Reliable information on what’s going on in China is notoriously difficult to come by, but here’s a notable exception. On the roof of the US Embassy in Beijing there’s an air-quality monitoring station which continuously measures PM2.5 particle pollution (i.e the concentration of particles less than 2.5 micrometers in diameter in the air). These particles are so small they can be detected only with an electron microscope. The station sends out a tweet every hour with the data plus an assessment of overall air quality (AQI) and a one-word verbal summary, as for example here:

It’s been ranging between Unhealthy, Very Unhealthy and Hazardous all day. And since I’ve been following it, most days seem to be like that. So if you were thinking of a nice cosy, tax-free ex-pat posting to the Chinese capital, think again.

Twitter users can follow the service at www.twitter.com/BeijingAir