As public outrage mounted in the world's most polluted capital, the Delhi government ordered the closure of all primary schools on Wednesday.
Delhi shut all primary schools on Wednesday as pollution hit 70 times the World Health Organisation's safe level, prompting doctors in the Indian capital to warn of a public health emergency.
Dense grey smog shrouded the roads of the world's most polluted capital, where many pedestrians and bikers wore masks or covered their mouths with handkerchiefs and scarves.
TRT World's Neha Poonia reports.
The US embassy website showed the concentration of PM 2.5-the microscopic particles that are the most damaging to health - topped 700 early on Wednesday morning, 70 times the WHO guidelines on long-term exposure, before dropping slightly.
Delhi Govt decides to shut down all schools for all classes till Saturday due to high level of pollution. Review on Sunday (Order Copy) pic.twitter.com/kSMU3LhRHf— Ankit Tyagi (@Ankit_Tyagi01) November 8, 2017
"We have decided to shut schools up to primary level for a day, and will evaluate the situation on an hourly basis to see if such a closure needs to be extended," Delhi's deputy chief minister Manish Sisodia told reporters.
Almost 2 million students are enrolled in primary schools in Delhi, according to government data from 2015.
Public health emergency declared
A public health emergency was declared in New Delhi on Tuesday as a choking blanket of smog descended on the world's most polluted capital city.
The Indian Medical Association's declaration came as the US embassy website said levels of the fine pollutants known as PM2.5 that are most harmful to health reached 703 – well over double the threshold of 300 that authorities class as hazardous.
"We have declared a state of public health emergency in Delhi since pollution is at an alarming level," the head of the Indian Medical Association (IMA) Krishan Kumar Aggarwal said.
"Delhi authorities have to make every possible effort to curb this menace."
The World Health Organisation in 2014 classed New Delhi as the world's most polluted capital, with air quality levels worse than Beijing.
Since then authorities have closed power plants temporarily and experimented with taking some cars off the road.
But on Tuesday many residents said too little was being done to tackle the scourge.
New Delhi this morning, unacceptable levels of Air Pollution! The health of citizens deserve better! pic.twitter.com/JvOsa9cExR— Dr Maria Neira (@DrMariaNeira) November 7, 2017
Low visibility caused by the smog forced the closure of one of the runways at Delhi airport, delaying some flights.
Delhi's air quality typically worsens ahead of the onset of winter as cooler air traps pollutants near the ground, preventing them from dispersing into the atmosphere, a phenomenon known as inversion.
Firecrackers set off to celebrate the Diwali festival of lights in the city add to the toxic mix created by pollution from diesel engines, coal-fired power plants and industrial emissions.
The problem is further exacerbated by the burning of crop stubble by farmers after the harvest in northern India, a practice that remains commonplace, despite an official ban.
On Monday telecoms giant Airtel threatened to pull its sponsorship of the event, due to be held on November 19, if authorities failed to improve the situation.
A report in the Lancet medical journal last month said pollution had claimed as many as 2.5 million lives in India in 2015, the highest in the world.
India's Central Pollution Control Board said high levels of moisture in the air and a lack of wind meant emissions had become trapped in the environment.
The hashtag #smog was the top trending topic on Twitter early Tuesday as angry residents demanded stronger measures to curb pollution.
"This is the state of air quality this morning in Delhi-NCR! Horrific!" posted one resident beside a picture of thick smog.