Beijing, like many Chinese cities, has not what we would ever dare call excellent air. So for the past several months, the US embassy in Beijing has been posting hourly updates on their measurements of air quality in the ‘Jing via Twitter feed. Set up out of concern for the health of the embassy staff, the reports range from “good” to “very unhealthy” based on the levels of airborne pollutants (particles) that can enter a person’s body.
However, Beijing’s environmental protection bureau has their own air pollution statistics, and from comparisons between the two, their reports are slightly more optimistic.
From the China Daily:
The air quality for June 18, when the sky was murky at noon, was “slightly polluted,” according to the official data, but the result was different on the BeijingAir Twitter, with the hourly measure creeping into the “hazardous” range for seven hours.
China Daily calculated that only five days were above “moderate” level in May on BeijingAir, but the local environment bureau said on its website on May 31 that the capital’s air quality was the clearest during the same period since 2000, with 25 blue-sky days.
So why the discrepancies? We could point our fingers and yell “liar liar pants on fire”, but let’s first note that different measuring systems are being used. The US embassy uses EPA standards from back home that measure particles less than 2.5 micrometers in diameter (PM 2.5); the Chinese government measures those less than 10 (PM 10). Scientific speak explained:
PM 2.5s will be part of the air quality evaluation system to offer people a clearer picture of air quality. The bigger particles are seen as less dangerous because they can usually be expelled from the body by coughing.
Also, the embassy pulls their results from within the central business district. An embassy spokesperson says to keep in mind, “This is a single site. It cannot be used to measure the air quality across the city. They can’t be compared.”
Whichever report you choose to believe, it’s still useful information for a city’s citizens to access. If anyone scientifically-minded in Shanghai has some free time to set up a pollution monitor, we at Shanghaiist would be highly interested (though maybe slightly scared) in seeing how dirty our skies are… and how the results compare to what’s officially released.