Vaping may raise the risk of cancer because it leads to DNA damage, even though it contains fewer carcinogens than tobacco smoke, a US study has found.
The report in the Proceedings of the National Academy of Sciences did not compare the cancer-causing potential of traditional cigarettes to e-cigarettes.
Exposed cells more likely to mutate
In studies on lab mice, those exposed to e-cigarette smoke "had higher levels of DNA damage in the heart, lungs, and bladder, compared with control mice exposed to filtered air," it said.
Similar effects were seen when human lung and bladder cells were exposed to nicotine and nicotine-derived nitrosamine ketone (NNK), a carcinogenic nicotine derivative.
These exposed cells are more likely to mutate and become cancerous than control cells.
"Thus, although e-cigarette smoke has fewer carcinogens than tobacco smoke, e-cigarette smokers might have a higher risk than non-smokers of developing lung and bladder cancers and heart diseases," said the study, led by Moon-shong Tang of the Institute of Environmental Medicine at New York University.
According to outside experts, much more work is needed to uncover the true risk of vaping, which is widely seen as a safer alternative than traditional cigarettes.
Vaping not without risk
Peter Hajek, director of the Tobacco Dependence Research Unit at Queen Mary University of London, said the study methods are of "unclear relevance for effects of vaping".
"Human cells were submerged in nicotine and in off-the-shelf bought carcinogenic nitrosamines. It is not surprising of course that this damaged the cells, but this has no relationship to any effects of e-cigarettes on people who use them," he said.
"No comparison with conventional cigarettes was made, but in the text of the article, the authors acknowledge the key bit of information that is of crucial relevance in this story: Vapers show a reduction in these chemicals of 97% compared to smokers. They should have added that his may well be the level that non-smokers obtain from their environment."
A comprehensive review of the scientific literature, released earlier this month by the US National Academies of Science, found that vaping is likely less harmful than cigarettes, but may lead to addiction in young people.
However, it cautioned that the true health effects of the habit remain unclear, since the trend is relatively new.
In 2000, South Africa became one of the first countries in the world to ban smoking in public places. Vaping, with an estimated 200 000 people has been, so far, seen as an acceptable alternative in this country.
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