A report by the Centre for Research on Energy and Clean Air (CREA) found that at least 81 per cent of sulphur dioxide emissions from coal-fired power plants within 300 km of Delhi-NCR originated from units exempted from installing flue gas desulphurisation (FGD) systems. CREA analysed emissions from 25 of the 37 coal-fired power plants in the zone for which public data were available and estimated total emissions of 154,000 tonne (t) of SO2 in 2025.

CREA noted that about 90 per cent of that estimated SO2 came from plants operating without FGD systems and that 81 per cent of the emissions were attributable to Category C plants removed from mandatory SO2 control by the July 2025 notification. The analysis therefore attributed the bulk of regional SO2 releases to units no longer required to fit controls under the revised rules.

Under the government’s 2015 emission standards all coal-fired power plants were required to install FGDs, but the Ministry of Environment, Forest and Climate Change revised the obligation in July 2025. The notification resulted in 78 per cent of India’s coal-fired units being exempted from mandatory SO2 control, with 11 per cent assessed on a case-by-case basis and 11 per cent remaining subject to the requirement.

The report recalled that India is the world’s largest SO2 emitter in the power sector, releasing over six mn t annually, and used plant-level comparisons to illustrate the impact of controls. Mahatma Gandhi Thermal Power Plant Units one and two, fitted with FGDs, generate roughly 3,400-4,000 mn units of electricity each year while emitting an estimated 1,775 t and 2,154 t of SO2 respectively.

By contrast, Rajpura Thermal Power Plant Units one and two log similar generation but emit an estimated 20,851 t and 22,690 t of SO2 without effective controls, making them the largest emitters in the assessed set. CREA recommended reinstating mandatory FGD installation for all coal-fired plants, making Continuous Emission Monitoring Systems (CEMS) data publicly available and disclosing the operational status of FGDs to strengthen compliance and reduce air pollution and health harm.