During the 13 days of the new Iranian year, which started on March 21 and coincides with the Norouz holidays, Tehran experienced five days of unhealthy air quality, an exceptional record in 10 years.
Tehran is known for its less crowded streets and clean air during the springtime holiday season when many take trips outside the city. This year's figures, however, caused surprise.
Vahid Hosseini, director of Tehran's Air Quality Control Company—a subsidiary of Tehran Municipality, attributed the condition to dust particles blowing from domestic sources, along with the exceptional traffic across the city.
"Dusty winds directly affected AQI, but the unexpected amount of traffic on the first days of the holiday contributed to the drop in air quality," he told IRNA.
Based on Air Quality Index, conditions are categorized into six health levels, namely Clean (0-50), Healthy (51-100), Unhealthy for Sensitive Groups (101-150), Unhealthy (151-200), Very Unhealthy (201-300) and Hazardous (301- 500).
Under this definition, Tehran's air quality was Unhealthy for Sensitive groups for five days with the AQI ranging from 103 to 131, according to data from TAQCC.
This is while the same period of last year registered its worst index at 59, which is still described as Healthy.
Besides, the number of clean days has shrunk to one while the previous year and the year before that registered seven days of below-50 AQI.
The only day with good air quality was March 23, but unhealthy days immediately followed. The worst day in terms of air pollution was the fifth of Farvardin (March 25) with AQI standing at 131.
Tehran had not seen poor air quality in Norouz for eight years. The last time the index hit unhealthy levels was 2008 when AQI reached 129 on March 26.
According to Hosseini, on average, Tehran sees around 15 days of clean air throughout the year, most of which is in the first month of the Iranian year.
"With this record, Tehran is expected to experience more polluted days this year," he said.
