Interesting article. These superfund sites are pretty scary, especially how they can be 100 years old or so. In the meantime, new stuff has been built over it, which hampers the clean up exponentially, and no one really knows about the danger that lurks. From the linked article, this [0] talks a little more in-depth about the gowanus canal.

[0] http://www.popsci.com/science/article/2013-08/fyi-what-would...