Mexico City, Mexico
Bandar Seri Begawan-Brunei Darussalam
This is very interesting. What is your source for this information, please? :)
Googling gets you to http://factspy.net/top-10-most-polluted-places-around-the-world/
I never heard of Bandar Seri Begawan...
But for the others that are in the middle east... blame the war... or Bush...
Peking used to suffer much from air pollution, then they clean up their act for the Olympics and it was an eye opener.