India, Sept. 27 -- The pollution seems to be knocking on Delhi's doors already, with the national capital's air quality index (AQI) deteriorating to 169 on Saturday.

Saturday's AQI number was well above the 120 recorded on the previous day and the worst since June 14 this year.

Delhi's skies were engulfed in a grey haze for the first time in several months, likely a portent of the weeks to come, when Delhi will perform its annual dance with toxic air.

As to the cause of Delhi's pollution on Saturday, it was largely due to the formation of a cyclonic circulation that pulled dust into the city.According to the CPCB, an AQI between zero and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301...