Is the air quality good in Kolkata?
On September 21, 2025, at 10:00 PM PT, Kolkata, India, is experiencing poor air quality due to urban emissions and stagnant conditions. The AQI over 150, classified as "unhealthy," with PM2.5 concentrations dominating.
These conditions can cause respiratory issues, worsen heart problems, and impair lung function, especially for children, the elderly, and those with health vulnerabilities. To stay safe during this temporary spike, limit outdoor time, seal windows, wear masks if venturing out, and use air purifiers indoors for cleaner breathing air.
Air quality is dynamic and, like the weather, can change frequently. Kolkata ranked as the most polluted major city in the world on Monday morning (local time), with nearby cities like Delhi also affected.
Click here for a real-time air quality map of Kolkata.
While the air quality conditions today are unusually poor, with PM2.5 at 74.5 µg/m³ (14.9 times the WHO annual guideline of 5 µg/m³), it is important to keep in mind that the average PM2.5 concentration in 2024 for Kolkata was 45.6 µg/m³. This corresponds to an AQI of 126, which falls into the “unhealthy for sensitive groups” category and was 9.1 times the WHO annual guideline.
Kolkata, India ranked as the most polluted major city on Sept 22, 2025. Source: IQAir.
When will the air quality improve in Kolkata?
The hourly forecast suggests that AQI will slightly improve by late evening, dropping below 130 into the “unhealthy for sensitive groups” range.
Hourly air quality forecast for Kolkata, India on Sept 22, 2025. Source: IQAir.
The daily forecast indicates that air quality in Kolkata usually remains in the “moderate” range, but for the past couple two days it has surged to unhealthy levels. It is expected to improve to 93 on Tuesday and 75 on Wednesday as ongoing rain and winds help disperse pollutants, though fluctuations may occur with changes in humidity.
Daily air quality forecast for Kolkata, India for last 30 days. Source: IQAir.
Air quality map of Kolkata, India on Sept 22, 2025. Source: IQAir.
What is causing poor air quality in Kolkata?
Kolkata’s poor air quality is the result of multiple overlapping factors. Vehicular emissions are a major contributor, as the city has seen a steep rise in four-wheelers and two-wheelers running on fossil fuels, with traffic congestion further slowing the dispersion of exhaust pollutants (1).
Industrial activity, road dust, and waste burning also significantly elevate particulate levels, with construction sites, uncovered roads, and the burning of organic waste and biomass serving as major sources.
In addition, secondary pollutants are playing an increasing role, fine particles formed through chemical reactions between gases such as SO₂ and NH₃ now account for a large share of the PM2.5 mass, often originating from coal power plants and other large sources (2).
Seasonal and climatic factors further aggravate the situation; during dry seasons and winter, temperature inversions, low wind speeds, and reduced rainfall trap pollutants near the ground, while events such as Diwali and other festivals add short but intense bursts of pollution from fireworks.
How can I protect myself from poor air quality?
- Get a free air quality app for real-time air quality alerts and forecasts.
- Shut doors and windows and set the HVAC to recirculate mode.
- Contribute to your community’s outdoor air quality data.
- Stay indoors when air quality is poor; if you do need to go outdoors, wear a KN95/FFP2 mask.
- Run a high-performance air purifier to filter particles, gases, and other pollutants.
