Most polluted capital cities based on PM2.5 concentration globally 2023

New Delhi was the most polluted capital city in the world in 2023, with an average PM2.5 concentration of nearly 93 micrograms per cubic meter of air (μg/m³). PM2.5 particulate matter concentrations in the Indian capital were over nine times higher than the World Health Organizations PM2.5 target of 10 μg/m³. Despite having such high PM2.5 levels, New Delhi isn't the most polluted city worldwide.

Sources of PM2.5

PM2. 5 refers to atmospheric particulate matter that have a diameter of less than 2.5 micrometers. There are many sources of PM2.5 emissions, including road transport, industrial activities, crop burning, and energy industries. Domestic combustion, such as burning wood for fuel, is also a major source of PM2.5 emissions. As a result, PM2.5 concentrations are typically higher in developing countries. In comparison, PM2.5 levels in European capitals are considerably lower.

Health impacts of air pollution

Exposure to levels of PM2.5 ranging from 55.5 to 150.4 μg/m³ is considered unhealthy, increasing the likelihood of heart and lung problems. Air pollution is one of the leading causes of premature deaths worldwide, cutting millions of lives short every year. While this is especially the case in Asia, the impacts of these pollutants are felt everywhere. Globally, nearly 2.8 billion people were exposed to hazardous levels of air pollution in 2022.