Tehran Air a Tad Cleaner

Air quality in Tehran has slightly improved over the past few days after a blanket of pollution descended on metropolis last week that for several days made breathing hard for large sections of the residents.
According to data released by Tehran Air Quality Control Company on airnow.tehran.ir, over the past seven days, the Air Quality Index has improved.
National AQI categorizes conditions based on the amount of polluting matters into good (0-50), moderate (51-100), unhealthy for sensitive groups (101-150), unhealthy (151-200), very unhealthy (201-300) hand hazardous (301-500).
Charts of the company show that in the week the first two days had an AQI standing at 139 and 140 respectively on Dec. 5 and 6 -- unhealthy for sensitive groups.
During the period, Tehran had 4 days of moderate air quality with the index standing between 52 and 97, and one day with almost clear skies with the index dropping to 40.
A week earlier, conditions were significantly worse, as the air quality was reported to be unhealthy for sensitive groups when the elderly and children were urged to limit their outdoor activities for 5 days. The AQI was ‘moderate’ barely for two days.