Dhaka, one the most polluted cities in the world, ranked worst in the Air Quality Index (AQI) on Sunday morning.
It had a score of 188 at 10:24am. The air was classified as 'unhealthy'.
When the AQI value is between 151 and 200, everyone may begin to experience health effects. Members of sensitive groups may experience more serious health effects.
Pakistan's Lahore and India's Delhi occupied the second and third spots in the list with scores of 178 and 176 respectively.
The AQI, an index for reporting the daily air quality, informs people how clean or polluted the air of a certain city is and what associated health effects might be a concern for them.
In Bangladesh, the AQI is based on five criteria pollutants - Particulate Matter (PM10 and PM2.5), NO2, CO, SO2 and Ozone.
World's most polluted country
Bangladesh topped the list of the world's most polluted countries in 2019 for PM2.5 exposure, according to an IQAir AirVisual report.
The 2019 World Air Quality Report is based on data from the world's largest centralised platform for real-time air quality data, combining efforts from thousands of initiatives run by citizens, communities, companies, non-profit organisations and governments.
It includes only PM2.5 (fine particulate matter) data as acquired from ground-based air quality monitoring stations with high data availability.
To track outdoor air quality, the report focused on the concentrations of two pollutants in particular: fine particle air pollution (particulate matter measuring less than 2.5 micrometers in aerodynamic diameter, or PM2.5) and ozone found near ground level (tropospheric ozone).
This assessment also tracked exposure to household air pollution from burning fuels such as coal, wood, or biomass for cooking.
Air pollution consistently ranks among the top risk factors for death and disability worldwide. Breathing polluted air has long been recognized as increasing a person's chances of developing heart disease, chronic respiratory diseases, lung infections, and cancer, according to the report.
As per the World Health Organization (WHO), the air pollution kills an estimated seven million people worldwide every year largely as a result of increased mortality from stroke, heart disease, chronic obstructive pulmonary disease, lung cancer and acute respiratory infections.
Over 80 percent living in urban areas which monitor air pollution are exposed to air quality levels that exceed WHO guideline limits, with low- and middle-income countries most at risk, WHO estimated.