Overview
- Using NASA’s MERRA-2 reanalysis for 2024, the assessment estimates ammonium sulfate contributes 17%–42% of PM2.5 across states, with most clustering between 30% and 40% annually.
- In Delhi, ammonium sulfate accounts for roughly 33% of annual PM2.5 and surges to 49% post-monsoon and 41% in winter, pointing to region-wide secondary formation rather than only local sources.
- India is the world’s largest SO2 emitter, and coal-fired power plants contribute at least 60% of national SO2, underscoring the importance of controlling precursor gases.
- CREA says about 78% of coal power units are exempt from flue gas desulphurisation, and it urges restoring mandatory requirements and adding precursor-focused controls in the National Clean Air Programme revisions.
- Coal-heavy states show the highest shares—Chhattisgarh at 42%, Odisha at 41%, Jharkhand and Telangana at 40%—while southern Haryana districts record ammonium sulfate near 19–20 µg/m³, forming about 29%–34% of annual PM2.5.