Smog disrupted traffic and caused flight delays in northeast China on Tuesday (December 3), Chinese state media reported.<br/> <br />In Harbin, a frigid northeastern city of 11 million people, smog reduced visibility levels to less than 50 metres (164 feet), state broadcaster CCTV said.<br/> <br />Buildings in Harbin were shrouded in thick fog.<br/> <br />The speed limit on express highways surrounding Harbin was tightened to 40 kilometres per hour (24.85 miles per hour), state-run news agency Xinhua said.<br/> <br />The local Harbin Taiping International Airport confirmed that a significant number of flights had been delayed early Tuesday morning due to the smog.<br/> <br />An index that measures PM2.5, or particulate matter with a diameter of 2.5 micrometers (PM2.5), reached 378 on Tuesday, local media reported.<br/> <br />A level above 300 is considered hazardous, while the World Health Organisation recommends a daily level of no more than 20.
