Delhi was the worst among all cities monitored by CPCB.On Sunday, air quality was visibly poor with a light smog over the city. "The onset of winter pollution has begun and as conditions begin to get colder, pollution levels will rise slowly," Chowdhury said. the onset of winter pollution has begun and as conditions begin to get colder, pollution levels will rise slowly," Chowdhury said. Leading up to Diwali, the air is expected to stay very poor," she added.Chowdhury said, other contributing factors such as crop burning would also affect air pollution levels. "The temperature is starting to dip and the air quality has been fluctuating between poor and very poor in our data.

Source: Times of India October 23, 2016 23:33 UTC