Delhi gasps: Worst Diwali air quality since 2022

The Delhi Pollution Control Committee (DPCC), in its report, said PM 10 levels saw an increase of 11% while PM 2.5 levels dipped by 4% on the day of Diwali compared to last year.

The DPCC also mentioned that the noise levels increased in 70% of its stations, compared to last Diwali. The only station which showed a significant reduction in noise levels was Sri Aurobindo Marg at 11%. In all the residential zones including Mundka, Nehru Nagar, and Ashok Nagar, the night time noise levels were above 45 dB (A) Leq which is the permissible limit for residential areas, as per the DPCC. Najafgarh saw the highest jump in noise levels compared to Diwali last year with an 8% increase, followed by Mundka, Karol Bagh, Connaught Place and Alipur. The overall noise levels ranged from 58 dB (A) Leq to 88.7dB (A) Leq.

PM 2.5 levels shoot up

On October 31, several monitoring stations saw high levels of PM 2.5 — an “indicator” of firecrackers, as per experts. Despite a strict ban imposed by the Delhi government on the production, storage, and sale of firecrackers, the Diwali night sky was lit with colours while high-decibel firecrackers were also heard rumbling throughout the evening.

Sunil Dahiya, founder and lead analyst at Envirocatalysts, said, “A crude way of inferring the contribution of firecrackers from pollution levels is to check the PM 2.5 peak levels and compare it with last year. In 2023, Diwali was celebrated in November when cooler conditions had set in, but the average PM 2.5 pollution levels then were around 600 µg/m3 during peak hours. This year, even with warmer temperatures, we found that the PM 2.5 levels during peak hours on Diwali were the same as last year. The peak was reached after an increase on an hourly basis from 100 to 120 µg/m3 at 6 pm to the next day around 1 am, with a few stations like Nehru Nagar crossing 1,500 µg/m3. This shows that the firecracker ban didn’t really work.”

Asked about important indicators to check the contribution of firecrackers, Anumita Roychowdhury, Executive Director, Research and Advocacy, Centre for Science and Environment (CSE), explained, “Normally several parameters including PM2.5, NOX, SO2, CO are looked at. But PM (particulate matter) is an important parameter and is also an indicator of toxicity.”

Dahiya also said PM 2.5 levels are a better indicator than PM 10 because the PM 2.5 level has a more hazardous effect, with the particles penetrating deeper into the respiratory system.

According to CPCB data, the 24-hour-average PM 2.5 level was 144.3 µg/m3 at 8 pm on Thursday, which increased to 168.4 µg/m3 by midnight. Even at 7 am Friday, it was as high as 209.1 µg/m3. By 4 pm, it reduced to 198.1 µg/m3.

Similarly, the average PM 10 levels saw a steep increase on an hourly basis from 8 pm Thursday — it was as high as 288.6 µg/m3 by midnight. By 6 am, owing to calm wind conditions, it touched 322.6 µg/m3. It then dipped to 308.1µg/m3 by Friday noon.

This year, the highest PM 2.5 level was recorded at Vivek Vihar — 1,853 µg/m3 at midnight. The highest PM 10 level was in Jahangirpuri, with the peak touching 1,906 µg/m3 at 11 pm. These levels were 30 times more than the national prescribed standard of 60 µg/m3 for PM 2.5 and around 20 times more than the national prescribed limit of 100 µg/m3 for PM 10.

DPCC data also showed that at several AQI monitoring stations, the PM 2.5 and 10 levels soared after 8 pm, and peaked at midnight, before a gradual drop from 4 am onwards. For instance, at India Gate, the PM 2.5 level peaked at 3 am at 703 µg/m3 and the PM 10 load was the highest at 2 am at 1,101µg/m3.

At other stations such as Anand Vihar, Wazirpur, Bawana, Patparganj and Mundka, the pollution levels remained four to five times higher than the permissible limit until 6-7 am.

According to the India Meteorological Department (IMD), the wind speed picked up on Friday morning to around 10 kmph, favourable for the dispersal of pollutants.

Stubble-burning adds to pollution load

On Diwali day, stubble-burning contribution increased significantly to 27.61%, according to data from the Decision Support System developed by the Indian Institute of Tropical Meteorology (IITM) Pune. This indicates that the PM 2.5 mass concentration in Delhi increased due to stubble burning contribution as well.

According to data from the Indian Agricultural Research Institute, Punjab recorded 484 stubble-burning events on Thursday — the highest count in a day so far from September 15 onwards. This took the state-wise total to 2,950 cases, which is yet the lowest recorded count in Punjab compared to the same period (September 15-October 31) in previous years (2020-2024).

Among regional sources, the transport sector was the second-most significant pollutant with a 13.35% mean contribution to PM 2.5 levels on Diwali day.

Meanwhile, IITM’s forecast shows that the AQI is likely to be in the upper end of the ‘very poor’ category till Monday (November 4). The latest analysis by the Centre for Science and Environment shows that Delhi’s pollution load in the pre-winter season this year was majorly caused by vehicular emissions rather than stubble-burning cases.

In its six-day outlook, it has forecast the AQI to be ‘very poor’. “Meteorological conditions are likely to be extremely unfavorable for the dispersal of pollutants from tonight onwards,” read the IITM’s Friday bulletin.