Dhaka's air has been ranked as the third most polluted city in the world with "very unhealthy" air quality this morning.

Dhaka's air quality index (AQI) score was 239 at 9:00am today.

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

Pakistan's Karachi and India's Delhi occupied the first two spots in the list, with AQI scores of 428 and 241 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. The 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. 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.