Photo-collected.
Online Reporter/

The capital Dhaka has once again topped the list of the world’s most polluted cities.

Dhaka’s air quality index (AQI) at 8 am on Friday (January 20) was recorded at 317, which is considered hazardous for air quality.

An AQI score between 101 and 200 is considered unhealthy for sensitive air quality groups. An AQI score between 201 and 300 is considered very unhealthy. And an AQI between 301 and 400 is considered risky.

India’s Kolkata and Mumbai are ranked second and third in the list with AQI scores of 196 and 189 respectively.

The AQI of pollution in Bangladesh is determined based on five characteristics. They are particulate matter (PM10 and PM2.5), NO2, CO, SO2 and ozone (O3).