Beijing's air pollution levels soared on Friday after thick smog engulfed the capital. The US embassy air quality monitor for PM2.5 - airborne particles small enough to enter the lungs and blood - reached levels “hazardous” and hit 440 micrograms per cubic metre about 2pm. The Ministry of Environmental Protection in Beijing advised residents to avoid outdoor activities on Friday, saying pollution levels were “severe,” according to its website. A sand storm combined with strong winds is expected to hit the city on Saturday, according to weather reports. Sand storms were prevalent in early spring in northern China when the frost melts in the Gobi desert and strong winds push dust into neighbouring provinces. "It's time our NPC delegates meet the real Beijing," said a blogger on Sina Weibo, China's twitter-like service.