Dhaka, May 24 -- Dhaka has ranked first on the list of cities with the worst air quality, with an Air Quality Index (AQI) score of 157 at 10:10am on Friday morning.

Friday's air was classified as "unhealthy," referring to a health threat, according to the AQI index.Though Friday is a weekend with low vehicular pressure on city streets, the air quality still turned unhealthy.

When the AQI value for particle pollution is between 50 and 100, air quality is considered "moderate", usually sensitive individuals should consider limiting prolonged outdoor exertion, between 101 and 150, air quality is considered "unhealthy for sensitive groups", between 150 and 200 is "unhealthy", between 201 and 300 is said to be "very unhealthy", while a reading...