Dhaka's air quality continued to be in the 'unhealthy' zone as winter is approaching.

With an air quality index (AQI) score of 161 at 9:03am today, Dhaka ranked sixth in the list of cities worldwide with the worst air quality.

An AQI between 101 and 200 is considered 'unhealthy', particularly for sensitive groups.

India’s Delhi, Pakistan’s Lahore, and India’s Kolkata occupied the first three spots in the list, with AQI scores of 261, 246 and 204, respectively.

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

In Bangladesh, the AQI is based on five criteria pollutants -- Particulate Matter (PM10 and PM2.5), NO2, CO, SO2 and Ozone.

Also read: Effects of Air Pollution on Unborn Children, Neonates, Infants

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.

Also read; Dhaka's air quality still 'unhealthy'

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.