Tehran is on red alert with kindergartens, schools and universities shut for the whole week due to thick smog that has blanketed the Iranian capital.

Local authorities and international monitoring firms announced that levels of particulate matter 2.5 (PM2.5) micropollutants were five times the normal average of 185 microgrammes per cubic metre in central and south Tehran on December 18. Only one area in the north of the city remained in the clear due to winds from the north reaching the edge of the city.

The smog situation has been exacerbated this year because the rain and snow which usually starts in late November has been scarce. Since October, it has only snowed once in Tehran, in northern parts of the city. Rain has also been at a record low.

The pollution issue in the capital city of 15mn people becomes much worse during daylight hours due to the metropolis being surrounded by the Alborz mountain range. It acts as a wall which traps the cold winter air heavy with pollutants.

Other pressing issues include a push by the Iranian government to sell new cars with outdated engines that release too much pollution. It is estimated that 1.5mn new vehicles will be built in the country by the end of March 2018, while many old cars remain on the roads due to a lack of credit among consumers to buy new ones.

The smog has also affected other cities including Karaj, Robat Karim, Tabriz and Urumieh near the border of Turkey.

On top of the school closures, all major sporting events in the city have been cancelled. One scheduled football match between Esteghlal and Iranjavan Bushehr was scrapped.

Air pollution costs Iran more than €30bn a year in lost working time, a World Health Organisation (WHO) report estimated in 2016.

Earlier this year, the Iranian parliament rejected a cabinet-approved clean air bill which would give schoolchildren a two-week break in late December. The idea was among a raft of measures aimed at curbing the effects of the annual winter shutdown.

The original proposal was also welcomed by the environment department which said the two-week break could be advantageous in terms of spurring tourism. Several parliamentarians noted that the cost of pulling parents out of work to provide daycaer was having unforeseen consequences for the economy.

Other parts of the blocked bill were aimed at forcing the country’s state carmakers to improve the quality of their engines. Annual vehicle inspections, meanwhile, would become more difficult to pass.

Iranian statistics suggest that annually some 26,000 people die due to pollution in urban areas. In the last weeklong smog shutdown in 2014, more than 400 people were hospitalised with heart and respiratory conditions

Currently, petrol costs IRR10,000 per litre (€0.20). However, the government intends to increase the price in the next month by IRR5,000 in a bid to address over-consumption.

The Tehran Municipality has in recent years worked to limit private vehicle access to downtown areas of the city. The previous city mayor, Mohammad Baqer Qalibaf, was awarded for his push to move people from cars to public transport.

During his 12 years running the city, Qalibaf massively expanded the city’s metropolitan railway line from two lines to six and created the Bus-Rapid-Transit (BRT) system stretching across Tehran.