The Air Quality Index (AQI) in densely populated north Kolkata remained 'severe' for the third day in a row.

The AQI at WBPCB's air monitoring station at Rabindra Bharati University, the only computerised monitoring station of north Kolkata, was 407 PM 2.5, which was 'severe' in air monitoring terms, at 2 pm on Monday.

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.

The monitoring station recorded an AQI of 423 PM 2.5 at 3 pm on Sunday and 434 PM 2.5 at 1 pm on Friday.

The AQI at the WBPCB's second automatic air monitoring station at Victoria Memorial, which is considered a green zone, however, read at 327 PM 2.5, "very poor", at 2 pm Monday.

Various organisations of the city assembled at Rabindra Sarobar area and organised a rally to protest against the air pollution in the metropolis.

"In November 2018 alone, the air pollution level was "Poor" or "Very Poor" in 21 of the 30 days. This is unprecedented by any standard," said Ajay Mittal of the 'Kolkata Clean Air', one of the organisations that arranged the rally here on Sunday.

Mittal said, "We all need to come together to address these issue as none of us are really immune to this. Citizens want to come forward and work with the administration in addressing this issue to ensure clean and breathable air."

"Most of the countries would issue an Emergency under this scenario," said environmentalist S M Ghosh.

WBPCB Chairman Kalyan Rudra earlier said the reading at Rabindra Bharati cannot be representative of the entire city.

"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 had said.

(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)