Agence France-Presse: Beijing's official smog reading for PM 2.5 - small airborne particles which easily penetrate the lungs and have been linked to hundreds of thousands of premature deaths - stood at 501 micrograms per cubic metre on Wednesday afternoon. The World Health Organisation's recommended safe limit is 25. An alternative measure by the US embassy in Beijing said PM 2.5 levels were at 542 in the city. The capital was on its sixth day of an "orange" smog alert - the second-highest on the scale - with the air...