They concluded that although vaping delivers fewer carcinogens than tobacco smoke, e-cigarette smokers might have a higher risk than nonsmokers of developing lung and bladder cancers and heart diseases.
By the end of the trial, the smoke had caused DNA damage in the animal's lungs, bladders and hearts, as well as limiting lung proteins and important DNA fix.
That might be even harder to do for e-cigarettes, since many users are either former or current smokers, and there'd be no easy way to tell where the cancer risk from smoking ends and the cancer risk from vaping begins. The mice were exposed to high levels of e-cigarette smoke and the effects may be very different in people who inhale nicotine from vaping, critics caution. The study, conducted by scientists at the University of CT, concluded that the nicotine liquid-filled devices can cause as much damage to human DNA as standard tobacco products.
Laboratory mice were exposed to e-cigarette vapour, which contains both nicotine and liquid solvents, at the normal level it would be consumed by a human user.
Vaping could increase the risk of youth smoking but would be less unsafe to health than smoking cigarettes, according to a report from the Academies of Science and Medicine published Tuesday, presented as the most extensive on the subject so far.
Tobacco smoke contains thousands of chemicals and at least 70 are known either to cause or drive cancer in the body.
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The next step of the research is under way, in which the mice will be exposed to e-cigarette vapour for a long period to see if they develop diseases caused by the DNA damage, Professor Tang added.
Tang went on to look at human lung and bladder cells and found that exposing the cells to nicotine and its breakdown products made the cells turn into tumour tissue more easily.
The new study by Moon-shong Tang, of the environmental medicine department, was an investigation into the belief that other products in tobacco - not nicotine - are the ones that cause cancer and other health woes.
It said that the hazard to health arising from long-term vapour inhalation from the e-cigarettes available today is unlikely to exceed 5% of the harm from smoking tobacco.
Adults who buy cigarettes for underage smokers could be setting them up for a life of health problems and financial costs, a charity boss has warned.
E-cigarettes may carry health risks, but these are nowhere near the risks of continuing to smoke tobacco.