How Safe is Vaping (contiued)

This is Part 2 of a two-part series. The previous installment discussed the effects of nicotine, flavourings and other ingredients in e-liquids.

Clinical effects of EC

Lung immune response is altered by e-cigarette (EC) usage, impairing innate immunity, altering bacterial defences, causing oxidative stress and inflammatory responses.1-3 Exposure to EC increases neutrophils and alters mucin secretion. Staudt et al4 suggested that EC may be toxic to airway cells, resulting in dose-dependant cell death. In their study using mice, they found that exposure to EC vapour caused

  • a decrease in both macrophage function and neutrophil antimicrobial function

  • an increase in markers of inflammation

  • staphylococcus aureus to become ‘more virulent’

  • the promotion of bacterial growth in the airways

  • impairment of innate immune defences.

A recent study of over 28,000 adults found that when compared with non-users, the risk of both wheezing and related respiratory symptoms was significantly higher in current EC users. While the link was not a causative one, it confirmed an association between vaping and wheezing and other respiratory symptoms – compared to non-users, adults who vaped were 1.7 times more likely to have symptoms. These symptoms are early warning signs of lung damage.

Other studies4,6-10 have listed the clinical abnormalities that result from inhalation of EC. These include

  • increased cough

  • lower levels of FeNO

  • increased diastolic blood pressure

  • increased respiratory flow resistance

  • endothelial disruption

  • oxidative stress

  • arterial stiffness

  • negative effects on autonomic control

  • reduced level of inflammatory cell recruitment

  • delayed clearance of pathogens

  • changes to hundreds of genes involved in defense of the upper airway

  • (cause of) biological changes

  • damage to DNA

A presentation at the American College of Cardiology11 meeting listed the heightened health risks incurred by EC users, which when compared to non-EC users, included

  • myocardial infarction (56%)

  • circulation problems (44%)

  • stroke (30%)

  • coronary artery disease (10%)

After adjusting for all confounding variables, the odds ratio in comparison with non-users for a myocardial infarction was 1.34 for daily EC users and 1.25 for frequent but not daily users. A comparison among EC and CC users found that EC users were twice as likely to report anxiety, depression or emotional problems with EC users having a 55% higher level of risk than non-users.

Hot or Cold?

Chemical flavourings, when combined with solvents such as polypropylene glycol and glycerol, produce compounds known as acetals. Chemical changes hence occur prior to heating the e-liquid, while the mixture is simply in storage within the EC. Tests conducted by Erythropel and colleagues12 showed that 40% of the flavouring compounds converted to acetals and anywhere up to 80% of the liquid acetals transferred to the inhaled vapour. While flavour aldehydes cause irritation on inhalation, the acetals created by combining flavours with e-liquids were more powerful in activating receptors involved in lung irritation.

The vapour produced by EC contains toxic substances. When the elements in EC are heated, they produce aerosols that can contain up to 31 compounds such as nicotine, nicotyrine, carbonyls, glycidol, acrolein, acetol and diacetyl. Glydicol is a possible carcinogen. Acrolein is a potent irritant of the nasal cavity, damaging the lining of the lung. It may also contribute to cardiovascular disease. The researchers concluded that thermal byproducts are formed when vapour is generated.13 They also found that increasing the voltage (inside the EC device)

  • doubles the mass of e-liquid consumed

  • triples total aldehyde emission rates

  • increases acrolein ten-fold

Researchers agree that high heat settings could produce toxic substances. However, Peyton and colleagues found that even when EC were used at lower, more common heat settings, new formaldehyde compounds in excess of recommended OSHA workplace levels were detected. The new forms of formaldehye were 5 to 15 times higher than the formaldehyde in regular cigarettes. Because the new forms of formaldehyde are attached to particulates in the EC aerosols, they can be deposited more deeply into the lungs than gaseous formaldehyde.14

When devices of high power that contain high e-liquid nicotine levels are combined with large puff volumes, the amount of nicotine released is “comparable to the amount of nicotine emitted from regular cigarettes”. Furthermore, EC vaping emissions produced anywhere from 2 to 63 times the nicotyrine per unit nicotine produced by regular cigarette smoking.15


Electronic Nicotine Delivery Systems (ENDS) come in a variety of forms. They may be single-use, disposable, rechargeable, refillable, with and without cartridges. Closed systems are non-refillable and non-rechargeable. Open systems are both rechargeable and refillable.

There is one serious safety concern with the ENDS themselves.16 When when not in use, these devices which contain lithium-ion batteries can burst into flame and explode causing burns and projectile injuries. The risk of this occurring is increased when the

  • batteries are of poor quality

  • device is improperly stored

  • device is modified by the users

The FDA suggests keeping EC batteries away from all metal objects including coins; not using a phone or tablet charger to charge the device and not leaving it charging unattended.17

Upon suction the electronic sensors note the change in airflow and activate a heating element that vaporizes the liquid ingredients. Some EC devices can be customised to deliver the aerosol at an individual’s preferred setting. When devices are operated at high power, the emissions included benzene, a known carcinogen. Benzene has been linked to a number of diseases including bone marrow failure and leukemia. The level of benzene is higher if the e-liquid contains benzoic acid or benzaldehyde.18 While lower than that produced by CC, the levels of benzene are higher than those found in ambient air.

The temperature, age and type of device affect emission levels. Some have one heating coil while others have two. The emissions of formaldehyde, acetaldehyde and acrolein increase with usage. A study19 found that when vaporized, the solvents in the EC produced significant levels of 31 harmful compounds with two new compounds detected. These were the probable carcinogens propyleneoxide and glycidol. Further, increasing the voltage in a single-coil device

  • doubled the amount of e-liquid consumed

  • tripled the amount of aldehyde emitted

  • increased acrolein rates ten-fold

In effect, the number and quantity of toxins increase with heat and use.

The internet, while it provides instruction for adjusting the device to an individual’s personal preferences, also provides information on using illegal drugs in the e-liquids.20

Children and Vaping

Vaping increases the level of nicotine and the concentration of airborne particulate matter in indoor environments. In other words, it increases pollutants in indoor air. As the first part of this document reported, EC emit a number of potentially toxic chemicals. Just as with second– and third-hand tobacco smoke, these particles not only are initially suspended in air but over time settle on walls, furniture, furnishings, carpets and clothing putting them into close contact with toddlers, children and youths. Second- hand smoke inhalation of EC results in the same blood levels of nicotine as second-hand CC.21 Emissions from EC are as prevalent as those for CC.

In children, exposure to e-liquids can occur through eye or skin contact or through drinking. Nicotine absorption can occur through the lungs, oral mucosa, skin or gut. This may be either accidental or intentional. Nicotine targets the organs of the peripheral and central nervous systems such that paralysis of the respiratory muscles can occur and result in death. Drinking (whether intentionally or not), or injecting e-liquids can be fatal. A lethal dose of nicotine is about 10 mg in children (30-60 mg in adults).22 Nicotine is one of the many chemicals that the CDC has designated as Immediately Dangerous to Life or Health.23

The combination of a large amount of e-liquid with high levels of nicotine poses a formidable threat to children. Enticed by attractive labelling and fruity flavours in devices that mimic familiar foods such as Fruit Loops,24 children are drawn to EC, with regrettable results. Between January 2012 and April 2017 there were more than 8,200 calls to US poison centres about children younger than 6 years exposed to liquid nicotine and EC. That is, more than 4 calls every day. Ingestion was the most common form of exposure in children under three and accounted for 93% of the calls. Liquid nicotine used in EC remains a danger to children.25

Youth and Vaping

Adolescents tend to use rechargeable, refillable devices and avoid cartridge systems.26 The marketing of EC has been targeted to youth with special emphasis on fruit flavours that are enticing. EC promotions have been extremely successful in that between 2017 and 201827

  • the increase in EC use was 78% among high school students and 48% among middle school students

  • 81% said that the appealing flavours was the primary reason for use

A study on adolescent use of EC found that one in ten reported use of EC while the majority of students were motivated to try EC becausesup>28

  • of appealing flavours

  • it looked “fun, new, cool”

  • of curiosity

  • they had friends and/or family who use tobacco

  • they viewed EC as less harmful than CC

Other reasons59 given by adolescents included29,30

  • low cost

  • use by peers

  • ability to hide use from adults

  • ability to use anywhere

  • aid to quit smoking CC

Vendors have stressed the reduction in toxic substances as compared with CC. The ‘health benefits’ of EC have been touted. That together with prices that vary greatly – with starter kits ranging from free to $130 – makes EC attractive. EC are readily available to young people and can be ordered over the internet where age verification is not rigorous and easily overcome.. Promotions, customer testimonials and marketing claims on thousands of websites on the internet make it increasingly difficult to regulate the retailing of EC.31

Marketing ploys have been clever. Take for instance the Blu advertising campaign of 2017 titled “Something Better”. It included the placement of fake warning labels (in anticipation of the law) that state “Contains flavor” and “Less harmful to your wallet” with legitimate warnings provided in small print at the bottom of the ads. The fake warnings were placed where the FDA required a warning that clearly stated that the product contained nicotine. A study found that the fake warnings were remembered by adolescent males to the point that the actual warnings were ignored.32 These type of campaigns are disallowed by the FDA now.

There is increasing concern that EC use could be the gateway to CC use.33 Nicotine is addictive particularly in the adolescent’s developing brain. Hammond et al34 studied over 44,000 students in Canada and found that youth who used EC in the month prior to the start of the study were likely to start smoking CC and to continue smoking after one year. EC use was associated with future CC use but the reverse is not true.35,36

There is yet another safety issue. In a special announcement in early April, the FDA announced that there is a potential seizure risk associated with EC for youth and young adults.37 Symptoms may include a lapse in consciousness or awareness, staring blankly into space for a few seconds, sudden lack of movement or even convulsions. The after effects may leave the individual sleepy, confused, or with a headache. Prompt medical attention is essential.


The risk to children and youth must be seriously considered when framing laws restricting the marketing and prohibition of flavourings in EC. The trend among adults is also rising significantly in both CC smokers and nonsmokers.38

What we are seeing is the fight over tobacco all over again, and parents and healthcare professionals have a major role to play in counselling youth. EC can no longer be seen as a CC reduction method. The implications of EC use is far-reaching. It is, in fact, breeding a new generation of addicts hooked on nicotine.

The EC marketing approach has resulted in the normalization of cigarette smoking targeted towards youth. Education – both of youth with reference to the nicotine content of vaping, and of parents who use tobacco – is essential to stop this epidemic in its tracks. Educators should inform youth, parents, adults that39,40

  • vaping devices contain nicotine

  • nicotine is addictive

  • inhalation of vapor will result in irritation, inflammation and respiratory disease

  • nicotine from vaping may be similar to levels from CC

  • exhaled EC vapors contain nicotine that is deposited on indoor surfaces

  • EC vapor is toxic

  • EC, while less harmful than CC are not harm less

  • EC is associated with progression to more dangerous forms of smoking

  • there exists a possible risk of seizures in youth and young adults

Health care professionals have a duty to provide education, counseling and tobacco cessation resources to both EC and CC users.

There is clear evidence that not only do EC products contain and emit harmful, toxic substances but the quantity and type of substance emitted depends on the device, ingredients in the EC and how the device is operated.41 Finally, the long-term effects of these many chemicals, both those contained in EC and those formed by thermal degradation when vaping, are not known. That does not mean that EC are safe.

While exposure to the toxins in CC is currently considered more harmful, the risk associated with EC usage warrants recommendations to avoid or at least minimize use of EC.

For more information on sales, usage, hardware, passive exposure and concerns about EC, please read our booklet Vaping – yet another smokescreen.


CC conventional tobacco cigarette

CDC Centers for Disease Control and Prevention

EC electronic cigarette

ENDS Electronic Nicotine Delivery System

FeNO fraction of exhaled nitric oxide

GRAS generally regarded as safe

OSHA Occupational Safety and Health Administration

PAH polycyclic aromatic hydrocarbons

VOC volatile organic compounds


  1. Reidel B, Radicioni G et al. E-cigarette use causes a unique innate immune response in the lung, involving increased neutrophilic activation and altered mucin secretion. Am J Respir Crit Care Med. 2018;197:492–501.

  2. Hwang JH, Lyes M, et al. Electronic cigarette inhalation alters innate immunity and airway cytokines while increasing the virulence of colonizing bacteria. J Mol Med (Berl). 2016 Jun;94(6):667-79. doi: 10.1007/s00109-016-1378-3

  3. Lerner CA, Sundar IK, et al. Vapors produced by electronic cigarettes and e-juices with flavorings induce toxicity, oxidative stress, and inflammatory response in lung epithelial cells and in mouse lung. PLoSOne. 2015;10:e0116732

  4. Staudt MR, Salit J et al. Altered lung biology of healthy never smokers following acute inhalation of E-cigarettes. Respiratory Research 2018; 19:78

  5. Li D, Sundar IK et al. Association of smoking and electronic cigarette use with wheezing and related respiratory symptoms in adults: cross-sectional results from the Population Assessment of Tobacco and Health (PATH) study, wave 2. Tobacco Control, 2019; tobaccocontrol-2018-054694

  6. Stratton K et al. Public health consequences of e-cigarettes. National Academies Press 2018; DOI:10.17226/24952.

  7. Lerner CA, Sundar IK, et al. Vapors produced by electronic cigarettes and e-juices with flavorings induce toxicity, oxidative stress, and inflammatory response in lung epithelial cells and in mouse lung. PLoSOne. 2015;10:e0116732

  8. Schweitzer KS, Chen SX, et al. Endothelial disruptive proinflammatory effects of nicotine and e-cigarette vapor exposures. Am J Physiol Lung Cell Mol Physiol. 2015;309:L175–87.]

  9. Yu V, Rahimy M, et al. Electronic cigarettes induce DNA strand breaks and cell death independently of nicotine in cell lines. Oral Oncol. 2016 Jan;52:58-65. doi: 10.1016/j.oraloncology.2015.10.018.

  10. Martin E, Clapp PW, et al. E-cigarette use results in suppression of immune and inflammatory-response genes in nasal epithelial cells similar to cigarette smoke. Am J Physiology - Lung Cellular and Molecular Physiology, 2016; ajplung.00170.2016 DOI: 10.1152/ajplung.00170.2016

  11. Vindhyal MR, et al. Impact on cardiovascular outcomes among E-cigarette users: a review from National Health Interview Surveys. ACC 2019; Abstract 911-12.

  12. Erythropel HC, Jabba SV, et al. Formation of flavorant–propylene glycol adducts with novel toxicological properties in chemically unstable E-cigarette liquids. Nicotine & Tobacco Research, 2018; DOI: 10.1093

  13. Sleiman M1, Logue JM et al. Emissions from electronic cigarettes: key parameters affecting the release of harmful chemicals. Environ Sci Technol. 2016 Sep 6;50(17):9644-51. doi: 10.1021/acs.est.6b01741.

  14. Salamanca JC, Meehan-Atrash J et al. E-cigarettes can emit formaldehyde at high levels under conditions that have been reported to be non-averse to users. Scientific Reports, 2018; 8 (1) DOI: 10.1038/s41598-018-25907-6

  15. Son Y, Wackowski O et al. Evaluation of E-vapor nicotine and nicotyrine concentrations under various e-liquid compositions, device settings, and vaping topographies. Chem Res Toxicol. 2018 Sep 17;31(9):861-868. doi: 10.1021/acs.chemrestox.8b00063.

  16. Stratton K et al. Public health consequences of e-cigarettes. National Academies Press 2018; DOI:10.17226/24952

  17. Accessed March 14, 2019

  18. Pankow JF, Kim K, et al. Benzene formation in electronic cigarettes. PLoS ONE 2017; 12(3): e0173055. doi:10.1371/journal.pone.0173055

  19. Sleiman M, Logue JM et al. Emissions from electronic cigarettes: key parameters affecting the release of harmful chemicals. Environ Science & Technology, 2016; DOI: 10.1021/acs.est.6b01741

  20. Stratton K et al. Public health consequences of e-cigarettes. National Academies Press 2018; DOI:10.17226/24952

  21. Flouris AD, Chorti MS, et al. Acute impact of active and passive electronic cigarette smoking on serum cotinine and lung function. Inhal Toxicol 2013;25:91-101

  22. Mishra A, Chaturvedi P et al. Harmful effects of nicotine. Indian J Med Paediatr Oncol. 2015; 36(1):24-31. doi: 10.4103/0971-5851.151771

  23. Accessed March 13, 2019

  24. Accessed March 13, 2019

  25. Jackler R, Ramamurthi D. Nicotine arms race: Juul and the high-nicotine product market. BMJ Tobacco Control 2019; DOI: 10.1136/tobaccocontrol-2018-054796

  26. Govindarajan P, Spiller HA et al. E-cigarette and liquid nicotine exposures among young children. Pediatrics. 2018 May;141(5). pii: e20173361. doi: 10.1542/peds.2017-3361.

  27. McMillen R, Ranski S et al. Adolescent use of different e-cigarette products. Pediatrics. 2018 Oct;142(4). pii: e20180260. doi: 10.1542/peds.2018-0260.

  28. Accessed March 14, 2019

  29. Khoury M, Manlhiot C et al. Reported electronic cigarette use among adolescents in the Niagara region of Ontario. CMAJ 2016 doe:10.1503/cmaj.151169

  30. Soneji SS, Knutzen K and Villanti AC. Use of flavored e-cigarettes among adolescents, young adults, and older adults: findings from the Population Assessment for Tobacco and Health Study. Public Health Reports, 2019; 003335491983096 DOI: 10.1177/0033354919830967

  31. Bold KW, Kong G et al. Reasons for trying e-cigarettes and risk of continued use. Pediatrics 2016; DOI: 10.1542/pediatrics.2016-0895.

  32. Williams RS, Derrick J et al. Content analysis of e-cigarette products, promotions, prices and claims on Internet tobacco vendor websites, 2013–2014. Tobacco Control, 2017; tobaccocontrol-2017-053762 DOI: 10.1136/tobaccocontrol-2017-053762

  33. Keller-Hamilton, Roberts ME et al. Adolescent males’ responses to Blu’s fake warnings. Tobacco Control, 2019; tobaccocontrol-2018-054805 DOI: 10.1136/tobaccocontrol-2018-054805

  34. Klein JD. E-Cigarettes: A 1-way street to traditional smoking and nicotine addiction for youth. Pediatrics 2017; DOI: 10.1542/peds.2017-2850.

  35. Hammond D, RFeid JL et al. Electronic cigarette use and smoking initiation among youth: a longitudinal cohort study. Canadian Med Assoc Journal, 2017; 189 (43): E1328 DOI: 10.1503/cmaj.161002

  36. Bold KW, Kong G et al. Trajectories of e-cigarette and conventional cigarette use among youth. Pediatrics 2018; 141(1) doi/10.1542/peds.2017-1832.

  37. Accessed March 8, 2019

  38. 65 Huang LL, Kowitt SD et al. Electronic cigarette use among high school students and its association with cigarette use and smoking cessation, North Carolina Youth Tobacco Surveys, 2011 and 2013. Prev Chronic Dis 2016;13150564 DOI:10.5888/pcd13.150564.

  39. McMillen RC, Gottlieb MA, et al. Trends in electronic cigarette use among U.S. adults: use is increasing in both smokers and nonsmokers. Nicotine Tob Res. 2015 Oct;17(10):1195-202. doi: 10.1093/ntr/ntu213.

  40. Leventhal AM, Stone MD et al. Association of e-cigarette vaping and progression to heavier patterns of cigarette smoking. JAMA 2016; DOI: 10.1001/jama.2016.14649.

  41. Soneji SS, Knutzen K and Villanti AC. Use of flavored e-cigarettes among adolescents, young adults, and older adults: findings from the Population Assessment for Tobacco and Health Study. Public Health Reports, 2019; 003335491983096 DOI: 10.1177/0033354919830967

  42. Stratton K et al. Public health consequences of e-cigarettes. National Academies Press 2018; DOI:10.17226/24952.