On Wednesday (March 24, 2021), Dhaka occupied the third position in the list of world cities with the worst air quality. The capital's air quality index (AQI) was recorded at 198 around 11.35 am.

India’s Delhi and Nepal’s Kathmandu occupied the first two positions in the list, with AQI scores of 266 and 213, respectively.

Read Dhaka is world's most polluted city

An AQI between 101 and 200 is considered 'unhealthy', particularly 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.

Read Public health issues like air pollution, environment not getting due attention

In Bangladesh, the overall 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.

The densely populated capital of Bangladesh has long been grappling with air pollution issues. The air quality usually improves during monsoon.

Read Lung cancer on the rise in Bangladesh: Report

A report by the Department of Environment (DoE) and the World Bank in March 2019 pointed out that the three main sources of air pollution in Dhaka "are brick kilns, fumes from vehicles and dust from construction sites".

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.

Also Read: No respite from pollution as Dhaka's air quality still 'unhealthy'

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.

Over 80 percent living in urban areas which monitor air pollution are exposed to air quality levels that exceed WHO guideline limits, with low- and middle-income countries most at risk.

Also Read:  Dhaka keeps grappling with 'hazardous' air