The World's Most Polluted Capital Cities
Among the capital cities of 138 countries and territories analyzed in the 2024 World Air Quality Report published by equipment manufacturer IQAir, Chad's capital N'Djamena ranked first ahead of India's capital New Delhi. Both cities had an average annual PM2.5 concentration of more than 90 micrograms per cubic meter of air. This number exceeds the most recent World Health Organization goal 18 times.
In rank 3, Dhaka, the capital of Bangladesh, exhibited an annual average PM2.5 concentration of 78 micrograms per cubic meter of air, followed by Kinshasa in the Democratic Republic of the Congo and Islamabad in Pakistan at 58.2 and 52.4 micrograms, respectively. The first capital city not located in Asia or Africa on the list is Sarajevo with 30.8 micrograms. IQAir's World Air Quality Report analyzed data from 8,954 cities, adding four new African, one Asian and two new countries in the Americas to its covered area compared to its 2024 edition.
The biggest share of PM2.5, which stands for ambient particular matter with a diameter of less than 2.5 microns, stems from human activity, according to a 2021 paper published in nature communications. Emissions from road transport and the energy sector are the biggest contributors to a higher concentration of PM2.5, while smaller-scale sources like agricultural waste burning as well as household cooking and heating can also be a factors, especially in developing countries.