Delhi’s pollution-control strategy is being rebuilt around a more detailed map of where emissions come from, as a new source apportionment and emissions inventory study covers the capital and 27 districts across the National Capital Region. The exercise is intended to establish how the region’s pollution profile has changed since earlier assessments and provide the evidence base for control measures through 2040.
The study is significant because Delhi’s pollution mix is not static. Vehicle technologies, fuel standards, industrial practices, pollution-control equipment, urban development, waste management and agricultural activity may all have altered the relative contribution of different sources over the past decade. Yet the most widely used assessments are based on different methodologies, geographical boundaries, source classifications and base years, making direct comparisons difficult.
The new exercise, being undertaken for the full year from January 1 to December 31, uses 2026 as its base year. It will be analysed by the middle of 2027 and will generate future emissions and air-quality scenarios for 2030, 2035 and 2040. The stated objective is not simply to produce another pollution estimate, but to create a common framework that can guide long-term planning across Delhi-NCR.
## Why Delhi pollution source apportionment needs a new baseline
Delhi’s first source apportionment study was conducted by IIT-Kanpur in 2016. It followed an earlier Central Pollution Control Board emissions-inventory exercise carried out between 2007 and 2010 across six cities, including Delhi. A further assessment was conducted by the Automotive Research Association of India and TERI in 2018.
These studies remain important reference points, but the new assessment is being designed to address the limits created by variation between them. Earlier exercises did not use identical geographical coverage, base years or source-sector classifications. As a result, an apparent change in the contribution of a pollution source may reflect a real shift, a methodological difference or both.
The Commission for Air Quality Management developed a framework for emissions inventory and source apportionment for Delhi-NCR in April 2025. The CPCB is funding the project and implementing it through a consortium led by ARAI, Pune, along with IIT-Delhi, TERI and the Indian Institute of Tropical Meteorology, Pune. SD Attri, member technical at CAQM, is heading the project review committee monitoring its progress.
The institutional arrangement matters because pollution in the capital does not respect municipal or state boundaries. The study will cover Delhi and 27 NCR districts, while also extending into the wider north Indian domain to examine regional transport. That approach places local emissions within the larger movement of pollutants across the region, rather than treating Delhi as an isolated administrative unit.
## A finer map of emissions
The inventory will use a 500-metre by 500-metre grid. Each cell covers 0.25 square kilometres, allowing the study to identify emission hotspots at a much more detailed scale than a broad citywide estimate. The framework combines activity data, emission factors, geographic information, seasonal variation and field verification.
The study will assess particulate matter and gaseous pollutants, including PM10, PM2.5, nitrogen oxides, sulphur dioxide, carbon monoxide, non-methane volatile organic compounds and ammonia. It will also cover elemental carbon, organic carbon, methane and hydrogen chloride. This wider pollutant set can help distinguish different source profiles instead of reducing the region’s air-quality problem to a single particulate measure.
The work will use satellite imagery and artificial-intelligence-based mapping to identify smaller sites and emission patterns. Field teams are being deployed to verify the mapped information on the ground. The combination is intended to reduce the risk of relying solely on reported or modelled activity data, particularly in a region where roads, industrial sites, construction activity and smaller facilities can be distributed across a complex urban and peri-urban landscape.
For vehicles, the assessment will draw on road networks, traffic volumes, vehicle categories and activity patterns. Industrial emissions will be assessed using information on industrial locations, production, fuel consumption and pollution-control equipment. Road-dust emissions will require data on road characteristics, silt loading and related activity patterns.
This level of detail changes the administrative question. Instead of asking only how much pollution Delhi produces, authorities will be able to examine where emissions are concentrated, which sources dominate particular locations and how those patterns vary by season. The study’s usefulness will therefore depend not just on its final regional totals, but on whether its findings can be connected to specific enforcement and mitigation responsibilities.
## The policy landscape is changing, but the evidence has lagged
The new assessment is being conducted against a background of changes in the region’s energy and regulatory systems. CAQM has said that coal has been banned in NCR except for specified processes, while industries have shifted towards cleaner fuels. Vehicle technologies and fuel standards have also changed, and pollution-control measures have evolved.
Those changes make older source estimates less reliable as a direct guide to current interventions. If an earlier inventory assigned a large share of emissions to a source whose operating conditions have since changed, continuing to base policy on that estimate could misdirect limited administrative capacity. Conversely, a source that has received less attention may now deserve greater scrutiny if its relative contribution has increased.
The new inventory is expected to provide scenario assessments under different mitigation pathways for 2030, 2035 and 2040. These scenarios are intended to help evaluate how emissions and air quality could change under different approaches. The supplied information does not establish which measures will be selected or what their eventual outcomes will be. It does establish that future planning will be linked to a common emissions baseline rather than to separate assessments produced for different purposes.
The proposed monitoring network is another part of that effort. IITM’s Decision Support System currently estimates the contribution of local and regional sources to Delhi’s winter PM2.5, but it relies on a 2021 emissions inventory. CAQM has indicated that the system will use the new inventory once it is prepared.
The distinction is important. A decision-support system can help authorities assess pollution conditions and source contributions, but the quality of its outputs depends on the inventory and assumptions behind it. Updating the underlying inventory can improve the relevance of the system, although the supplied material does not yet provide a performance assessment of the current or future model.
## Supersites could connect regional modelling with local conditions
To complement the inventory, a network of real-time source-apportionment supersites has been proposed across NCR. IITM’s supersite at New Rajendra Nagar was inaugurated on the Saturday before the report, while the Delhi Pollution Control Committee’s supersite at Rouse Avenue is to be revived. Four additional sites have been proposed at Sonipat, Rohtak and Rewari in Haryana and Greater Noida in Uttar Pradesh.
These locations would extend monitoring beyond Delhi’s administrative boundary and create a more distributed view of regional pollution. The proposed network also reflects the practical challenge of distinguishing pollution generated within a city from pollution transported into it. A Delhi-only monitoring structure cannot fully answer a regional question.
The proposed sites will not, by themselves, resolve the policy problem. Their value will depend on how real-time measurements are integrated with the inventory, satellite mapping, field checks and the Decision Support System. The current announcement establishes the planned components, but not the final operating design, data-sharing arrangements or implementation timetable for every proposed site.
## The bigger urban question
The study represents a shift from broad pollution attribution towards a more granular account of how a metropolitan region functions. Delhi-NCR’s air quality is shaped by transport networks, industrial locations, fuel use, road conditions, seasonal activity and sources beyond the capital. An effective response therefore requires coordination across agencies and jurisdictions, not only episodic action during severe pollution periods.
The central test will be whether the new evidence changes decisions on the ground. A 500-metre grid can identify hotspots, but institutions must still decide which agency is responsible, what intervention is feasible, how compliance will be checked and how progress will be measured. The study can improve the information available to policymakers; it cannot substitute for implementation.
For now, the evidence confirms that Delhi-NCR is moving towards a new pollution baseline after nearly a decade of changing technologies, fuels, regulations and urban activity. The next important milestones are the completion of the year-long data collection, analysis by mid-2027, the integration of the inventory into IITM’s Decision Support System and the development of the promised 2030, 2035 and 2040 scenarios.
