Following the Deepavali celebrations in October 2025, air pollution levels in Delhi surged dramatically, nearing some of the worst concentrations recorded in the past five years. Data from the Central Pollution Control Board (CPCB) revealed that particulate matter (PM) 2.5 levels across various locations in the city soared above 400 micrograms per cubic meter (µg/m³), a hazardous threshold not seen since 2021. This spike in pollution underscores the ongoing challenges that urban centres like Delhi face in balancing cultural festivities with environmental health.
On Deepavali day itself, nine cities nationwide registered an Air Quality Index (AQI) exceeding 300, categorizing their air quality as ‘very poor’. This number nearly doubled to 16 cities the following day, with most situated in northern India’s Indo-Gangetic plains—a region notorious for its susceptibility to severe air pollution during the autumn and winter months. Among these, Dharuhera in Haryana reported the highest AQI on October 21, reaching a staggering 462, which falls into the ‘severe’ pollution category and poses significant health risks to the population.
An in-depth analysis conducted by Climate Trends, an independent weather and climate research agency, examined PM 2.5 trends using data from the CPCB’s automatic air quality sensors. Their findings highlighted a sharp escalation in particulate matter concentrations from late afternoon on Deepavali day, October 20. Around 4 p.m., PM 2.5 levels hovered near 150 µg/m³ but escalated rapidly to nearly 650 µg/m³ by 11 p.m. This timing closely aligns with the legally permitted window for bursting firecrackers, which was from 8 p.m. to 10 p.m., as permitted by a Supreme Court (SC) reprieve.
The Supreme Court had allowed the use of only CSIR-validated ‘green crackers’ during this limited timeframe. These eco-friendly crackers are designed to emit at least 30% less smoke than traditional firecrackers, intending to mitigate the environmental impact of the festival. However, the overwhelming volume of firecrackers reported, alongside anecdotal evidence suggesting limited availability of these green crackers, points towards widespread non-compliance with the court’s restrictions. This is further corroborated by the deteriorated air quality observed on the day following Deepavali, indicating that the measures fell short in curbing pollution.
Meteorological factors played a crucial role in exacerbating pollution levels on Deepavali night. Typically, wind speed and ambient temperature significantly influence how pollutants disperse in the atmosphere. Cooler temperatures tend to trap smoke and chemical pollutants close to the ground, creating a haze that lingers rather than dissipates. Interestingly, this Deepavali witnessed night temperatures ranging between 23 to 25 degrees Celsius—the warmest in five years. Despite the relatively higher temperatures, low wind speeds and the sheer quantity of smoke prevented effective dispersion, causing pollutants to accumulate over Delhi and the wider Gangetic plain airshed.
The Climate Trends report emphasized the interplay between these factors, noting, “When examined together, PM 2.5 and temperature data reveal a consistent pattern: high emissions from fireworks and low night-time temperatures jointly contribute to elevated PM 2.5 concentrations. The sharp post-Deepavali spikes indicate both sustained emissions and poor atmospheric dispersion.” This analysis highlights how even marginal variations in environmental conditions can profoundly impact air quality, especially when combined with anthropogenic pollution sources like firecrackers.
Palak Balyan, Research Lead at Climate Trends, commented on the findings, stating, “The Diwali of 2025 was one of the most polluted in recent years. The spike between the nights of the 19th and 20th directly corresponds to the widespread use of firecrackers across Delhi-NCR. Moreover, visuals and ground data confirm that burning so-called ‘green’ crackers made no measurable difference compared to regular ones. It’s now evident that allowing firecrackers during this time of year is simply not sustainable for the NCR region’s already critical air quality.” Her statement underscores a growing consensus among environmental experts that festival-related fireworks pose a severe and recurrent threat to public health in the National Capital Region (NCR).
Comparing recent pollution levels to historical data further illustrates the severity of this year’s Deepavali air quality. On November 13, 2023—post-Deepavali—the AQI in Delhi stood at 358, categorized as ‘very poor.’ In contrast, on October 20,