air in beijing hazardous

BeijingAir is currently reporting hazardous air quality in Beijing (there was an error in the most recent hour, but you can see the PM2.5 concentration slowly creeping up over the course of the morning and early afternoon):


Note, though, that with the AQI maxed out at 500, the air quality is theoretically worse than "hazardous," whatever that might be.

On the other hand, MEP is reporting an API today of 104, "slightly polluted."

A few people have asked me about this blatant discrepancy, so here's a brief comment:

It's important to remember that MEP's reported API for 6/18/09 is actually an average API for the period noon to noon 6/17 to 6/18. Given that this current pollution spike seems to have rolled in over the course of the late morning and early afternoon, it is reasonable that the impact has not yet registered in the MEP reported data. From the perspective of MEP's official reporting, we will have to wait until around 2pm tomorrow to see the results of this episode.

Of course, this discrepancy highlights the necessity of working towards a system of real-time air quality reporting (like the AIRNow program in the US) in Chinese cities. (More on this in another post.)

Final note: during my time in Beijing (3.5 years), I've only experienced a handful of days in which MEP reported a 500 API. The most recent ones were 12/28/2007 and 12/12/2006, plus a few during the sandstorm season of the spring of 2006. I am curious to know if tomorrow will yield another.