@Bisa,

These rankings are becoming commonplace and both SH and BJ deserve it. The smog isn't just from car exhaust in the city or factory exhaust in the western districts and upwind in Suzhou, Wuxi, Nanjing, etc but from the sun-baked filth that exists everywhere in both cities.

HK has crappy air and water because of the PRD, a few power plants are a political excuse to deflect criticism of careless mainland operating procedures, but HK still has clean sidewalks and streets.

HK is clearly superior to anything on the mainland.

I can imagine Ralph Wiggam saying: "China smells worse than Mr. Simpson!"

@nanheyangrouchuan

I don't disagree with the fact that the majority of air pollution in HK comes from the PRD (although almost all of it in Central is caused by local car exhaust) but the ranking doesn’t take into account where the pollution comes from, just the fact that it's there. Having seen your blog i can tell your view of China isn't exactly great, explaining the "HK is superior to anything on the mainland comment" - which i don't necessarily disagree with having lived there, but i would exactly put it like that. China does cover up most of it's polluting factory problems but the reality is that it's changing and fast. In terms of the PRD alone my company is working right now to clean up polluting factories and un-sustainable development projects with full gov't support....now i'm not naive to think that everything they do is so great, and probably the reasons for them to be so eager and willing is to cover their asses since the world is finding out about these problems (esp. cause of the Olympics), but in the end one has to think: who cares why they are doing it as long as they're changing.... This is getting off track so to get back to my point without having identified indicators for what they based their decisions it's impossible to find out why SH got such a low ranking; maybe i'm wrong but from what i've seen it doesn't make sense to me...

That's exactly what air pollution does when it's trapped in by high rise buildings, and you can't seriously tell ME that Central has only a FEW cars and buses, when was the last time you went to HK?? The reason why SH has lower traffic pollution in SOME PLACES is because it has a chance to disperse while in that particular area of HK it becomes trapped...thus "sticking in one neighborhood" as you put it. The air pollution activists in HK don't even fully agree that most of the air pollution comes from the PRD anyway, this is from their website:

"While I wholeheartedly encourage the government to continue such efforts [greening PRD factories], they will not provide meaningful improvement for at least a decade. We first need to understand that this oft-quoted "80 per cent of our air pollution comes from the delta" is a misconception: that is not the pollution we breathe.

In fact, about 50 per cent of the air pollution you breathe while walking, shopping or living next to a typical Hong Kong city street comes from the traffic right in front of you - mostly from diesel trucks and buses.

This statistic is clearly illustrated by the Environmental Protection Department's air pollution index (API) for last year. Air pollution was rated "high" or worse over 42 per cent of the year (measured hourly) at general testing stations - and 77 per cent of the year at roadside testing stations."

What would be interesting to compare is pollution levels in Central against those found under our elevated highways here in SH during rush hour.....

I'm not trying to blindly defend the PRC but i think that it has ALREADY gotten a lot better than it was; especially in Sh. It's just that as lao wai we don't see or hear about many of the programs that are actually in place to educate the people and improve things. And trust me, the random poor Chinese on the street might not know what things to do in his daily life to improve the environment (like don't burn your damn garbage on the street) but he/she feels the impacts of pollution much more than you do, so they definitely understand. It going to get worse, yes, but the environmental movement is developing here faster than it did in the States so in the end some areas will improve while other will lag behind. When push comes to shove the gov't (for whatever reason) is on board with many of the programs and are really pushing the green agenda; just look at Dongtan..