"The WHO’s key announcement yesterday was that it has included outdoor air pollution [PDF] on its definitive list of the world’s known carcinogens—an addition that, it hopes, will get governments to do something about it," write Ritchie King and Lily Kuo. "Air pollution is the world’s worst environmental carcinogen and more dangerous than second-hand smoke, for instance, the health body said."
The WHO also identified the global cities with the worst outdoor air pollution. Surprisingly, Beijing did not top the list. Though the Chinese capital's noxious air has gotten a good deal of press lately, the city's air quality is only the fifth worst in China and far better than the globe's most hazardous places. Three of the six worst cities are in Iran, with the southwestern city of Ahwaz topping them all. "As the chart above shows, the cities with the worst air are often not big capitals, but provincial places with heavy industry in them or nearby."