More than 150 flights to and from Beijing have been cancelled or delayed as a thick cloud of acrid smog shrouded the city, with US figures saying the pollution was so bad it was off the scale. The national meteorological centre said the Chinese capital had been hit by thick fog that reduced visibility to as little as 200 metres in some parts of the city, while official data judged air quality to be “good”. But the US embassy, which has its own pollution measuring system, said on its Twitter feed that the concentration of the smallest, most dangerous particles in the air was “beyond index” for most of the morning.
The US system measures particles in the air of 2.5 micrometers or less, known as PM2.5, considered the most dangerous for people’s health.
Today’s reading on its air quality index, which rates anything over 150 as unhealthy, over 200 as very unhealthy and over 300 as hazardous, breached the upper limit of 500, at which it stops giving figures.