Actually there are quite a few places that are no-longer occupied that are much more-polluted than the 80216 zip code.  Picher, OK is one of them, Times Beach, MO is another, and Uruvan, CO is still another.  Gilman, CO is also extremely-polluted and the town has been abandoned since 1984. 

Even the town of Monticello, UT suffered the loss of 450 contaminated structures and 30% of its residents got cancer thanks to a uranium-processing mill that once operated there.  Residents living around the nuclear site at Hanford, WA also suffered far-worse health consequences than have residents in 80216.  

Now Monticello is still occupied so you can't even say that 80216 is the most-polluted zip code still being lived in.  Here is some info on the issue at Monticello. 

http://www.toxipedia.org/display/wanmec/Processed+uranium+from+Monticello%2C+UT

Toxipedia says that Hanford is the most-polluted site in the western hemisphere.

http://www.toxipedia.org/display/wanmec/Environmental+Effects