Dhaka once again topped the list of cities around the world with the worst air quality this morning.

With an air quality index (AQI) score of 370 at 8:55am today, Dhaka ranked first among cities with the most polluted air.

An AQI between 151 and 200 is said to be "unhealthy" while 201 and 300 is considered "very unhealthy", and 301 to 400 is considered "hazardous", posing serious health risks to residents.

India's Delhi and Mumbai occupied the second and third spots in the list, with AQI scores of 251 and 220, respectively.

In Bangladesh, the AQI is based on five criteria 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.

Air pollution consistently ranks among the top risk factors for death and disability worldwide. Breathing polluted air has long been recognised as increasing a person's chances of developing a heart disease, chronic respiratory diseases, lung infections and cancer, according to several studies.