GREATER NOIDA, Dec. 16 -- Greater Noida emerged as the most polluted city in the country on Monday, followed closely by Ghaziabad and Noida, according to Central Pollution Control Board (CPCB) data. Residents suffered another day of difficulty breathing and itchy eyes as a heavy smog hung over the region.

Greater Noida recorded a 24-hour average AQI of 447 in the 'severe' category, according to the CPCB's 4 pm national bulletin. It was followed by Ghaziabad at 444 and Noida at 437 - also in the 'severe' category.

On Sunday, Noida, with an AQI of 466, was the most polluted in the country, followed by Ghaziabad at 459 and Greater Noida at 435.

An AQI of 51 to 100 is classified as "satisfactory", and between 101 and 200 is classified as "...