Sometimes businesses leave toxic waste in their wake when they shut down a factory. What should be done with that contaminated land? That's where the EPA's Superfund program comes in. Its mission is to clean up the land and makes it usable for someone else. But who really wants to buy a Superfund site? For the latest of Parts Per Billion, Bloomberg Environment reporter Sylvia Carignan talks about the agency's efforts to make these rehabilitated properties more attractive to potential buyers and why often times that can be a really difficult task.