Ministry supports revised SO2 emission norms, slams critics
The statement came days after the Union environment ministry on July 11 extended deadlines and exempted a large number of coal plants from installing flue gas desulphurisation units
The government on Monday defended its recent move to ease sulphur dioxide (SO₂) emission norms for thermal power plants, saying the decision was based on detailed scientific studies and stakeholder consultations, and that media reports terming the move a “regulatory dilution” have “grossly misinterpreted” the notification.
The statement came days after the Union environment ministry on July 11 extended deadlines and exempted a large number of coal plants from installing flue gas desulphurisation units.
“The media reports misrepresent both the scientific evidence and the environmental policy rationale underlying the revised notification,” the ministry said in its statement on Monday.
It said the revised norms were framed after “extensive consultations with stakeholders and research institutions regarding the effectiveness and rationale behind stack emission standards for SO2 on 537 TPPs throughout the country, and its role in overall ambient air pollution of the region.”
Further, the ministry said sulfate aerosols from SO2 constitute a relatively small fraction of PM 2.5, suggesting that was not a major public health issue, as suggested by environmental groups. “Current exposure levels provide no credible evidence to suggest that SO2, under prevailing ambient conditions, is a major public health concern. Moreover, sulphate aerosols formed from SO2 constitute a relatively small fraction of PM2.5,” it said.
Addressing SO2 emissions is critical due to their contribution to secondary particulate pollution, experts have warned.
{{/usCountry}}Addressing SO2 emissions is critical due to their contribution to secondary particulate pollution, experts have warned.
{{/usCountry}}Quoting a study by IIT Delhi, the ministry said, “A detailed analysis carried out by IIT Delhi shows that sulfate contributes only 0.96 per cent to 5.21 per cent of PM2.5 and 0.57 per cent to 3.67 per cent of PM10 in cities near TPPs (thermal power plants).”The ministry said the assertion that sulphur compounds contribute 12-30 per cent 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.
{{/usCountry}}Quoting a study by IIT Delhi, the ministry said, “A detailed analysis carried out by IIT Delhi shows that sulfate contributes only 0.96 per cent to 5.21 per cent of PM2.5 and 0.57 per cent to 3.67 per cent of PM10 in cities near TPPs (thermal power plants).”The ministry said the assertion that sulphur compounds contribute 12-30 per cent 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.
{{/usCountry}}On July 12, Centre for Science and Environment said: “The revised notification weakens India’s clean air ambitions by diluting or removing SO₂ norms for Category B and C thermal power plants, which together represent most of the country’s coal capacity. Together, these exemptions threaten to derail progress on industrial air pollution control, compromise public health, and reduce the effectiveness of India’s environmental regulations.”
{{/usCountry}}On July 12, Centre for Science and Environment said: “The revised notification weakens India’s clean air ambitions by diluting or removing SO₂ norms for Category B and C thermal power plants, which together represent most of the country’s coal capacity. Together, these exemptions threaten to derail progress on industrial air pollution control, compromise public health, and reduce the effectiveness of India’s environmental regulations.”
{{/usCountry}}“Further, the norms were based on detailed scientific studies which were carried out by premier institutions such as IIT Delhi, National Institute of Advanced Studies as well as by the National Environmental Engineering Research Institute (NEERI) -- a constituent laboratory of Council of Scientific and Industrial Research (CSIR) besides scientific examination by Central Pollution Control Board,” it said.
Responding to criticism over the rollback of deadlines and exemptions for Category C plants, which make up the bulk of India’s coal fleet, the ministry said, “The media reports misrepresent both the scientific evidence and the environmental policy rationale underlying the revised 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.
The ministry also rejected suggestions that the National Ambient Air Quality Standards (NAAQS) for SO2, last revised in 2009, are outdated.
“The contention that the existing SO2 NAAQS, last updated in 2009, are obsolete simply due to their age is scientifically unfounded,” it said.
In the July 11 notification, the ministry said the compliance deadline for Category A plants, located within a 10-km radius of the National Capital Region or cities with a population of more than one million, remains December 2027.
Category B plants, situated within a 10-km radius of critically polluted areas or non-attainment cities, will now be assessed on a case-by-case basis instead of adhering to the earlier 2025 deadline.
Category C plants -- all others not falling under Category A or B -- have been completely exempted from the sulphur dioxide norms, provided they meet the prescribed stack height criteria by December 31, 2029. These plants were earlier required to comply by December 2026.
India established stringent sulphur dioxide emission standards for coal-based power plants in December 2015, requiring compliance within two years.
Even after four extensions, most of coal-fired power plants have not yet installed flue gas desulphurisation units to control SO2 emissions, a major air pollutant that converts into fine particulate matter (PM2.5) and causes a range of diseases.
According to US Environment Protection Agency, control measures that reduce SO2 can generally be expected to reduce people’s exposures to all gaseous SOx. This may have the important co-benefit of reducing the formation of particulate sulfur pollutants, such as fine sulfate particles.
Emissions that lead to high concentrations of SO2 generally also lead to the formation of other SOx. The largest sources of SO2 emissions are from fossil fuel combustion at power plants and other industrial facilities, EPA has said.
Following the July 11 notification, Shiv Sena (UBT) leader Aaditya Thackeray reached out to Union environment minister Bhupender Yadav and said that the notification has diluted the existing norms.
“The notification dilutes the 2015 notification issued by the government to install flue gas desulphurization (FGD) units for all coal plants. I am sure you are aware that FGD units are critical because they remove sulphur dioxide from the air-- a major pollutant and a health hazard. Installing FGD units can help avoid up to 48,000 deaths annually in India,” Thackeray said in his letter.
“the recent notification exempts almost 80% of all thermal power plants in the country from installing this crucial pollution control measure. Only 50 thermal power plant units across the country have FGD measures installed and this policy exempts 462 of 600 from installing these measures,” Thackeray wrote.
“We are seeing air quality consistently deteriorate across cities and in our villages. While we talk about ‘Viksit Bharat’ and ‘panchamrit’ goals at global forums...I am compelled to critique such policies that enable pollution under the name of development,” the letter, shared by the former Maharashtra environment minister on X, said.
Meeting SO2 norms requires the installation of Flue Gas Desulphurisation (FGD) systems, which remove sulphur compounds from fossil fuel emissions.
Minister of state for power Shripad Naik had said, in response to a Rajya Sabha question last year, that no SO2 norms were applicable until the end of 2015, and hence, FGD system manufacturing capacity was almost non-existent in the country.
“Coal-based power generation is one of the biggest contributors to air pollution after transportation, primarily due to sulphate formation from SO2 emissions. However, repeated delays in implementing emission standards for coal-based power plants since 2017 have hindered progress toward cleaner air. Exempting category C plants, which account for nearly 80% of India’s installed power capacity, from SO2 controls will severely undermine efforts to achieve clean air across the country,”said Envirocatalysts founder and lead analyst Sunil Dahiya.
