The air quality in Delhi worsened on Sunday with the Air Quality Index recording a figure of 421 at 11 am, which falls in the “severe” category, according to the Central Pollution Control Board. On Saturday, the air quality was “very poor” for most of the day.

The levels of PM2.5 (particles with a diameter of less than 2.5 micrometres) were recorded at 472 in Wazirpur, 465 in Mundaka, 458 in Nehru Nagar, 455 in Anand Vihar, 454 in Ashok Vihar and Rohini, 452 in Jahangirpuri and 449 in Okhla Phase 2 – all in the severe category. The air quality in some locations in the city was “hazardous”, according to aqicn.org.

“The concentration of PM2.5 is likely to shoot up over the weekend,” an unidentified scientist working with Delhi’s early warning system told the Hindustan Times earlier. “Its levels could breach the severe or emergency category. Such conditions are likely to linger till Sunday.”

The air quality improved significantly compared to Thursday, when it reached the “severe plus” emergency category because of smog caused by firecrackers burst during Diwali. However, it started to deteriorate again by Saturday evening due to an increase in the level of pollutants, IANS reported.

“Currently Delhi is receiving very calm winds from East and South East direction, which are not enough to disperse the pollutants and are getting calmer during night,” said Skymet Director Mahesh Palawat. “The situation may improve from Monday.”

Meanwhile, the Supreme Court-appointed Environment Pollution Control Authority on Saturday extended till November 12 its ban on entry of trucks into the city, construction activities, and a ban on industries using coal and biomass, ANI reported.

Environment Pollution Control Authority Chairperson Bhure Lal wrote to Delhi Chief Secretary Anshu Prakash and also asked the government to extend the ban in Mundka industrial area and in a plastic factory complex situated there.

Traffic authorities on Saturday turned away 481 heavy and medium goods vehicles from Delhi’s borders after a ban was enforced on their entry to check pollution, reported The Times of India.