Bangladesh's capital Dhaka was ranked second worst in the Air Quality Index (AQI) on Wednesday, reports news agency UNB.
Dhaka had a score of 197 at 9:45pm, indicating that the air quality was unhealthy.
A numerical value between 151 and 200 indicates that everyone may begin to experience health effects. Members of sensitive groups may experience more serious health effects.
India's Delhi, China's Hangzhou and Indonesia's Jakarta were at first, third and fourth places of the table with scores of 229, 164 and 161 respectively.
Air quality between 201 and 300 is classified as 'very unhealthy'. If the score is between 301 and 500, then it is classified as 'hazardous'.
The AQI, an index for reporting daily air quality, tells people how clean or polluted the air of a certain city is, and what associated health effects might be a concern for them.
Dhaka, one of the most densely populated cities in the world, has been grappling with air pollution for a long time.
The air quality generally worsens during summer and shows signs of improvement in monsoon when the dust settles.