smog

WHO's worst urban pollution: 

1. Ahwaz, Iran

2. Ulan Bator, Mongolia

3. Sanadaj, Iran

4. Ludhiana, India

5. Quetta, Pakistan

6. Kermanshah, Iran

7. Peshawar, Pakistan

8. Gaberone, Botswana

9. Yasouj, Iran

10. Kanpor, India                              

     jpr: According to Nat Geo. half the world's population lives in urban areas.