If you thinking of visiting Beijing and you have respiratory problems (like asthma), bring an inhaler or stay indoors. Yesterday, more than 150 flights to Beijing were cancelled because of fog (official explanation), but in addition to the fog was an excessively high level of pollution, so high it was “off the charts”. The US Embassy in Beijing monitors air pollution levels in the city and measures particles that are 2.5 micrometers or less, known as PM2.5. These tiny particles are the most hazardous to humans. Yesterday (January 10), the US Embassy’s pollution meter – where 150 is unhealthy and over 300 is hazardous – went past 500 and simply stopped measuring any further. Most Chinese cities have poor air quality and so if you are going to China, bring the proper medical accoutrements (inhalers, asthma medication, etc.).