Delhi's toxic winter air returns as new pollution plan faces its first test

Delhi's toxic winter air has returned days after the city's Winter Action Plan came into force on 1 November, with residents reporting eye irritation, breathing difficulty and a smoky haze across India's capital.

Every winter, falling temperatures and slower winds trap pollutants close to the ground. Smoke from crop residue burning in neighbouring states adds to emissions from vehicles and factories, construction dust and firecrackers used during festivals.

This week a grey haze hung over Delhi with a distinct smoky smell. For those who can afford them, air purifiers have become a household necessity; outdoors, people wear masks or cover their faces with cloth.

What the new plan does

The Delhi government announced its Winter Action Plan months before the worst smog arrived, and it runs from 1 November to 28 February. It restricts the entry of older, more polluting vehicles registered outside Delhi, denies fuel to vehicles without a certificate showing they meet emission standards, and temporarily bans demolitions and dusty outdoor construction. Offices have been asked to let half their employees work from home, staff timings have been staggered and parking charges doubled. The government says it will also strengthen pollution monitoring and enforcement and promote public transport and electric vehicles.

Separately, the Graded Response Action Plan (Grap), overseen by the federal Commission for Air Quality Management, imposes restrictions in stages. Its second stage is in force this week, restricting diesel generators and the burning of coal and firewood.

Experts: enforcement is the test

Experts called the early planning a step in the right direction, saying measures in previous years were often rolled out only after air quality became too bad to ignore. But they say enforcement will decide the outcome. "There are a lot of positive changes as far as planning is concerned, but when it comes to execution, we probably still stand at the same level," said Parthaa Bosu, strategic adviser at the Environmental Defense Fund.

Manoj Kumar, an analyst at the Centre for Research on Energy and Clean Air, said targets should be set for every sector, including power generation, industry and transport, not just vehicle entry, construction and stubble burning. Bosu said secondary pollutants — formed when gases react with sunlight and water vapour — plus dust, coal and fly ash, brick kilns and urban waste burning are still not being stopped. Pollutants also travel into Delhi from neighbouring states, he added, so the city's own measures can achieve only so much.

Health toll

During winter, government monitoring stations in Delhi frequently record Air Quality Index readings above 300, classified as "very poor", and readings can reach 500, the highest point on India's scale. Swiss-based tracker IQAir has recorded readings close to 1,000. The World Health Organization recommends 24-hour average PM2.5 levels should not exceed 15 micrograms per cubic metre; in Delhi, levels are often more than 25 times that limit during pollution season.

Dr Manoj Goel, pulmonology unit head at Fortis Memorial Research Institute near Delhi, said the particles can penetrate deep into the lungs and enter the bloodstream, triggering inflammation and affecting multiple organs. A 2025 report by the Energy Policy Institute at the University of Chicago estimated air pollution could reduce life expectancy in Delhi by up to 8.2 years.

The restrictions also disrupt daily life. Queues form at Delhi's borders as vehicles are stopped and checked, leaving commuters heading to and from the satellite towns of Noida and Gurugram stuck for hours. Teacher Meenu Rana, 43, keeps her windows closed and curtains drawn and has added indoor plants. She is not planning to move out of Delhi. "What option do we have? It is unfair but we will have to live with it," she said.

Source: BBC Science.