Delhi Records Third-Worst Diwali Pollution Since 2021; Monitoring Data Gaps Raise Questions

Delhi experienced its third-worst Diwali pollution episode since 2021, with air quality deteriorating sharply during the celebrations as firecracker emissions added to the capital's existing pollution burden. However, gaps in data from air-quality monitoring stations have raised concerns about whether the available figures accurately reflect the full extent of the pollution spike. An analysis of air-quality data showed that more than half of Delhi's monitoring stations stopped reporting continuous readings around midnight on Diwali night, a period when pollution levels were rising significantly.

At 9 pm, 61% of the 57 monitoring stations reporting data recorded an Air Quality Index (AQI) of 400 or above, falling in the severe category. Between 10 pm and 6 am, around 80% of the stations that continued transmitting readings reported severe air quality. The data disruptions have made it difficult to establish how widespread the pollution surge was across the city, particularly during the hours when firecracker activity was at its peak.

For a historical comparison, data from six monitoring stations with relatively consistent records since 2021 was examined. The average peak hourly PM2.5 sub-index across these locations stood at 655 this year, making it the third-highest Diwali reading during the period. The corresponding figures were 812 in 2021, 483 in 2022, 583 in 2023, 489 in 2024 and 752 in 2025. The six stations included Alipur, Aya Nagar, Bawana, IHBAS-Dilshad Garden, Narela and Punjabi Bagh.

Weather conditions may have played a role in preventing this year's pollution levels from reaching the peaks recorded in 2021 and 2025. Relatively warm temperatures and favourable wind conditions during certain periods helped disperse pollutants, limiting their accumulation near the ground. Weather data from the Palam meteorological station indicated that Diwali night this year was among the warmest since 2021. The comparatively favourable atmospheric conditions may also explain the improvement in Delhi's pollution ranking later in the evening. The overall air-quality situation remained concerning. Delhi's average pollution readings until the morning of November 8 were reportedly the worst for the comparable period since 2021 before improving later in the day.

The monitoring disruptions have also renewed questions about the reliability of Delhi's air-quality surveillance network. Continuous readings from monitoring stations are essential for assessing pollution levels, identifying affected areas and issuing timely health advisories. Repeated interruptions during periods of severe pollution could leave important gaps in the official assessment of residents' exposure to harmful pollutants.

The health implications remain significant, particularly because Diwali coincides with the beginning of Delhi's winter pollution season. High concentrations of PM2.5, or fine particulate matter, can penetrate deep into the lungs and contribute to respiratory and cardiovascular problems. Children, elderly people and those with existing health conditions are particularly vulnerable. Apart from firecrackers, vehicular emissions, construction dust, industrial activity, waste burning and pollution from neighbouring regions continue to contribute to Delhi's poor air quality.

The latest findings highlight the need for stronger pollution-control measures as well as improvements in the city's monitoring infrastructure. Ensuring uninterrupted data transmission, investigating equipment failures and maintaining transparency in pollution reporting will be important for assessing future pollution episodes. Delhi's latest Diwali pollution figures once again underline the scale of the capital's air-quality challenge. While weather conditions may have prevented an even worse outcome this year, the combination of high pollution levels and missing monitoring data has raised fresh concerns about the effectiveness of the city's efforts to track and tackle its air pollution crisis.

Disclaimer: This image is taken from Hindustan Times.