Fight for clean air continues

Dhaka has ranked first in the list of cities across the world with the worst air quality.

According to AirVisual, Dhaka showed an average air quality index (AQI) score of 189 at 8:51pm on Wednesday. The air quality was classified as "unhealthy" at the time.

Residential areas like Baridhara and Bashundhara showed AQI scores of 218 and 206, respectively.

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.

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.

Cambodia's Phnom Penh, Kyrgyzstan's Bishkek and China's Shanghai occupied the second, third and fourth spot in the list of cities with worst air quality with AQI scores of 169, 161, and 160 respectively. 

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.

As one of the most densely populated countries in the world, Bangladesh has been struggling with air pollution for a long time. Dhaka continuously ranks among the world's most polluted cities.

Brick kilns, vehicles run on fuel containing higher levels sulphur, as well as construction work, have all been identified as major sources of air pollution.

Air quality further declines during the dry months -- from October to April -- but improves during the monsoon.