Although  the air quality of Dhaka showed a sign of improvement on Friday morning  it  was  classified as ‘unhealthy’ in the Air Quality Index (AQI).   The capital ranked 12th worst in the Air Quality Index (AQI) with a score of 104.   Pakistan’s Lahore, India’s Delhi and China’s Shenyang, occupied the first three spots in the list of cities with the worst air with scores of 183, 169 and 144 respectively.   When the AQI value is between 101 to 150 it means ‘Unhealthy for Sensitive Groups’.   Although general public is not likely to be affected at this AQI range, people with lung disease, older adults and children are at a greater risk from exposure to ozone, whereas persons with heart and lung disease, older adults and children are at greater risk from the presence of particles in the air.   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.   Dhaka has long been grappling with air pollution. Its air quality usually improves during monsoon.