Guardian: The pollution monitor on the roof of the US Embassy in Beijing was catapulted into the international spotlight as air pollution deteriorated in the Chinese capital in mid-January. The instrument broadcasts a Twitter bulletin each hour providing a record of the airborne particle pollution. This peaked at 25 times the World Health Organisation (WHO) guidelines on the 13th implying an increased daily death rate of around 50%. This was a classic example of wintertime smog with cold air settling over...