Dhaka has topped the list of cities with the worst air quality with an AQI index of 239 at 08:55am today.

The air was classified as 'very unhealthy'.

An AQI between 151 and 200 is considered 'unhealthy' while 201-300 is 'very unhealthy', and 301-400 is considered 'hazardous', posing severe health risks to residents.

India's Mumbai and China's Chengdu occupied the second and third spots in the list of cities worldwide with the worst air, with scores of 199 and 197, respectively.

The AQI, an index for reporting 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.

The AQI in Bangladesh is based on five pollutants: particulate matter (PM10 and PM2.5), NO2, CO, SO2, and ozone.

Dhaka has long been grappling with air pollution issues. Its air quality usually turns unhealthy in winter and improves during the monsoon.

As per World Health Organization (WHO), air pollution kills an estimated seven million people worldwide every year, mainly due to increased mortality from stroke, heart disease, chronic obstructive pulmonary disease, lung cancer, and acute respiratory infections.