Delhi Is Breathing Toxic Air Again: Why Does Pollution Return Every Winter, and Who Is Responsible?

Every November, Delhi runs the same experiment on itself. The sky turns the colour of milk tea, eyes sting on the morning commute, and a familiar question returns: how did we end up here again?

This year is no different. On 6 November 2026, Delhi's air quality was reported in the very poor range, with readings in the high 300s and several areas nearing or crossing 400. The Commission for Air Quality Management, known as CAQM, invoked Stage III of the Graded Response Action Plan across the region that same day. And in the Supreme Court, the Chief Justice pointed to vehicular emissions as a major contributor and asked pointed questions about traffic moving in and out of the capital.

So why does this happen every winter, and who is responsible? Let us take it apart, piece by piece.

What AQI Actually Means

The Air Quality Index, or AQI, converts several pollutant readings into a single number so that ordinary people can understand the air they are breathing. The categories run from Good and Satisfactory to Moderate, Poor, Very Poor, and Severe.

The index is built on pollutants including:

• PM2.5: extremely fine particles, smaller than 2.5 micrometres, that can travel deep into the lungs.
• PM10: coarser particles, such as dust.
• Nitrogen dioxide: largely from combustion, especially vehicles.
• Sulphur dioxide: from burning fuels containing sulphur.
• Carbon monoxide: from incomplete combustion.
• Ground level ozone: formed when other pollutants react in sunlight.

In Delhi's winter, PM2.5 and PM10 usually dominate the picture.

Why Winter Makes Everything Worse

Delhi does not become a different city in November. The weather changes, and the weather traps what the city already produces.

Cold air near the ground is heavier than the warmer air above it. This creates something called a temperature inversion, a lid that stops pollutants from rising and dispersing. Wind speeds fall, so there is little to push the haze away. The mixing layer of the atmosphere becomes shallow, which means the same amount of pollution gets squeezed into a smaller volume of air.

Imagine cooking in a closed kitchen with the exhaust fan switched off. The smoke is not new. It simply has nowhere to go.

The Sources, Piece by Piece

The most common mistake in this debate is to blame a single cause. In reality, Delhi's pollution has several sources, and their shares change with the season, the weather, the location, and the period over which they are measured.

Vehicles. Delhi-NCR has an enormous number of vehicles, and traffic congestion keeps engines running longer. Older, more polluting vehicles add disproportionately to emissions. On 6 November, the Chief Justice described vehicular pollution as a major cause and referred to bumper to bumper traffic across the region.

Road dust and construction. Dust from roads, demolition, and building sites adds heavily to coarse particles.

Industry and power. Factories and other industrial units contribute emissions, depending on fuels and controls.

Crop residue burning. In October and November, farm fires in neighbouring states add smoke to the regional air. According to figures cited in court, stubble burning contributed about 14 percent to Delhi's pollution on 5 November, though this share swings from day to day.

Waste burning and local sources. Burning of garbage and biomass, and even cooking and heating fuel in some localities, add to the load.

Firecrackers. Around Diwali, fireworks cause sharp, short term spikes in particulate pollution.

Weather. Meteorology does not create pollution, but it decides how much of it stays.

No single source explains Delhi's winter. Anyone who says otherwise is simplifying the problem.

Why NCR Makes It Complicated

Air does not respect borders.

Delhi shares its airshed with neighbouring districts of Haryana, Uttar Pradesh, and Rajasthan, and pollutants move across state lines with the wind. A cleanup in Delhi can be cancelled out by emissions in a neighbouring district, and the reverse is also true.

That is why a coordinated body like CAQM exists, and why the debate keeps returning to a basic question: who is accountable when pollution crosses boundaries?

The Stubble Burning Debate

Stubble burning is the most politically charged part of the story, so it deserves fairness.

Farmers in Punjab and Haryana often have only a few weeks between harvesting paddy and sowing the next crop. Clearing the field by burning is fast and cheap. Alternatives exist, including machines like the Happy Seeder and ways to use crop residue as fuel or feedstock, but they cost money, need access, and require support systems that smaller farmers may not have.

During the Supreme Court hearing on 6 November, the bench questioned whether the focus on stubble burning alone was enough, and asked what had been done about vehicles, including those of wealthier households. The message was clear: fixing one source while ignoring the others will not clear the air.

Why Restrictions Are Not Enough

Every winter, the same toolkit appears. Under GRAP, restrictions on construction, certain vehicles, and some activities kick in as air quality worsens. On 6 November, Stage III brought curbs on dust generating construction and limits on older petrol and diesel vehicles, among other measures.

These steps help, but they are emergency tools, and emergency tools have limits.

• Enforcement gaps. Rules on paper do not always translate to action on the ground.
• Vehicle compliance. Checking millions of vehicles is hard.
• Construction monitoring. Thousands of sites need regular inspection.
• Public participation. Residents need clear information and practical alternatives, such as reliable public transport.
• Seasonal thinking. When action begins only after the air turns bad, the damage has already started.

The Court itself asked on 6 November whether old measures that have not fully worked are all we have, and sought expert backed medium and long term solutions.

What It Costs Us

The price of dirty air is paid in bodies and wallets.

Fine particles are linked to respiratory and heart problems, with children, older people, pregnant women, and people with existing illness at higher risk. Outdoor workers, from traffic police to delivery riders and construction labourers, are exposed the longest and can least afford to stay home.

The economy pays too: lost working days, school disruptions, healthcare costs, and reduced productivity. The burden is not equal. People with air purifiers and sealed homes breathe differently from those who work on the street.

So Who Is Responsible?

The honest answer is all of us, in different proportions.

Governments are responsible for planning, enforcement, public transport, and coordination across states. Industries and builders are responsible for compliance. Farmers need support, not just blame. And citizens make daily choices about travel, waste, and celebration.

Pollution is a shared problem with shared responsibility, and treating it as someone else's fault is the surest way to see it return next year.

The Way Forward

Delhi does not need a better emergency. It needs fewer emergencies.

That means steady, year round reduction in emissions: better public transport, cleaner fuels, strict dust control, support for farmers, and clear, honest data. We explore what such a framework could look like in our companion article on what the government should actually do.

Until then, protect yourself. Check the AQI before outdoor exercise, use a well fitted mask like an N95 on bad days, and keep vulnerable family members indoors when readings spike.

For students and professionals who spend long hours commuting through this air, small choices matter. Aspiro Living in Karol Bagh, a girls' PG for serious UPSC aspirants, keeps every top major UPSC institute within a 2-minute walk, which means less time on the road each day.

Know someone in Delhi-NCR who needs this explainer? Send it along.