What you need to know:
- Smog is blamed for more than a million deaths in India annually, and a recent University of Chicago study found that air pollution was likely to reduce life expectancy by more than nine years for four in every 10 Indians.
Stinging eyes, an unrelenting cough and chronic lung disease have taken their toll on Bhajan Lal, an auto rickshaw driver navigating the Indian capital's chaotic roads and poisonous air.
For the last three decades, Lal carted passengers along bumpy thoroughfares to temples, markets and offices in New Delhi, working every day through the winter months when a pall of toxic smog settles over the sprawling megacity.
"The pollution causes a lot of problems for my throat," the 58-year-old told AFP, after a morning spent in the driver's seat of his motorised three-wheeler.
"My eyes sting... My lungs are affected, which creates breathing problems. Mucus builds up and collects in my chest."
Delhi is consistently ranked the world's worst capital for air quality and on its most polluted days the smog can cut visibility on the roads to barely 50 metres.
Levels of PM2.5 pollutants -- the microparticles most harmful to human health, which can enter the bloodstream through the lungs -- last week reached more than 30 times the maximum daily limit recommended by the World Health Organization.
"I feel so sorry looking at children and their health," said Lal. "They are already getting sick."
Lal's business suffers and he sometimes drives around the streets for an entire day without finding passengers, who prefer paying extra to sit through their commutes inside a cab.
For those without the luxury of escaping the choking air, the health impacts are severe.
AFP accompanied Lal to a doctor's check-up where he was diagnosed with Chronic Obstructive Pulmonary Disease, a progressive condition that gradually limits airflow to the body.
"If he doesn't take the regular medication now, he will go into a state where the airways will go narrowing and narrowing, and progressively worsening," said Vivek Nangia, Lal's doctor.
Factory emissions, vehicle exhausts and crop-clearing fires from farms in neighbouring states combine to cast the city of 20 million people in an otherworldly coat of yellow-grey haze near the end of each year.
Piecemeal efforts to mitigate the smog, such as a public campaign encouraging drivers to turn off their engines at traffic lights, have failed to make an impact.
'A gas chamber'
"I don't know from where the solution will come for this pollution, which is killing us," Delhi resident Vijay Satokar told AFP. "We have become a gas chamber."
This week authorities took the drastic step of ordering six of the 11 coal power plants in Delhi's vicinity to close down until further notice.
City officials also shut schools indefinitely, barred trucks except those carrying essential goods from entering the capital until next week, and told civil servants to work from home.
But they stopped short of accepting a call by India's Supreme Court to declare the city's first "pollution lockdown", which would have restricted the population to their homes.
Smog is blamed for more than a million deaths in India annually, and a recent University of Chicago study found that air pollution was likely to reduce life expectancy by more than nine years for four in every 10 Indians.
Authorities have struggled to address the root causes, with national coal consumption nearly doubling in the last decade.
India fought more ambitious curbs on dirty energy at this month's COP26 climate summit, a move driven by its need for cheap fuel to power its booming economy.
Rural agricultural workers meanwhile constitute a powerful voting bloc and year-end farm fires -- the cheapest way to clear fields before the next growing season -- continue unabated despite a ban two years ago.
Winters in the capital, once appreciated for their mild weather after the long and scorching summer months, have become an annual endurance test for its inhabitants.
"I find it so difficult to breathe living in Delhi," said local resident Dinesh Doval.
"Sometimes I feel I should leave the city. But then where should I go?"