Top 10 Most-Polluted Cities in World; Mumbai Overtakes Delhi - In Pics

1. Lahore (Pakistan): Lahore has been ranked as the world's most polluted city according to the latest Swiss air tracking index IQAir (a real-time worldwide air quality monitor) between January 29 and February 8. 

2. Mumbai (India): Mumbai has left behind the national capital Delhi as the most polluted city in India. It is now the second most polluted city in the world. 

3. Kabul (Afghanistan): PM2.5 concentration in Kabul is currently 5 times the WHO annual air quality guideline value.

4. Kaohsiung (Taiwan): PM2.5 concentration in Kaohsiung is currently 5.4 times the WHO annual air quality guideline value.

5. Bishkek (Kyrgyzstan): The current PM2. 5 concentration in Bishkek is 3.2 times above the recommended limit given by the WHO 24 hrs air quality guidelines value.

6. Accra (Ghana): PM2.5 concentration in Accra is currently 5.2 times the WHO annual air quality guideline value.

7. Krakow (Poland): More than 46,000 people die prematurely due to poor air quality each year. Krakow, Poland's second-largest city, ranks 7th in global air pollution rankings. 

8. Doha (Qatar): Dust storms and emissions from vehicles and from industry are the main causes of polluted air in Doha. PM2.5 concentration in Doha is currently 3 times the WHO annual air quality guideline value.

9. Astana (Kazakhstan): The main sources of urban air pollutants are stationary types of thermal power stations, boilers, motor vehicle emissions and construction sites, production sites, cement works and asphalt plants. PM2.5 concentration in Astana is currently 7 times the WHO annual air quality guideline value.

10. Santiago (Chile): The main contributors to the accumulation of PM2.5 are vehicle exhaust fumes, fossil-fuel-powered power stations, various industrial processes, agricultural burning and ammonium emissions from agricultural processes.