NEW DELHI: The share of stubble burning in Delhi's PM 2.5 concentration was 6 per cent on Thursday, according to a central government agency.
It was only around one per cent on Wednesday and around 3 per cent on Tuesday, Monday and Sunday, according to the Ministry of Earth Sciences' air quality monitor SAFAR.
PM2.5 refers to fine particulate matter less than 2.5 microns in diameter which can penetrate deeply into lungs, impairing their function, and even the bloodstream.
A layer of smoky haze lingered over Delhi-NCR on Thursday with air quality in the region hitting 'very poor' levels, even as stricter anti-air pollution measures, including a ban on electricity generators, came into force under the Graded Response Action Plan (GRAP).
"Delhi's overall AQI was recorded in the very poor category. The calm and variable surface wind condition continues and the AQI is likely to remain very poor on Friday," it said.
According to SAFAR data, the contribution of farm fires to Delhi's PM 2.5 concentration was around 6 per cent on Thursday.
An increase was observed in stubble burning incidents around Haryana, Punjab, and neighbouring border regions on Wednesday. The farm fire count was 740, it said.
The wind direction is partly favourable for transport of smoke from farm fires and "hence, an increase in contribution in Delhi's PM 2.5 is expected", SAFAR said.
NASA's satellite imagery also showed a large cluster of farm fires near Amritsar, Patiala, Tarn Taran and Firozpur in Punjab, and Ambala and Rajpura in Haryana.
Earlier in the day, Union Environment Minister Prakash Javadekar asserted that only 4 per cent air pollution in Delhi is due to stubble burning and rest are local factors, prompting a sharp response from the Delhi government.
hief Minister Arvind Kejriwal tweeted, "Staying in denial will not help. If stubble burning causes only 4% pollution, then why has pollution suddenly increased last fortnight? Air was clean before that. Same story every year. There's no massive jump in any local source of pollution in last few days to cause this spike?" he said.
Later, a spokesperson of the Union Environment Ministry clarified that Javadekar was referring to the contribution of stubble burning only for this year, which is 4 per cent till now.
Last year, it was much higher.
The ministry also tweeted, "Share of stubble burning changes every day. Last year, between 08 Oct-09 Dec, the share of Stubble burning in #AirPollution in Delhi (as per SAFAR data), was greater than15% on six days, while on a single day it was greater than 40%".