Delhi begins its slow descent into smog season every October. The sky turns grey, schools close early to protect the children and advisories are issued to not step out unless absolutely necessary. Yet the pattern is not inevitable; it is predictable. Therefore, it can be fixed. The solution lies in science, data, and collective coordination across the airshed that Delhi shares with its neighbouring districts.
Recent research at IIT Kanpur shows that Delhi-NCR’s air behaves like one connected atmospheric system, extending across 35 districts in Delhi, Haryana, Uttar Pradesh, and Rajasthan. Using machine learning–based clustering, researchers identified this “airshed,” demonstrating how pollutants move seamlessly across boundaries. Recognising this shared atmosphere is crucial for designing targeted, science-led mitigation.
Data from October 2024 and 2025 illustrate the challenge. In October 2024, the city’s PM2.5 levels rose from around 57 micrograms per cubic metre in the first week to 128 by mid-month, pushing the Air Quality Index (AQI) from “moderate” to “very poor.” A year later, in October 2025, PM2.5 climbed from roughly 45 to 153 micrograms, and the AQI reached about 286. These shifts coincided with a sharp fall in the ventilation coefficient — the measure of how efficiently air disperses pollutants — from nearly 7,880 square metres per second to under 2,000 in 2024, and to about 600 in 2025. The science explains the familiar pattern: As temperatures drop and dispersion weakens, local emissions accumulate rapidly.
Satellite data for the same period show that crop-residue fires contribute episodically but are not the primary driver of Delhi’s poor air quality. While Punjab and Haryana recorded several hundred fire events each week this year, the chemical composition of Delhi’s air indicates a broader regional influence. The city’s air quality is shaped largely by the Delhi-NCR airshed — a connected zone spanning districts across Delhi, Haryana, Uttar Pradesh, and Rajasthan — rather than by isolated local sources alone. Studies led by IIT Kanpur reveal that the dominant components of PM2.5 — organic aerosols, black carbon, nitrates, and ammonium — originate mainly from unregulated burning of waste and biomass in open areas, roadside combustion, emissions from transport and construction, and industrial activity in surrounding towns. In essence, much of the pollution is generated within or near the wider airshed that Delhi belongs to.
The findings reshape how we think about mitigation. Solutions must address Delhi’s everyday emission sources, not just seasonal spikes. Using the Comprehensive Air Quality Model with Extensions and the Particulate Source Apportionment Technique, IIT Kanpur’s team has simulated what different interventions can achieve. The modelling shows that improving the transport mix — by expanding clean, reliable public transport and transitioning fleets to BS-VI and electric vehicles — can reduce traffic emissions by more than 50 per cent. Delhi currently has only about 0.2 electric buses per 1,000 people; increasing this ratio to even one electric bus per 1,000 would dramatically cut private vehicle dependence. In this framework, the onus lies not on individual car owners but on the system: Providing affordable, accessible, and user-friendly public transport that is non-polluting and efficient. Complemented by reducing unregulated open burning and residential biomass use by 80 to 100 per cent, total PM 2.5 could decline by nearly 40 per cent. Together, these actions could lower average PM 2.5 levels from about 116 micrograms to nearly 50, shifting the AQI from “very poor” to “moderate.”
The mitigation pathways are clear and within reach. Expanding low-cost sensor networks, drone-based monitoring, and satellite-linked imaging will improve real-time hotspot detection. Hyperlocal data, when integrated with AI-based forecasting, can help anticipate pollution episodes and guide timely response. Promoting cleaner fuels across industries, waste management systems, and informal settlements will tackle the root of uncontrolled combustion. In transport, scaling up electric mobility, strengthening public bus systems, and improving last-mile connectivity can together reduce both congestion and emissions. For construction, enforcing dust recycling and material reuse can significantly cut particulate levels.
At the community level, curbing small-scale burning — of trash, leaves, or debris — remains one of the most direct ways citizens can contribute to cleaner air. Incentives and small subsidies for safe waste collection, recycling, and the use of clean-burning equipment could accelerate adoption. Such steps not only reduce pollution but also create employment, support local innovation, and make the city visibly cleaner.
Recent global experiences show what sustained, science-led coordination can achieve. Across major cities, targeted interventions in energy transition, mobility reform, and air quality monitoring have led to dramatic reductions in pollution levels within a decade. Delhi-NCR, with its scientific capacity and data infrastructure, is well placed to do the same — by complementing existing government initiatives with a stronger emphasis on modelling, prediction, and public engagement.
Delhi’s air can be cleaned through science, not sentiment. The data is clear, and the pathways are known. Cleaner air will not only improve health but also quality of life — more blue skies, fewer lost school days, safer streets, and a more vibrant cityscape. What is needed now is consistency in implementation and collaboration across the airshed. With coordinated science, policy, and participation, Delhi can indeed breathe easier — perhaps sooner than we think.
The writer is dean, Kotak School of Sustainability and Project Director, Airawat Research Foundation — Centre of Excellence on AI for Sustainable Cities, IIT Kanpur
Solutions must address Delhi’s everyday emission sources, not just seasonal spikes.(Representative image: Unsplash). 
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