The surface has only been scratched. There are many, many more cities that have filthy air. Another is Novosibirsk, Siberia. Denver, Phoenix, etc. A huge amount of work and billions of dollars is needed to correct these problems. If they can be corrected - I am sorry to say.

The surface has only been scratched. There are many, many more cities that have filthy air. Another is Novosibirsk, Siberia. Denver, Phoenix, etc. A huge amount of work and billions of dollars is needed to correct these problems. If they can be corrected - I am sorry to say.

how many city considered highly contaminated? more than a hundred i presumed.. the third world country is always suffer the worst.. :(

the third world may be bad, but are we that much better. Huge factories, overconsumption, everything is bad.

the.nerd.herd.group.googlepages.com

Could you have picked a more misleading picture for Pittsburgh if you'd tried? Follow the link to the photographer's Flickr page, and you'll see that the title is "Pittsburgh under an unusual morning fog". The vantage point for the picture, near the intersection of Penn Ave. and 34th St., is kind of run down, explaining the appearance of the buildings in the foreground, and there's a river between there and downtown, which would account for the fog in the picture.

Why not use this picture instead?

http://www.panoramio.com/photo/1201423

or this?

http://www.panoramio.com/photo/311608

Having been in virtually every city in the USA and in many different provinces in China. There is no compare, China from the soil to the clouds is by far, 100 years behind, filthy country. From healthcare, food sanitation, environmental controls, personal hygeine, the list goes on it is terrible.

I have not been to Pittsburg or any of the cities named therefore not qualified to critique the classification and/or comments posted by other members. But on a general observation, those who claim Pittsburg is not dirty should consider whether they are making that observation based on what they SEE or scientific measurements. Some pollutants are invisible to eyes. Also whether the pollution comes from somewhere else is immaterial. The issue here is that this city IS polluted. From here we can discuss how to stop the pollution coming in.