Dhaka, the overcrowded capital of Bangladesh, has topped the list of cities worldwide with the worst air quality with an AQI score of 228 at 9:00am today.

Dhaka's air was classified as 'very 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.

Pakistan's Lahore, Iraq's Baghdad and India's Delhi occupied the second, third and fourth spots in the list, with AQI scores of 226, 219 and 215, 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.

Dhaka has long been grappling with air pollution issues. Its air quality usually turns unhealthy in winter and improves during the monsoon.