Following the interesting thread from last post, I attach a link to an article about “Revolymer”, which promotes the polymer named Rev7 and claims that this material can degrade after a couple of years on the pavement.
According to the article, chewing gums containing the novelty can be found in some shops in USA (also named “Rev7”).
Here is the link to the company web-site: http://www.revolymer.com/ and if you want to know about the product http://rev7gum.com/
By Oliver Nieburg 4-Jan-2012
Copyright Willian Reed Business Media SAS
Chewing Gum Consultant 
This is a fascinating development in the world of sustainable chewing gum.