It is likely that e-cigarettes might be less dangerous than combustible tobacco. However, the safety of e-cigarettes has been questioned by the fact that although they do not produce tobacco smoke, e-cigarettes contain not just nicotine but other potentially harmful chemicals as well. Testing of some e-cigarette products found the vapor to contain known carcinogens and toxic chemicals (such as formaldehyde and acetaldehyde), as well as potentially toxic metal nanoparticles from the vaporizing mechanism. The health consequences of repeated exposure to these chemicals are not yet clear. Clinical studies have not been done yet to assess the efficacy of e-cigarettes for smoking cessation. Until we learn more about the long-term impact of these chemicals, it would be advisable to stick with the known and approved nicotine replacement therapies.