New Delhi, Nov 26 (IANS): "Good", "satisfactory" and "moderate" air quality days together increased from 159 in 2018 to 198 up until November 23, 2021, according to a Delhi Department of Environment report.

"'Good', 'satisfactory' and 'moderate' days together increased from 159 in 2018 to 182 in 2019, 227 in 2020, and 198 in 2021. 'Poor',' very poor' and 'severe days' together reduced from 206 in 2018 to 183 in 2019 and 139 in 2020 and 129 in 2021," the report reads.

According to the report, the source apportionment study of NCT of Delhi was carried out through IIT Kanpur in 2016 and The Energy Research Institute (TERI) in 2018. Source apportionment of ambient particulate matter during winter season in Delhi (IIT-Madras) in 2018 and Carrying capacity of Air Environment, NCT Delhi (School of Planning and Architecture) in 2020 was also carried out. Source Apportionment and Forecasting for Advance Air Pollution Management in Delhi on real time basis: An agreement, with IIT Kanpur led consortium for executing a study on Real Time Source Apportionment Study in Delhi has been signed on October 22.

In addition to these, 13 hotspots have been identified based on higher levels of PM 2.5 and PM 10.

Delhi Environment Minister Gopal Rai has repeatedly emphasised that the majority of the national capital's air pollution is due to stubble burning in the neighbouring states of Punjab and Haryana, whereas Delhi's own sources of pollution are very minimal or limited.

However, Mukesh Khare from IIT Delhi, who is also a former expert member of the now-dissolved Environment Pollution (Prevention and Control Authority) told IANS: "The only reason air quality has not deteriorated as much as previous year is because of the prolonged rainy season, which extended till October this year."

There are still 50 more days to get the overall air quality of the national capital and its adjoining areas, he added.