The air quality index of Kolkata, which hovered between ‘satisfactory’ and ‘moderate’ levels since March 2019, again turned ‘poor’ on Wednesday in the run-up to Kali Puja-Diwali.

At 9 pm, the air quality index at the automated Fort William air monitoring station stood at 218 which falls in the ‘poor’ category, despite being located in the green belt Maidan area, an official of West Bengal Pollution Control Board said.

At the more congested north Kolkata’s Rabindra Bharati, the air quality index stood at 265 which too comes under the ‘poor’ category.

The AQI read 169 at Jadavpur, followed by Ballygunje (115)– both termed as moderate, the official said.

An AQI between 0 and 50 is considered ‘good’, 51 and 100 ‘satisfactory’, 101 and 200 ‘moderate’, 201 and 300 ‘poor’, 301 and 400 ‘very poor’, and 401 and 500 ‘severe’.

Data from Victoria air monitoring station was not available, the official said.

Kolkata’s AQI had surpassed the 200 mark on Sunday.

WBPCB Chairman Kalyan Rudra said the high moisture level in the air during this time of the year has led to a rise in fine particulate matter 2.5 (PM 2.5), the tiniest pollutants.

But the board is using sprinklers and working towards checking the pollutants which will show results in the coming days, he said.

Environmentalist SM Ghosh said the AQI could further shoot up to an alarming level in the run-up to Diwali-Kali Puja and on the day of Diwali if the WBPCB and government machineries do not stop bursting of firecrackers – both emitting light and sound.

He said the WBPCB should promote ‘green fireworks’ which are less polluting and stop pilferage of banned fireworks into the city by conducting raids.

Rudra said while 5000 firecrackers have already been seized and destroyed in the past seven days, the WBPCB in association with the state police was continuing their clamp down on illegal fireworks on a sustained basis.