Dhaka occupied the top spot in the list of cities around the world with the worst air quality Friday morning.

With an air quality index (AQI) score of 323 at 9:30am, Dhaka's air remained in the 'hazardous' zone, according to IQAir.

Pakistan's Lahore, and India's Kolkata and Delhi occupied the second, third, and fourth spots in the list, with AQI scores of 306, 284, and 216, respectively.

An AQI between 151 and 200 is considered "unhealthy," 201 and 300 "very unhealthy," and 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.

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.