Delhiites woke up to a hazy Diwali morning as the air quality oscillated between 'poor' and 'very poor' categories due to reduced wind speed and increase in pollutants from stubble burning, authorities said Wednesday.
The overall air quality index was recorded at 268 which falls in 'poor' category, according to data by the Central Pollution Control Board.
On Wednesday, PM2.5 (particles in the air with a diameter of less than 2.5 micrometres) level was recorded at 134, while PM10 (particles in the air with a diameter of less than 10 micrometres) level was recorded at 276 in Delhi.
Twenty-eight areas in Delhi recorded 'poor' air quality, six recorded 'very poor' air quality, while two areas recorded 'moderate' air quality, according to the CPCB data.
The Indian Institute of Tropical Meteorology said the winds coming from north-westerly direction is bringing influence of biomass burning pollutants in Delhi-NCR which may continue up to Thursday morning.
"The increase in PM2.5 concentration is due to change in wind direction, decrease in wind speeds and contribution from biomass burning," the IITM said.
Shallow fog and haze during daytime is expected on Wednesday and Thursday, it said.
About 9 per cent of PM2.5 pollution in Delhi was caused due to stubble burning, according to the Centre-run System of Air Quality Forecasting and Research (SAFAR).
Delhi's air quality is expected to deteriorate to 'severe plus emergency' category after Diwali, SAFAR said.
"Even if 50 per cent of the total load of toxic firecrackers as compared to Diwali 2017 is added, the prevailing weather conditions will aggravate the high smoke level and make air quality to persist in severe range for at least two days on November 8 and November 9," SAFAR said in a report.
PM10 concentration is expected to reach 575 and PM2.5 to 378 a day after Diwali, recording the worst air quality of the year, it said.