Beijing: Obscured by toxic clouds 6 Photos . Updated: 14 Jan 2013, 12:29 PM IST Livemint Dense fog has enveloped swathes of east and central China, with pollution levels in Beijing reaching dangerous levels and residents advised to stay indoors, according to the state media. 1/6Data released via the US embassy twitter feed showed that Beijing’s air quality index levels were so hazardous that they were classed as ‘Beyond Index’. AP 2/6According to the Beijing Municipal Environmental Monitoring Center, the density of PM2.5 particulates (particles less than 2.5 micrometers in diameter) had surpassed 700 micrograms per cubic meter in many parts of the city. AFP 3/6The World Health Organization considers a safe daily level to be 25 micrograms per cubic meter. Reuters 4/6Vehicles drive on the Third Ring Road in Beijing. The city’s pollution monitoring centre warned residents to stay indoors. Reuters 5/6A visitor wearing a mask walks outside the Forbidden City in Beijing. In 2012, air pollution killed some 8,600 people prematurely and cost $1 billion in economic losses, according to a study by Beijing University and Greenpeace. Reuters 6/6Two men walking along a railway line in Beijing. Commentators say the air pollution illustrates China’s persistent challenge to address environmental issues while maintaining its economic growth momentum. AFP