Bangladesh's capital Dhaka has once again ranked worst in the Air Quality Index (AQI).
The city had a score of 177 at 2:58pm on Thursday, indicating that the air quality was "unhealthy."
In the index, Kathmandu of Nepal, Kolkata and Mumbai of India occupied the next three slots with a score of 173, 159 and 157 respectively.
When the AQI value is between 151 and 200, every city dweller may begin to experience health effects. Members of sensitive groups may experience more serious health effects in this situation.
Though, in the later part of the day, Dhaka ranked third worst in the index, its AQI score rose to 184 at 9:12pm.
But with higher AQI scores of 254 and 194, Mongolia's Ulaanbaatar and India's Delhi respectively slated to be the two most polluted cities by then.
Earlier in the morning, Dhaka ranked fourth worst in the index with a score of 208 at 9:27am, reports UNB.
The air quality was classified as "very unhealthy."
Ulaanbaatar, Delhi and Kolkata occupied the top three positions with worst air with scores of 352, 230 and 220 respectively.
When the AQI score is between 201 and 300, everyone may experience health effects and it gives a warning of emergency conditions. The entire population is more likely to be affected in this state.
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. The air quality usually improves during monsoon.
