Bangladesh’s capital, Dhaka, has topped the index of the world’s cities with the worst air quality.
In the real-time air quality ranking, Dhaka scored 361 on Tuesday, according to AirVisual. The air was classified as “hazardous.”
Dhaka was followed by Afghanistan’s Kabul and India’s capital Delhi.
Bangladesh, one of the most densely-populated countries in the world, has been struggling with air pollution for a long time; and Dhaka continuously ranks among the world’s most polluted cities.
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Brick kilns, vehicles run on fuel containing higher levels sulphur, as well as construction work have 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 rank air quality. The AQI is divided into six categories, indicating increasing levels harm to one’s health.
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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.
