Dhaka ranked second among the world's most polluted cities on Wednesday morning, recording an Air Quality Index (AQI) score of 165 at 9:50 am.

The air quality was classified as 'unhealthy', indicating that pollutant levels had reached a level that could pose health risks to the general population, according to the AQI scale.

Malaysia's Kuala Lumpur topped the list with an AQI score of 194.

Vietnam's Ho Chi Minh City and Kinshasa of the Democratic Republic of Congo ranked third and fourth, respectively, with AQI scores of 162 and 156.

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.