With an air quality index (AQI) score of 199 at 9:20 am today, Dhaka ranked fifth in the list of cities worldwide with the worst air quality.

China's Beiijng, India's Delhi, and Pakistan's Lahore occupied the first three spots on the list, with AQI scores of 482, 359 and 263, respectively.

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

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.

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.