Delhi's air quality index (AQI) worsened from the 'poor' to the 'very poor' category ahead of Diwali. The city recorded an AQI of over 300 on Sunday, with some areas witnessing levels above 400. According to Central Pollution Control Board (CPCB) data at 9:30 am, Anand Vihar recorded an AQI of 430, Akshardham 426, Wazirpur 364 and Vivek Vihar 351.