Identifying sources, sustained action needed to solve bad air

The Aravallis can't be raised again to serve as a barrier between the Thar and Delhi, although we would do well to preserve what's left of them.

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The weather isn't in our control - winter will follow autumn (or what passes for it in Delhi) - although we would do well, again, to acknowledge the climate crisis, and do everything in our powers to not make things worse.

That leaves a small list of things we can do to control air pollution in Delhi.

The first thing is to identify year-round causes of bad air.

There are four significant ones: road dust (caused by proximity to the Thar, construction activity, and potholed roads, in that order); vehicular exhausts; industrial emissions (including power plants); and biomass (garbage) burning. And their impact gets amplified as the temperature drops and winds are calm in the winter, particularly in a city that does not have clearly defined residential and commercial zones.

The second is to identify the external causes of severe seasonal spikes. There is only one, which causes the air quality index in Delhi to lapse into severe territory - stubble burning soon after the harvest of the monsoon crop in Punjab (the state that is the primary culprit), Haryana, and parts of Uttar Pradesh. Of the 96 "severe" air days Delhi has experienced In the past five years (2018 to 2022), 43% took place in November, according to AQI bulletins issued by the Central Pollut Control Board (CPCB), more than any other month. November was also the month when the most active fires were detected in the three states listed above: 39% of the over 600,000 fires detected during 2018-2022 through the VIIRS instrument on the Suomi-NPP satellite. Punjab accounts for more than half of the fires lit in November (56%) in India, while Haryana and Uttar Pradesh account for just around 5% each.