The densely populated capital of Bangladesh continues to dominate the list of cities with the worst air quality in the world. On Saturday, Dhaka was ranked the world's second-most polluted city, as its air quality index (AQI) was recorded at 302 at 8.56am, which is considered ‘hazardous’. Russia’s Krasnoyarsk and Pakistan’s Karachi occupied the first and third spots with AQI scores of 307 and 224, respectively, in the latest list of world cities with the worst air quality. An AQI above 300 is considered 'hazardous' for everyone and doctors advise people to avoid all outdoor activities. AQI, an index for reporting daily air quality, is used by government agencies to inform 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. Read Public health issues like air pollution, environment not getting due attention