Dhaka is world's second-most polluted city

Air pollution still remains one of the top most challenges for Bangladesh -- its capital has been ranked as the second-most polluted city in the world.

On Saturday, Dhaka occupied the second position in the list of world cities with the worst air quality. Dhaka's air quality index (AQI) was recorded at 159 around 9.15am, which is considered 'unhealthy'.

The cities of Kolkata and Mumbai in neighbouring India occupied the first and third spots, respectively, with an AQI of 193 and 158.

An AQI between 100 and 200 is considered 'unhealthy for sensitive groups'. Similarly, an AQI between 201 and 300 is said to be 'poor', while a reading of 301 to 400 is considered 'hazardous', posing serious health risks to residents.

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 overall AQI is based on five criteria pollutants – Particulate Matter (PM10 and PM2.5), NO2, CO, SO2, and Ozone (O3).

Dhaka has long been grappling with air pollution issues. Generally, Dhaka's air starts getting fresh when monsoon rains begin in mid-June. The air remains mostly acceptable from June to October.

Air pollution consistently ranks among the top risk factors for death and disability worldwide. 

Breathing polluted air has long been recognised as increasing a person's chances of developing heart disease, chronic respiratory diseases, lung infections and cancer, according to several studies.

As per the World Health Organization (WHO), air pollution kills an estimated seven million people worldwide every year, largely as a result of increased mortality from stroke, heart disease, chronic obstructive pulmonary disease, lung cancer and acute respiratory infections.

What experts say

Authorities need to chalk out a special action plan to control Dhaka's terrible dust pollution as it turns worse every winter, particularly from November to February, posing a serious health hazard to city dwellers, according to experts.

With the advent of winter, the city's air quality starts deteriorating sharply due to the massive discharge of pollutant particles from construction sites, rundown roads, brick kilns and other sources, they say.

To control dust pollution, they suggest regular sprinkling of water on the city's roads and stopping the movement of unfit motor vehicles in the city. They also urge the Bangladesh government to ensure that all construction sites are covered.

Ainun Nishat, Professor Emeritus at BRAC University, told UNB that dust particles from construction sites, earth filing and roads, black smoke from overloaded motor vehicles and traditional brick kilns located on the outskirts of Dhaka are largely responsible for making the city's air quality worse in winter.

"So, all traditional brick kilns should be modernised as soon as possible," he added.