Dhaka's air most polluted in world --

Dhaka, the overcrowded capital city of Bangladesh, has topped the list of cities with the worst air quality with an AQI index of 173 at 09:05am on Saturday, reports UNB.

The air was classified as 'unhealthy', according to the air quality and pollution city ranking.

An AQI between 151 and 200 is considered 'unhealthy' while 201-300 is 'very unhealthy' and 301-400 is considered 'hazardous', posing severe health risks to residents.

India's Delhi, Vietnam's Hanoi and Nepal's Kathmandu occupied the second, third and fourth spots in the list, with AQI scores of 149, 147 and 125, respectively.

The AQI, an index for reporting daily air quality, informs people how clean or polluted the air of a certain city is and what associated health effects might be a concern for them.

The AQI in Bangladesh is based on five pollutants: particulate matter (PM10 and PM2.5), NO2, CO, SO2, and ozone.