Dhaka's air quality was ranked second worst in the world for the second consecutive day today.

With an air quality index (AQI) score of 208 at 8:58am, Dhaka's air was categorised as "very unhealthy".

An AQI between 101 and 200 is considered "unhealthy", particularly for sensitive groups, while an AQI between 201 and 300 is said to be "very unhealthy".

India's Kolkata and Delhi occupied the first and third spots on the list, with AQI scores of 247 and 171, 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.

As per the World Health Organization (WHO), air pollution kills an estimated seven million people worldwide every year, largely as a result of increased mortality from stroke, heart disease, chronic obstructive pulmonary disease, lung cancer and acute respiratory infections.