Face masks sell out as smog worsens in China

Rising smog levels are forcing China's biggest online sellers of face masks out of stock. Smog has shrouded areas of northern China for the past week, much of it caused by coal-burning power stations, and has seen sales of face masks and air purifiers increase exponentially. 

In Beijing, the PM 2.5 readings - the number of airborne particles per cubic metre, which have been linked to a whole host of diseases and premature deaths - stood at between 486 and 557 this morning. The safe limit recommended by the WHO is 25. 

A new four-tier alert system, unveiled last October, was raised to Orange alert status for the first time last week. Residents are advised to remain indoors and to wear protective masks should they need to go outside.