Number of pupils, students and civil servants in Iran were told to stay indoors today and tomorrow, Thursday, due to severe air pollution that Tehran and several cities are facing, state media reported.

The Iranian capital was shrouded in a thick yellow haze, a common occurrence for its roughly 10 million residents, but especially intense in winter.

Every year between November and February, air pollution peaks in Tehran, a city at an altitude of 1,400-1,800 meters, due to a phenomenon called “temperature inversion” in which cold air at altitude prevents the removal of warm, polluted air.

In Tehran, air quality today is considered “dangerous“, with an AQI index of 200, i.e. the concentration of suspended microparticles PM2.5 in the air exceeded ten times that considered acceptable by the World Health Organization (WHO).

Banks and museums it is closed in the Iranian capital, while the iconic Miland Tower (435 meters high) was not visible this morning.

The pollution is also affecting other major Iranian cities, including Isfahan in central Iran, Tabriz in the northwest, and Ahvaz in the southwest, according to state television.

Aging industrial infrastructure, an aging car fleet and poor-quality gasoline contribute to air pollution, according to Iranian media.

The government has also blamed fuel oil used in some power plants in recent weeks.

Air pollution causes premature death of about 50,000 people annually in the country, according to Iranian Health Minister Mohammad Reza Zafargadi.

In recent years, Iranian authorities have shut down several times the schools in Tehran, mainly in 2019 when they remained closed for a whole week.