Delhi’s first Diwali with legally permitted firecrackers in years resulted in the most severe air pollution surge since 2021. Fine particulate matter (PM2.5) concentrations soared, reaching levels equivalent to an Air Quality Index (AQI) of 812, far exceeding the official scale’s limit of 500. This occurred despite warmer temperatures and reduced farm fires, conditions that typically help maintain cleaner air.
The official 24-hour average AQI, recorded at 4 pm on Tuesday, was 351, a slight increase from the previous day’s 345. However, this average doesn’t fully capture the rapid build-up of pollutants during the firecracker bursting hours. Across eight monitoring stations with consistent historical data, average PM2.5 concentrations peaked at 785.6 micrograms per cubic metre (µg/m³), the highest recorded since 2021. In AQI terms, this translates to a level of 802.
Some areas experienced even more alarming spikes. Nehru Nagar saw PM2.5 levels reach a staggering 1,763 µg/m³ for an hour, while Anand Vihar in East Delhi recorded 1,710 µg/m³ until 1 am. These levels were nearly 29 times the safe limit of 60 µg/m³.
While warmer temperatures and moderate winds the following morning helped disperse some pollutants, the AQI reading of 351 still signifies ‘very poor’ air quality, prompting the National Centre for Disease Control (NCDC) to recommend avoiding outdoor physical activity. PM2.5 particles, a byproduct of combustion, can penetrate deep into the lungs, enter the bloodstream, and cause immediate health issues like asthma and bronchitis, as well as long-term cardiovascular problems.
The Supreme Court’s allowance of ‘green firecrackers’ on a trial basis, with strict time limits from 8 pm to 10 pm, was widely violated. Compounding the issue, data collection was marred by significant gaps, with nine out of Delhi’s 39 air quality stations ceasing to record data during peak pollution hours. This blackout raises questions about the accuracy of official assessments.
An analysis of the eight most consistent monitoring stations revealed a stark deterioration: air quality worsened from an AQI of 233 at 4 pm to a peak of 812 within seven to nine hours. The celebration also saw increased noise levels, with 23 out of 26 monitoring stations exceeding permissible limits.
In contrast, the contribution from farm fires was notably lower this year, with satellite data showing a significant decrease in incidents compared to previous years. This highlights the substantial impact of firecrackers on the city’s air quality.
Despite the evidence, the Delhi government has claimed the city ‘responsibly celebrated Diwali’, citing the modest AQI jump as proof that firecrackers are not the primary cause of pollution. Environment minister Manjinder Singh Sirsa attributed the air quality issues to farm fires in Punjab and claimed the city’s measures ensured stability. However, environmental experts largely attribute the rapid clean-up to favourable meteorological conditions rather than enforcement or responsible celebration.