James Fallows has talked about it a lot over the years.
I was thinking that there must be poor areas around the world that have worse pollution, and maybe there are. But the scale in China is astounding.
http://www.nasa.gov/...alth-sapping.html
Africa seems to be catching up, though it's not clear how much of that is due to human activities and how much is due to desertification. :-(
Cheers,
Scott.