New Delhi, Dec. 16 -- Delhi residents woke up to another day of toxic smog blanketing the city skyline, as air quality levels, ironically, improved to the "very poor" category on Tuesday, with an AQI of 380.

The marginal improvement in Delhi AQI today was reported days after the implementation of GRAP 4 restrictions, as the city breathed air in the hazardous "severe" zone.

According to the Central Pollution Control Board data for 8:00 AM on Tuesday, Delhi's AQI was recorded at 378 in the "very poor" category.

On Sunday, official index readings exceeded 450 at several monitoring stations, up from 430 on Saturday and the highest so far this winter season, according to data from CPCB. On Monday, it stood at 449.

An AQI between 301 and 40...