Iran is to close schools for two days in Tehran, state media said Saturday, following air pollution three times the acceptable level that has blanketed the city in smog.
Air quality in Iran's capital was the worst in at least nine months this week, media said, and floating particles from car emissions were at "seven times the standard level".
Traffic will also be limited in the center of town and some factories will be closed, according to reports.
The Air Quality Index on Monday showed an average reading of 162 — a "red status" warning that the air is unhealthy for everyone, according to World Health Organization standards.
A normal healthy level is between zero and 50.
Authorities advised the elderly, the sick and children to stay indoors and emergency services were on standby.
Peak pollution hit 180 in some areas of Tehran, where poor air is worsened due to high altitudes — between 1,100 and 1,700 meters (3,600-5,600 feet) above sea level — in a basin surrounded by mountains.
Visibility was low as a grey fog blanketed the capital, a megacity of an estimated 14 million people.
The snow-capped mountains of the Alborz range were invisible from the city center.
Exhaust fumes from five million cars make up 80 percent of Tehran's pollution, which increases in winter as emissions fail to rise above cold air.
Iran's government has tried to cut pollution by supplying lower emission fuel in large cities, Masoumeh Ebtekar, a vice president responsible for environmental protection, said this week.
In 2012, pollution contributed to the premature deaths of 4,500 people in Tehran and about 80,000 in the country, according to the health ministry.
