Dhaka ranked first among the world's most polluted cities on Tuesday morning, recording an Air Quality Index (AQI) score of 213 at 11:10am.
The air quality was classified as "very unhealthy", signalling a serious health alert where everyone may experience health effects, according to the AQI scale.
Kuala Lumpur in Malaysia ranked second with an AQI score of 208, while Singapore in Singapore ranked third with a score of 179 and Kolkata in India ranked fourth with an AQI score of 177.
According to AQI standards, a reading between 101 and 150 is considered "unhealthy for sensitive groups", while 151 to 200 is classified as "unhealthy". A reading between 201 and 300 is considered "very unhealthy", while levels above 301 are deemed "hazardous", posing serious health risks.
The AQI provides daily updates on air quality, indicating how clean or polluted the air is and highlighting potential health impacts.
In Bangladesh, the AQI is calculated based on five major pollutants: particulate matter (PM10 and PM2.5), nitrogen dioxide (NO2), carbon monoxide (CO), sulfur dioxide (SO2) and ozone.
Dhaka has long struggled with air pollution, with air quality typically deteriorating during winter and improving during the monsoon season.
The World Health Organization estimates that air pollution causes around seven million deaths globally each year, mainly from stroke, heart disease, chronic obstructive pulmonary disease, lung cancer and acute respiratory infections.