Delhi recorded a 24-hour average air quality index (AQI) of 353 on Monday. (Representational)
A layer of toxic haze lingered over the national capital on Monday as the city recorded its air quality in the ''very poor'' category for the fourth consecutive day.
A central government air quality monitoring agency said the air quality was likely to remain ''very poor'' till October 31.
The city recorded a 24-hour average air quality index (AQI) of 353 on Monday. It was 349 on Sunday, 345 on Saturday and 366 on Friday.
Most of the air quality monitoring stations in the city recorded the air quality in the ''very poor'' category, while pollution levels rose to ''severe'' levels at Vivek Vihar (AQI 414), Wazirpur (404) and Anand Vihar (418).
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''.
According to the Ministry of Earth Sciences'' air quality monitor, SAFAR, the wind direction and wind speed were favourable for the transport of pollutants from the farm fires in Punjab, Haryana and neighbouring regions.
The share of stubble burning in Delhi's PM2.5 concentration was 16 per cent on Monday. It was 19 per cent on Sunday and nine per cent on Saturday.
NASA's satellite imagery also showed a very dense cluster of fires in Punjab, Haryana and nearby regions.
SAFAR said the farm fire count was 1,275 on Sunday.
According to Punjab Pollution Control Board, the state has recorded 14,461 incidents of stubble burning between September 21 and October 25 as compared to 9,796 during the corresponding period last year.
Haryana has recorded around 4,284 incidents of stubble burning this season so far.
The central government's Air Quality Early Warning System for Delhi said the predominant surface wind direction is northwesterly with wind speed up to 12 kmph, favourable for transport of pollutants from farm fires.
A large number of farm fires were observed over Punjab, Haryana and Uttar Pradesh, which is likely to impact Delhi-NCR's air quality, it said.
"The very poor air quality is likely to persist till October 31," it said.
The air quality warning system said the ventilation index - a product of mixing depth and average wind speed - was around 12,500 meter square per second on Monday - favourable for dispersion of pollutants.
Mixing depth is the vertical height in which pollutants are suspended in the air. It reduces on cold days with calm wind speed.
A ventilation index lower than 6,000 sqm/second, with average wind speed less than 10 kmph, is unfavourable for dispersal of pollutants.
Earlier in the day, Delhi Environment Minister Gopal Rai said air pollution was not a problem of the Aam Aadmi Party alone and everyone, irrespective of their party affiliations, should join efforts to tackle it.
"It is the responsibility of all governments and citizens of Delhi to contribute in reducing pollution. The problem is not of the AAP alone. I want to appeal to everybody to participate in this campaign, keeping the party affiliations aside," Mr Rai said.
Mr Rai said switching vehicles off at red lights can reduce vehicular pollution by 15-20 per cent.
Severe air pollution in Delhi is a year-round problem, which can be attributed to unfavourable meteorological conditions, farm fires in neighbouring regions and local sources of pollution.
According to an analysis by the Council on Energy, Environment and Water, a Delhi-based think tank, transportation contributes the most -- 18 to 39 per cent -- to Delhi's air pollution.
Road dust is the second largest source of air pollution in the city (18 to 38 per cent), followed by industries (2 to 29 per cent), thermal power plants (3 to 11 per cent) and construction (8 per cent).
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)