Dhaka ranked first in the list of cities with the most polluted air in the world on Sunday (January 5).

At 10 am this morning, Dhaka's Air Quality Index score was 445, which is considered 'very unhealthy'.

Baghdad, Iraq, is in second place in this list of air pollution with a score of 444. Karachi, Pakistan, is in third place, with a score of 248. Hanoi, Vietnam, is in fourth place, with a score of 216. Ulaanbaatar, Mongolia, is in fifth place, with a score of 212.

The AQI score, which is based on daily air quality, gives people information about how clean or polluted the air is in a particular city and whether they may be at risk of any health risks.

Air quality between 101 and 150 is considered 'unhealthy for sensitive groups', AQI scores between 150 and 200 are considered 'unhealthy'. Between 201 and 300 is called 'very unhealthy', and AQI scores of 301 or higher are considered 'hazardous', posing a serious health risk to residents.