Mumbai’s unusually foul air

[Sreenivasulu Angayreddy]

This is not the first time Mumbai’s air has been so toxic, but it has never lasted more than 1-2 days. Though Mumbai generates pollutants in equivalent amounts as compared to Delhi, it has an important location advantage.Reasons for this unusual foul air:

• Change in flow patterns: In Mumbai, winds move from land to sea for a few days and then from sea to land and this cyclic pattern usually repeats every 3-4 days.
• Mumbai’s relatively clean air is the result of strong sea breezes that sweep air pollutants away from the land.
• When the wind is not moving away from the land, air pollutants accumulate over the city. But then the wind direction changes, and it all gets cleaned.
• This cycle is delayed this year. Instead of repeating every 3-4 days, it is happening after a week, even 10 days.
• Even when the wind direction turns favourable, the lack of adequate speed means that the air is not entirely cleaned.

Possible Reasons for the change in the cycle:

• This can be attributed to some unusual global events like the third consecutive year of La Niña.
• La Nina is an abnormal cooling of the Pacific Ocean that impacts weather events across the world.
• More construction activities: Large infrastructure projects, like the Mumbai Metro or the Coastal Road Project, could be generating significantly higher amounts of pollutants.

• This could be possible, as Mumbai is currently witnessing a rise in PM10 (particulate matter of the size of 10 micrometres or smaller) levels as well.