India’s Delhi topped the index, followed by Nepal's Kathmandu
Bangladesh’s capital, Dhaka, has ranked third-worst on the world Air Quality Index (AQI) — as its extreme air pollution makes it one of the most polluted cities.
On the real-time rankings, Dhaka scored 163 on Thursday, according to AirVisual, which monitors global air quality.
Dhaka's air quality was classified as “unhealthy.”
Meanwhile, India’s Delhi topped the index with a score of 393; and Nepal's Kathmandu ranked second with a score of 170.
As one of the most densely-populated countries in the world, Bangladesh has been struggling with air pollution for a long time. Dhaka continuously ranks among the world’s most polluted cities.
Brick kilns, vehicles run on fuel containing higher levels sulphur, as well as construction work, have all been identified as major sources of air pollution.
Air quality further declines during the dry months—from October to April—but improves during the monsoon.
The United States Environmental Protection Agency developed the Air Quality Index (AQI) to measure air quality. The AQI is divided into six categories, indicating increasing levels of harm to one’s health.
An AQI value over 300 represents hazardous air quality, and below 50 the air quality is good.
The index is based on the five criteria of pollutants regulated under the Clean Air Act: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide.
The AQI debuted in 1968, when the National Air Pollution Control Administration undertook an initiative to develop an air quality index, and to apply the methodology to Metropolitan Statistical Areas.