The number of people using e-cigarettes or e-cigarettes has grown rapidly over the past decade, and they have helped many people quit smoking cigarettes. However, because e-cigarettes have only been around for a relatively short period of time, there is still uncertainty about their potential health effects, especially with long-term use. The experiment divided 85 mice into 3 groups and exposed each group to different conditions over a 1-year period: e-cigarettes (including nicotine), e-cigarette vapor (without nicotine), and normal air filtration. It was found that of the 40 mice exposed to e-cigarette smoke, 9 developed lung tumors, while none of the smoke-free mice developed lung tumors, and more than half of the mice exposed to e-cigarette smoke also showed signs of potential bladder cancer. At this time, it is not possible to say that e-cigarettes definitely cause lung cancer or bladder changes because humans are biologically somewhat different from mice, so continued surveillance of e-cigarette users and evidence on the potential health effects of e-cigarettes will need to be collected. There is evidence that e-cigarettes are less harmful to health than smoking, but not without risk, and evidence is still being gathered in this area, including on long-term health effects, where studies have found that the combination of nicotine and carrier vapor in e-cigarette smoke appears to cause lung and bladder cancer cell changes in mice. So one way to reduce any potential risk is for people to use e-cigarettes only as a short-term measure to help them quit smoking, rather than using them in place of cigarettes in the long term, much less to vape out of curiosity.