Describe the key points of the revised Global Air Quality Guidelines (AQGs) recently released by the World Health Organisation (WHO). How are these different from its last update in 2005? What changes in India’s National Clean Air Programme are required to achieve revised standards?

Theme

T155 Air pollution: smog, WHO guidelines, NCAP

What UPSC asks in this theme

Questions ask why Delhi's pollution is worse than Mumbai or Kolkata, photochemical smog and the Gothenburg Protocol, WHO's 2021 guidelines, and NCAP.

What to cover

• Delhi: geography, stubble burning, vehicles, inversion
• Photochemical smog chemistry
• WHO AQG 2021 changes
• NCAP targets and gaps

Writing the answer

• Causes → measures

These notes are for the whole theme, built from all 4 of its PYQs. UPSC does not publish model answers.