Delhi's air quality was on the brink of turning severe for the second time on Thursday as stubble burning in the adjoining regions continued coupled with unfavourable meteorological conditions, authorities said. The overall air quality index of Delhi was recorded at 393, which falls in the 'very poor' category and is just seven points away from plunging to severe.

On Tuesday, Delhi's air quality slipped to severe category, prompting authorities to bring in steps falling under emergency situation of Graded Response Action Plan. These included ban on construction activities along with halting operations of industries using coal and biomass as fuel between November 1 and 10.

Meanwhile, the Indian Institute of Tropical Meteorology said the prevailing meteorological conditions will pose a problem in dispersal of pollutants for the next two days due to low wind speed.Moreover, authorities further warned that due to pollutants caused by biomass burning in neighbouring Punjab, Haryana, Uttar Pradesh, and unfavorable meteorological conditions, the air quality is likely to remain in the 'very poor' category on Thursday and Friday.

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".The centre-run System of Air Quality Forecasting and Research said about 12 per cent of pollution by PM2.5 (presence of particles in the air with a diameter of less than 2.5 micrometres) on Thursday was caused due to stubble burning.The PM2.5 was recorded at 235. Fine particulates can be a matter of more serious health concern than PM10 (particles in the air with a diameter of less than 10 micrometres).

According to the Central Pollution Control Board (CPCB) data PM10 level in Delhi stood at 425.The CPCB has on Thursday put up guidelines for the public to file complaints of air pollution in Delhi-NCR on its social media page, website, and through its mobile application.

It has also directed pollution control bodies of Punjab, Haryana and Delhi to start criminal prosecution against agencies or individuals who do not comply with directives to check pollutant levels.