The U.S. Embassy operates a single station in eastern Beijing that records levels of PM2.5, fine particles considered particularly dangerous to human health...Before the story came out, there were around 300 followers of the feed; now there are more than 1,100 and rising fast.
While the U.S. doesn't actively promote the information, it has slowly been getting more attention from Beijing residents concerned about the city's air quality. "The U.S. Embassy has an air quality monitor to measure PM 2.5 particulates on the Embassy compound as an indication of air quality," says Susan Stevenson, a State Department spokesperson. "This monitor is a resource for the health of the Embassy community." She cautions that citywide analyses cannot be done from a single machine, but because the embassy has the data available, it makes it available to others.
Beijing experienced some bizarre and extremely rapid changes in air quality on Thursday and Friday of last week. On both days, BeijingAir reported maximum pollution levels (hazardous air, AQI = 500) for brief periods in the afternoon. However, hazardous air was never reported by either the Beijing EPB or MEP, presumably because the pollution spikes on both days were short-lived enough that the overall 24-hour averages evened out as just "light pollution." (More discussion here and here.)
Here's a graph showing BeijingAir and MEP-reported air quality over the period noon Tuesday to midnight Sunday last week. Because MEP has no system for real-time reporting, the extreme pollution spikes on the 18th and 19th were never truly reflected in MEP's air quality data:
The events of last week highlight the need for real-time reporting of air quality in Beijing. I wonder if the growing popularity of the embassy's twitter feed will ratchet up pressure on MEP / Beijing EPB to implement such a system here in Beijing.
Final note: the speed of the drop in pollution levels during the afternoon of 6/19 was stunning. With no technical background in air quality modeling or meteorology, I have no idea how this is even possible: