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Scientific assessment of
tobacco heating technology

Why is it important to eliminate combustion?

Scientific researches show that the primary cause of smoking-related disease is the high levels of Harmful and Potentially Harmful Constituents in smoke formed during the combustion of tobacco.

We have conducted several studies to demonstrate the absence of combustion in tobacco heating system, including temperature measurements, experiments demonstrating the absence of net exothermic processes, and measurements of constituents that represent typical markers of combustion.*

Our studies also support that the aerosol emitted using tobacco heating system does not contain solid particles that are produced when tobacco is burned.**

In addition, since burning requires oxygen, we have tested tobacco heating system in an oxygen-free atmosphere. The results showed that oxygen does not play a major role in the thermochemical degradation or the aerosol formation. Combustion does not occur while heating tobacco.

Important information: This product is for use by adults and not risk free. Nicotine is addictive.
*Cozzani, V., et al. (2020). An experimental investigation into the operation of an electrically heated tobacco system. Thermochim Acta 684: 178475.
**Pratte, P., et al. (2017). Investigation of solid particles in the mainstream aerosol of the Tobacco Heating System THS2.2 and mainstream smoke of a 3R4F reference cigarette. Hum Exp Toxicol 36: 1115-1120.

Composition of aerosol emitted by heating tobacco

By eliminating combustion, the levels of harmful are on average 95% lower compared to those in cigarette smoke.*

Important information: It does not necessarily equal a 95% reduction in risk. IQOS is not risk-free. Heated tobacco products contain nicotine, which is addictive.

Do you want to find out why we can conclude this? Learn more about some of the key pieces of scientific evidence on IQOS.

*Average reductions in levels of a range of harmful chemicals (excluding nicotine) compared to the smoke of a reference cigarette (3R4F).

How is aerosol being tested?

We have been studying the chemical composition of a variety of aerosols for over a decade. Based on the guidelines and regulations of health authorities, such as the World Health Organisation*, U.S. Food and Drug Administration ** we have consolidated a list of 58 chemicals that are relevant to the analysis of cigarette smoke and smoke-free aerosols. The list contains constituents that may pose health risks to humans – which is why our products are specifically designed to reduce them at the lowest possible levels.

Through careful monitoring, we are able to determine whether we can effectively reach our aim of eliminating or substantially reducing these constituents. Besides targeting known constituents, we also perform analyses to identify constituents that may emerge via the evolution of our products.

*WHO Study Group on Tobacco Product Regulation Report on the Scientific Basis of Tobacco Product Regulation. WHO Technical Report Series, no. 951 ISBN: 978 92 4 120951 9 2008 on 01 January 2008.
**Federal register. Harmful and Potentially Harmful Constituents in Tobacco Products and Tobacco Smoke; Established List. A Notice by the Food and Drug Administration on 04/03/2012.

Comparing cigarette smoke and heated tobacco aerosol

We measured a number of harmful chemicals in the aerosol of heated tobacco and compared it to the levels found in the smoke of a standard reference cigarette (3R4F). On average, a 95% reduction in the levels of harmful and potentially harmful chemicals in heated tobacco aerosol was observed.*

In order to ensure that the use of new technologies does not introduce any new risk to adult smokers when compared to the use of cigarettes, we perform analyses to determine whether any new or unexpected chemical compounds are present in the aerosol. In addition to the quantitative analysis of 58 harmful and potentially harmful constituents, we also adopt a strategy for the comprehensive, non-targeted screening of Reduced Risk Product aerosols.

Important information: It does not necessarily equal a 95% reduction in risk. IQOS is not risk-free. Heated tobacco products contain nicotine, which is addictive.
* Average reductions in levels of a range of harmful chemicals (excluding nicotine) compared to the smoke of a reference cigarette (3R4F).
*Schaller, J. P., et al. (2016). Evaluation of the Tobacco Heating System 2.2. Part 2: Chemical composition, genotoxicity, cytotoxicity, and physical properties of the aerosol. Regul Toxicol Pharmacol 81 Suppl2: S27-S47. * Average reductions in levels of a range of harmful chemicals (excluding nicotine) compared to the smoke of a reference cigarette (3R4F).

Aerosol chemistry

The comprehensive chemical characterization of heated tobacco aerosol using untargeted analytical screening methods revealed that a total of 532 chemical constituents (including water, glycerin, and nicotine, which were measured using different methods) were present at concentrations ≥ 100 ng/heated tobacco unit.*

All compounds that were detected in aerosol ≥ 100 ng/heated tobacco unit were also found to be present in smoke from the standard reference cigarette 3R4F. Only a minority of compounds in heated tobacco aerosol were present at concentrations exceeding those measured in cigarette smoke.

To identify any potential new hazards presented by exposure to heated tobacco aerosol, untargeted differential screening was also performed, which only looked for chemicals that were significantly more concentrated in aerosol compared with cigarette smoke. The compounds that were found to be significantly higher in Platform 1 aerosol compared with cigarette smoke, including three compounds that were unique to aerosol (all with concentrations < 100 ng/ heated tobacco unit), were submitted for toxicological evaluation. Four compounds were subsequently highlighted to be of potential toxicological concern. The levels of these four compounds were very low and the U.S. Food and Drug Administration concluded that “Although some of the chemicals are genotoxic or cytotoxic, these chemicals are present in very low levels and potential effects are outweighed by the substantial decrease in the number and levels of HPHCs found in combusted cigarettes.”**

*Bentley, M. C., et al. (2020). Comprehensive chemical characterization of the aerosol generated by a heated tobacco product by untargeted screening. Anal Bioanal Chem 412:2675-2685. 20 U.S.
**Food and Drug Administration. Premarket Tobacco Product Marketing Order TPL (Technical Project Lead Review); PM0000424-79. 29 Apr 2019; Section 6 – Summary of Toxicological Findings: p42.

What is important to know about tar?

Tar is the weight of solid and liquid residue in cigarette smoke, after nicotine and water have been removed. So, is tar measurement useful? If we only take the weight into account, no it’s not.

According to World Health Organization, “Tar need not be measured, as it is not a sound basis for regulation, and the levels can be misleading.”* When people consider the risk of harm of a product in relation to tar it’s more important to look at the content of the residue rather than its weight.

When we look at the content of cigarette smoke, there are thousands of chemicals released and of those the U.S. Food and Drug Administration has listed 93 known toxicants. It is the presence of and exposure to these chemicals that plays a role in the development of smoking-related diseases, not the tar measurement.

Heated tobacco does not produce tar because tobacco heating system heats tobacco, instead of burning it. Heated tobacco generates an aerosol residue that is fundamentally different from “Tar” and consists of significantly lower levels of harmful chemicals.**

Important information: Although IQOS does not produce tar, IQOS is not risk free. Heated tobacco products contain nicotine, which is addictive.
*World Health Organization (2015). WHO study group on tobacco product regulation: Report on the scientific basis of tobacco product regulation: Fifth report of a WHO study group. WHO Technical Report Series, no. 989.
** Average reductions in levels of a range of harmful chemicals (excluding nicotine) compared to cigarette smoke.

Aerosol effect on indoor air quality

In accordance with international recommendations and ISO standard, a specific study was done targeted to investigate what effect aerosol has on indoor air quality. The data showed that heating tobacco in an indoor environment, where regulatory norms of adequate ventilation are respected, has significantly less effect on indoor air quality than cigarette smoke.

At the research and development centre Cube, a room dedicated specifically to perform Indoor Air Quality tests under various conditions was installed. It is a fully furnished office with the ability to host a group of people of the size required by the simulated setting. The ventilation in the room can be adjusted to simulate different environments, such as homes, offices and restaurants. It is equipped with several tools that allow tracking and measuring of the compounds in the air.

We compared IAQ data after using tobacco heating system and cigarettes to the levels of compounds measured in the background air. We measured 24 compounds including carbonyls, tobacco-specific nitrosamines, and volatile organic compounds under simulated residential conditions. When using tobacco heating system, the levels of 21 of these compounds did not increase beyond the levels already present as background in our dedicated Indoor Air Quality room. Only the nicotine, acetaldehyde and glycerin were measurably higher than the background, although well below the exposure limits established in air quality guidelines.*

Important information: This product is for use by adults and not risk free. Nicotine is addictive.
*Mitova, M. I., et al. (2016). Comparison of the impact of the Tobacco Heating System 2.2 and a cigarette on indoor air quality. Regul Toxicol Pharmacol 80: 91-101; Mitova, M. I., et al. (2019). Air quality assessment of the Tobacco Heating System 2.2 under simulated residential conditions. Air Qual Atmos Health 12(7): 807-823; Nordlund, M., et al. (2019). Scientific substantiation of the absence of Environmental Tobacco Smoke (ETS) emission during use of the Electrically Heated Tobacco System (EHTS). Version 1.0, available on

Aerosol effect on teeth staining

Aerosol, emitted by using heated tobacco products, leaves significantly less stains on teeth than cigarettes.

Teeth that had cavities filled with dental resins were exposed to cigarette smoke or aerosol for four days a week, followed by brushing and incubation. After three weeks of such exposure, color match, marginal discoloration, marginal integrity, and surface texture of the restoration were assessed according to a modified U.S. Public Health Service criterion.

Marked discoloration of enamel and dentin was observed following 3 weeks of cigarette smoke exposure, and color mismatch occurred between the composite resin restorations and dental hard tissues. Discoloration was minimal in the enamel, dentin, and composite resin restorations in the aerosol group, and no color mismatch was observed after 3 weeks of heated tobacco aerosol exposure.*

Important information: If teeth are already stained, switching to IQOS will not reverse the color of those stains.

Please, find our verification programs here:

*Zanetti, F., et al. (2019). Effects of cigarette smoke and tobacco heating aerosol on color stability of dental enamel, dentin, and composite resin restorations. Quintessence Int 50(2): 156-166.

Find out more about independent studies and reviews

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