Dhaka ranked third on the list of cities worldwide with the worst air quality this morning.

Its air quality continued to be in the "unhealthy" zone with an air quality index (AQI) score of 174 at 9:10am.

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

Thailand's Chiang Mai, India's Delhi and Nepal's Kathmandu occupied the first, second and fourth spots in the list, with AQI scores of 191, 185 and 169, 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.

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.