As the world's second largest economy steams ahead, it is leaving a dense smog in its wake. Pollution in China has reached dangerously high levels in recent days. Dozens of cities are affected by thick smog and haze, 40 times the limit deemed safe by the World health Organisation (WHO). More than 100 million citizens have been affected; from Beijing to Guiyang, factories have been asked to close and people are being urged to stay indoors. So, is China's rapid development damaging the quality of life for its people?