Heated tobacco products – are they less harmful than cigarettes?

In the past few years, there has been a noticeable increase in the popularity and use of tobacco heating devices (i.e. heat-not-burn tobacco products or heated tobacco products, often abbreviated in literature as HTP). These are electronic devices that, according to the manufacturer, heat tobacco instead of causing it to burn, thus providing the user with an aerosol that contains fewer toxicants than regular cigarette smoke. Is this claim true, and how does the harm of heated tobacco smoke compare to burning tobacco smoke?

 

How do they work?

Although the idea of ​​”delivering” nicotine from tobacco while limiting the amount of carbon monoxide and tar going alongside it is quite old, these types of heating devices have only appeared on the market in the middle of the last decade. While lighting regular cigarettes usually results in temperatures above 600 °C, heating tobacco in these devices reaches temperatures around 350 °C. They should be distinguished from electronic cigarettes (colloquially vapes), which do not deliver nicotine from tobacco, but evaporate nicotine suspended in humectants.

There are several devices on the market; IQOS, glo, iFuse, and Ploom Tech to name a few. They include a charger, holder and inserts. The tobacco insert is heated in the holder via an electronically controlled heating element. According to data from 2021, in the European Union, 6.5% of people used to use heated tobacco products, 1.3% still use them currently, and 0.7% use them on a daily basis. Each of these percentages is on the rise, and the most common reasons for usage cited by respondents are the perception that heated tobacco products are less harmful than cigarettes (37.5%), the fact that they are used by friends (28.4%), and the desire to reduce or stop smoking (28.2%).

 

Comparison with cigarettes

In general, it is important to know that there is not much scientific literature that has investigated the health consequences and impact of heated tobacco products (HTPs), whether in the short or long term. Also, most papers on HTPs have been published or funded by the tobacco industry, which suggests the need for more independent studies.

More than 7,000 chemicals have been identified in regular cigarette smoke, of which approximately 100-250, depending on the source, are listed as harmful or potentially harmful substances. Polycyclic aromatic hydrocarbons (e.g. benzopyrene), nitrosamines (NNK, NNN), aldehydes (acrolein, formaldehyde), carbon monoxide, hydrogen cyanide, nitrogen oxides, benzene, toluene, phenols, aromatic amines, and radioactive isotopes are particularly important toxicologically. Tobacco use is the world’s leading cause of preventable death. Smoking is a major risk factor for pneumonia, heart attack, stroke, chronic obstructive pulmonary disease (COPD), lung cancer, throat and mouth cancer, bladder cancer, pancreatic cancer, and hypertension and peripheral arterial disease, among others.

Taking everything into account, studies (including independent and manufacturer-related ones) have come to several conclusions. Aerosol HTPs, compared to cigarette smoke, have less nicotine (20-80% as that of cigarettes, depending on the manufacturer). In terms of suppressing the need to smoke, HTPs reduced the urge as much as cigarettes, but respondents in turn increased the number of used tobacco inserts (more than those in the group that smoked cigarettes). Respondents also reported that the use of heated tobacco products was less satisfying and rewarding compared to the use of cigarettes.

 

Study problems

Several studies have shown a significant reduction in exposure to carbon monoxide, tar and other harmful and potentially harmful substances in tobacco smoke. However, there are some limitations regarding the interpretation of this data as definitive evidence that heated tobacco products are less harmful than cigarettes.

Firstly, these are mostly studies funded by the tobacco industry. This makes impartiality in data collection, analysis and interpretation a possible occurrence. Several researchers working on research on tobacco-heated tobacco products in the media pointed out the shortcomings and questionable quality of the studies conducted. For example, data in studies supporting manufacturers’ positive claims about HTPs typically analyse only 40 of the 93 substances that the FDA classifies as harmful or potentially harmful. A large number of these substances, which were omitted from the data provided by the manufacturer, were found to be present in higher concentrations in smoke from HTPs than from cigarettes. Such substances, with significant toxicities, are α, β-unsaturated carbonyl compounds (2-cyclopentene-1,4-dione), 1,2-dicarbonyl compounds (1,2-cyclohexanedione), furans and epoxides.

Also, it is not solely the burning of the tobacco that makes it dangerous and carcinogenic. During the heating process, pyrolytic processes take place, which can also result in the production of carcinogenic substances, even different from those that occur during ‘classic’ smoking. It is necessary to identify and determine in detail such substances, which may also originate from additives not found in ordinary cigarettes. One analysis of data from clinical studies conducted by the manufacturer showed hepatotoxic effects of switching to HTPs, an effect not typically seen with regular cigarettes.

 

Short and long term effects

And even if a heated tobacco product does produce fewer toxicants, it is possible that the difference is not biologically significant. The acute effect of HTP use is similar and comparable to the acute effect of cigarette use. According to one U.S. cohort study, only one in 24 monitored biomarkers showed improvement. There are no significant differences in heart rate, blood pressure, and oxidative stress when comparing HTP users and cigarette users. Vascular endothelial function is also approximately equally impaired. People who replace cigarettes with HTPs do not show an improvement in lung function or inflammatory processes in the lungs. In terms of long-term effects, independent analyses of industrial data from clinical trials have found that HTPs do not reduce the risk of cardiovascular disease or chronic obstructive pulmonary disease (COPD).

It is also important to keep in mind that the target market for heated tobacco products is not only pre-existing smokers, but also non-smokers, especially young people. In Italy, for example, 45% of HTP smokers have not smoked cigarettes before. It is worth noting that health organisations around the world, including the WHO, FDA, CDC and EMA, point out that more research is needed to understand the short and long term effects of heated tobacco products, and that it has not been found to help smokers quit, that use of any tobacco product is harmful and that people who have never used tobacco products should never start smoking. After all, nicotine itself is highly addictive and can harm the adolescent brain and foetus during pregnancy. Some countries, such as Finland, Australia and Singapore, have banned heated tobacco products.

The key next step is to conduct and analyse a large number of independent studies. Until then, it is important to know that there is not enough scientific data, and the existing data is not enough to conclude that heated tobacco products are safe or in some ways safer than cigarettes.

 

Translation by Vanda Petrak