Unprecedented air pollution levels prompt authorities to take emergency measures.

Pakistan’s second-largest city of Lahore will close primary schools for a week after it saw “unprecedented” pollution levels, government authorities have said.

For days, the city of 14 million people has been enveloped by smog, a mix of fog and pollutants caused by low-grade diesel fumes, smoke from seasonal agricultural burning and winter cooling.

The air quality index, which measures a range of pollutants, exceeded 1,000 on Saturday – well above the level of 300 considered “dangerous” – according to data from IQAir.

The Punjab government also recorded peaks of over 1,000 on Sunday, which it said was “unprecedented”.

“Weather forecast for the next six days shows that wind patterns will remain the same. Therefore we are closing all government and private primary schools in Lahore for a week,” Jahangir Anwar, a senior environmental protection official in Lahore, told the AFP news agency.

“This smog is very harmful for children. Masks should be mandatory in schools. We are keeping an eye on the health of children in senior classes,” Punjab senior minister Marriyum Aurangzeb told a news conference on Sunday.

Smog counters have been established in hospitals, she added.

Breathing the toxic air can have catastrophic health consequences, with the World Health Organization (WHO) saying that strokes, heart disease, lung cancer and respiratory diseases can be triggered by prolonged exposure.

On Saturday, the concentration of deadly PM2.5 pollutants – fine particulate matter in the air that causes the most damage to health – was more than 40 times the level deemed acceptable by the WHO. PM2.5 levels on Sunday morning exceeded that before decreasing slightly.

Children particularly vulnerable

Last week, the provincial environmental protection agency announced new restrictions in four “hot spots” in the city.

Tuk-tuks equipped with polluting two-stroke engines are banned, as are restaurants that barbecue without filters.

Government offices and private companies will have half their staff work from home starting Monday.

Children are particularly vulnerable because they have less developed lungs and breathe more rapidly, taking in more air relative to their size than adults.

Last month, authorities banned schoolchildren from outdoor exercise until January and adjusted school hours to prevent children from travelling when the pollution is most punishing.

Pollution in excess of levels deemed safe by the WHO shortens the life expectancy of Lahore residents by an average of 7.5 years, according to the University of Chicago’s Energy Policy Institute.