In 2018, Delhi bade farewell to its last thermal power plant. Before this, the other two had wound up their operations in 2009 and 2015. The closures were meant to stop toxic gases spewing from their stacks from worsening the city’s air quality.

But the closure didn’t end the impact on Delhi’s air from such plants. In fact, the capital has continued to endure pollution from 12 thermal power plants situated within 300-km of its radius. 

As much as 9 percent of Delhi’s pollution is caused by such plants, if a recent study is to be believed.

Experts said this reinforces that sources of pollution are not limited to geographical or political boundaries and that North India needs a coordinated regional plan. 

Data contradicts theory

According to the study by Indian and international researchers, 65 percent of Delhi’s PM2.5 load drifts in from neighbouring states, notorious for coal-fired power plants and fossil fuel-based industries. While episodic events like farm fires and Diwali receive disproportionate attention, thermal power plants escape a similar government and media scrutiny.

In July, the Central government let around 80 percent of India’s thermal power plants skip installing pollution-controlling devices, called flue gas desulfurisation (FGD) systems. These devices reduce sulphur dioxide (SO₂) emissions, which can react in the atmosphere to form harmful fine particulate matter (PM2.5).

The Ministry of Environment, Forest and Climate Change had already granted multiple extensions since 2017 for thermal power plants to install FGDs. A CSIR-NEERI study sponsored by NITI Aayog even claimed such devices offered “no significant environmental benefits”.

But the government’s own data contradicts this theory.

Power Minister Manohar Lal Khattar informed Parliament in December 2024 that FGDs had, in fact, helped reduce SO₂ emissions. But of the 36 units at 12 power plants around Delhi, only 14 units – including at Dadri (Uttar Pradesh) and Jhajjar (Haryana) – have installed FGDs.

Coal remains the backbone of India’s power sector, accounting for 55 percent of installed capacity and 74 percent of total power generation. Per capita electricity consumption has risen by nearly 46 percent in the past decade. India has pledged that 50 percent of its total power capacity will come from non-fossil sources by 2030. The share of non-fossil fuels in the installed capacity has already increased from 32 percent in 2014 to 45 percent in 2024 – suggesting progress toward that target.

Meanwhile, a new coal plant has begun operation much closer to Delhi. 

The Khurja Thermal Power Plant in Bulandshahr, about 120 km from the capital, started its first 660 MW unit in January 2025. The second unit, of equal capacity, began trial runs in August and is expected to be fully operational soon.

Delhi’s thermal troubles

Thermal power plants’ share in Delhi’s PM2.5 load is pegged around 9 percent, according to a research paper published by the Environment Research Letters journal and authored by scientists at IIT-Bombay and universities in France, the US, and China on September 3. Titled ‘Transboundary Emission Contribution to PM2.5 concentrations in Indian Cities’, the study covered 144 cities covered under the national clean programme and million-plus cities to track transboundary pollution. 

It’s not only Delhi with the energy sector contributing significantly to PM2.5 pollution in neighbouring cities. As much as 16 percent of Noida’s pollution is caused by the energy sector. For Ghaziabad, it also stands at 16 percent, shows an analysis of the primary data of the research paper. The Dadri power plant is located in Noida. 

Raj M Lal and Ajay S Nagpure, co-authors of the paper, told Newslaundry that emissions from TPPs can travel hundreds of kilometres, thereby polluting nearby cities. The study also observed that 65 percent of Delhi’s PM2.5 load is coming from nearby cities. The average transboundary pollution for all 143 cities is even higher: around 85 percent.

There are other signs that emissions from nearby TPPs are polluting Delhi’s air.

According to the decision support system developed by IITM-Pune, the regional contribution to Delhi’s PM2.5 load is significant. 

For example, Jhajjar’s contribution to Delhi has been predicted to be between 9.43 percent and 1.6 percent from October 5 to 8. It has five thermal power plants. 

Among the rest of the plants are three in UP’s Dadri, Aligarh’s Harduaganj and Bulandshahr’s Khurja; five in Haryana at Jhajjar, Panipat, Hisar and Yamuna Nagar; and four in Punjab at Patiala, Mansa, Bhatinda and Rupnagar.   

As per the commission for air quality management in April, only 13 thermal power plant units had installed FGDs. These were two units at Indira Gandhi STPP in Jhajjar; two units at Mahatma Gandhi STPP; all six units in Dadri; two units at Rupnagar; one unit at Aligarh. One unit at the Khurja plant, not part of the CAQM data, also has FGD.

In July, the environment ministry government exempted around 78 percent of the thermal power plants from installing FGDs. The rest of the plants, located within 10 km of NCR or in cities with one-million population, were mandated to install these pollution controlling devices. But of the 36 units, only 14 units at four plants (Dadri, Jhajjar and Panipat) fall under this category. And only 10 of them had installed FGDs as per the CAQM affidavit.

In November last year, the National Green Tribunal was shocked to learn that thermal power plants are more polluting than the episodic event of farm fires chiefly in Punjab and Haryana. It took suo muto cognisance of the study by Centre for Research on Energy and Clean Air arguing that the thermal power plants in Delhi-NCR produce 16 times more sulphur dioxide than caused by stubble burning. 

“...The study estimates that coal-fired thermal power plants in the NCR released a staggering 281 kilotons of sulfur dioxide (SO₂) annually. In comparison, crop burning, which is often cited as a major source of pollution, emitted 17.8 kilotons of SO₂ from the burning of 8.9 million tons of stubble,” the NGT noted in its order in November last year. 

The case has been adjourned since the Supreme Court is also seized of a similar matter.

Govt’s reasons for exemption

Reasons behind the government’s decision to exempt nearly 78 percent of India’s thermal power plants (TPPs) from emission norms can be traced to a CSIR-NEERI report commissioned by NITI Aayog. The report argued that the concentration of sulphur dioxide (SO₂) in ambient air remains within the “safe” limit of 80 µg/m³.

“This is despite the fact that most TPPs have not installed FGDs,” the report noted, referring to flue gas desulphurisation units designed to cut SO₂ emissions. “Installation of FGDs in TPPs leads to higher capital investment, increased power consumption, higher consumer tariffs, and a greater water and carbon footprint—without corresponding environmental benefits.”

Citing data from the Central Electricity Authority (CEA), the report said installing FGDs costs about Rs 1.4 crore per megawatt. “As per recent CEA estimates, around Rs 1.47 lakh crore of capital investment will be required for the installation of FGDs in the remaining 105 GW of coal-based capacity,” it stated.

While the study dismissed the environmental benefits of FGDs, data from the power ministry tells a different story. In December last year, power minister Manohar Lal Khattar shared performance data of TPPs with and without FGDs. At the time, only 10 units within a 300-km radius of Delhi had installed FGDs. Their SO₂ emissions were within or only slightly above the prescribed limits of 600 mg/Nm³ and 200 mg/Nm³. In contrast, nearly all other units without FGDs violated these norms – some by a wide margin. For instance, a plant in Jhajjar emitted five times more SO₂ than the permissible limit.

On the claim that ambient SO₂ levels remain within limits, Sunil Dahiya, lead analyst at EnviroCatalyst, said: “If four people leave a house and midway change their clothes, can you say that no one has left the house?” He was referring to how SO₂ released by power plants undergoes chemical reactions in the atmosphere, transforming into secondary pollutants like sulphate ions that form PM2.5.

On the cost of installation, Manoj Kumar, analyst at CREA, said a delay in installing FGDs had resulted in higher costs. 

Citing various studies, Shripad Dharmadhikary, founder of Manthan Adhyayan Kendra, noted that emissions from thermal power plants can affect areas well beyond their immediate vicinity – up to 100 km or more depending on wind direction and weather conditions. “If TPP emissions are not polluting Delhi, they are certainly affecting other cities,” he said.

Dahiya added that transboundary studies further confirm emissions from these plants are reaching the capital. “SO₂ is coming to Delhi not just as a primary pollutant but also as secondary particulates,” he said.

Call for regional plan

“It’s not Delhi’s own creation. No doubt it’s a regional problem. Pollution knows no political boundaries. Neighbouring cities such as Gurugram, Ghaziabad and Faridabad share the same landscape,” said Vimlendu Jha, founder at Swechha India.

Raj M Lal and Ajay S Nagpure, co-authors of the transboundary study, also seconded Jha. “Policies need to be more regional in nature. City-action planning is important, but to meet targets, city-and region-specific interventions need to be carried out.”

Manoj Kumar of CREA termed mitigating TPP pollution as a “low-hanging fruit”. “There are 215 thermal power plants in the country. We know where they are located and their contribution to air pollution. Since it’s identifiable and can be controlled, it’s a low hanging fruit unlike other sources of pollution,” he said.

Newslaundry sought comments from the CAQM, asking the commission about any discussions on a regional or common airshed programme for Delhi-NCR, and transboundary pollution. This report will be updated if a response is received.

This report is part of a collaborative campaign to tackle air pollution. Here’s how you can join the Fight To Breathe. Click here to power this campaign.