Schools, universities and government agencies in Tehran will be closed on Tuesday and Wednesday due to pollution, the province's governor Morteza Tamadon said on state television.
"To avoid reaching distress levels, an order was given to shut down ministries, institutes, universities and schools across Tehran province except for the towns of Damavand and Firouzkooh" in the north, said Tamadon.
"Banks will not be closed. We urge people to cut down on unnecessary city travel," he told residents of the province who are officially said to number 12 million.
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Air pollution has reached a critical level in the past few days due to trapped smog in the Iranian capital, as well as several other major cities, including Isfahan and Arak.
Each year around this time, the pollution forces the closure of schools and government institutes for several days.
Principle air pollutants in Tehran are fumes from Iranian-made vehicles which on average consume more fuel than in other countries with a generally lower quality gasoline.