New Delhi, Oct. 22 -- Festive cheer can have its downside. As Diwali approaches, pollution levels in Indian cities start to rise sharply, due to the burning of crackers. While all cities are affected, among the largest tier-I cities, it is Delhi and its surrounding regions that stand out in terms of the extent to which pollution spikes.

This year was no different, as air pollution levels surged. The after-effects are likely to persist, as pollutants remain in the air and dissipate slowly. The bigger problem for Delhi, in fact, a large swathe of North India, is that pollution spikes after Diwali and persists through the winter months.

This year's Diwali was different for the Delhi National Capital Region (NCR) as the Supreme Court allowe...