Bengaluru: The Union environment ministry’s recent move to exempt a large number of thermal power units from installing a cleaning technology to limit sulphur emissions has come under scrutiny. In a notification on July 11, the ministry had announced that nearly 80% of thermal power units across the country would be exempted from installing technology to limit sulphur emissions. However, this move undoes the ministry’s earlier notification in 2015 that mandated all thermal power plants to implement the technology – Flue Gas Desulfurization systems (FDGs), specifically – in their units.An air pollution scientist told The Wire that the environment ministry’s decision takes India back 10 years, stressing that FDGs are the only way to control sulphur emissions from power plants and thus, reduce pollution at the source. The rationale such as India witnessing a lack of technology to implement FGD systems was “absurd”, they said. Additionally, studies such as this one in 2022 have even recommended that the technology be implemented effectively in India so as to reduce sulphur emissions further.Meanwhile, on Monday, July 14, the ministry defended its move. Facing severe criticism, the ministry released a statement, claiming that media reports have “grossly misinterpreted” its notification and that the rationale was based on “detailed scientific studies” and “extensive consultations with stakeholders and research institutions”. However, many justifications given by the ministry in its defence do not hold, experts told The Wire. For instance, if sulphur emission levels were not a public health concern, why was the first mandate in 2015 introduced at all in the country, a researcher asked.Extensions and exemptionsThermal power plants (which can have multiple units) that run on coal emit numerous pollutants. Sulphur dioxide, a gas, is one of them. Once released, sulphur dioxide also interacts with air, forming small particles called sulphates. This is considered a major air pollutant.Studies, such as this 2022 literature review, show that sulphur emissions can cause several health impacts including adverse ones on the human respiratory, cardiovascular and nervous systems.But this is where FDGs help: they filter out as much as 90-95% of sulphur from thermal power plant emissions. This is technology that many countries, including the United States and China have adopted, according to air pollution researcher Sunil Dahiya, Founder and Lead Analyst at Delhi-based think tank EnviroCatalysts. A 2017 study in the journal Scientific Reports found that while sulphur emissions in China had declined by 75% since 2007, thanks to sulphur-limiting mechanisms in place, emissions in India increased by 50% in the same time.“This finding…suggests effective SO2 [sulphur dioxide] control in China and lack thereof in India…In India, ~33 million people now live in areas with substantial SO2 pollution,” it stated.With most of India’s power plants running on coal, the Ministry of Environment, Forests and Climate Change had come out with a crucial notification in 2015, called the Environment (Protection) Amendment Rules, 2015: it mandated that all thermal power plants units install FDGs to limit sulphur emissions in two years. However, following murmurs of dissent from stakeholders including the Ministry of Power, the environment ministry extended the deadline. Thermal power plant units operating in the National Capital Region of Delhi were to install FDGs by December 2019, while all others across the country were mandated to do so by December 2022. Goalposts shifted againA notification from the ministry in March 2021 categorised thermal power plant units into three categories, setting different deadlines for each of them. Category A units (those within a 10 km radius of the National Capital Region or cities having a population of more than one million) had to install FDGs by December 2022. Category B units (those within a 10 km radius of Critically Polluted Areas such as Vapi in Gujarat, or Non-Attainment Cities such as Bengaluru in Karnataka which have not met national standards for specific air pollutants for at least five years) were to install FDGs by December 2023. All other thermal power plant units fell in Category C, and were to install FDGs by December 2024.Another notification in September 2022 changed deadlines, again. Timelines now extended to December 2024, December 2025 and December 2026 for Category A, B and C units, respectively. Again, in December 2024, a notification announced new deadlines, December 2027, December 2028 and December 2029 for Category A, B and C units, respectively.Currently, 537 thermal power plant units (that generate 2,04,160 megawatts of thermal coal-based power) have been identified for installation of FGDs as of December 2024, per a reply given in parliament by the Minister for Power. Of these, FGDs have been installed in 44 units (22,590 MW), while contracts have been awarded or are under implementation in 233 units (1,02,040 MW). Meanwhile, 138 units (43,987 MW) are under various stages of tendering processes and 122 units (35,543 MW) are in the pre-tendering process for installing FDGs.However, as if the delays were not enough, the government has now done away with the deadline for nearly 80% of thermal power plant units. In its latest notification published in the Gazette of India, the environment ministry announced that Category C units (which amount to nearly 400 in number across the country) would be completely exempted from installing FDGs and Category B units would need to install FDGs depending on the recommendations of an Expert Appraisal Committee in charge of thermal power projects. Category A units, meanwhile, have to comply with sulphur emission limiting norms by December 2027. In its notification, the ministry said that it had received “representations” from stakeholders regarding exemption or relaxation in timelines of sulphur emission standards due to several reasons: limited availability of technology providers, techno-economic feasibility, the negative impact on the supply chain that lockdowns and other events had caused during the COVID-19 pandemic, price escalation due to high demand and low supplies, a low sulphur dioxide concentration in ambient air and “heavy burden on consumer due to increase in electricity prices”. The ministry had also received the “explicit recommendation of the Ministry of Power” about this, the notification said.This comes right after a high-powered committee chaired by principal scientific advisor Ajay Sood recommended that India exempt all coal-fired thermal power plants from installing FDGs, per a report by The Hindu in June.‘Absurd’ rationaleMeanwhile, India has overtaken China to become the world’s highest emitter of sulphur dioxide, contributing to more than 15% of global anthropogenic emissions, according to a report published by Greenpeace in 2019. Nearly 70% of India’s sulphur emissions come from coal-fired power plants.A study by scientists at the Indian Institute of Technology Kharagpur in 2022 found that while there were monthly and seasonal changes in sulphur dioxide emission concentrations across the country from 1980 to 2020, high-capacity thermal power plants in the lower Indo-Gangetic Plains and Central India had caused “high” sulphur dioxide pollution in these areas. Meanwhile, it also found that sulphur emissions in India in the last decade (2010-2020) had decreased. “It is achieved primarily due to the strict control measures, adaptation of new technology, and shift towards renewable energy sources during the period. Therefore, both economic growth and air pollution control can be performed hand-in-hand by adopting new technology that helps to reduce SO2 emissions,” the study said.The study also recommended that coal-fired power plants be subjected to pollution standards, “similar to those in emerging (such as China) and developed (e.g., EU, Australia, and USA) economies”, citing FGDs as an example. Per the study, “mandating existing coal-fired power plants to install FGD and scrubber systems can reduce SO2 pollution”. The science is clear: FDGs help cut sulphur emissions drastically. The environment ministry’s move to exempt all Category C thermal power units from installing FDGs “takes us back ten years” in terms of controlling sulphur emissions, Dahiya told The Wire.Emissions from power plants do not just impact cities nearby, but can be felt for up to 200 kilometres away, depending on the geography of the area and meteorological conditions, he said. Villages or small towns in this radius can also be affected by such pollution. Moreover, the notification to exempt Category C units from installing FGDs takes away the opportunity to reduce fine particulate matter or PM2.5 levels as well, because sulphates also contribute to fine particulate matter which is another major pollutant in the country, Dahiya added. “It is always more efficient and faster to control pollution at the source of emission, at the point source,” he said.On the environment ministry’s reasoning on lack of technology, Dahiya said, it was “a very absurd argument”. “If this was supposed to be true then no power plants in India should have been able to install this technology. On the contrary, the NTPC [National Thermal Power Corporation], the biggest power producer in India and run by the government, has installed FDGs in many of their capacities, and has awarded tenders for several others. So the question of lack of technology does not arise,” he said.“It was purely a question of intent – or lack of it – in the power sector to install this technology which would have increased the cost of electricity generation,” he added. However, Dahiya also pointed out that the government had clarified in 2019 that this increase in cost can be passed on to the consumer. The increment in cost would have possibly been from 35 to 50 paisa per unit, not more, depending on the size of the power plant. That is not a huge increase in cost; every few years, discoms have to increase electricity rates by this much due to inflation and other cost increments, Dahiya noted.What will now happen to plants that have installed FGDs?“It is a question that the government has to answer,” Dahiya said. “Does this mean that power plants that have installed it operate the FGDs and risk a higher cost in terms of electricity produced per unit and possibly going down the merit order dispatch, while others that have not installed FGDs benefit financially from not doing so by supplying electricity before plants with FGDs due to lower cost?” If FGD units are not used, the investments on them would be a waste of public funds, Dahiya pointed out.Senior Congress leader and former Union environment minister Jairam Ramesh has also slammed the government for its July 11 notification.“Sulphur dioxide is a direct threat to public health and has also been known to impact cloud formation, disrupting the monsoon that is the lifeline of the Indian economy,” Ramesh said in a post on social media platform X on July 13. “More damagingly, research has increasingly shown that a large part of India’s ambient PM2.5 (fine particulate matter of diameter less than 2.5 mm) is attributable to secondary particulate matter formed when sulphur dioxide reacts with other compounds. Estimates suggest that anywhere between 12% to 30% of PM2.5 is attributable to such sulphur dioxide compounds.”The Modi Government has already achieved the dubious distinction of having made India the global leader in sulphur dioxide emissions. Now we learn that the Environment Ministry has exempted 78-89% of India’s thermal power plants from installing flue gas desulphurisation (FGD)… https://t.co/ZGcuZqJbqP— Jairam Ramesh (@Jairam_Ramesh) July 13, 2025Ministry on back footFollowing criticism, on July 14, the environment ministry claimed in a post on X that media reports have “grossly misinterpreted” its notification. The ministry said that the decision was based on “extensive consultations with stakeholders and research institutions” such as the Council of Scientific and Industrial Research’s National Environmental Engineering Research Institute (NEERI), National Institute of Advanced Studies (NIAS) and IIT Delhi, and that norms were decided based on detailed studies undertaken by these institutes. However, the statement does not specify what these studies are, or the methods the studies used to arrive at their findings. Yet, it claims anyway that media reports misrepresented “both the scientific evidence and the environmental policy rationale” behind the notification. “Contrary to claims of regulatory dilution, the ministry’s decision represents a rational, evidence-based recalibration anchored in current ambient air quality data, sectoral emission trends, and broader sustainability imperatives,” it said.Arguing that Indian coal is low-sulphur (containing less than 1% of sulphur), the statement added that sulfate aerosols formed from sulphur dioxide “constitute a relatively small fraction of PM2.5”. The revised sulphur dioxide emission policy was “not a rollback of environmental safeguards, but a pragmatic, scientifically justified shift toward more targeted, cost-effective, and climate-coherent regulation”, the statement read.“It reflects declining ambient sulphur dioxide levels, recognizes the limited role of sulphur dioxide in driving PM2.5 health impacts, and weighs the disproportionate resource and environmental costs of indiscriminate FGD mandates. The media report is not aligned with empirical evidence, exaggerates the health and air quality impacts of sulphur dioxide, and underestimates the trade-offs of large-scale FGD implementation,” the ministry stated.It added that the “assertion that sulfur compounds contribute 12–30% of PM2.5 is an unsubstantiated claim and not supported by any rigorous scientific studies conducted in major Indian cities, and it significantly overstates the contribution of SO₂ in India’s particulate pollution burden”.The statement also went so far as to say that there is no “credible evidence” to suggest that sulphur dioxide emissions at the current exposure levels is a major public health concern. Science, meanwhile, clearly shows that sulphur emissions are a health hazard. “If sulphur emission levels were not a public health concern, why was the first mandate in 2015 introduced at all in the country,” Dahiya asked The Wire.Contradictions and excusesA statement by the Centre for Research on Energy and Clean Air (CREA) on June 13 this year highlighted how institutional reports that the ministry has cited actually “undercut FGD policy with contradictions”. CREA stated that FDGs are “proven” technology that remove sulphur dioxide but studies by institutions like NEERI, NIAS, and IIT Delhi (2022 and 2024) were now “being selectively used” to justify not installing FDGs, by citing low levels of sulphur dioxide or small increases in carbon dioxide.“These arguments simply don’t hold up,” the statement said. “The claim made by the NEERI that ambient SO₂ levels are already low is highly misleading. The air quality monitoring stations (CAAQMS) don’t capture the real impact of power plant pollution because they don’t track whether emissions drift upwind or downwind, and they certainly don’t account for chemical reactions that convert SO2 into other pollutants like PM2.5. Just because the station reading is low ambient SO2 doesn’t mean the plant is not polluting.”“It is clear that by contradicting their own earlier reports and relying on misleading scientific arguments, much of the power sector barring NTPC appears intent on delaying FGD installation. This approach prioritises profit over public health, placing the burden of inaction on the very people it is meant to serve: Indian citizens,” CREA’s statement read.