Delhi gasps before Diwali as air turns toxic. Here’s what the AQI forecast shows

On Dhanteras, two days before Diwali, Delhi was already gasping for clean air.

At 9 am on Saturday, Anand Vihar fared the worst — its hourly particulate matter of 10 or less micrometres (PM 10) spiked at 843 µg/m³. At the same time, western and northern parts of the city like Dwarka, Wazirpur, and Ashok Vihar also hit hazardous levels.

While the World Health Organisation’s 24-hour guideline for PM 10 is 45 µg/m³, Delhi’s hourly readings were already over 16 times higher, showing how high pollution levels had surged even before the festival night.

The readings suggest Delhi could face even higher pollution levels as Diwali celebrations and firecracker use are expected to increase — even with time caps in place. According to the Supreme Court’s October 15 order allowing verified “green” crackers, these can only be set off on October 19 and 20 (6-7 am and 8-10 pm) across the NCR.

What’s in the air

Throughout the morning up to noon, PM 10 levels at Dwarka Sector 8 rose to 702 µg/m³, Wazirpur was 669 µg/m³, Ashok Vihar recorded 637 µg/m³, Mundka was 484 µg/m³, and Pusa (DPCC) was 470 µg/m³. These were also higher than the national 24-hour limit of 100 µg/m³.

Fine particulate pollution — PM 2.5 — also climbed sharply through the morning.

At several stations, PM 2.5 concentrations reached extreme levels: 490 µg/m³ at Ashok Vihar, 327 µg/m³ at Mundka, and 214 µg/m³ at Anand Vihar. The city-wide average was about 135 µg/m³, more than double the national 24-hour limit of 60 µg/m³.

The WHO’s 24-hour safe limit for PM 2.5 is 15 µg/m³; Delhi’s readings this morning exceeded that by more than 20 times at several locations.

Doctors have said that these fine particles are far smaller than PM 10 and can penetrate deep into the lungs and bloodstream, aggravating asthma, heart disease, and other respiratory conditions.

Sunil Dahiya, lead analyst and founder of Delhi-based think tank Envirocatalysts, said: “Meteorological conditions and local emissions are resulting in hazardous [pollution] levels at multiple locations in Delhi; it is very likely that pollution levels around festive celebrations are going to shoot up even further and make it very difficult to breathe.”

As per forecasts from the Indian Institute of Tropical Meteorology (IITM), on October 20 (Diwali day), air quality is likely to reach the upper end of the ‘very poor’ category. “The air quality may reach the ‘severe’ category on 21.10.2025 in case of enhanced emissions from firecrackers,” it stated.

A comparison with previous years

Delhi’s current build-up mirrors the same pattern that has driven hazardous Diwali-night peaks in recent years.

Studies have previously shown that the city’s particulate matter levels spike sharply in the days leading up to and during Diwali, and NOx (nitrogen oxide) emissions increase, too, because of traffic emissions.

A 2024 analysis by the Centre for Science and Environment (CSE) found that PM 2.5 levels rose by 46% between October 28 and October 31, peaking at 603 µg/m³ around midnight on Diwali night (October 31).

That was 13% higher than Diwali peaks recorded in 2022 and 2023, when the festival fell on October 24 and November 12, respectively.

The same study reported a massive build-up of pollution across the city on Diwali night, with 9 of Delhi’s 38 monitoring stations recording PM 2.5 levels above 900 µg/m³. The highest was at Nehru Nagar (994 µg/m³), followed closely by Anand Vihar (992 µg/m³), Pusa IMD (985 µg/m³), Wazirpur (980 µg/m³) and JLN Stadium (963 µg/m³) — all categorised as severe on the national air quality index.

Other heavily affected sites included Okhla, CRRI-Mathura Road, Karni Singh Stadium, Lodi Road and Siri Fort, showing city-wide deterioration rather than localised spikes.

Weather conditions also play a major role in amplifying these pollution surges. So far, Delhi has experienced calm winds, including westerlies that can carry smoke and particulates from crop-residue burning in neighbouring states. Data shows that in six states, 991 burning events have been recorded this season, adding to the pollution burden in the NCR.

A multi-year comparison by SAFAR-IITM in 2021 noted that high PM concentrations during the Diwali period result from a combination of local emissions, stagnant winds and limited vertical mixing that prevent pollutants from dispersing. The study added that weather factors such as rainfall, strong winds, or sunlight-driven convection can briefly ease pollution.

Meanwhile, the Delhi Police, with officials from the Delhi Pollution Control Committee, have been on patrol since October 16, tasked with taking legal action against the sale or use of non-certified firecrackers and conducting surprise inspections. Only green crackers certified by NEERI (with valid QR codes) will be allowed, sold through licensed traders at designated locations.