With an Air Quality Index (AQI) score of 191 at 10:30am on Tuesday, Dhaka ranked 4th in the list of cities worldwide with the worst air quality.

Pakistan's Karachi, China's Beijing, and Pakistan's Lahore occupied the first, second, and third spots, with AQI scores of 214, 214, and 205 respectively.

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

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.