How Safe is Vaping

Vaping, so called because it consists of inhaling the vapour emitted by a device, usually involves a variety of electronic vapour-producing products including e-cigarettes (EC), e-cigars, e-pipes, e-hookahs, hookah pens, vape pens and vaping pipes. Vaping is the fashionable new way to smoke without actually placing a conventional tobacco cigarette (CC) between one’s lips.

The design and flavours of the vapour-emitting materials are deliberately targeted towards young people, as is the marketing, which suggests EC are safer and less harmful than CC. As such, they are assumed to be less of a risk than CC. However, the variability in EC products, particularly the nicotine concentration and flavourings between brands, is what determines the risk and severity of EC dependence. EC aerosols generally contain nicotine, flavourings, additives, propylene glycol, glycerol and sometimes an assortment of other chemicals.

(For more information on how EC actually work, their working parts, a comparison between EC and CC, etc. please refer to the January 2016 e-book titled “Vaping – Yet Another Smokescreen”.)

Some of the reported side effects of using EC include

  • eye, mouth and throat irritation

  • dizziness

  • headache

  • cough

  • nausea

  • trouble breathing

  • nose bleeds

  • chest pain

  • heart palpitations

  • allergic reactions

The side effects are most likely due to one of the many ingredients in EC, including nicotine.


Nicotine is a health hazard. It affects all organs and increases the risk for disorders of the respiratory, cardiovascular, gastrointestinal, ocular, renal, hormonal, reproductive and immunologic systems. Nicotine affects brain development at the fetal stage and through adolescence.1 It impairs the body’s antibacterial defences, suppresses the immune system, causes oxidative stress, apoptosis, leads to DNA mutations, decreases epithelial cell viability and immune response.2 It is a carcinogen that is known to be addictive. It has been linked to lung, pancreatic and breast cancer. It is also known to induce resistance to chemotherapy and radiotherapeutic agents.3-6

The latest research7 on nicotine has found that exposure to nicotine in the womb has long-term effects aside from elevated risks of miscarriage, small size for gestational age, premature birth and sudden infant death syndrome. Pregnant women who smoke tobacco can cause unintended effects on individual embryonic cells, disrupting cellular communication, altering cell survival, affecting gene expression and disrupting pivotal functions that include the regulation of heart muscle cell contractions. Nicotine affects cardiovascular, endocrine, metabolic, respiratory and neurobehavioural systems. The researchers found that not only did nicotine exposure result in altered gene expression with respect to metal toxicity and mitochondrial function but it also was implicated in

  • brain malformations

  • muscle development

  • arrhythmias

  • disease, including lung disease and

  • intellectual disability.

Common effects of nicotine include eye irritation, increased salivation, nausea, abdominal pain, vomiting, diarrhea, lethargy, tachycardia and increase in blood pressure. More severe side effects include apnea, cyanosis, convulsion, dyspnea, seizures, coma, muscular fasciculations (brief spontaneous contractions of muscles fibres under the skin), cardiac dysrhythmias and cardiac arrest.8

Nicotine in EC

Nicotine levels in EC are inconsistently reported. Prior to the introduction of the brand Juul, most EC and vaping liquids had 1.5 - 2 mg/mL of nicotine. Anything above 3% in weight was considered “super high intended for two packs/day smokers”. Juul’s popularity has resulted in a nicotine race, with both EC and e-liquid manufacturers increasing nicotine content. Juul has 5% nicotine by weight versus other EC products that have 5.9% by volume. Over 70 e-liquid brands sell high-nicotine products which at > 5% are equivalent to more than a 40-cigarette pack.9

In short, nicotine is a horror story. But the other chemicals in EC are also a cause for concern.

Flavourings and their dangers

The marketing of EC has been very successful. Between 2011 and 2015, the use of EC among young people increased by a shocking 900%, with 11.3% of high school students in the US reporting use of EC.10 A CDC report on the Youth survey of 2017 found that 13.2% of high school students vaped.11 Flavours with names such as Double Dark Chocolate, Cotton Candy, Kool Aid, Gummy Bears, Butterscotch, Wild Cherry, Green Apple, Grape, Belgium Cocoa, Cherry Crush, Vivid Vanilla, Java Jolt, and so on, are designed to appeal to young people. Currently, more than 7,500 different flavours of EC exist, with menthol, sweet and fruity flavours the most popular.12 Many of the chemical flavourings added are “generally regarded as safe” (GRAS) for ingestion – but not inhalation – by the US Food and Drug Administration. Therein lies the risk.

EC products do not either identify or list the levels of specific flavouring chemicals that are contained within individual products. An analysis of 30 EC products available in the US market found that in of them flavour chemicals constituted more than 1% of weight.13 While high doses of some flavour chemicals may be safe for ingestion, they may become toxic when inhaled.

Vaping occurs at high temperature. The researchers noted that when vaped, the flavour chemicals degraded into toxic products such as aldehydes (including formaldehyde and benzaldehydes) and vanillin, which irritate the respiratory tract. Formaldehyde is a known carcinogen.

A Salford study14 tested nine flavoured liquids on normal lung tissue – blueberry, bubblegum, butterscotch, cherry, ice-mint, menthol, strawberry, tobacco and vanilla. All proved toxic, with varying levels of toxicity to bronchial cells, and with prolonged exposure resulting in complete cell death.

Fetterman and colleauges15 studied nine chemical flavours that included banana (isoamyl acetate), butter (diacetyl), burnt flavour (acetylpyridine), clove (eugenol), cinnamon (cinnamaldehyde), strawberry (dimethylpyrazine), spicy cooling (eucalyptol) and mint (menthol). When vaped, all nine

  • caused acute changes in endothelial function in culture

  • impaired nitric oxide production

  • increased markers of inflammation

Nitric oxide inhibits inflammation and regulates the ability of blood vessels to broaden in response to increased blood flow. Loss of nitric oxide and increased inflammation are initial changes related to cardiovascular disease, and hence of great concern.

Another study16 found that a single acute exposure to synthetic cinnamon affected human airway epithelial cells by impairing mitochondrial function, reducing intracellular energy production, halting cilia motility and reducing mucociliary clearance. The authors suggested that this effect may increase susceptibility to both respiratory infections and the development of lung diseases in the long term. This was echoed by another study that found EC vapour could potentially increase susceptibility to pneumococcal infection17 by increasing adherence to epithelial cells. Pneumococcal bacteria often exist in airways without causing illness, but irritation of the epithelial may increase the risk of a bacterial lung infection.

Other ingredients in EC

Nicotine and flavours are not the only culprits. A number of harmful substances have been identified in EC fluid and vapor18-23 including:

  • ultrafine particles

  • traces of silver, tin, nickel, cadmium and aluminium

  • carcinogenic tobacco-specific nitrosamines

  • volatile organic compounds (VOC)

  • carbonyls (aldehydes, ketones and acetol)

  • alkaloids

  • alcohol (ethanol)

  • propylene glycol (PG) (derived from propylene oxide)

  • acetals (created from mixing flavours with solvents such as PG)

  • glycerin (thermal degradation produces glycidol and acrolein) and

  • heavy metals

Five heavy metals such as cadmium, chromium, manganese, lead and nickel were found in an analysis of multiple EC brands. These are toxic or carcinogenic when inhaled; were found in all brands; and suspected to have been released from the coil that heats the liquid.24 Nickel is a carcinogen. Cadmium can damage different organs and toxicity can cause early pregnancy loss, changes in placental nutrition, loss of bone mineral density, damage to the liver and kidneys, and respiratory distress.22

The simplest form of carbonyls are the aldehydes and ketones. The former include formaldehyde, acetaldehyde, benzaldehyde, acrolein, etc., while the ketones include acetone and diacetyl, among others. Researchers look for these carbonyls to assess the risk involved in EC. A comparison of pre- and post-vaping25 exhalations found that significant amount of cancer-causing chemicals were absorbed by the respiratory tract during a vaping session, with aldehydes and methyl ethyl ketone levels varying anywhere from 2 to 125 times higher after vaping than before vaping. The low levels in exhaled EC breaths were linked to high retention (above 95%) in the human respiratory tract. The researchers concluded that EC affects lung function.

The range of alcohol in EC varies from 0.4% to 23.5%. The consequence of EC containing alcohol are not yet known.26

The US National Library of Medicine states that propylene oxide, used in the production of propylene glycol, is a volatile compound thought to be a possible carcinogen. Acute inhalation of this vapour can result not only in eye and skin irritation but also in dyspnea and pulmonary edema leading to pneumonia. Inhalation of a high concentration for even a short time can cause headache, motor weakness, lack of coordination, ataxia and coma.27

The VOC include polycyclic aromatic hydrocarbons (PAH) such as α-pinene, β-pinene, γ-terpinene, and benzene. Benzene is considered carcinogenic and causes acute myeloid leukemia28 for it affects chromosome changes in bone marrow cells. Benzene has also been linked to multiple myeloma and non-Hodgkin’s lymphoma. These particular VOC may be carcinogenic, neurotoxic and hematotoxic. They are known to irritate tissues.29

. . . to be continued


CC conventional tobacco cigarette

CDC Centers for Disease Control and Prevention

EC electronic cigarette

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


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