TEHRAN — Tehraners have breathed 21 days of excellent air since the beginning of the new Iranian calendar year (March 21), ISNA news agency reported on Tuesday.

The report adds that since March 21 to April 15 Tehraners experienced 21 days of excellent air quality and 5 days of good air quality.

An air quality index (AQI) is used to communicate to the public how polluted the air currently is or how polluted it is forecast to become.

The index categorizes conditions according to a measure of polluting matters into excellent (0-50), good (51-100), lightly polluted or unhealthy for sensitive groups (101-150), moderately polluted (151-200), heavily polluted (201-300) and severely polluted (301-500).

Hossein Shahidzadeh, acting director of Tehran Air Quality Control Company, explained that such high number of clean air days have been unprecedented in Tehran during the first month of the year, stating that rainfalls and wind have had dominant roles in improving the quality of air in the capital.

Normally, due to reduced number of vehicles in the streets in the first half of the year the number of polluted days drop, however, current climatic conditions have improved air quality as well, he added.

Last year in the same period only three days of clean air were reported, while 5 days were lightly polluted or unhealthy for sensitive groups.

MQ/MG