The Air Quality Index (AQI) in densely populated north Kolkata was found to be 'severe' on Friday, but the West Bengal Pollution Control Board (WBPCB) said it was due to present weather situations in this time of the year.
The AQI at WBPCB's air monitoring station at Rabindra Bharati University, the only computerised monitoring station of north Kolkata, was 434 PM 2.5 at 1 pm, which was 'severe' in air monitoring terms.
The AQI is an indicator of air pollution caused by three pollutants - NO2, PM 10 and PM 2.5. The index indicates air quality as 'good' for values of 0-100, 'moderate' for 101-200 and 'poor' for 201-300.
Even after Diwali, the PM 2.5 count was 330 at the Rabindra Bharati air monitoring station.
The AQI reading at US Consulate's air monitoring station in South Kolkata read 196 PM 2.5 at 5 pm during the day marked as 'unhealthy'.
While environmentalists described the situation as alarming, WBPCB Chairman Kalyan Rudra said the reading at Rabindra Bharati cannot be representative of the entire city.
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"Besides, there are factors like the overcast sky and flow of north-easternly wind from areas like Jharkhand into the city which don't allow suspended particulate matters to move upwards," Rudra said.
Environmentalist S M Ghosh said the situation was turning very very serious here.
Ghosh demanded the 10-year-old diesel commercial vehicles and 15-year-old private vehicles be banned immediately and food stalls and road side clothes ironing centres using low quality coal be shut down to stop the city from turning into the pollution capital in India.
Refusing to comment on the view of the environmentalist, Rudra said the WBPCB has already undertaken a number of measures to curb air pollution in the twin cities of Kolkata and Howrah including vehicular pollution.