The PM 2.5 count shot up to 330 at the Rabindra Bharati automatic air monitoring station on B T Road in northern part of the city and the count was 373 at the Victoria Memorial monitoring station in central Kolkata at 11 am on Thursday.
The US Consulate's air quality index on Thursday showed PM 2.5 count as "very unhealthy" at 211 AQL -- meaning everyone may experience serious health effects.
A US consulate official, however, said the consulate index, which only projects the air quality of the area surrounding Ho Chi Minh Sarani, was not reflective of the entire city.
When questioned about the air quality readings, West Bengal Pollution Control Board chairman Kalyan Rudra refused to draw any conclusion about the improvement or deterioration in the air pollution during Kali Puja and Diwali on Tuesday and Wednesday respectively.
"Our monitoring stations will monitor the situations till a week after Diwali and we will chalk out an action plan to combat any situation in future, as the Supreme Court order envisaged."
"Due to the present weather situation when the sky is overcast and wind speed is low, amid light drizzle for past two days, the suspended particles could not move up and hung around in the air," Rudra told PTI.
Terming the WBPCB a "toothless tiger", environmentalist Subhas Dutta said the authorities should have been more careful in preventing illegal fireworks and crackers coming from the districts and flooding the city markets.
Dutta, however, corroborated Rudra's statement saying the high air quality index was not solely due to bursting of firecrackers, but due to present weather conditions as well.
Environmentalist S M Ghosh said the metropolis got the dubious distinction of being one of the most-polluting cities on Diwali night.
As many as 93 people were arrested for bursting firecrackers in the city till midnight on Diwali.
Till 11 pm, the Kolkata Police received a total of 50 complaints regarding the bursting of firecrackers, mainly from areas like EM Bypass, Kasba, Patuli, Thakurpukur and Dum Dum, a top police officer told PTI.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)