Delhi smog hits 'very poor' as illegal Diwali fireworks fill the sky

Delhi woke up choking on Monday. At 9 a.m. local time the capital recorded an air quality index of 370 — 'very poor' on the Central Pollution Control Board's scale, where anything up to 50 counts as 'good'. In several pockets of the 20-million-strong city, readings blew past 400 into 'severe' territory.

The culprit: Diwali fireworks that went off in defiance of the Supreme Court, which ruled earlier this month that only certified low-polluting crackers could be used, and only during limited hours across the festival weekend. Residents in Delhi and Mumbai reported bursts of firecrackers crackling late into the night. Reuters TV footage showed a thick layer of smog swallowing India Gate, the landmark sitting near parliament and government offices.

Delhi ranked as the third-most polluted city in the world on Monday morning, per Swiss tracking group IQAir's live list. Lahore in Pakistan held the top spot with an AQI of 563, rated hazardous.

This is a familiar winter ritual across northern India, where cold, heavy air traps vehicle exhaust, construction dust and smoke from crop-waste burning. Big cities like Delhi feel it hardest, and residents have been fighting respiratory problems through more than a week of bad air.

Authorities triggered a graded action plan on Friday, ordering schools to shift to online classes among other curbs. That was before the fireworks.