Tehran Experiencing Relative Improvement in Air Quality 

The city of Tehran’s air quality has slightly improved in the first half of autumn compared to the same time period last year, head of Tehran Air Quality Control Company, Mohammad Mahdi Mirzaei Qomi, stated on Monday. 
Between September 23 to November 6, the number of days with “acceptable” air quality increased from previous year’s 33 to 37, Mirzaei was quoted as saying by ISNA. 
The count of days with “unhealthy” air quality for sensitive groups declined by five from last year’s 12 to seven, the official said. 
Pollutants present in the air during the first 45 days of autumn were fine particles, which are 2.5 micrometers or less in size, expect for September 26 when Tehran experienced a simultaneous rise in concentrations of PM2.5  as well as PM.10 particles. 
“On that day, Air Quality Index [for PM.10] reached 205, ‘very unhealthy’,” Mirzaei said, adding that “at the same time, the AQI for PM2.5 rose to 124, ‘unhealthy for sensitive groups.’”
This phenomenon happened on two consecutive days last year. 
“Considering this, air quality in this time period is better than a year earlier,” he said. 
According to the official, with temperatures dropping over the next few months and a decline in rainy days, concentrations of pollutants are expected to rise due to inversion. 
Inversion traps pollutants near ground, which will help the particles enter the body through the mouth and nose and travel to the bloodstream through the lungs. 
During the first half of the current year, Iran faced frequent and intensive episodes of sandstorms with high levels of PM10 that can cut visibility and cancel flights. 
Iran is cooperating with regional nations to come up with a solution to worsening air quality in the Middle East.