Beijing West Railway Station is engulfed in dense smog on May 6, 2013. Beijing Municipal Environmental Monitoring Center?showed that the density of PM2.5 in some areas hit 400 micrograms per cubic meter early on Monday, well above national and international standards. Residents are advised to spend less time on outdoor activities. The lingering smog is unlikely to disperse soon, according to Beijing’s environment authorities. [Photo/Xinhua]?