Diwali coincides with the annual period of peak pollution in New Delhi when apart from vehicles, industries, and construction, a traditional agricultural practice in the north Indian countryside acts as another source of PM 2.5 in the city.

In the few days between harvesting their monsoon crop and planting seeds for the new season, farmers across New Delhi’s neighbouring states of Punjab and Haryana burn the residue of their old crop to clear their fields. Winds carry the smoke from these farm fires to the Indian capital.

But crop residue burning till Oct. 28 contributed only 15% of PM 2.5 in New Delhi, according to ministry of earth sciences. Now, its share is expected to rise, further worsening pollution in the city.

The national and Delhi administrations have agreed to enforce much stricter traffic rules in Delhi-NCR if the concentration of PM 2.5 stays at the emergency level for two days. Odd- and even-numbered private cars will only be allowed on the road on odd- or even-numbered calendar days, respectively. The entry of trucks will be banned.

These restrictions may just be easier to enforce than those on the sale and bursting of firecrackers, which several local residents and businesses have been violating year after year.

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