Vaping Damages DNA and Increases Lung Cancer Risk In Mice

E-cigarettes and vaping damage DNA and its repair mechanisms, increase mutation rates, and increase cells’ susceptibility to cancer. That’s the verdict of a new study published this week in Proceedings of the National Academy of Sciences that examined how nicotine inhalation without burning tobacco affects genetic material. 

E-cigarettes and vaping devices deliver nicotine as an aerosol. The nicotine in these devices is dissolved in a relatively innocuous liquids such as glycerol (which is used as a filler in cookies) and propylene glycol, which is safe enough to put in ice cream. E-cigarettes are often advertised as a safer alternative to cigarettes, as they don’t include the more than 7,000 extra chemicals that are produced when tobacco is burned. This list of extra chemicals includes allergens, irritants, and cancer-causing carcinogens.

What surprised the study’s authors, led by Dr. Moon-shong Tang, a Professor of Environmental Medicine, Pathology and Medicine at New York University’s School of Medicine, was that e-cigarette smoke (ECS) seemed to cause damage to DNA in the same way that tobacco smoke is known to do, despite having none of these extra chemicals in the formula. They identified that this unexpected effect was due to the way the body processed the nicotine which makes up 80% of ECS. This processing results in chemical by-products such as nitrosamines. Nitrosamines are known to cause tumor formation when animals are exposed to them, and some nitrosamines, such as nitrosamine ketone (NNK) are then broken down further into chemicals like methyldiazohydroxide (MDOH) which can actually bind to and alter DNA directly.

Vaping Risks Currently Unknown in the Long Term 

The effects of e-cigarettes and vaping on long-term health are relatively unknown, as cancer induced by carcinogens can take decades to emerge. To simulate the effects of long-term e-cigarette use on the body, researchers exposed mice to ECS over a 12-week period. Tang explains that this level of exposure is equivalent to 10 years of light smoking (about 10 cigarettes a day), although stresses the estimation isn’t exact.

Post-ECS, the mice showed increased evidence of adducts, modifications to DNA that form when a chunk of DNA binds to a chemical, altering the structure of the DNA and increasing the risk for mutation. DNA adducts do not inevitably result in mutation, and if the DNA is repaired in time, such damage can be avoided. However, when the team measured levels of XPC and OGG1/2, repair proteins that fix errors such as adducts, they found them to be reduced compared to ECS-free mice. 

To examine whether this effect also occurred in humans, the team exposed human lung and bladder cells to nicotine and its nitrosamine by-product. This produced similar DNA damage and DNA repair reduction. They then observed that when the cells treated with nicotine were subsequently exposed to environmental causes of mutation, such as UV rays, the nicotine-exposed cells had between two and four times more spontaneous mutations, suggesting that the nicotine predisposed cells to mutation from other sources. 

Dr Tang highlighted the increasing popularity of e-cigarettes and vaporisers in recent years as motivation for the research. A report by the Office of the US Surgeon General in 2016 warned of their appeal to young people, noting statistics that suggested that over 11% of high school students had used electronic cigarettes in the last 30 days, compared to 8% who had smoked tobacco cigarettes. The wide variety of flavors, which has produced exotic taste combinations such as lychee and lemon sorbet, are the biggest draw for young smokers. A study published in Tobacco Regulatory Science, that examined tobacco cigarettes, found that a startling 75% of young smokers would not smoke if cigarettes were unflavored. 

Give up Vaping to Avoid Cancer?

Does that mean that smokers trying to escape the myriad health risks associated with tobacco will have to give up e-cigarettes and vaping too? On this, Tang is bullish: “Both tobacco smoke and E-cigarette smoke cause DNA damage, inhibit DNA repair and enhance mutations, and the degree of these effects are not much different between E-cig and tobacco. Based on these results I cannot conclude that E-cig smoke is safer than tobacco smoke in terms of cancer susceptibility of smokers.” He also points out that e-cigarettes and vaporisers are both implicated by this research: “As long as nicotine is in the vapor, vapor would have the same effect as E-cig smoke. In both conditions nicotine is in aerosol state and reaches lung via the same path.”

Nevertheless, an important point to consider is that other health risks associated with smoking tobacco are most definitely avoided by e-cigarettes. NNAL, another member of the nitrosamine family that damaged the smoking mice’s DNA, was found to be reduced by 97% in E-cigarette smokers as opposed to tobacco smokers in another recent study.

All in all, a rather unclear picture emerges. Tang’s group have pointedly said their results have more implication for those that think e-cigarettes are without harm than those switching from cigarettes to a non-tobacco alternative, but until a direct comparison of the effects of tobacco and e-cigarette smoke is conducted (Tang’s team have research on this topic in the pipeline) we won’t know for sure whether e-cigarettes are the safer option when it comes to damaging your DNA. The study is released at the same time as a report by The National Academies of Science, Engineering and Medicine, which declares that “e-cigarettes are likely to be far less harmful than combustible tobacco cigarettes”. Whether or not Tang’s research into nicotine by-products changes that conclusion remains to be seen. 

This article was based on research published in  Proceedings of the National Academy of Sciences.

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