In the real-time air quality ranking, Dhaka scored 164 and was classified as ‘unhealthy’, according to AirVisual. On Tuesday, Dhaka remained on top of the air quality index for some time, scoring 361, and was also classified as 'hazardous'. United States environmental experts developed the Air Quality Index (AQI) to rank air quality. An AQI value over 300 represents hazardous air quality, and below 50 the air quality is good. The AQI debuted in 1968, when the National Air Pollution Control Administration undertook an initiative to develop an air quality index and to apply the methodology to Metropolitan Statistical Areas.

Source: Dhaka Tribune February 20, 2019 14:56 UTC