Mumbai, Delhi and Kolkata are the three mega cities of the country but the air pollution is much more…

Question

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?

Ghissu Editorial · Accepted Answer

Delhi's air is worse than Mumbai's and Kolkata's because it is landlocked, suffers winter temperature inversions and calm winds, and lies downwind of stubble burning, while sea breezes and heavy rain flush the coastal cities. A 2014 WHO database ranked Delhi the world's most polluted city by PM2.5.

**Introduction**

A 2014 WHO database ranked Delhi the world's most polluted city by PM2.5. Mumbai and Kolkata have similar populations and traffic, but Delhi combines a landlocked location, a continental winter and a ring of regional pollution sources.

**Geography and Weather Work Against Delhi**

SKETCH: comparison | Why Delhi Chokes More
a: Delhi
b: Mumbai and Kolkata
- Landlocked plain :: Coastal or deltaic
- Calm winter, inversion :: Milder, humid winter
- Downwind of stubble fires :: Far from stubble belt
- Dry, dusty winds :: Humid, high rainfall

1. **Landlocked location**: Sea breezes flush Mumbai daily and moist Bay of Bengal winds reach Kolkata, while Delhi, hundreds of kilometres inland, gets no such flushing.
2. **Winter inversion**: Cold, calm winter nights create a temperature inversion and low mixing height that trap smoke near the ground, and fog from western disturbances turns it into smog.
3. **Wind direction**: In October and November north-westerly winds carry stubble smoke from Punjab and Haryana into Delhi, and the Indo-Gangetic plain holds it.
4. **Dry climate**: Dust blown from the Thar and degraded Aravallis, with scant winter rain, leaves Delhi's air unwashed, unlike rain-rich coastal cities.

**Human Sources Concentrated in Delhi-NCR**

1. **Vehicles and road dust**: IIT Kanpur's 2016 source-apportionment study named road dust the largest PM10 source and vehicles a major winter PM2.5 source.
2. **Industry, construction and waste**: Brick kilns, small industrial clusters, NCR coal plants, construction dust and landfill fires at Ghazipur and Bhalswa add to the winter load.

**Conclusion**

Delhi's geography traps what its region emits, while coastal winds rescue Mumbai and Kolkata. Regional action through the Commission for Air Quality Management, the Graded Response Action Plan and the National Clean Air Programme across the Indo-Gangetic plain is the only lasting answer.

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?

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