Why does deadly smog envelop Delhi in winter?

Each winter, smog envelops Delhi and other cities in the north. Delhi’s air quality turned “severe” on Tuesday for the first time this season. If the situation worsens, the use of private vehicles may be curbed in the capital from 1 November. Mint analyses the problem and its impact.

What causes the pollution?

Vehicle and industrial emissions contribute year-round, as do road and construction dust and domestic fires. A grim extra wallop comes late in the year from the burning of crop stubble, which continues despite being banned in surrounding Punjab, Uttar Pradesh, Haryana and Rajasthan. Harvesting by combine leaves 80% of the residue in the field as loose straw that ends up being burnt. Disposal by means other than burning costs time and money, two things that farmers say they can’t afford.Compounding the problem: the trough-like topography of north India means polluted air lingers in colder months.

How serious is the health risk?

The Lancet estimates 6.5 million people die annually around the world because of air pollution, mostly in India and China. The most dire threat is from PM 2.5, the fine particles that lodge in the lungs and enter the bloodstream. World Health Organization (WHO) guidelines say PM 2.5 exposure above 300 micrograms per cubic metre is hazardous. New Delhi’s readings have crossed 1,000. The air quality index hit 469 in parts of Delhi on Tuesday, up from 299.4 a week ago. Ten of the world’s most polluted cities, as measured by PM 2.5, are located in India, as per WHO’s 2016 rankings. Kanpur was worst, with New Delhi sixth.

What’s the impact on the economy?

World Bank says healthcare fees and productivity losses from pollution cost India up to 8.5% of GDP. At its current size of $2.6 trillion that works out to around $221 billion every year.

Does the problem end when the burning stops?

The worst of the pollution does dissipate as spring begins, but New Delhi’s air remains dirty all year. On every day in 2017, PM 2.5 readings exceeded the level deemed healthy by WHO (up to 50 micrograms per cubic metre). And there were 39 days when readings topped 300, as per US embassy data. The environment ministry says the ban is proving more effective this year and that the number of fires had fallen ahead of peak burning season in late October and early November.

What action is being taken and what more can be done?

Environment Pollution Control Authority chairman Bhure Lal said on Tuesday that the use of private vehicles might be stopped if the situation worsened in the country’s capital. New Delhi did shut its Badarpur coal-fired power plant in October. The apex court in 2016 mandated government action such as banning construction as pollution levels reach thresholds. Continuing to adopt cleaner fuels and introducing policies to boost electric car usage would also help ease the problem.