Dhaka ranked eighth among the world's most polluted cities on Sunday morning, recording an Air Quality Index score of 177 at 8:50am. The reading placed the capital's air in the “unhealthy” band, a level that can pose health risks to the general population.

Lahore in Pakistan topped the list on 239, followed by Delhi in India on 207 and Singapore on 204.

The AQI scale treats a reading of 101 to 150 as “unhealthy for sensitive groups”, 151 to 200 as “unhealthy”, 201 to 300 as “very unhealthy” and anything above 301 as “hazardous”.

In Bangladesh, the index is calculated from five main pollutants: fine particulate matter (PM10 and PM2.5), nitrogen dioxide, carbon monoxide, sulphur dioxide and ozone.

Dhaka has long struggled with air pollution, which usually worsens in winter and eases during the monsoon. The World Health Organization estimates that air pollution causes about seven million deaths worldwide each year, mainly through stroke, heart disease, chronic obstructive pulmonary disease, lung cancer and acute respiratory infections.