The problems would be the same they were in the early 20th century. Pollution doesn't stay contained in neat little political boundaries and half the major contributors will be bankrupt when you finally want to clean up the mess. It also ends up being a shitty situation for the workers who have to endure the environment through no particular fault of their own.
The idea was, of course, 95% tong-in-cheek but I think there is merit to environmental tourism of superfund sites. There are enough places in the US, and the world, that have been destroyed that we can, and should, bring people to them to show how bad things were. There are probably a lot of chunks of cities that could be used too. Hunter's Point in SF maybe?