Environment and Disaster Management › Pollution

Air pollution

The National Clean Air Programme and the sources of polluted air, from vehicles and power plants to crop burning, dust and indoor fuel. Prelims has asked which gases are used to calculate the Air Quality Index and about the World Health Organization (WHO) air quality guidelines.

Foundation notes: The Graded Response Action Plan · Air quality: the standards and the index

Showing 1 of 7 articles, those that changed from 1 to 31 July 2026.Show all

Flue gas desulphurisation norms

Prelims and Mains

Flue gas desulphurisation removes sulphur dioxide from a coal plant's exhaust, usually with a limestone slurry.

It was made mandatory in 2015.
A 2021 notification split plants into three categories by location, and Category C, close to four fifths of the fleet, has since been exempted.
Sulphur dioxide turns into sulphate particles in the air, so a distant plant adds to a city's particulate pollution.

What changed

14 Jul 2026New
- A study found that 20 of 37 coal plant units within 300 km of Delhi emit sulphur dioxide above the limit, and that the largest share comes from plants exempted from installing the equipment.
Mains: an airshed does not respect city limits, so a programme built city by city cannot fix a regional source.
The Indian Express, 14 Jul 2026: Study finds most sulphur dioxide around Delhi comes from the very coal plants exempted from installing scrubbers (opens in a new tab)