According to IQAir, levels of PM2.5 pollutants -- cancer-causing microparticles small enough to enter the bloodstream through the lungs -- hit 227 micrograms per cubic metre, 15 times the World ...

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 ...