10. Lake Washington, Washington
Once the site of a plant that manufactured creosote — an especially sticky petrochemical — the southeastern shore of Lake Washington has since served as a storage site for even more cancer-causing fossil-fuel swill. The lake occupies prime real estate in the middle of the Seattle-Tacoma-Bellevue metro area, so there are two beaches near the dumping site, not to mention habitats for animals like threatened Chinook salmon and bald eagles. It was listed as a Superfund site in 2006.
