5 Most Polluted Cities in the World

4. Delhi, India

Annual average PM2.5 concentration (μg/m³): 96.4

In November 2017, an event occurred which is now known as the Great Smog of Delhi, where air pollution levels far exceeded acceptable levels. The air pollution in Delhi is significant enough to irreversibly damage the lungs of 50% of all children, a number going in the millions.