E-cigarettes are devices used to inhale aerosol to mimic the effects of smoking through vaping. It is an alternative to real cigarettes to help people quit smoking. However, a new study has revealed that e-cigarettes can cause cancer if the liquid for vaping contains nicotine.
E-cigarettes work by heating a liquid, which usually contains nicotine, to produce an aerosol that people breathe in as if smoking a cigarette. The nicotine in the liquid has been added to help with the cravings of smokers, without the other dangerous additives found in traditional cigarettes. The device has been considered the most effective way to quit smoking. Previous studies found that vaping has lower amounts of harmful chemicals than tobacco.
But a study from the School of Medicine at New York University suggested that vaping can increase the risk of developing cancer and heart disease. The researchers subjected mice models in "light" vaping equivalent for 10 years or 12 weeks in reality. The mice have been found with DNA damage to several organs, such as the bladder, heart, and lungs. They also found that the chemicals in vaping inhibit the mice's cellular ability to repair DNA and lung proteins.
"It's the first evidence we have that nicotine can be carcinogenic in and of itself. It's certainly concerning, and certainly gives pause if one were to say e-cigarettes were safe and could be used by all people without consequences," said Dr. Roy Herbst, Chief of Medical Oncology at Yale Cancer Center.
One of the chemicals detailed by the researchers is the 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone or Nicotine-derived nitrosamine ketone (NNK), a compound found in tobacco leaves. NNK is naturally synthesized from the leaves when exposed to light, such as when burning a cigarette. Certain enzymes in the body are needed to metabolize NNK, which can trigger its adverse effects. Upon activation, NNK becomes a mutagen and starts a series of cellular processes associated with abnormal cell reproduction or carcinogenesis.
"We found the solvent alone does not cause DNA damage. Nicotine with e-cigarette solvent caused the same damage as nicotine alone," said Moon-shong Tang, the lead researcher of the study and a professor of environmental medicine
Mutagens like NNK are substances that alter the genetic composition of an organism leading to mutation. According to the National Cancer Institute, mutagens are anything that can change DNA in cells, such as x-rays, radioactive substances, UV radiation, and certain chemicals. It also means that many people are exposed to mutagens depending on where they live or what they do for a living. Mutagens change DNA in cells by deleting or adding one or more bases into the DNA molecule. That simple editing shifts the frame of the genetic code. The frameshift also changes the string of amino acids in cells that causes the production of abnormal proteins, which often leads to uncontrolled and rapid multiplication.
Cells encounter mutations on a daily basis like in cell division. Enzymes inside cells are capable of restoring abnormal DNA to its original state. But some circumstances can impair the body's ability to restore mutated DNA, such as smoking and aging, which lead to diseases. Scientists argue about the involvement of certain substances that can help reverse DNA mutation. Some experts believe that antioxidants like vitamins A and C, and carotenoids can reduce DNA damage.
The study findings support the approach of the US Food and Drug Administration in regulating e-cigarettes. According to the finalized rule of the government agency in May 2016, e-cigarettes are classified as tobacco products and should not be sold to minors.
"We have more to do to help protect Americans from the dangers of tobacco and nicotine, especially our youth. As cigarette smoking among those under 18 has fallen, the use of other nicotine products, including e-cigarettes, has taken a drastic leap. All of this is creating a new generation of Americans who are at risk of addiction," said Sylvia Burwell, the Secretary of the US Health and Human Services during the time of the announcement.
The finalized regulation has been drafted to fight the growing use of e-cigarettes among high school students. In 2015, about 3 million students in middle school and high school use such device, and some of them vape at the same rate as smoking. While e-cigarettes have been deemed safe to use in the past few years, the point of Dr. Robert M. Califf, the Commissioner of US FDA, about the devastating effects of smoking may be warranted with the new study.
The researchers are planning to make more studies about the effects of vaping. The next study involves the exposure of mice models to vapors of e-cigarettes and determines the development of diseases caused by DNA damage.
[메디컬리포트=Ralph Chen 기자]