2015, while the rest of the days having an unhealthy air quality. In 2017, AQI was “moderate” in 20 days, “unhealthy for sensitive groups” in 237 days, “unhealthy” in 107 days, and "very unhealthy” in 1 day. The obtained results indicated that about 4878 (3238, 6359(  of deaths due to all (natural) causes were attributable to long-term exposure to PM_2.5 in Tehran in 2017.

Studies showed that air pollution has a considerable share in the number of attributed deaths. Moreover, there were substantial differences between the results of national and international studies in the burden of disease attributed to air pollution. Therefore, there is a crucial need for accessing to reliable data on air pollution as well as baseline mortality and morbidity in order to study the status of air quality and its effects on health over the country. 

Air quality status and its health effects in Tehran City