On Friday, Dhaka occupied the second position in the list. The city of Kolkata in neighbouring India occupied the first place. The third and fourth spots were grabbed by Karachi and Lahore of Pakistan.

Dhaka's air quality index (AQI) at 10.27 am read 289, which is considered 'poor' that is 'very unhealthy'.

Also read: Dhaka's air quality 'very unhealthy'

An AQI between 201 and 300 is considered 'poor', while a reading of 301 to 400 is said to be 'hazardous', posing serious health risks to city residents.

The capital's poor air quality has become a serious cause of concern for residents as long-term exposure to air pollution has been linked to an increased risk of dying from Covid-19.

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.

Also read:Dhaka's polluted air makes Covid fight harder

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

Bangladesh has a subtropical monsoon climate characterised by wide seasonal variations in rainfall, high temperatures and humidity. 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.

Also read:Air Quality Index: Dhaka ranks 2nd worst

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.

Written by ST, Edited by JM