Veicoli viaggiano su una strada di smog pesante a Pechino, in Cina, il 2 novembre 2013. Pechino si è costretti a prendere in considerazione le restrizioni dopo l'aria dei citys
Vehicles travel on a road in heavy smog in Beijing, China, 2 November 2013. Beijing is being forced to consider the restrictions after the citys air quality index (AQI) shot above 300 late on Friday (1 November 2013) night and remained there Saturday. The municipal government issued its third blue alert in a week to notify the public that the air was highly polluted. A monitoring station at the US embassy showed the air was hazardous, with readings of PM2.5 higher than 400 micrograms per cubic metre. That was more than 20 times the World Health Organisations recommended daily limit of 20 micrograms. Many people throughout northern China opted to stay indoors Saturday as visibility in some areas fell to 20-30 metres, according to China National Radio. The smog was blamed for delays and cancellations of several flights at Beijing Capital International Airport and the closure of at least 16 highways leading to and from Beijing.