Electronic Cigarettes: Harmful,
Unclear if Less So

The modern electronic cigarette was invented in 2003 by Chinese pharmacist Hon Lik, after his father died of lung cancer. As of 2015, most electronic cigarettes are manufactured in China. Since they were first sold in 2004, their global popularity has skyrocketed. They are particularly popular in the U.K. and the U.S., especially among teenagers.

Unlike regular cigarettes, which burn a blend of tobacco and other compounds, in the electronic cigarette, liquid is heated to create vapor, which the smoker inhales into the lungs instead of smoke. The liquid, also called e-liquid, usually contains propylene glycol, glycerin, nicotine, flavorings, and additives (some electronic cigarettes do not contain nicotine). These compounds are found also in regular tobacco cigarettes, together with many others.

The device is a battery-operated atomizer. Its main parts are the mouthpiece, cartridge, heating unit or atomizer, micro-processor, battery, and sometimes a LED light (a light-emitting diode) at the edge. The atomizer is comprised of a heating element that vaporizes the liquid and a material that pulls the liquid into a coil by capillarity.

The heating element is activated by pressing a button or by inhaling air, which activates a pressure sensor, and when warmed to a temperature of 100-250° Celsius, the liquid turns into a spray. The LED light is also activated when inhaling, to indicate the device is active. Rather than smoke, the user inhales a flavorful spray, which provides a sensation similar to tobacco smoking. Electronic cigarette use is termed ‘vaping’ because of this vaporizing process.

A review article from 2018, which examined tens of previous research articles about electronic cigarettes and regular tobacco cigarettes, concluded that there are fewer dangerous compounds in electronic cigarettes, and therefore, they may be useful for smokers who cannot stop smoking, by reducing their exposure to dangerous compounds. However, it was also emphasized that electronic cigarettes could still be harmful and their long-term effects are unknown, and that the nicotine they contain is as addictive as it is in regular tobacco cigarettes.

What about their effectiveness as a means of quitting smoking? A study published in January 2019 in the New England Journal of Medicine seemingly showed that electronic cigarettes were more effective than nicotine replacements in helping to stop smoking. The study included 886 people who turned to a smoking cessation center in England. They were divided into two groups of similar size: The first received nicotine replacement products of their choice (nicotine patches, gums, or a combination of both) for three months and the other used electronic cigarettes.

Members of both groups also participated in weekly support meetings for at least one month. After a follow-up of one year, which included testing of the air that they exhaled, it was found that 18% of those using electronic cigarettes stopped smoking regular tobacco cigarettes, compared to 9.9% of the nicotine replacement group. Eventually, most participants in both groups were unable to stop cigarette use, and only in the nicotine replacement group were some people successful in quitting to smoke altogether. 

Of the 79 electronic cigarette users who abstained from smoking regular cigarettes after one year, 63 (about 80%) were still using the electronic cigarettes. On the other hand, of the 44 people from the nicotine replacement group who managed to stop smoking, only four (9%) continued using replacements. The researchers concluded that the electronic cigarette was more satisfying than nicotine replacements. Another conclusion was that most of those who transferred to using electronic cigarettes kept their nicotine addiction. This means that they might go back to smoking tobacco cigarettes.

A study from 2018, funded and supported by the electronic cigarette maker ‘Puritane,’ examined the effects of electronic cigarette use for two years. Users did not note unusual effects aside from headaches, colds, sore throats, and coughing, experienced by less than a third of the users, and these effects also disappeared gradually. Their lung and heart functions were not impaired. Those of the users who also smoked tobacco cigarettes reduced their tobacco smoking and so reduced their exposure to the harmful compounds, such as carbon monoxide, in the smoke.

One of the primary concerns with smoking regular tobacco cigarettes lies in the exposure of smokers and those around them to toxic heavy metals, which begs the question whether electronic cigarettes reduces such exposure.

A 2018 study by researchers from the Johns Hopkins University found high and toxic levels of 15 heavy metals, including nickel, chrome, and lead, in the fluid the encases the heating element within the electronic cigarette and in the vapor it produces. The findings were collected from e-cigarettes of different manufacturers, received from 56 users. 

The study was a continuation of the same team’s initial study, which found toxic levels of these metals in smokers’ urine and saliva. However, there were significant differences in the levels of the metals between individuals, and some of them did not exceed the level considered safe. It is important to remember that there is no lack of heavy metals in regular tobacco cigarettes. Therefore, it is also important to compare the levels of heavy metals in electronic cigarette users and tobacco smokers.

This comparison was performed in a 2018 study, which included more than 5,000 participants aged 35 to 54, 250 of them electronic cigarette users; 2,400 tobacco cigarette smokers; 800 mixed users of both kinds of cigarettes; and 1,600 nonsmokers. The results showed that electronic cigarette users had 30% less cadmium, a toxic metal, in their urine, compared with tobacco smokers.

The study also measured the levels of nicotine metabolism products, multi-ring aromatic carbohydrates (flammable compounds that might cause cancer) and volatile organic compounds in the urine of participants. Electronic cigarette users were exposed to less of these compounds than regular smokers. However, the exposure levels of mixed users were similar to tobacco smokers, sometimes even higher. This means that smoking tobacco cigarettes, exclusively or in addition to electronic cigarette use, is linked to higher concentrations of tobacco components compared to using electronic cigarettes exclusively.

A smaller study from the same year repeated the findings and also showed that levels of lead in the blood of electronic cigarette users was lower than that of tobacco smokers. Both studies found that users who used only electronic cigarettes absorbed less harmful compounds to their blood even compared to mixed users.

A review article from 2016 surveyed 16 studies from the four previous years, which examined damage due to passive exposure to electronic cigarettes, i.e., exposure to vapor emitted by another person using an electronic cigarette. Several articles indicated that they emit a variety of toxic compounds in the vapor such as the compounds in the vaporizing liquid, small particles whose size is less than 100 nanometer (one millionth of a millimeter), and metals that affect air quality. In the past, it was found that exposure to small particles and to nicotine lead to health problems such as an increase in the incidence of heart and respiratory diseases. Long-term exposure to volatile organic compounds can irritate the respiratory tract and even cause cancer, and heavy metals can be toxic to certain organs.

These studies should be taken with caution, as the studies reviewed had several limitations. For example, there were large differences in the types of electronic cigarettes tested and in the types of fluid within them, and also in the number of repeated measurements.

It is not clear whether it is possible to conclude from these findings about passive exposure tp electronic cigarettes of any kind. Emission of toxic compounds from electronic cigarettes changes significantly according to the voltage supplied by the battery, the length of inhalation, and the time gaps between inhalations. There are no uniform scientific methods to examine cigarette vapor, and the concentrations reported change according to the methods of sampling the fluid and measurement systems.

Most of the studies measured the emission of one user or a smoking machine, from a few minutes to one hour. This scenario resembles cases in which people are exposed to a single user by chance, but they don’t say much about the risks of exposure to many people using electronic cigarettes simultaneously in closed spaces, such as in night clubs, bars, and coffee shops.

A study from February 2019 showed that chemicals in electronic cigarettes, which are also responsible for the buttery flavor of microwave popcorn, cause genetic changes in cultured human respiratory tract cells. Some of the affected genes are linked to the function of cilia in the bronchi of the lungs and play an important role in clearing away foreign particles in the lungs. Treating the cultured cells with the flavor molecules reduced the number of cells that expressed cilia, hinting that these compounds may damage lung function. Further research is obviously needed in order to further establish this finding.

Another study, using more physiological conditions, was published in January 2019. Its found genetic changes in the cells lining the inside the mouth, both in tobacco cigarettes smokers (24 participants) and electronic cigarette users (42 participants), compared to nonsmokers (27 participants). Even though in both experimental groups there were many genetic changes as compared with the control group (nonsmokers), more genetic changes were found in the tobacco smokers’ group than in the electronic cigarette users (1,726 compared with 1,152).

Further analysis of the genes whose expression altered in both groups showed that more than 60% of the genes were involved in cancer-related processes, although it is not possible to conclude that the changes directly lead to cancer. In this case again, further research that will examine more participants and delve deeper into how the affected genes are linked to disease, if at all, is needed.

A 2018 meta-analysis – a statistical analysis of numerous studies – of 141 studies conducted from 1946, altogether examining millions of people, found that smoking a single tobacco cigarette a day increases the risk of coronary disease by 1.7 among men and 2.2 among women, in comparison to nonsmokers. Thus, understanding how electronic cigarette use affects cardiovascular function is a key point.

A study from 2016 found that transitioning from smoking tobacco cigarettes to vaping reduced smokers’ blood pressure a year after the transition, which was previously abnormally high (high blood pressure is a risk factor for cardiovascular disease). No change in the blood pressure of those who continued to smoke tobacco cigarettes was found after a parallel amount of time. However, it is not clear whether the reduction is due to changing the cigarette type, because six months after the transition, those who transitioned to electronic cigarettes also changed their habits and reduced the amount of regular tobacco cigarettes smoked to 10% of what they previously smoked. In any case, the result is encouraging.

Another study from the same year showed that electronic cigarettes increase blood pressure and lead to arterial stiffness, like tobacco cigarettes. Perhaps this is a clue that the reduction seen in the previous study was due to an overall reduction in smoking tobacco cigarettes over time, and not the transition to vaping. In any case, it is clear that electronic cigarettes are no innocent bystanders.

Another study supporting this claim showed that daily use of electronic cigarettes increased the odds of a heart attack by 1.8 in comparison to nonsmokers. The increased risk due to smoking tobacco cigarettes was slightly higher, 2.7. However, since the gap was not statistically significant, it is possible that there is no difference in risk level between the two types of cigarettes.

While there are findings indicating that electronic cigarettes help smokers quit the habit, there is still some concern that in nonsmokers – especially children – the electronic cigarette will lead to a nicotine addiction, which will, in turn, instill the desire to smoke regular cigarettes. A 2017 article reviewed nine longitudinal studies, i.e., studies that follow the same participants over time. More than 17 thousand smokers between the ages of 14 and 30 answered questions about their habits of electronic and tobacco cigarette use.

The primary finding was that 30.4% of those who had ever used electronic cigarettes also tried tobacco cigarettes, compared to only 7.9% of those who had never used electronic cigarettes at all – an almost four-fold difference. In fact, it became apparent that electronic cigarette use is an even greater risk factor to start smoking tobacco cigarettes than parents, friends, or siblings who smoke.

The article’s authors identified several reasons for this. First, electronic cigarette use mimics behaviors typical of smoking tobacco cigarettes, such the hand-to-mouth movement, inhalation into the lungs, and exhaling smoke or vapor. Therefore, teenagers and young adults, who use electronic cigarettes without nicotine, may acquire smoking habits, making the transition to tobacco cigarettes more natural for them.

Second, those who use electronic cigarettes with nicotine may become addicted, since the vapor contains nicotine at its most addictive form, which is easily absorbed by the body. Moreover, inhalation of certain flavor compounds creates a pleasant sensory experience, similar to that reported by tobacco smokers.

The third reason is that the use of electronic cigarettes can engage conceptual or behavioral processes that increase the risk of smoking tobacco. For example, in electronic cigarette users, there is a stronger concept of smoking as a positive thing, in addition to the feeling of belonging to a group of smokers of the same age group.

The article’s findings were critically received by tobacco addiction experts around the world. The primary criticism was that the findings did not establish a causative connection between using electronic cigarettes and smoking tobacco cigarettes. Another criticism regarded the authors’ call to ban electronic cigarette use in order to minimize the tendency to start smoking tobacco cigarettes. The critics claimed that such a ban might do exactly the opposite and encourage smoking tobacco, as those interested in smoking would have no alternative.

A further claim was that in contrast to what the article’s authors wrote, access to electronic cigarettes was accompanied by a decline in teenage smoking of tobacco cigarettes in U.S. and Britain. The article’s critics also noted that its authors did not distinguish between teenagers simply trying electronic cigarettes and those who became chronic users, while many studies show that nonsmokers who try electronic cigarettes rarely become addicted or begin smoking chronically. Furthermore, smokers trying to stop smoking often do so through electronic cigarettes.

The article’s authors themselves identified several limitations in it: The type of electronic cigarettes used by the studies’ participants was unknown, nor the percentage, among them, of those using electronic cigarettes that contain nicotine – even though these are of a new type of nicotine-containing electronic cigarettes that administer more nicotine into the blood than the first-generation electronic cigarettes. Additionally, all the studies reviewed were from the U.S. and therefore, are not necessarily indicative about other countries. Finally, the studies were relatively short and did not follow up on the teenagers for long enough to assess the nicotine addiction ratio and dependence on cigarettes in their adult lives.

Subsequent studies supported the claim that using electronic cigarettes predicts future smoking of tobacco cigarettes. A 2017 study, conducted on 4,000 high school students in Scotland, found that 40% of the students who used electronic cigarettes started smoking tobacco cigarettes a year later, compared to 13% of those who did not use electronic cigarettes – a three-fold difference. Another study from 2018 included 808 high schoolers in Connecticut, and found that the risk of smoking tobacco cigarettes increased by a factor of 4 to 7 in teenagers who used electronic cigarettes in the month prior to the study, in comparison to those who didn’t. On the other hand, smoking tobacco cigarettes did not predict the use of electronic cigarettes. That is, the tendency among tobacco cigarette smokers to use electronic cigarettes is not greater than nonsmokers. A study following 2,500 college students in Texas also found a connection between vaping and smoking tobacco cigarettes later in life.

An extensive review from 2018 by the U.S. National Academy of Science summarized the link between electronic cigarettes and tobacco cigarettes: “There is significant evidence that using electronic cigarettes increases the risk of starting to smoke tobacco cigarettes among teenagers and young adults. Among those who already use regular cigarettes, there is moderate evidence that electronic cigarettes increase the frequency and intensity of smoking regular cigarettes.”

In August 2019, the Washington Post reported a mysterious lung disease that afflicted almost a hundred electronic cigarette users in 14 states across the U.S. Seven people have died, after being hospitalized with lung disease which was suspected to be associated with vaping.

Based on these, and similar, cases, the U.S. Center for Disease Control and Prevention (CDC) conducted a study that found 805 cases of suspected lung diseases and 16 cases of death related to the use of electronic cigarettes in 46 states and one territory (the Virgin Islands) in the U.S. However, a report published in September 2019, stated that a specific cause for the mysterious disease was not found and that no specific type of electronic cigarette causing it could be identified. A recommendation accompanied this statement, not to use electronic cigarettes – emphasizing teenagers, young adults, and pregnant women – primary target audiences for the product. Following the recent discoveries, the Israeli Ministry of Health announced, on September 24, 2019, that it is considering prohibiting the marketing and sales of electronic cigarettes in Israel.

Currently, there is no broad consensus about the damage of electronic cigarettes compared to tobacco cigarettes, mostly because of the large variance among the different types of vaping devices and the lack of control of many variables. The long-term effects of using them is unknown chiefly because they are in the market not long enough to be fully understood. Further and more comprehensive research about the dangers of using electronic cigarettes is needed, and in parallel, to emphasize the caution needed, primarily among teenagers who are subject to peer pressure and tend to take more risks than others in of society.