Eighty-One Per Cent of Delhi's Coal Sulphur Comes From Plants Legally Excused

Article summary

An analysis by the Centre for Research on Energy and Clean Air finds that nearly 81 per cent of estimated sulphur dioxide emissions from coal-fired power plants within a 300-kilometre radius of Delhi-NCR come from units exempted from installing flue gas desulphurisation equipment under the Union government's notification of July 2025. That notification substantially reversed emission standards first set in 2015, replacing a universal FGD requirement with a three-category framework: Category A plants must still comply by 2027, Category B plants are assessed case by case, and Category C — accounting for roughly 78 per cent of India's coal-fired units — is exempted altogether. The environmental significance lies in what sulphur dioxide becomes rather than what it is. SO₂ is a precursor of secondary particulate matter: once emitted it oxidises in the atmosphere to form sulphate aerosols that contribute directly to PM2.5, the pollutant associated with respiratory disease, cardiovascular illness, stroke and premature death. Because these reactions occur over hours to days, the particles form far downwind of the stack — which is why coal plants up to 300 kilometres away are relevant to air quality over the capital, and why source-region regulation cannot be replaced by city-level measures.