Air pollution still remains one of the top-most challenges for Bangladesh, and among cities around the world.

Dhaka’s air quality was ranked as the most polluted on Wednesday morning.

The capital’s air quality index score was recorded at 259 at 9:20am on Wednesday.

India’s Kolkata and Delhi occupied the next two spots, with AQI scores of 232, and 225, 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.

Dhaka has long been grappling with air pollution issues. Its air quality usually turns unhealthy during winter.