Schools have been shut in New Delhi after “hazardous” toxic smog worsened.
Authorities in India‘s capital, which is home to more than 33 million people, have also halted construction as part of efforts to control the air pollution.
Airlines have warned of delays due to visibility dropping to around 100 metres due to the worst pollution of the season so far.
The air quality is many times worse than the World Health Organization’s (WHO) recommended safety limit.
Live rankings by Swiss technology company IQAir warn New Delhi is the most polluted city in the world, according to Reuters. IQAir also says the air quality is “hazardous”, with pollution levels which can cause diseases and cardiac problems.
India’s main environmental agency SAFAR has said the pollution is severe.
Delhi residents walking through the toxic smog. Pic: AP
Classes for most school grades are being held online, while no trucks will be allowed to enter the city except those carrying essential items.
Some older, diesel-guzzling vehicles have been banned inside the city. Authorities also urged children, the elderly and others with respiratory issues or chronic diseases to avoid going outside as much as possible.
The pollution level has been steadily increasing in recent weeks, with forecasts predicting the poor air quality will continue in the coming days.
New Delhi residents have complained of headaches and coughs on social media.
Air pollution in northern India rises every year, particularly in winter, as farmers burn crop residue in agricultural areas.
Farmers burning crop residue after harvest near the Bundelkhand expressway around 200 miles from New Delhi. Pic: AP
The burning of crop residue coincides with colder temperatures, which traps smoke in the air, which is then blown into cities. Pic: AP
The burning coincides with colder temperatures, which traps smoke in the air.
The smoke is then blown into cities, where vehicle emissions add to the pollution.
Farmers in neighbouring Uttar Pradesh state burned their fields over the weekend, releasing plumes of grey smoke that winds likely carried into New Delhi and other nearby areas.
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Emissions from industries and the burning of coal to produce electricity are also linked to pollution.
Studies have estimated more than a million Indians die each year from pollution-related diseases.
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Indian authorities often use short-term measures, including water sprinklers and anti-smog guns, in an effort to control the haze.
But others have urged officials to introduce a long-term solution that significantly reduces the pollution itself, instead of actions that aim to mitigate the effects after it hits cities.