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New Delhi in India was the most polluted capital city in the world in 2025, with an average annual PM2.5 concentration of nearly **** micrograms per cubic meter of air (μg/m³). PM2.5 particulate matter concentrations in Indian capital were over ** times higher than the World Health Organizations PM2.5 guideline of 5 μ²µ/³¾Â³. Dhaka in Bangladesh followed closely in second place, with PM2.5 levels of ** μ²µ/³¾Â³.

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.

Health impacts of air pollution

Exposure to high levels of PM2.5 increases the likelihood of heart and lung problems, and can lead to premature death. Air pollution is one of the leading causes of premature deaths worldwide, cutting millions of lives short every year. Although the highest number of annual air pollution-related deaths are observed in East Asia and Pacific, the health and lives of people in all regions of the world are at risk from harmful pollutants like PM2.5.