Tehran Air Quality Control Company said on Saturday that the index was 177 which is unhealthy for all groups.
It advised people with heart or lung disease, the elderly and children to avoid prolonged or strenuous outdoor activities, and others to reduce them.
The Iranian capital had the worst air quality index in the world on Friday followed by Beijing and Pakistan’s Lahore.
Droughts in the Middle East region and dust storms coming from the west have contributed to the growing air pollution problem in Iran.