Introduction

India celebrated Diwali, the grand festival of lights, with its characteristic splendour and spirit of togetherness. Across homes and streets, lamps illuminated the night, and hearts were filled with warmth and joy. In eastern India, the festivities also coincided with Kali Puja, adding to the cultural vibrancy of the season. Yet, as every light casts a shadow, the celebrations once again revealed an environmental reality often overlooked- air pollution immediately after Diwali.

Kolkata’s air quality deteriorated significantly in the pre-Diwali period. The city witnessed widespread and prolonged bursting of firecrackers, many of which violated prescribed time limits and green norms. By the next morning, a thick haze blanketed the city, leaving behind the burnt smell of gunpowder and visible discomfort among residents, especially children and the elderly.

This blog analyses Kolkata’s Diwali air quality trends, compares them with other metropolitan cities, and outlines immediate and long-term actions for both citizens and authorities to mitigate the recurring pollution surge.

Amid this growing concern, SwitchON Foundation continues its efforts toward Clean Air and Sustainable Cities. Through evidence-based research, citizen engagement, and policy-oriented communication, the organisation works to drive behavioural change and support policymakers in shaping a cleaner, healthier future.

Kolkata’s air quality during Diwali

Kolkata’s air quality was very good in the initial days of October due to untimely rainfall caused as a result of the depressions at the Bay of Bengal. As the rains withdrew and the winter chill set in, pollution levels began to rise again. Kolkata is already challenged by high vehicular emissions, and air pollution remains a concern in the city, especially during the winter. 

Data from the CPCB’s Sameer App revealed nitrogen dioxide (NO₂) as the dominant pre-Diwali pollutant. At this time, the city’s AQI remained within the ‘Moderate’ range (101–200) but showed a gradual upward trend. On Diwali day (20 October 2025), the AQI dropped to 88 — categorised as ‘Satisfactory’. However, on the very next day the AQI spiked to 174 (‘moderate’), with PM₁₀ emerging as the primary pollutant during Diwali. This sharp post-Diwali deterioration reflected the delayed impact of widespread firecracker emissions.

Figure 1: Kolkata Air Quality Status in October Source: Sameer App by CPCB [* red dot denotes diwali day AQI]

Kolkata’s air quality displayed distinct pre- and post-Diwali patterns across its seven CPCB monitoring stations. In the pre-Diwali period (13–19 October), pollution steadily accumulated, with Rabindra Bharati University (RBU) recording the highest AQI, peaking at 281 on 17th October, followed by Jadavpur at 247, indicating levels capable of causing discomfort even among healthy individuals. Victoria Memorial and Ballygunge remained in the Moderate range, primarily due to PM₂.₅ and PM₁₀, while Fort William, Rabindra Sarobar, and Bidhannagar experienced relatively better air quality. Across stations, PM₂.₅ and PM₁₀ were dominant in Victoria, Jadavpur, and Ballygunge, whereas NO₂ was significant at Rabindra Sarobar, highlighting spatial variation in pollution sources.

On Diwali day (20 October), AQI temporarily decreased at all the locations, and all the locations recorded satisfactory air quality, with major polluted stations like Rabindra Bharati at 69 AQI and Jadavpur at 100 AQI.  Despite this, PM₁₀ remained the key pollutant on the day, reflecting the initial impact of firecracker emissions. 

The next day (21 October) saw a sharp AQI surge across all stations—Jadavpur at 204, Bidhannagar 189, Ballygunge 173, RBU 134—driven mainly by PM₂.₅ and PM₁₀, demonstrating the cumulative and delayed effect of festive activities. Overall, Jadavpur and RBU emerged as persistent hotspots, emphasizing the heightened post-festival health risks from particulate pollution. Jadavpur again reached the status of poor air quality.

Table 1: Air Quality Calendar for the CPCB Stations at Kolkata Source: Sameer App by CPCB

Comparison with previous years

A comparison of Kolkata’s pre-Diwali air quality from 2023 to 2025 reveals distinct patterns. In 2023, the city experienced severe pollution in the week before Diwali, with AQI peaking pre-festival and improving afterwards. In contrast, 2024 saw a significant improvement during the pre-Diwali week, likely due to cyclone, which cleared the atmosphere with heavy rainfall.

Figure 2 shows the 2025 diwali AQI pattern mirrors 2024. While in 2024 it was between good to satisfactory, in 2025 it remained between moderate to satisfactory. In both 2024 and 2025, air quality was relatively better on Diwali day itself but deteriorated sharply the following day—AQI jumped from 57 to 242 (peak) in 2024, and from 88 to 174 (till now) in 2025.

This contrasts with 2023, when pollution peaked before Diwali. The last two years indicate a consistent post-festival spike, highlighting the impact of fireworks and festive emissions, and underscoring the need for heightened public awareness and precautionary measures.

Figure 2: Diwali AQI Trend of Kolkata with Previous Years Source: Sameer App by CPCB

AQI comparison with other metro cities

Across major Indian cities, air quality patterns during Diwali 2025 varied, reflecting geography, local emissions, and meteorological conditions. Delhi consistently recorded the highest AQI, reaching 345 on 20th October and peaking at 351 the following day, reflecting the city’s chronic pollution challenges driven by PM and ozone accumulation in a landlocked, winter-bound environment. Mumbai exhibited moderate pollution, with AQI from 139 pre-festival to 188 on Diwali and 211 post-Diwali, largely due to PM₁₀ and ozone.

While Kolkata (88), Bhubaneswar (54), Ranchi (150), Chennai (80) experienced a temporary dip in AQI on Diwali, Mumbai (188) and Delhi (345) has seen steady increase pollutants in the air. 

Kolkata saw a sharp post-festival increase to 174, driven primarily by PM₂.₅ and PM₁₀, similar to Bhubaneswar and Ranchi, with AQI rising from 54 to 139 in Bhubaneswar and 150 to 172 in Ranchi. Bengaluru remained the cleanest, fluctuating between 54 and 97, while Chennai showed moderate variation, peaking at 142 post-Diwali. Mumbai and Delhi reached record high pollution on 21st October. 

Overall, Delhi, Mumbai and Kolkata emerged as the polluted metro cities during the festival. Southern cities like Bengaluru, Chennai, maintaining relatively better air quality. The data underscores the post-Diwali surge as a consistent trend across all cities.

Figure 3: City-wise Diwali-time Air Quality Comparison Source: Sameer App by CPCB & JSPCB

What can be done to reduce the impact of post-Diwali pollution?

Short-Term Measures

With pollution levels rising sharply after Diwali, citizens can adopt the following precautions:

• Limit outdoor exposure, particularly during early mornings and late evenings when smog concentration is high.
• Avoid morning walks for a few days after the festival.
• Wear pollution-protective masks and use indoor air purifiers to reduce exposure.

At the city level:

• Urban Local Bodies (ULBs) can deploy street water spraying and dust suppression measures to reduce suspended particulate matter.
• Public awareness campaigns can be intensified to highlight health risks and encourage responsible festive practices.

Next year pledge

As the celebrations fade, Diwali leaves behind not just memories of light and joy but also a visible reminder of its environmental cost. It is important to recognise these after-effects and act collectively towards a cleaner future.

Let us pledge to make the next Diwali cleaner and healthier — by choosing green crackers, celebrating responsibly, and following the prescribed time limits for bursting firecrackers. Small, mindful actions can preserve our traditions while safeguarding the air we breathe.

“Let’s promise that next Diwali, our joy will not come at the cost of our breath.”

Cleaner Air, Brighter Diwali — Let’s Switch ON Together.

Conclusion

Although the festivities have ended, the impact of Diwali on air quality persists. The haze may fade from the skyline, but its effects on health and the environment persist for days after the celebration. This recurring pattern is a reminder that air pollution is not merely a festival-time concern — it reflects a larger behavioural and governance challenge.

Citizens must take this moment as an opportunity for reflection and responsibility. Behavioural change must begin at the individual level — through conscious consumption choices, reduced firecracker use, and active participation in community awareness. At the same time, policy enforcement and administrative action are equally critical. Stronger implementation of existing environmental norms, continuous monitoring, and localised awareness drives can together help cities breathe cleaner after every celebration.

Diwali’s light should symbolise not just joy, but also our shared commitment to cleaner air and sustainable living.