India, Dec. 20 -- An overly familiar and now-routine smog returned to the National Capital Region (NCR) on Friday, pushing the region to the top of India's pollution charts, with Noida, Greater Noida and Delhi emerging as the three most polluted cities in the country.

According to the Central Pollution Control Board's (CPCB) daily bulletin, seven of the 10 most polluted cities in India on Friday were located in NCR, underscoring the scale and persistence of the air quality crisis gripping the region as winter conditions tighten their hold.

Noida topped the national list with an air quality index (AQI) of 410, firmly in the "severe" zone. Greater Noida followed with an AQI of 376, while Delhi ranked third with a 24-hour average AQI of 37...