Mumbai, Delhi and Kolkata are the three mega cities of the country but the air pollution is much more serious problem in Delhi as compared to the other two. Why is this so?

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.