Dhaka, one the most polluted cities in the world, ranked worst in the Air Quality Index (AQI) on Monday morning.
It had a score of 323 at 10:35 am. The air was classified as 'hazardous' and in this condition, everyone may experience more serious health effects.
When the AQI value is more than 300, people are advised to avoid all outdoor exertion.
Pakistan's Lahore and India's Kolkata occupied the second and third spots in the list with scores of 294 and 293 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.
What experts say
As the densely-populated Dhaka city started to experience serious air pollution in the dry season like previous years, health experts warn that dirty air during this winter may help coronavirus turn deadlier in terms of mortality rate.
They said the exposure to a high level of air pollution weakens people's respiratory and immune systems, causes various cold-related diseases, making them more susceptible to Covid-19.
The World Health Organization (WHO) has also recently cautioned that the cities which have a higher level of air pollution should reinforce their preparedness against the deadly corona pandemic.
The experts said the government should immediately take effective preventive measures to contain the virus infection as well as combat air pollution during the winter.
The also said the use of masks by all must be ensured by enforcing law and motivating people as it is the most effective way to protect oneself from pollution and Covid-19.