The Harm of E-Cigarettes

The electronic cigarette industry has risen rapidly in recent years. Under the banner of “No harm” and “safer than traditional tobacco”, the electronic cigarette (hereinafter referred to as “e-cigarette”) is becoming more and more popular around the world and it is also preferred by more and more smokers, especially youngsters. However, in fact, this kind of new product have a variety of hazards to the human body. The ingredients of e-cigarettes are complicated and could generate various kinds of substances in the aerosols. It has been confirmed that many substances are toxic and even carcinogenic. These substances can not only significantly impact the cardiovascular system and respiratory system, but also result in serious lung diseases. For adolescents, consuming e-cigarettes are “everything to lose and nothing to gain”, because premature exposure to nicotine in fetuses and adolescents may cause long-term adverse consequences for the brain development. In addition, the use of e-cigarettes may also lead to the exposure to traditional tobacco. Furthermore, it is found that some harmful ingredients in e-cigarettes are even higher than those in traditional tobacco. The World Health Organization (hereinafter referred to as “WHO”) has pointed out that there is no evidence that e-cigarette can help people quit smoking. Therefore, in order to protect your health, you should stay away from both traditional tobacco and e-cigarettes.

The ingredients of the e-cigarette solutions or preparations are complicated. In addition to nicotine, a variety of harmful substances, such as carbonyl compounds, volatile organic compounds (VOC), polycyclic aromatic hydrocarbons, tobacco-specific nitrosamines (TSNA), metals, particulates and other components, etc. are also found in its solutions and aerosol^1,2.

• Nicotine
  The reports from the WHO and the U.S. Centers for Disease Control and Prevention have clearly pointed out that nicotine is harmful to health. It is highly addictive and brings about health hazards not only for pregnant women, but also for the developing fetus and baby. Since the brain development continues to the 20s, the exposure to nicotine in children and adolescents will cause long-term damage to the brain development, such as learning disabilities and anxiety disorders^3,4. Moreover, it is also found that nicotine has the negative impact on the cardiovascular system, mainly sympathetic nerve stimulation and the release of various neurotransmitters that can affect the cardiovascular system, such as epinephrine, norepinephrine, dopamine, vasopressin, etc., which may cause coronary vasoconstriction, and/or impair endothelial function by transiently increasing blood pressure and heart rate. Therefore, smoking may increase the risk of cardiovascular events ⁵. Although nicotine itself is not a carcinogen, it may act as a “tumor inducer.”¹
  In addition, the liquid nicotine of the e-cigarette has the risk of accidental ingestion, especially for children. Calculated according to the nicotine concentration of 20 mg/ml, a typical 5ml vial of the e-cigarette’s solution may contain 100 mg of nicotine. For children, the known lethal dose of nicotine is about 10 mg. And oral or gastrointestinal ingestion/skin contact of nicotine can also do harm to human body (especially in young children), such as nausea, vomiting, lethargy and tachycardia. And some exposure may even lead to seizures, hypoxic brain injury, lactic acidosis, and death.
  In reality, it is difficult for consumers to know what ingredients are contained in the e-cigarette product. Even for some e-cigarettes marked with zero nicotine content have been found to contain nicotine⁶.
• Carbonyl Compounds and Oxides
  As the humectants, propylene glycol and glycerin are the major components of most e-cigarette solutions². After being heated at high temperature, they can be decomposed to produce carbonyl compounds (such as formaldehyde, acetaldehyde, and acrolein), which can cause oxidative stress and inflammation. When the solutions are exposed to higher voltages and higher temperatures, more thermal degradation products will be generated⁷. Among them, acrolein has been proved to cause oxidative stress, leading to accelerated atherosclerosis, which is prone to increase the risk of thrombosis and cardiovascular disease. While formaldehyde, classified as a carcinogen, has also been proved to have many effects on the cardiovascular system. Acetaldehyde is also a toxic irritant and possible carcinogen⁷.
• Tobacco-Specific Nitrosamines (TSNA)
  In some e-cigarettes, tobacco-specific nitrosamines (TSNAs) have been detected^1,2. TSNAs are known as potent carcinogens, usually formed by the nitrosation of tobacco alkaloids in the process of extracting nicotine from tobacco or adding tobacco flavorings.
• Metal
  When some e-cigarette devices are used at high power, the heating coil will also release some heavy metals such as lead, chromium, and nickel, etc³. The WHO reports have pointed out that the levels of certain heavy metals (such as nickel and chromium) in second-hand aerosols of e-cigarettes are higher than those in second-hand smoke and the air¹. In addition, it has been proved that metals act as catalysts for the oxidation of cellular proteins in tobacco smoke (CS). Therefore, their roles in the e-cigarette may be similar⁷.
• Particulates
  High concentrations of ultrafine and fine particulates (PM0.1, PM2.5) have been found in the e-cigarettes. It is already known that these particulates can impact on cardiovascular health and are associated with respiratory diseases. And they also contribute to a number of health conditions, including atherosclerosis, thrombosis, coronary heart disease and hypertension⁷.
• Effects of Sweeteners
  The e-cigarette solutions are often added with various sweeteners, with more than 7,000 flavors to choose from. Prior research has found that cytotoxicity is associated with certain flavors used in the e-cigarette solutions, especially sweet and cinnamon flavors⁸. And some studies have pointed out that the presence of benzaldehyde, a compound in many flavored e-cigarettes, is associated with respiratory irritation, and cherry flavored⁹ e-cigarettes have the highest level of benzaldehyde. In addition, diacetyl, a kind of chemical substance that is associated with severe lung disease, has been found in many flavored e-cigarettes¹⁰. The WHO reports also show that the long-term use of most flavoring agents may lead to significant health risks¹.
• Others
  EVALI, an acronym for “E-cigarette or Vaping use-Associated Lung Injury”, is a kind of severe acute lung disease that has been reported since 2019. As of February 2020, the U.S. Centers for Disease Control and Prevention has reported more than 2,800 EVALI cases, which are associated with tetrahydrocannabinol (THC) and/or vitamin E acetate in the e-cigarette. However, the cases may also be involved with other additives². A survey of more than 45,000 students in Hong Kong (average age 14.6 years) also showed that e-cigarette use is associated with respiratory symptoms such as cough or phlegm¹¹.
  Since smoking is a risk factor for COVID-19, and young people are the major users of e-cigarettes, a survey of more than 4,300 young people aged 13-24 in 50 states in the United States was conducted during the COVID-19 pandemic. The results show that people who ever-users of e-cigarettes only are five times more likely to be COVID-19 diagnosed, and people who ever use both traditional cigarettes and e-cigarettes are seven times more likely to be diagnosed¹².

With batteries installed in most devices, there have been many explosions of e-cigarette devices around the world due to malfunctioning during storage (e.g. in the pocket) or during use, causing the burns in thighs, groin, face and/or hands.

The use of e-cigarette increases the risk of nicotine dependence for new users who are not tobacco smokers, which may lead to their eventual use of combustible tobacco. And since the use of e-cigarettes for many young people often precedes their use of traditional cigarettes, the use of e-cigarettes may be a way to let teenagers become nicotine dependent². The WHO has pointed out that the use of e-cigarettes by minors who have never smoked combustible tobacco makes them at least double the likelihood of starting smoking¹. Furthermore, the use of e-cigarettes may normalize the smoking behavior, which may also promote the use of traditional cigarettes².

The quantities and levels of certain known toxicants produced by e-cigarettes may be lower than those produced in tobacco smoking, but the levels of toxicants produced by different brands and different products of the same brand may vary widely. And sometimes e-cigarettes are producing even higher levels of toxicants than those in tobacco smoking, which may be caused by the increased thermal decomposition of the ingredients of the e-cigarette solutions due to the increased temperature of the device¹; And it has been proved that the concentrations of metals and particulates in e-cigarettes are higher than those in tobacco smoking.

Toxic effects might be generated even the toxic substances are at low or very low concentrations. And there is no established safe threshold for toxic substances in terms of health. In addition, various catalytic or synergistic effects may also be generated between different compounds, resulting in some unknown effects⁷. The long-term use may lead to significant health risks.

The WHO has pointed out that there is no sufficient evidence to prove the effectiveness of e-cigarettes in helping smokers quit smoking¹, and no e-cigarettes have been approved by the U.S. Food and Drug Administration (FDA) for smoking cessation, and the FDA has not recognized their safety or effectiveness for smoking cessation.

Free smoking cessation services are available in all Health Centres of the Health Bureau. Please enquire the healthcare staff for details if you want to quit smoking.
Smoking cessation hotline: 2848 1238