Dhaka’s air quality continued to be in the 'unhealthy' zone on Saturday morning.

With an air quality index (AQI) score of 199 at 8:56 am, the capital of Bangladesh ranked second in the list of cities worldwide with worst air quality.

Pakistan’s Lahore and Mongolia’s Ulaanbaatar occupied the first and third spots, with AQI scores of 223 and 195, respectively.

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

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

Also read: Dhaka's air quality still ‘very unhealthy' as it ranks 2nd worst polluted city

Dhaka has long been grappling with air pollution issues. Its air quality usually turns unhealthy in winter and improves during the monsoon.

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 a 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.