Dhaka, the densely populated capital of Bangladesh, prevails over world cities for its worst air quality.
Dhaka ranked first in the list of world’s most polluted cities. China’s capital Beijing occupied the second position. Nepal and India’s capital Kathmandu and Delhi grabbed the 3rd and 4th position respectively.
Dhaka's air quality index (AQI) was recorded at 237 at around 2:00am, which is considered “very unhealthy”.
An AQI between 201 and 300 is considered "poor," while a reading of 301 to 400 is known to be "hazardous", and poses serious health risks to city dwellers, according to UNB.
AQI, which is the index for reporting daily air quality, is used by government agencies to notify people how clean or polluted the air of a certain city is. It also informs them about the concerning health effects that are associated with it.
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 that is distinguished by wide seasonal variations in rainfall, high temperatures and humidity.
Generally, Dhaka’s air gets fresh when monsoon rains begin in mid-June. The air remains mostly tolerable from June to October.
In February last year, Bangladesh's Environment, Forests and Climate Change Minister, Md Shahab Uddin acknowledged the fact that air pollution levels in the capital "has reached an extreme level."
This is mainly due to uncontrolled discharge of dust from construction projects, smoke from vehicles and brick kilns," he said.
"Brick kilns are responsible for 58 percent of air pollution in the capital. There are plans to shut down (traditional) kilns in operation. We plan to stop the burning of bricks at all kilns by 2025 and use block bricks to construct buildings under government projects," he added.
Directions were given by the High Court to the authorities concerned to shut down all illegal brick kilns by February 18.
Air pollution exists among the top risk factors for death and disability worldwide. It increases the chance of heart disease, chronic respiratory diseases, lung infections, and cancer, according to several studies.
According to 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 of people living in urban areas are exposed to air quality levels that exceed WHO guideline limits, with low- and middle-income countries most at risk.