Delhi AQI hits five-year high after Diwali: What went wrong - Did green crackers totally fail?

Despite a sharp 77.5% drop in stubble burning this year, Delhi’s air quality plummeted to its worst post-Diwali level in five years on Tuesday morning.

The city woke up on Tuesday to a thick blanket of smog, with PM2.5 levels averaging 488 micrograms per cubic metre, nearly 100 times higher than the World Health Organization’s safe limit. On Diwali night, readings touched 675 micrograms per cubic metre, the highest of the season.

This was despite the Supreme Court’s order allowing only ‘green firecrackers’ for limited hours. However, widespread violations were reported across the city.

As a result, this year’s Air Quality Index (AQI) on Tuesday crossed 451, much higher than last year’s 328, and worse than 2023 (218) and 2022 (312). Data from the Central Pollution Control Board (CPCB) confirmed that Diwali 2025 was one of the most polluted in recent times.

Delhi air quality: What went wrong?

According to climate experts, Diwali always brings a sharp rise in PM2.5 levels, but this year’s jump was extreme. “Post-Diwali PM2.5 levels averaged around 488, compared to 156.6 before the festival, a threefold increase,” NDTV quoted Palak Balyan, a researcher at Climate Trends, as saying.

Weather conditions made things worse. Wind speeds fell below one metre per second, preventing pollutants from dispersing. A sudden drop in temperature from 27 degrees Celsius to 19 degrees Celsius created a temperature inversion, trapping the smoke near the ground on Monday night and early Tuesday morning. As a result, pollutants stayed suspended in the lower atmosphere, leading to the choking haze across Delhi-NCR.

However, a rise in wind speed later on Tuesday and above-normal temperatures prevented a further spike in pollution during the day.

Delhi air pollution: Did green crackers fail?

The results have also cast serious doubt on the effectiveness of ‘green firecrackers’, which were introduced to reduce pollution. Delhi University professor Dr S K Dhaka said that “pollution this year was overwhelmingly local in nature,” indicating that emissions from these so-called eco-friendly crackers significantly increased particulate matter.

“We conclude that green firecrackers enhanced the particulate matter at a rapid rate. The pollution is of local nature, not transported from outside,” he was quoted by NDTV as saying. This means that even if stubble burning was reduced, Delhi’s local activities, from firecrackers to vehicular and industrial emissions, were enough to push air quality to hazardous levels.

Stubble burning drops, but pollution persists

Stubble burning in Punjab and Haryana is usually blamed for Delhi’s winter smog. However, this year’s floods in those states offered a unique opportunity to measure its actual contribution. Data showed a 77.5% fall in stubble-burning incidents, which led to a 15.5% drop in Delhi’s PM2.5 levels during October.

Despite this, the air quality worsened after Diwali, proving that local urban sources, vehicles, industries, road dust, and fireworks, are now the major culprits.