Noida, Faridabad among 4 NCR cities yet to complete pollution-source studies

Four cities in the National Capital Region (NCR), including Noida and Faridabad, are yet to complete studies identifying the main sources of air pollution under the Centre’s National Clean Air Programme (NCAP), despite the deadline for the exercise having passed nearly a year ago.

The Central Pollution Control Board (CPCB) had set November 15, 2025, as the expected deadline for completing source apportionment studies.

In Faridabad, the study was commissioned in 2022, but its final report is still awaited, The Indian Express has learnt. Noida, Meerut and Khurja are the other three NCR cities among the 23 NCAP cities where source apportionment and emission inventory studies remain incomplete.

Together, the four cities account for 17.4% of the pending studies.

Officials said that according to a recent CPCB review, studies have been completed in 107 of the 130 NCAP cities across 22 states. Work is still under way in 23 cities across eight states. Uttar Pradesh accounts for the highest number of pending studies, with 11 cities, including Noida, Meerut and Khurja.

The studies are meant to estimate the contribution of different sources, including vehicles, industries, road dust, construction and biomass burning, to a city’s air pollution.

The delay in Faridabad stands out, with nearly four years having passed since the study was commissioned.

Story continues below this ad

According to Haryana’s State Action Plan for Clean Air, the work was assigned to The Energy and Resources Institute (TERI) through the Municipal Corporation of Faridabad, with the work order issued in 2022.

Haryana State Pollution Control Board (HSPCB), meanwhile, awarded studies for Gurugram, Sonipat and Panipat to the Automotive Research Association of India (ARAI), Pune, in January 2023. While the studies in these three cities were completed this year, HSPCB is still analyzing the findings, officials said.

Measuring sources

Source apportionment studies estimate how different pollution sources contribute to particulate matter (PM) – a mixture of primary and secondary aerosols – in the air.

A senior CPCB scientist said, “…this involves collecting PM10 and PM2.5 samples at multiple locations over a period of time, across different seasons, and analysing their chemical composition. The findings are then matched with emission data and assessed using receptor models to estimate how much different sources are contributing to PM.”

Story continues below this ad

“The exercise takes time the data must be reliable and comparable before the findings can be peer-reviewed,” the scientist added.

An emission inventory is a related exercise that estimates pollution from activities such as transport, industries, construction, household fuel use and waste burning. The CPCB classifies these as point sources, such as industrial stacks; line sources, such as roads and traffic; and area sources, which include smaller, scattered activities.

The technical work is carried out by research and academic institutions appointed by State Pollution Control Boards and Pollution Control Committees.

Explained

Source apportionment studies are the first step towards preparing a comprehensive air quality management plan. They involve assessing air quality, preparing an emission inventory, and identifying the main sources of pollution. The studies estimate how much different sources, such as vehicles, industries, road dust, construction, and biomass burning, contribute to a city’s pollution. The findings help authorities identify priority sources and plan targeted measures to reduce emissions.

Delhi’s multiple studies

Story continues below this ad

Delhi and the wider NCR have seen several source apportionment and emission inventory studies. The CAQM’s April 2025 framework lists assessments conducted by NEERI in 2010, IIT Kanpur in 2016, SAFAR in 2018, TERI and ARAI in 2018, and TERI and IIT Kanpur in 2023.

The TERI-ARAI study, published in 2018, assessed PM2.5 and PM10 sources across Delhi-NCR using 2016 as the base year. A separate SAFAR inventory used 2018 as its base year, while the TERI-IIT Kanpur assessment used 2021-22 data.

However, CAQM has flagged considerable differences among existing emission inventories because of variations in methodology, assumptions, geographical boundaries, source categories, activity data and emission factors. It has also pointed to gaps in reliable and regularly collected data.

To address these limitations, CAQM issued a common framework in April 2025 for a fresh exercise across Delhi-NCR. It calls for high-resolution mapping of pollution sources on a 500-m-by-500-m grid, covering transport, industries, households, crop residue burning, road dust and waste burning.

Story continues below this ad

This January, CAQM said the work had been entrusted to CPCB. A consortium led by ARAI, Pune, along with IIT Delhi, TERI and IITM Pune, was awarded the project to prepare an updated inventory and source apportionment study using 2026 as the base year.

Peer review pending

Separately, reports from 53 cities where the studies have been completed are awaiting peer review, CPCB officials said. These are different from the 23 cities where the studies themselves remain incomplete.

The cities awaiting peer review include Guntur, Visakhapatnam, Patna, Guwahati, Raipur, Vadodara, Jammu, Hubballi, Jalandhar, Jaipur, Chennai, Lucknow, Dehradun, Kolkata, Indore and Nagpur.