Delhi AQI: What is PM2.5 and the row over air pollution data post Deepavali?

Deepavali night (November 8, 2026) in Delhi saw air pollution levels in the national capital reach alarmingly high levels after firecrackers were burst across the city well past the Supreme Court-permitted hours on the festival.

The national capital is under Stage III of the Graded Response Action Plan (GRAP) with multiple restrictions in place. A row has now been sparked after senior Congress leader Ajay Maken flagged the non-availability of PM 2.5 readings at 25 of Delhi’s 39 air quality monitoring stations on the night of Deepavali.

He pointed out that air pollution levels at the national capital’s nine stations reached 38.4 times the World Health Organisation’s (WHO) 24-hour limit (as per available data) Mr Maken, in a post on X, alleged discrepancies in the capital’s air pollution monitoring data, claiming that PM 2.5 readings in 25 stations were not recorded between 2 AM and 3 AM on the night of the festival.

He cited data from the Central Pollution Control Board (CPCB) and alleged that PM 2.5 readings at Anand Vihar, Ashok Vihar, Aya Nagar, Bawana, CRRI Mathura Road, Chandni Chowk, Dwarka Sector 8, IMD Lodhi Road, ITO, Jawaharlal Nehru Stadium, Mandir Marg, Mundka, NSIT Dwarka, Najafgarh, Narela, Nehru Nagar, North Campus DU, Okhla Phase 2, Punjabi Bagh, Pusa, R K Puram, Shadipur, Sirifort, Sri Aurobindo Marg, and, Wazirpur stations were not recorded.

The Aam Aadmi Party (AAP) also attacked the Bharatiya Janata Party (BJP) on November 9 over the alleged air quality data “manipulation” by shutting down of air quality monitoring stations. “The government which shuts down air quality monitoring stations on the night of Diwali, the government that does data fraud, how will you trust such a government?” asked AAP Delhi president Saurabh Bharadwaj in a video posted on X.

Delhi labour minister and BJP leader Kapil Mishra alleged that there was a “conspiracy” in AAP-governed Punjab to set stubble on fire in Punjab on Diwali evening, as per official data. He alleged that 1,200 stubble burning incidents happened in Punjab on Diwali evening, which was 10 times that of previous days.

“We got calls from farmers in Punjab that stubble is being set on fire. Someone is coming and setting stubble on fire and running away, when farmers are celebrating Diwali with their families. This is a very serious issue and a conspiracy against Delhi, Punjab, and farmers,” he said.

According to the Central Pollution Control Board (CPCB), an AQI between 0 and 50 is classified as ‘good’, 51 and 100 as ‘satisfactory’, 101 and 200 as ‘moderate’, 201 and 300 as ‘poor’, 301 and 400 as ‘very poor’, and 401 and 500 as ‘severe’.

Particulate matter, or particle pollution, is the general term for a mixture of solid particles and liquid droplets found in the air. A wide range of minute particles in the air can be seen only with an electron microscope.

It includes sulphates, nitrates, black carbon, particle-bound water, metals (cadmium, copper, nickel, zinc) and hydrocarbons. In addition, biological components such as allergens (pollen, dust mites) and microbial compounds (fungi) are also considered to be particulate matter.

There are two sizes of particulate matter (PM), i.e. PM 10 and PM 2.5. PM 10: inhalable particles, with diameters that are generally 10 micrometres (average human hair is about 70 micrometres in diameter). PM 2.5: fine inhalable particles, 2.5 micrometres and smaller.

The fine PM2.5 particles (about 30 times smaller than a human hair) travel into the respiratory tract, settle into the lungs and can even enter the bloodstream, triggering immediate and chronic concerns. According to an open-source air quality monitoring platform, AQI.in, Delhi’s AQI, at the time of publication, stood at 208.

The PM2.5 level stood at 132 µg/m³, and PM10 stood at 164 µg/m³. The Air Quality Early Warning System has forecast that Delhi’s air quality is likely to be in the ‘severe’ category during the day and will remain there over the subsequent few days.