Smoggy weather has become common in China. But these days, air pollution levels in the north eastern city of Harbin surpassed the previous record levels. The city was essentially shut down after PM2. 5, fine Particulate  pollution that is considered hazardous  . reached levels of 1000 micrograms per cubic meter-40 times the safety level remended by the World Health Organization. Schools, motorways and an airport were closed on Tuesday as visibility in some areas of the city dropped to less than 10 meters. Photos from Harbin showed residents covering their mouths with masks and scarves, and moving like ghostly shadows through the fog. Cars and motorcycles are moving slowly as traffic came to a standstill with traffic lights barely visible. . Just days previously , the World Health Organization's International Agency for Research on Cancer (IARC)  classified air pollution as a carcinogen  .  It stated that there  is  " sufficient evidence" that exposure to outdoor air pollution causes lung cancer and also linked it with an increased risk of bladder cancer.  It's said that exposure has increased significantly particularly in " rapidly industrial countries with large populations". "The air we breathe has become polluted with a mixture of cancer-causing substances" , Dr Kurt Straif , head of the IARC said in a press released.  "We now know that outdoor air pollution is not only a major risk to health in general, but also a leading environmental cause of cancer deaths. " On the Chinese social media site Weibo , many users complained about the pollution and shared their concerns. References to "feed people with smog "have become popular on Weibo and there is a sarcastic play on the expression "serve the people" , as the two have a similar pronunciation. "The impact of air pollution on people will be gradual. There won't be a sudden outbreak of symptoms, but normally three to five days after the smoggy weather occurs, there is a peak in the number of people seeing doctors, " Deng Ying,  a doctor at the Second Affiliated Hospital of Harbin Medical University was quoted as saying. As thick smog has become a common scene in Harbin,   _
students there can go to school as usual residents in the city can see as far as 20 meters traffic lights can be easily visible the urban traffic has been seriously influenced