Introduction
It is a well-known fact that traditional tobacco smoking is the major culprit for many different types of cancer in the oral tissues, respiratory organs, and even other body parts. The continuous awareness and actions from the responsible authorities have led to a major decline in the use of tobacco cigarettes. Electronic cigarettes/ E-cigs are marketed as a relatively safer alternative and have gained much popularity among adolescents and even never-smokers. However, their effect on cancer has not been widely studied, and there is limited evidence of their safety. The invention of E-cigarettes (E-cig) has replaced conventional tobacco cigarettes to some extent because they were considered relatively safer without significant evidence. However, studies over the past few years have shown that E-Cigarettes have led to the development of some malignant molecular changes in the cells of oral tissue, similar to the changes observed in tobacco cigarette smokers.
What Are E-cigs?
E-Cigs/ E-Cigaretts are handheld devices powered by a battery to produce smoke similar to normal tobacco smoking. Conventional cigarettes use tobacco leaves which are burnt to produce smoke. However, E-Cigs uses a mixture of a solution, of which the main constituent is propylene glycol. In addition, they contain glycerine, flavoring agents, and sometimes variable nicotine concentrations (optionally). Heating this mixture powered by the battery will produce aerosols that the user will inhale. Per the Centre for Disease Control (CDC), electronic cigarettes are called E-Cigs, E-hookahs, electronic nicotine delivery system (ENDS) vapes, and vape pens. Some e-cigs appear similar to regular cigarettes or pipes, while some may look like USB pen drives, pens, or other daily-use items. Soon after their introduction into the markets, their popularity increased significantly among teenagers, never-smokers, and smokers who wanted to quit tobacco smoking, fearing the health risks because they were advertised as a safer option. The long-term health effects of E-cigs on the human body have yet to be studied effectively, and limited evidence of their safety questions their popularity. Concern regarding nicotine and smoking addiction in adolescents with E-cigs is also rising. Therefore, it is important to investigate the risk of cancer from E-cigs.
Do E-cigarettes Cause Cancer-Related Genetic Changes?
Several studies have been conducted to find cancer incidence in E-cigarette smokers. One such crossectional study was NHANES (National Health and Nutrition Examination Survey). The study found that the risk of cancer in E-cig smokers was 2.2 times higher than the non-smokers and that for traditional smokers was 1.96 times higher than non-smokers. However, among the cancer patients studied, E-cigs had a lower prevalence than traditional smoking. A cancer diagnosis was made at an early age, approximately 45 years, in E-cig users compared to tobacco smokers at the age of 63 years.
In the past few years, an exponential increase in the use of E-cigs has been observed due to their promotion as a safer alternative to tobacco smoking. However, the underlying threat to public health is going unnoticed. Animal studies have revealed that vapors from E-cigarettes have co-mutagenic (causes a change in the DNA of the cells) and cancer-initiating effects in rats. Further studies showed that using E-cigs for even a short period will lead to the development of genetic changes leading to tumor formation and metastasis (the ability of the cancer to spread in different parts of the body) in small airway epithelium similar to that in lung cancer.
The nicotine vapors from E-cigarettes contain carcinogens with cancer potencies less than 1 % of that from tobacco smoke. Though smoking is not safe in any form, E-cigarettes are recommended by physicians as an alternative to tobacco smoking in the population group with a history of cancer who can't stop smoking at any cost or continue smoking despite all the advice.
How Do E-cigarettes Cause Genetic Changes?
Tobacco smoke has several carcinogenic components like polycyclic aromatic hydrocarbons (PAHs), nicotine-derived nitrosamine ketone, and nicotine. They play a major role in the development of cancer cells by causing genetic changes in the DNA, like point mutations (a genetic mutation where a single nucleotide base is changed), translocations (a part of a chromosome is transferred to another chromosome), and deletions (removal of at least one nucleotide). E-cigarettes produce aerosols with a low concentration of harmful substances. However, the low concentration does not render it harmless. When inhaled, the harmful substances from the aerosol move to the alveoli and get deposited there. Here they generate free radicals, which cause DNA damage. The aerosols from the E-cigarettes contain the following highly carcinogenic substances:
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Tobacco specific nitrosamines (TSSNAs).
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N-nitrosonornicotine (NNN).
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Glycidol
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Polycyclic aromatic hydrocarbons (PAHs)
The carcinogens in the vapor cause the DNA strands to break in a human epithelial cell line independent of nicotine and exaggerate the effects of DNA damage. They enhance malignancy-promoting properties that are similar to nicotine. However, E-cigarettes' carcinogens are fewer than tobacco cigarettes; their long-term safety is unknown. Besides cancer-inducing changes, E-cigarettes have also been shown to induce epigenetic alterations (genetic changes that alter the way a gene is expressed in the body). Animal studies have revealed that using E-cigarettes during maternity can lead to DNA methylation (a process by which methyl groups are added to the DNA) and cognitive problems like short-term memory loss and hyperactivity.
Conclusion
It is clear from the above discussion that E-cigarettes are not safer than traditional cigarettes and pose a serious risk for cancer in contrast to how they have been popularized as a safer alternative. Studies found that E-cigarette users had an early onset of cancer and a higher risk of developing genetic changes leading to cancer than non-smokers. E-cigs were more prevalent among females and displayed more risk of developing thyroid, cervical, and skin cancers. Since E-cigs have become prevalent in the past few years, only limited studies have been conducted to evaluate their safety, and the evidence of possible cancer threats is very few. More prospective studies should be planned in this area for better guidelines regarding using E-cigs and their associated risks.
