check out this article. A bit creepy, to think these compounds may actually be causing damage to the users DNA. While they study indicates that the cells ultimately die as a result of this damage, prolonged damage is often a cause of cancer... Keep in mind that this is IN VITRO. There may be reason to be concerned if you are high dosing or using for a long time. The study primarily focused on lymphocytes, so perhaps using these compounds could make one more susceptable to bacterial and viral infections?
http://www.aensi.org/aeb/2007/39-43.pdf