Dhaka's air quality is in the "very unhealthy" zone this morning.

With an air quality index (AQI) score of 256 at 9:10am today, the capital of Bangladesh ranked second in the list of world cities with the worst air quality.

An AQI between 151 and 200 is said to be "unhealthy," 201 and 300 "very unhealthy," and 301 to 400 is considered "hazardous," posing serious health risks to residents.

Mongolia's Ulaanbaatar and Iraq's Baghdad occupied the first and third places with AQI of 283 and 231, 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 heart disease, chronic respiratory diseases, lung infections and cancer, according to several studies.