Swiss air tracking index IQAir: In the week between January 29 and February 8, the Swiss air tracking index IQAir, a real-time air quality monitor, identified Mumbai as the second most polluted city in the world and the most polluted city in India. On January 29, Mumbai was ranked 10th in the rankings for the poorest position. Mumbai then clinched the second spot on February 2 before falling in the following days. Then it again rose to take the second place on February 8. On February 13, Mumbai took over Delhi as the most polluted city in India and was the third most unhealthy city worldwide for air quality worldwide.
Top 10 most-polluted cities worldwide:
| Ranks | City |
| 1 | Lahore (Pakistan) |
| 2 | Mumbai (India) |
| 3 | Kabul (Afghanistan) |
| 4 | Kaohsiung (Taiwan) |
| 5 | Bishkek (Kyrgyzstan) |
| 6 | Accra (Ghana) |
| 7 | Krakow (Poland) |
| 8 | Doha (Qatar) |
| 9 | Astana (Kazakhstan) |
| 10 | Santiago (Chile) |
What is IQAir?
IQAir, a Swiss air tracking index and a real-time worldwide air quality monitor, collaborates with UNEP and Greenpeace and measures air quality in India using data from the Central Pollution Control Board (CPCB). According to US air quality index (AQI) standards, which are stricter than those in India, the cities are divided into three categories: “healthy,” “unhealthy,” and “hazardous.”