Dhaka ranked sixth on the list of cities worldwide with the worst air quality today.

With an AQI index of 158 at 9:10am, the air was classified as 'unhealthy', according to the air quality index.

When the AQI value for particle pollution is between 101 and 150, air quality is considered 'unhealthy for sensitive groups', between 151 and 200 is 'unhealthy', between 201 and 300 is said to be 'very unhealthy', while a reading of 301+ is considered 'hazardous', posing serious health risks to residents.

India's Delhi and Mumbai and Pakistan's Lahore occupied the first three spots on the list, with AQI scores of 345, 174 and 170, 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.