How safe is vaping?

August 8, 2018 by Simon Cotton, The Conversation
Safe smoke? Credit: Shutterstock

A survey of adolescents carried out by researchers at Coventry University has shown that than less than half of e-cigarette users knew that vape products contain nicotine or that they are addictive, raising the possibility that they could be a gateway to smoking normal cigarettes. Nicotine addiction is a real problem but the health issues posed by e-cigarettes are potentially greater than just addiction.

The first Europeans to arrive in America at the end of the 15th century soon encountered the local custom of smoking tobacco – and they in turn introduced the practice to Europe. Successive English monarchs were opposed to it – King James I famously wrote a book entitled A Counterblaste to Tobacco – but, in the end, governments settled on taxing it.

The compound responsible for the pleasurable aspects of smoking tobacco (and for its addictive properties) is , a "secondary metabolite" produced by the tobacco plant Nicotiana tabacum as a defence against herbivores.

Smoking tobacco destroys most of the molecules present in it, including nicotine, but the small amount of nicotine that survives (around 10%) is carried from the lungs, via the blood, to the brain within less than ten seconds. Once in the brain, it stimulates the release of neurotransmitters, including the "pleasure molecule" dopamine. The link between taking a "drag" on the cigarette and the brain's "pleasure" response explains why smoking can be so addictive, as it associates pleasure with the act of smoking.

A dangerous game

Most of the dangers of smoking do not come directly from nicotine. Cigarette smoke contains around 4,000 different compounds and the most dangerous molecules are carcinogens such as benzo[a]pyrene and nitrosamines such as N'-nitrosonornicotine (NNN), which is derived from nicotine. Tobacco "tar", which is carried in the smoke to the mouth and lungs, is rich in these toxic substances.

If you smoke tobacco, the smoke damages the DNA in organs exposed to it as well as others indirectly exposed, speeding up genetic mutations and increasing the risk of cancer – not just of the lung, but also of the mouth, larynx, liver, cervix, oesophagus, pancreas, bladder and kidney. Not all these mutations lead to cancer, but the more of them there are, the more likely it is that cancer-causing mutations will occur.

According to the World Health Organisation (WHO), smoking-related disease causes around six million deaths a year (about 600,000 of these from "passive smoking"). Around 100,000 of these deaths occur in the UK and half a million in the US. Nicotine does not cause these deaths directly, but addiction to nicotine does.

Within the past decade or so, e-cigarettes have been marketed as a way to enjoy smoking with fewer of the health risks of traditional cigarettes – for one thing, as e-cigarettes don't burn tobacco, they should eliminate the risks associated with tar. They contain a battery, a metal heating element and a reservoir of liquid, which is converted to a vapour by the heating element and is inhaled by the smoker. The liquid is made up of a solvent, either glycerol or , nicotine, and often food-grade flavourings.

So what's the problem with e-cigarettes, if they do not produce carcinogenic tar? Well, nicotine or other molecules found in e-cigarettes can still affect lung health. A significant number of the flavour chemicals used in many liquids are aldehydes, and these are often irritants of the mucosal tissue in the respiratory tract when inhaled.

Typical examples are cinnamaldehyde (cinnamon), vanillin (vanilla) and diacetyl (buttery). Tests on endothelial cells, the cells which line the and the inside of the heart, show that some e-cigarette flavourings and their constituents (such as vanillin, cinnamaldehyde, diacetyl, isoamyl acetate and menthol) may harm blood vessels. They caused higher levels of an inflammatory marker (interleukin-6) and lower levels of nitric oxide, a molecule with several roles, such as inhibiting inflammation and clotting, and dilating blood vessels. In the body, these two changes are considered to be an early predictor of heart disease. Although the food flavourings are in themselves safe when used in food (as are the solvents) that does not mean they necessarily are entirely safe for a different use, such as in e-cigarettes.

Studies have shown that some of these molecules, notably the solvents, can be decomposed when heated to above 300°C by the in the e-cigarette. Three substances, all aldehydes, formed on the breakdown of glycerol and propylene glycol have come in for particular attention – acrolein, methanal and ethanal.

You've probably met acrolein (propenal) – it's the chemical formed when cooking oil is heated until it begins to smoke. It is toxic and can severely irritate eyes and nasal passages. Ethanal (acetaldehyde) and methanal (formaldehyde) are also toxic – methanal, in particular, is a well-known carcinogen.

These substances may also be formed by decomposition of the flavouring molecules.

The verdict

So are these molecules produced at dangerous concentrations in e-cigarettes? While use of e-cigarettes has been shown to lead to significantly lower levels of certain carcinogenic metabolites in the urine of their smokers, compared to the levels found in smokers of traditional cigarettes, they have been linked with of some particulates, including the metals cadmium, nickel, chromium, lead and zinc. These may have originated in the heating coil.

There is particular concern that the rapid growth in the use of e-cigarettes has not been accompanied by proper assessment of the risks accompanying their use, especially over the long term. While some reports have said that e-cigarettes are much safer than conventional cigarettes, one study has concluded that regular use of e-cigarettes by young people leads to them becoming heavier smokers of conventional cigarettes; another American study concluded that use of e-cigarettes by teenagers doubles the risk of coughs and bronchitis compared with non-smokers.

E-cigarettes are freely available in the UK, and US, but are banned or restricted in some countries, including Norway, Brazil, Singapore and Australia. A letter published in the British Medical Journal also warned: "Further basic science and epidemiological research is needed to increase our evidence base on the benefits and harms of vapour. Until then patients should not be misled into thinking that the likelihood of future harm is negligible when there is insufficient evidence to advocate this."

At present, then, the bottom line is that no one knows whether there are long-term risks associated with e-cigarettes. Caution is required.

Explore further: AMA calls for greater electronic cigarette regulation

Related Stories

AMA calls for greater electronic cigarette regulation

August 7, 2018
(HealthDay)—The American Medical Association (AMA) has adopted several policies to improve the regulation of tobacco products, including electronic cigarettes (e-cigarettes), according to an article published in the association's ...

New study finds that e-cigarettes increase cardiovascular risk as much as cigarettes

July 9, 2018
The usage of e-cigarettes containing nicotine has a significant impact on vascular functions claims new study. Research published in the SAGE journal, Vascular Medicine, has brought new research to light on the significant ...

FIRS: guidance offered for protecting youth from e-cigarettes

June 20, 2018
(HealthDay)—Youth should be protected from electronic cigarettes and other nicotine delivery devices, according to a position statement from the Forum of International Respiratory Societies published online May 31 in the ...

Ex-smokers might be better off with high rather than low nicotine e-cigs

June 7, 2018
Vapers using low rather than high nicotine e-cigarettes may be using their devices more intensely, potentially increasing the risk of exposure to toxins in the vapour, according to new research funded by Cancer Research UK ...

E-cigarettes safer than smoking, says long-term study

February 6, 2017
E-cigarettes are less toxic and safer to use compared to conventional cigarettes, according to research published in Annals of Internal Medicine today (Monday).

Smokers consume same amount of cigarettes regardless of nicotine levels

August 22, 2014
Cigarettes with very low levels of nicotine may reduce addiction without increasing exposure to toxic chemicals, according to a new study from the University of Waterloo.

Recommended for you

Removing sweets from checkouts linked to dramatic fall in unhealthy snack purchases

December 18, 2018
Policies aimed at removing sweets and crisps from checkouts could lead to a dramatic reduction to the amount of unhealthy food purchased to eat 'on the go' and a significant reduction in that purchased to take home, suggests ...

Junk food diet raises depression risk, researchers find

December 18, 2018
A diet of fast food, cakes and processed meat increases your risk of depression, according to researchers at Manchester Metropolitan University.

Children of problem drinkers more likely to marry someone with a drinking problem: study

December 18, 2018
Children of parents who have alcohol use disorder are more likely to get married under the age of 25, less likely to get married later in life, and more likely to marry a person who has alcohol use disorder themselves, according ...

A co-worker's rudeness can affect your sleep—and your partner's, study finds

December 14, 2018
Rudeness. Sarcastic comments. Demeaning language. Interrupting or talking over someone in a meeting. Workplace incivilities such as these are becoming increasingly common, and a new study from Portland State University and ...

Study shows magnesium optimizes vitamin D status

December 14, 2018
A randomized trial by Vanderbilt-Ingram Cancer Center researchers indicates that magnesium optimizes vitamin D status, raising it in people with deficient levels and lowering it in people with high levels.

A holiday gift to primary care doctors: Proof of their time crunch

December 14, 2018
The average primary care doctor needs to work six more hours a day than they already do, in order to make sure their patients get all the preventive and early-detection care they want and deserve, a new study finds.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.