India could prevent an estimated 1,24,564 deaths every year by fully mitigating sulphur dioxide (SO₂) emissions from coal-fired power plants (CFPP), according to a study conducted by researchers from IIT Delhi, published in the Nature journal this week.
The study is among the first comprehensive attempts to quantify how SO₂ from CFPPs contributes not only to ambient SO₂ levels, but also to the formation of secondary fine particulate matter, or PM2.5.
The researchers found that a decrease in these emissions could reduce annual PM2.5 exposure by 0.3-12 microgrammes per cubic metre and ambient SO₂ levels by 0.1-13.6 parts per billion across states.
The CFPPs emit SO₂, which reacts in the atmosphere to form secondary inorganic aerosols, including sulphate, nitrate and ammonium. These pollutants add to PM2.5, the fine particulate matter linked to cardiovascular and respiratory diseases.
“Multiple existing source apportionment studies show that the energy sector is the leading contributor to air pollution. Along with the household sector, thermal power plants are also among the leading contributors. So, we wanted to quantify the exact contribution from this sector,” Debajit Sarkar from IIT Delhi, one of the co-authors of the study, said.
“The overall goal was to check if we can quantify and provide to different states their specific emissions volume, so that they could make specific policies,” he said.
The researchers used air pollution models and satellite data on SO₂ emissions from CFPPs. They also used the ‘Global Burden of Disease’ framework – which measures the impact on health across places, time, age, and sex – to estimate deaths that could be prevented from diseases linked to air pollution, including heart and respiratory illnesses. Further, they matched air quality data with National Family Health Survey-5 data — conducted in 2019–21 — to see how the benefits would differ across gender, caste and income groups.
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What the study shows
The study found that complete mitigation of SO₂ emissions from CFPPs could prevent 14,777 cardiovascular deaths and 8,476 respiratory deaths annually, apart from the all-cause mortality reduction.
Maharashtra, Tamil Nadu and Karnataka were estimated to see the highest number of avoidable deaths due to high population exposure to pollution. Chhattisgarh and Odisha were expected to see the biggest improvement in air quality because they have several coal power-based pollution hotspots.
Further, the study found that the benefits would not be evenly distributed. People from Other Backward Classes, Scheduled Castes and Scheduled Tribes, and poorer and middle-income groups are expected to see larger air quality gains than wealthier and general category groups. According to the researchers, this makes SO₂ mitigation not only an air pollution issue, but also an environmental equity issue.
“We made sure that meteorology and emissions were both included in the study model. Season-specific contribution of pollutants was also important. During winter, power plants are major contributors to pollution,” Sarkar said, adding that location, transported air pollution and population exposure were all significant in assessing the health impact of SO₂ emissions.
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Weighing costly tech
The study comes amid continuing debate over the installation of flue gas desulphurisation (FGD) systems in CFPPs. The FGD is a technology that removes SO₂ from exhaust gases of fossil fuel power plants and industrial boilers, reducing acid rain and air pollution.
A key argument against FGD installation has been that Indian coal has relatively low sulphur content, making the technology expensive. The study, however, argues that health-related monetary gains from reduced emissions are likely to outweigh the cost of installing emission-control technologies.
Manoj Kumar, a researcher at the Centre for Research on Energy and Clean Air, said the findings are significant because earlier estimates did not fully quantify SO₂-linked health impacts. “The observations are significant, especially that the cost of saving lives will outweigh FGD-related expenses.”
Kumar said the findings should be read in the context of the 2015 emission norms for thermal plants and subsequent delays in compliance. “These kinds of assessments were not taken into account during the reversal of the 2015 policy. Most importantly, the study shows the health impacts on vulnerable people and also the distribution among states,” he said.
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On December 7, 2015, the Union Ministry of Environment, Forest and Climate Change had introduced mandatory emission norms for CFPPs, targeting significantly lower levels of SO₂, nitrogen oxides, mercury and particulate matter. On July 11, 2025, the Centre relaxed the 2015 emission norms for CFPPs, exempting roughly 79% of coal-fired units from installing FGD systems to curb SO₂ emissions.
According to the IIT Delhi study, while SO₂ emissions from CFPPs declined globally between 2005 and 2021, India moved in the opposite direction. Satellite-derived estimates showed India’s SO₂ emissions rose from 2.36 thousand kilotonnes per year in 2005 to 5.05 thousand kilotonnes per year in 2021, with a further increase of about 30% in 2023.
The study said that stronger implementation of SO₂ emission norms, wider adoption of FGDs and related control technologies, and prioritisation of hotspot regions are essential. “India needs to strictly enforce SO₂ emission rules, expand the use of FGDs and pollution-control technology in power plants, and prioritise highly-polluted areas. Also, use of cleaner cooking fuels and electric vehicles, as well as decrease in stubble burning incidents are necessary,” said Sarkar.
The study also said that implementation of SO₂ emission norms remains “slow, localised and uneven” in India, and that fully enforcing current limits could cut coal power plant-linked SO₂ and PM2.5 emissions by over 80% by 2030.
What the study shows