An analysis of 37 coal plant units within a radius of 300 km of Delhi-NCR has found that 20 of them are emitting sulfur dioxide above the safe limits set by the Ministry of Environment, Forest and Climate Change, and that the single biggest source of that pollution comes from plants the Centre has explicitly exempted from installing flue gas desulphurisation (FGD) systems, a vital industrial pollution control technology.The study, released Monday by the Finland‑based nonprofit Centre for Research on Energy and Clean Air (CREA), warns that exemptions granted to Category C plants — that form nearly four‑fifths of India’s coal fleet — are now directly responsible for the bulk of unchecked emissions drifting into the Capital’s air. With over six million tonnes of sulfur dioxide released annually, India’s emissions from its power plants already stand higher than any other country on earth, according to the report.In 2015, India gave its coal power plants two years to install the technology to cut sulfur dioxide emissions. Ten years, four deadline extensions, and one major rule dilution later, most plants still don’t have it, and as of last July, most never will have to.Even as the installation of FGD systems was made mandatory in 2015, this rule was deferred four times. Later, a 2021 notification had split coal-fired plants into three categories by location (Category A: near Delhi-NCR or million-plus cities; B: near critically polluted or non-attainment areas; C: everywhere else), each with different compliance timelines. Last July, the government notified that Category A still must comply by 2027 and Category B is now judged case-by-case, but all Category C units, 78% of India’s coal fleet, were fully exempted from installing any control technology.Key findingsThe assessment linked to Delhi-NCR has revealed that out of an estimated 154 kilotonnes of SO2 emitted annually by the units with data, 90% comes from plants lacking FGD, and 81% comes specifically from Category C plants. Several of the largest emitters, including Rajpura, Talwandi Sabo, Rajiv Gandhi TPS, Guru Hargobind TPS, Harduaganj and Ropar, have been operating without FGD.Even where FGDs are installed, some units still fail to meet emission limits, a pattern likely explained by scrubbers running below capacity, undergoing maintenance, or being temporarily offline rather than functioning as designed, the study noted.To measure the scale of the problem beyond compliance status alone, CREA estimated actual SO2 output for the 25 units with usable data, arriving at a combined 154 kilotonnes emitted annually.Story continues below this adSplitting this by technology reveals a lopsided pattern: units fitted with FGD accounted for just 16 kilotonnes, while those without contributed 138 kilotonnes, meaning nine out of every ten tonnes of SO2 in this dataset was observed from plants that were never equipped with scrubbing technology at all.Two plants illustrate what a functioning FGD system looks like in practice. Dadri and Mahatma Gandhi thermal power plants, both fitted with FGD, recorded the lowest SO2 output among the plants. Despite generating between 3,400 and 4,000 million units of electricity a year, output comparable to some of the region’s larger emitters, Mahatma Gandhi TPP’s two units emitted only an estimated 1,775 and 2,154 tonnes of SO2 respectively, a fraction of what similarly sized uncontrolled plants released.At the other end has been the region’s biggest polluters, Rajpura’s two units top the list, with estimated annual emissions of 20,851 and 22,690 tonnes of SO2 respectively, making each individually responsible for more sulfur dioxide than some entire uncontrolled plants combined. Several other stations, including Talwandi Sabo (units 8 and 9), Rajiv Gandhi thermal power station (units 1 and 2), Guru Hargobind thermal power station (units 1, 3 and 4), Harduaganj (units 8 and 9), and Ropar (unit 6), each contributed several thousand tonnes annually. None of these plants have FGD installedSO2: a cause of concernA precursor to secondary pollutants in the atmosphere, sulfur dioxide is a toxic gaseous pollutant. It is generated by anthropogenic activities through fossil fuel burning in coal-fired power plants (CFPPs) and industries, according to the report.Story continues below this adAfter India, the largest emitters of sulfur dioxide globally are South Africa, Turkey, Saudi Arabia and China. Despite having only about a fifth of China’s coal capacity, India’s emissions run nearly three times higher, which the report attributes to just 12% of Indian plants having the FGD systems installed, compared to much wider adoption in China and the US, where FGDs have helped cut national SO2 output several times over.The entire exemption structure hinges on where a plant sits, specifically, whether it falls within ten kilometers of Delhi-NCR, a million-plus city, or a critically polluted area. Plants outside that radius were placed in Category C and, as of last year, freed from any obligation to control emissions at all, researchers have noted that this has been a cause of concern.“Thus, to reduce the substantial amount of SO2 emitted and its contribution to particulate matter formation in India’s most polluted region, the mandatory installation of FGD must be extended to all coal-fired power plants in India to reduce pollution and human health impacts, regardless of category. Real-time online continuous emission monitoring data must also be made available to the public to verify compliance,” the study has recommended.