Bangladesh's capital Dhaka ranked second among cities with worst air quality on Sunday morning.
It had an AQI score of 230 at 08:27am. The air was classified as 'very unhealthy'.
Mongolia's Ulaanbaatar and Vietnam's Hanoi occupied the first and third spots in the list of cities with the worst air quality with AQI scores of 411 and 226 respectively.
When the AQI value is between 201 and 300, every city dweller is more likely to be affected and people with respiratory diseases are advised to limit outdoor activities.
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.
In Bangladesh, the AQI is based on five criteria pollutants – Particulate Matter (PM10 and PM2.5), NO2, CO, SO2 and Ozone (O3).
The Department of Environment has also set national ambient air quality standards for these pollutants. These standards aim to protect against adverse human health impacts.
Dhaka has long been grappling with air pollution. Its air quality usually improves during monsoon.