KOLKATA: Kolkata and Howrah's air quality deteriorated sharply on Kali Puja night as firecrackers were burst beyond the permissible hours of 8 pm to 10 pm, flouting guidelines issued by the West Bengal Pollution Control Board (WBPCB) and police, environmentalists said on Tuesday.

A WBPCB official said while the Air Quality Index (AQI) reached 186 PM 2.5 at Victoria Memorial in the city, it touched 364 at Belur in Howrah at 10 pm on Monday.

An AQI between 151 and 200 is considered 'poor', 201 to 300 'very poor', and above 300 is classified as 'severe'.

At Padmapukur, the AQI read 361, while it breached the 252 mark at Ghusuri, both in Howrah district.

In Kolkata's Ballygunge, the AQI touched 173, while at Jadavpur it was 169 at 10 pm, the PCB official said.

At Rabindra Bharati University in the Sinthi area in the northern part of the city, the AQI touched 167.

At 8 pm on Monday, the AQI was 164 at Victoria, 159 (Jadavpur), 117 (Fort William), 161 (Belur Math), 102 (Rabindra Bharati University) and 134 at Ballygunge.

Affirming the spurt, the official said they were analysing the results.

Environmentalist Somendra Mohan Ghosh said there was rampant and frequent use of sound-emitting firecrackers in north and south Kolkata and Howrah since evening.

"From Kashipur, Sinthi, Jorasanko, Maniktala to Kasba, Tollygunge, Regent Park, Behala and Jadavpur, high-decibel firecrackers were burst everywhere.

Both police and WBPCB remained mere spectators and failed to curb the sale and use of firecrackers," he alleged.

He said the situation in Howrah is worse, and authorities should brace for further worsening of the situation during the post-Kali Puja celebrations on Tuesday.

Naba Dutta of Sabuj Manch, an organisation of environmentalists, also blamed police and the pollution watchdog for having "failed" to enforce regulations, leaving elderly citizens, ailing persons, children and pets exposed to sound and air pollution.