Further to my earlier entry I finally took the time to table at least the results for the first 4 months of 2009. So, no more guessing – these are the official figures from the Beijing Environmental Protection Bureau. The API refer to one measuring point (exact location unknown) – Dongsi in Dongcheng District, Beijing. It is supposed to be not too far from where I live (Gongti Xi Lu).
The data normally refer to a 24 hour average from 12 noon – 12 noon on the mentioned date.
One can argue about the accuracy and the fact it is a 24 hour average. But this is what we got.
Those data you cannot find anywhere as the Bureau promptly removes them after one day, so the tables are unique!

I have the data now for nearly a full year.
Dongsi is not the best but also not the worst location.
In the past “Qianmen” was always by far the worst but it was simply dropped from the list – no explanation needed here!