Most health officials will tell you they believe e-cigarettes are less harmful than a conventional tobacco cigarette. But there is still plenty of uncertainty regarding the damage that e-cigarette vapor can cause to a person's body over time. A recent study published in the Proceedings of the National Academy of Sciences found that mice exposed to e-cigarette vapor experienced DNA damage to certain organs that could increase the risk of cancer and heart disease. Because there are so many unknowns and there is no scientific evidence that vaping is safe, Mayo Clinic experts urge e-cigarette users to be cautious. More health and medical news on the Mayo Clinic News Network. newsnetwork.mayoclinic.org/ Journalists: Clean and nat sound versions of this pkg available for download at newsnetwork.mayoclinic.org/ Register (free) at newsnetwork.mayoclinic.org/request-account/