BY MARIA BURKE | IMAGE: SHUTTERSTOCK
Irish researchers have used artificial intelligence to help identify multiple potentially harmful chemicals used in vaping devices.
With growing numbers of teenagers and younger children using vapes, they say there is a real risk of a new wave of vaping-induced chronic diseases emerging in 15 to 20 years.
Originally, the constituents of ‘e-liquids’ contained only nicotine, propane-1,2-diol, propane-1,2,3-triol and water. However, at least 180 chemicals are now known to be blended in various amounts to produce specific flavours, with some liquids containing up to 50 different chemicals.
Primarily derived from the food industry where they have a good safety record for specific uses, these chemicals were never intended to be heated to high temperatures or inhaled. The vape rapidly heats organic molecules, allowing the user to breathe in the thermal decomposition products of a pyrolysis reaction. Mapping all possible products, which are influenced by variations in e-liquids, devices and usage, is a daunting task.
As hundreds of chemicals are used in tens of thousands of e-liquid products, experimental analysis could take decades. In this study, a team from the Royal College of Surgeons Ireland’s Department of Chemistry combined artificial intelligence with previously published data to simultaneously predict what would happen to 180 known flavourings when heated in a vaping device. These included esters, ketones/aldehydes, alcohols/acetals, aromatics/heterocycles/carbocycles and carboxylic acids/amides.
The analysis revealed that pyrolytic decomposition would produce 127 ‘acute toxic’ chemicals, 153 ‘health hazards’ and 225 ‘irritants’. Significantly, these included volatile carbonyls (VCs), which were predicted to originate from the most popular fruit, candy and dessert-flavoured products (Scientific Reports, DOI: 10.1038/s41598-024-59619-x). VCs, such as formaldehyde, acetaldehyde and propionaldehyde, have known health risks.
‘We wanted to understand, before it’s too late, the likely impact flavoured vapes are having on the health of the growing number of vapers,’ says lead author Donal O’Shea.
‘Our findings indicate a significantly different profile of chemical hazards compared to what we are familiar with from traditional tobacco smoking. It is plausible that we are on the cusp of a new wave of chronic diseases that will emerge 15 to 20 years from now due to these exposures. We hope this research will help people make more informed choices and contribute to the conversation on the potential long-term health risks and the regulation of vaping, which this research suggests should be comprehensive.’
‘There is very little good quality evidence [on] these flavourings, so I welcome the novel strategies employed [here],’ says Jacob George, professor of cardiovascular medicine and therapeutics at the University of Dundee, UK. ‘Making sense of their effects will require a combination of techniques including automated mapping algorithms and creation of neural networks such as this.’
‘While [this study] cannot give us definitive answers to the risks of flavoured vapes on human health, it may be a helpful early step to identify signals that could lead to more in-depth research into heat-induced breakdown of chemicals used in flavourings.’
Other studies have also found significant health concerns related to e-liquids. For example, a US team in April 2024 confirmed previous work that found 200 vapers aged between 13 and 17 had biomarkers of exposure to cadmium, lead and uranium in their urine (Tobacco Control, DOI: 10.1136/tc-2023-058554). They reported that both intermittent and frequent users had higher lead levels than occasional users. Frequent users also had higher uranium levels compared with occasional users. Those who used sweet flavours had higher uranium levels compared with menthol/mint users.
‘This well-conducted study underscores the need to carefully monitor exposure in e-cigarette users and highlights the fact that e-cigarettes are not risk-free, and therefore should not be used by people who have never smoked, particularly adolescents,’ says Lion Shahab, co-director of the Tobacco and Alcohol Research Group at University College London.
‘However, these findings also need to be seen in context. Uranium has many different important sources of exposure (including food and water), which were not controlled for here. In addition, no control group was included in the analysis. This study therefore cannot tell us anything about absolute increase in exposure to heavy metals, only about relative exposure among less and more frequent e-cigarette users. Given that heavy metal exposure is mostly driven by the type of device used, future studies should investigate whether there are any meaningful differences between different e-cigarette types to inform regulators.’
Lastly, Shahab points out that it is difficult to translate these results into clinically meaningful effects. ‘However, we know that e-cigarettes expose users to much lower levels of harmful substances than cigarettes but to higher levels than fresh air, so the best advice remains: if you smoke, vaping is much safer; if you don’t smoke, don’t vape.’
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