New Delhi, the world’s most polluted capital, has banned non-essential construction and urged residents to avoid burning coal for heating to combat worsening air quality. The smog has disrupted flights and obscured the Taj Mahal.

These new measures, which include sprinkling water with dust suppressants on roads and mechanized sweeping, will come into effect on Friday morning.

Delhi’s Chief Minister Atishi has also directed all primary schools to shift to online classes.

The government release on Thursday also includes a ban on non-essential construction and an appeal to citizens to use more public transport and avoid using coal and wood for heating, but it did not say how long these measures would be in place.

Air quality in Northern India has deteriorated over the past week, with toxic smog obscuring the Taj Mahal, about 220 km (136 miles) from New Delhi, as well as the Golden Temple in Amritsar.

New Delhi has a severe air quality level of 424, according to live rankings kept by Swiss group IQAir, the worst amongst global capitals.

The city battles smog – a toxic mix of smoke and fog – every winter as cold air traps dust, emissions, and smoke from illegal farm fires.

Around 38% of the pollution has been caused by stubble burning – a practice where stubble left after harvesting rice is burnt to clear fields – in the neighbouring states of Punjab and Haryana.

Delhi flights faced delays, with tracking website Flightradar24 showing 88% of departures and 54% of arrivals were delayed as of Thursday afternoon due to smog.

ALLERGIES, COUGHS, ASTHMA

Officials blamed high pollution, combined with humidity, becalmed winds and a drop in temperature for the smog, which cut visibility to 300m (980 ft) at the city’s international airport, which diverted flights in zero visibility on Wednesday.

More patients flocked to hospitals, particularly children.

“There has been a sudden increase in children with allergies, cough and cold … and a rise in acute asthma attacks,” Sahab Ram, a paediatrician in Punjab’s Fazilka region, told news agency ANI.

Delhi’s minimum temperature fell to 16.1 degrees Celsius (61°F) on Thursday from 17 degrees C (63 degrees F) the previous day, weather officials said.

Pollution in New Delhi is likely to stay in the “severe” category on Friday, the earth sciences ministry said, before improving to “very poor”, or an index score of 300 to 400.

The number of farm fires to clear fields in northern India has risen steadily this week to almost 2,300 on Wednesday from 1,200 on Monday, the ministry’s website showed.

Lahore, the capital of Pakistan, was rated the world’s most polluted city on Thursday, in IQAir’s rankings. Authorities there have also battled hazardous air this month.