How does SO2 contribute to PM2.5 pollution in India?

SO2 in the atmosphere reacts to form ammonium sulfate, a major component of secondary particulate matter that significantly contributes to India's PM2.5 pollution.

Why are coal-fired power plants crucial for India's SO2 emissions?

Coal-fired power plants are identified as the largest national source of SO2, releasing at least 60 percent of the country's total SO2 emissions.

What is the role of flue gas desulphurisation (FGD) systems in India?

FGD systems are essential for controlling SO2 emissions directly at the source from power plants, playing a critical role in reducing secondary PM2.5 formation.

Home / Environment / India's Hidden Air Threat: SO2 Fuels PM2.5

India's Hidden Air Threat: SO2 Fuels PM2.5

24 Dec, 2025

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Summary

Secondary particulate matter, primarily ammonium sulfate, forms up to 42% of India's PM2.5.
78% of coal power plants are exempt from SO2 control systems.
Delhi's worst pollution episodes are driven by regional SO2 emissions.

India's Hidden Air Threat: SO2 Fuels PM2.5

A significant portion of India's PM2.5 air pollution originates from precursor gases, with secondary particulate matter, mainly ammonium sulfate, accounting for up to 42 percent. Coal-fired power plants are the largest national source of sulfur dioxide (SO2), a key component in forming this secondary pollution.

Despite this, a substantial 78 percent of these power plants are exempt from installing flue gas desulphurisation systems, weakening controls at the source. Current air quality strategies often overlook SO2 and other precursor gases, focusing instead on visible pollutants like PM10 and road dust.