Iranian authorities have ordered several schools in in Tehran and several other cities in the country to be closed today because of the dangerous air pollution, health reports stated.

Tehran lay under a thick cloud of smog considered hazardous to health for several days now. Yesterday, the cloud could be seen from the valleys more than 20 kilometers north of the city.

Schools may remain closed tomorrow.

Authorities are urging seniors, children and people with respiratory disabilities to stay home. Sports activities are also not recommended.

In addition to Tehran, there are also closed schools in the Alborz Province, as well as in the cities of Qom and Arak, in the central part of the country.

Average airborne concentration of the finest and most hazardous particles (PM2.5) was at 145 micrograms per cubic meter for the 24 hours until Sunday noon, according to government website air.tehran.ir.

That is close to six times the World Health Organization’s recommended maximum of 25 micrograms per m3, The Japan Times reported.

In an effort to reduce pollution, authorities have imposed restrictions on road traffic. Around 8.5 million people live in the city.

The atmospheric pollution in Tehran peaks every year in November and February. The reason is the thermal inversion - the cold altitude air prevents the contaminated and warm air from dissipating.

Official figures published in Iranian media indicate that pollution causes 30,000 deaths each year in Iran.