Vaping and e-cigarettes: What the research says

12 Oct 2019

Image: © eldarnurkovic/

An increasing number of countries are banning e-cigarettes. Queen’s University Belfast’s Prof Lorraine Martin and Dr James Reihill explain why.

A version of this article was originally published by The Conversation (CC BY-ND 4.0)

The White House recently announced plans to ban flavoured e-cigarettes – except for tobacco-flavoured products – because of a rise in the number of middle and high-school students using these products. A few days later, India’s cabinet approved an emergency order banning the production, import and sale of e-cigarettes.

To date, many countries (mostly in South America, the Middle East and south-east Asia), have banned or restricted the sale of e-cigarette products. Some countries have also banned possession of these products. Thailand has the strictest laws, while countries such as Australia, Canada and Norway have introduced tight restrictions.

Research suggests that e-cigarettes may help smokers quit regular cigarettes, benefiting their long-term health. But young people who have never smoked traditional cigarettes are taking up e-cigarettes, which are available in more 1,500 flavours including bubble gum and candy floss.

In a 2015 survey of US youths aged 12 to 17, 81pc of e-cigarette users reported that the first product they ever used was flavoured and that they use e-cigarettes because “they come in flavours I like”.

According to the US Centers for Disease Control and Prevention (CDC) more than 3.6m children in the US use e-cigarettes, with a jump from 11.7pc to 20.8pc of US high-school students reporting e-cigarette use from 2017 to 2018. In the UK, 1.6pc of those aged 11 to 18 now use e-cigarettes more than once a week, compared with 0.5pc in 2015.

Because of the highly addictive nature of nicotine, there is a risk that young e-cigarette users might switch to using traditional cigarettes. Indeed, some healthcare professionals refer to e-cigarettes as a ‘gateway drug.

Research into vaping risks

E-cigarettes create an aerosol by heating a complex solution of chemicals comprising oils, flavouring and nicotine. The fine particles released in the vapour are similar in size and concentration to tobacco smoke and so can reach deep into the lungs. Several of these chemicals are toxic to cells, but what makes research into their safety difficult is that each product is very different, with the final composition of chemicals being determined by the temperature at which the vaping device heats them.

Researchers have found that vaping irritates and inflames the airways, leading to the production of a greater amount of mucus and an increase in tissue-degrading enzymes called proteases. High levels of proteases can destroy sensitive lung tissue and reduce the ability of our lungs to function.

The resulting damage to the lungs is irreversible and over time can lead to severe lung conditions including emphysema, which is commonly found in chronic obstructive pulmonary disease (COPD). For those who already have a chronic lung disease such as COPD or asthma, vaping has been linked to an increase in the severity of symptoms.

Another study found that proteases are stimulated by e-cigarette vapour. The vapour was prepared from different e-cigarette brands and then used to treat isolated white blood cells in the lab. Levels of the enzymes were found to be similar, or more, when the cells were exposed to an extract prepared from cigarette smoke. The increase in enzyme levels was also found with nicotine-free e-cigarette products, suggesting that other components in the e-cigarette vapour were responsible.

A recent US study, published in the American Journal of Respiratory and Critical Care Medicine, investigated the effect of chronic e-cigarette use on markers of lung injury in the airways of vapers. Proteases linked to tissue damage were increased in both smokers and vapers, compared with non-smokers.

‘The evidence to date suggests that vaping is not a safe alternative to smoking tobacco. This, coupled with the worrying trend of young people being attracted to vaping, raises fears of another generation suffering from chronic lung disease’

The problem with investigating the potential harm of vaping is that there is such a vast array of products, devices and flavourings that it’s impossible to create a ‘standardised exposure’. Individual e-cigarette products are reported to have over six flavouring chemicals with the sweetest flavours having a significantly higher number of compounds.

Tests of 166 e-cigarette products showed that one in five (21pc) contains flavouring chemicals that can be toxic to the airways (benzyl alcohol, benzaldehyde, vanillin). Several other toxic chemicals were also found and measurable levels of tobacco-specific nitrosamines (TSNAs, an important group of carcinogens in tobacco products) were in 70pc of the products tested. The effect of inhaling these complex mixtures of chemicals are very difficult to determine.

Is it safe?

Recent reports of deaths in the US associated with vaping have further fanned concerns on safety.

The CDC has reported a rising number of cases (530 across 38 states) of a mysterious lipoid pneumonia associated with fats (lipids) in aerosols generated by e-cigarettes, which has been linked to eight deaths. It is worth noting that some who have developed lipoid pneumonia admitted that they vape THC (the active ingredient in cannabis), although others have insisted that they only used nicotine products with their e-cigarettes.

One substance called vitamin E acetate has been identified in all the samples tested by New York state health officials, but there isn’t enough evidence to say if this is the cause of disease. And, so far, no cases of lipoid pneumonia have been reported outside the US.

The evidence to date suggests that vaping is not a safe alternative to smoking tobacco. This, coupled with the worrying trend of young, previous non-smokers being attracted to vaping, raises fears of yet another generation suffering from chronic lung disease.

Indeed, a recent study in The Lancet estimates that, in 2040, COPD will be the only disease in the top 10 leading causes of death that will still be increasing. How much of that will be driven by vaping remains to be seen.

The Conversation

By Prof Lorraine Martin and Dr James Reihill

Lorraine Martin is a professor of biomolecular sciences in the School of Pharmacy at Queen’s University Belfast. Her research is focused on chronic airways diseases, with a particular focus on cystic fibrosis and COPD. Dr James Reihill is a senior research fellow in the School of Pharmacy with more than 10 years’ experience in chronic lung disease research.