Vietnam's capital blanketed by toxic smog

Thick smog blanketed Hanoi on Friday, obscuring buildings and leaving nine million residents choking on toxic air as the Vietnamese capital topped a list of the world's most polluted major cities. Authorities urged people to wear masks and limit time outdoors. 

Experts say pollution in Hanoi is a result of widespread construction, as well as emissions from the huge number of motorbikes and cars that crisscross the capital every day. According to a climate expert, Hanoi residents need to wait for a strong northeast monsoon with rain and strong convection for the pollution situation to improve. Rain does not typically arrive in the city until March.