Almost 20 years have passed: a view of heated tobacco and vape

Abstract

Introduction

The electronic cigarette (e-cig), introduced on the market in 2003, was a device designed for the intake of nicotine without burning tobacco. Its evolution over the last two decades has led to the creation of a vast range of models with increasingly sophisticated designs. The operating principle is based on the heating of a liquid, commonly called e-liquid, composed of a mixture of glycerol, vegetable glycerine, flavourings, and nicotine at different concentrations.

Furthermore, since 2014, we have witnessed the emergence of the so-called heated tobacco products (HTPs), a new category of electronic devices that use an alternative method of tobacco consumption. In these devices, tobacco is brought to temperatures below the combustion point, around 350°C, using a platinum and ceramic heating sheet, generating an aerosol different from that produced by e-cigs.

The substances contained

The spread of e-cigs and HTPs, presented as a less harmful alternative to traditional cigarettes, has required in-depth studies to demonstrate the real benefits or possible risks associated with their use. A study by Ruprecht et al.¹ showed that these devices produce numerous toxic substances, such as heavy metals, organic compounds, and aldehydes. Particularly worrying is the presence of formaldehyde (a group 1-IARC carcinogen), whose high presence in emissions should lead to a review of the regulations on the consumption of these devices in public environments and, in particular in the presence of more sensitive subjects, such as minors and pregnant women.¹ In a subsequent study, further analyses were carried out to characterize the substances present in the emissions of e-cigs and HTPs. The analysis of the ‘cold smoke’ produced by HTPs indicated that the emission of organic matter particulate matter from these devices is significantly different depending on the compound analyzed. While polycyclic aromatic hydrocarbons were mostly undetectable in HTP smoke, some alkanes and organic acids, as well as black carbon, were emitted at substantial levels. Heavy metal emissions were reduced in cold smoke compared with both e-cigs and conventional cigarettes. Finally, carcinogenic aldehyde compounds, including formaldehyde, acetaldehyde, and acrolein, were detected in emissions from HTPs, although the levels were substantially lower than in conventional cigarettes.²  Table 1 shows a comparison of substances emitted by the consumption of traditional cigarettes, HTPs, and e-cigs according to studies conducted by the Tobacco Control Unit of the Fondazione IRCCS Istituto Nazionale dei Tumori in Milan.

Are electronic devices a valid aid to quitting smoking?

The existing scientific literature presents conflicting results on the effectiveness of e-cigs as an aid to smoking cessation, not allowing definitive conclusions to be drawn.

A study whose results were published in the journal Tobacco Control¹ shows, for example, how these electronic devices are ineffective as a valid support in quitting smoking, and not only that: the data would demonstrate that they increase the probability of starting to use traditional cigarettes or of relapsing into the habit of smoking if one had managed to quit. Focusing on those who had never smoked traditional cigarettes, the researchers observed that those who, in the first interview, declared that they used e-cigs or HTPs, were more likely, in the second interview, to have started smoking traditional cigarettes. The risk turned out to be very high: nine and six times higher, respectively, compared with those who did not use e-cigs or HTPs. Among ex-smokers, those who used e-cigs or HTPs at the start of the study were four and three times more likely to have started smoking traditional cigarettes again than those who did not use these products.

Are e-cigarettes and heated tobacco products harmless?

The original purpose of e-cigs was to offer an alternative to traditional cigarettes, limiting the damage that they cause to health and helping smokers in the transition phase that leads them to become ex-smokers. Unfortunately, numerous studies are demonstrating that a qualitative and quantitative reduction of the substances contained in e-cig vapour does not necessarily result in a reduction in damage to health.

One of the first studies relating to the damage caused by the use of e-cigs was published in the New England Journal of Medicine.² This 2020 study talked about a real epidemic characterized by chemically induced acute lung injury renamed EVALI (E-cigarette, or Vaping, product use Associated Lung Injury). This harm was particularly associated with young users of e-cigs containing THC liquids.

At the respiratory level, it has been shown that the use of an electronic cigarette for a short period of 5 min can cause an increase in peripheral airway flow resistance and a decrease in FeNO among healthy smokers. The researchers comment on their data by arguing that the FDA, as well as other international regulatory bodies, should pursue the regulation of e-cigs until manufacturers provide scientific evidence to support their claims about the risks associated with their use.¹

The results of a major study that analysed epigenetic changes associated with tobacco and electronic cigarette use in over 3500 buccal/salivary and blood samples were recently published in the authoritative journal Cancer Research.² Comparing traditional cigarette smokers with those who had never smoked or used e-cigs, epigenetic changes associated with the development of cancer were observed among subjects who smoked traditional cigarettes; however, these same epigenetic changes were also found to be present in users of e-cigs, despite having never smoked traditional cigarettes.

In terms of cardiotoxicity, two Californian studies, one on murine models and the other on humans, have shown how the dual use of cigarettes and e-cigs could increase the negative effects at the endothelial level. The first study shows that there is no single constituent or class of constituents responsible for the acute impairment of endothelial function due to smoking; rather, the researchers propose that acute endothelial dysfunction due to different inhaled products is caused by stimulation of the vagus nerve due to generalized irritation of the airways.³ The second study showed how both the chronic use of e-cigs and tobacco smoke cause changes at the blood level that inhibit the release of endothelial NO. Vaping also causes changes in the blood that increase microvascular endothelial permeability with an impact on the intracellular oxidative state.⁴

In a very recent article⁵ analyzing the results of a case-control study of 4975 lung cancer cases and 27 294 healthy controls, American researchers found that the risk of developing lung cancer among those who combined vaping with cigarette smoking was four times higher than those who smoked traditional cigarettes exclusively. The results suggest that the addition of vaping to cigarette smoking may somehow accelerate and favour the risk of lung cancer.

Miech et al.⁶ analysed trends in e-cig use among young people. According to their analysis, the prevalence of e-cig use among adolescents had more than doubled from 2017 to 2019, with levels of daily vaping suggesting an already consolidated nicotine addiction. The researchers emphasize that efforts by government agencies and institutions have so far proven insufficient to stop the rapid spread of vaping among very young people. Therefore, further efforts are needed to protect young people from nicotine use during adolescence, when the developing brain is particularly susceptible to permanent changes resulting from this substance.

Finally, regarding HTPs, an article published in the European Respiratory Journal² shows how the IQOS product has the potential to increase oxidative stress and inflammatory status, to cause airway remodelling, and to initiate EMT-related changes in the respiratory tract of users.

In the literature, most studies focus on short-term effects, thus limiting knowledge on the damage caused by the consumption of these electronic devices and thus posing a major limitation.^7–12 We will be able to quantify the association between the use of e-cigs and HTPs and the risk of incidence and mortality for the main chronic diseases, including cancer, only when we have longitudinal data from large prospective cohorts with long follow-up periods.

Funding

No funding provided.

Data availability

No new data were generated or analysed in support of this research.

Disclaimer

This paper was originally published in the Italian language as ‘Sono passati quasi vent'anni: il punto su tabacco riscaldato e vape’, in the Volume degli Atti del Congresso “Conoscere e Cuare il Cuore 2025”, published by Centro per la Lotta contro l'Infarto for distribution at the CCC Conference. This paper was translated by Dr. Mario Albertucci, representative of the CLI Foundation, and republished with permission.

References

Author notes