In the survey for 2025, India emerged as the sixth most-polluted country in the world in terms of PM2.5 concentration levels.
India ranked as the third most polluted in 2023, while it was ranked fifth in 2024.
Delhi (99.6 µg/m³), Noida (80.5 µg/m³), Ghaziabad (89.2 µg/m³), Greater Noida (77.2 µg/m³) have been ranked among Central and South Asia region's top 15 polluted cities.
The data is sourced from 9,446 cities spanning 143 countries, regions, and territories and from more than 40,000 regulatory monitoring stations and low-cost sensors, managed by government agencies, universities, non-profit organisations, private enterprises and citizen scientists.