Smog shrouding Beijing on Sunday (February 16) morning highlighted the struggle China faces in controlling persistent and often dangerous air pollution.<br/> <br />Sunday was the third day that the Chinese capital saw hazardous levels of air pollution.<br/> <br />An index measuring PM2.5, or particulate matter with a diameter of 2.5 micrometers (PM2.5), reached 400 in much of the capital overnight, Beijing Municipal Environmental Monitoring Center said.<br/> <br />The previous night, it had exceeded 500, the highest level measured by the country's monitoring system.<br/> <br />A level above 300 is considered hazardous, while the World Health Organisation recommends a daily level of no more than 20.<br/> <br />Pollution is a rising concern for China's stability-obsessed leaders, keen to douse potential unrest as affluent city dwellers turn against a growth-at-all-costs economic model that has tainted much of the country's air, water and soil.<br/> <br />The stone walls and moat of the forbidden city, former residenc
