Most studies to date on the health effects of heated tobacco products have been funded by the manufacturers of the products. Manufacturers researching their own or competitor products experience a conflict of interest that can bias findings and interpretations.1 Industry-funded studies on heated tobacco products generally conclude that compared with cigarettes, heated tobacco products expose users and bystanders to substantially lower levels of particulate matter and harmful and potentially harmful compounds.2-10 Whether reduced exposure will lead to meaningful reductions in human health risks is yet to be established.11
Several independent studies find that the vapour from heated tobacco products contains toxic compounds including carcinogens, although some of these are at a markedly reduced level in relation to smoke emitted from conventional cigarettes.12-17 In the US, the Food and Drug Administration (FDA) supported earlier findings of the presence of harmful and potentially harmful compounds (HPHC) in the vapour of heated tobacco products, albeit at significantly lower levels than that found in the smoke of the conventional cigarettes.18 The FDA found that the iQOS vapour contains several probable or possible carcinogenic chemicals that are unique to iQOS or present in higher levels than conventional cigarette smoke. The aerosols also contain 15 other chemicals that are possibly genotoxic and 20 more compounds that have potential health effects. However, in its recent authorisation of the sale of iQOS in the US, the FDA concluded that because the products produce fewer or lower levels of some toxins than combustible cigarettes, their introduction to the market is appropriate from a public health perspective.19 This decision has been criticised by public health groups, who note that the presence of these toxic compounds likely pose significant health risks.20
There is evidence that heated tobacco product vapour contains levels of nicotine approaching those found in cigarette smoke. Exposure to nicotine can be particularly harmful to certain populations, including adolescents and pregnant women.21 The device’s limitations may also affect users’ levels of exposure: a study of iQOS users found that they speed up their ‘puff rate’ in order to inhale more nicotine because the heat stick only lasts for six minutes, potentially increasing their intake of nicotine and other harmful chemicals.15
Some independent studies demonstrate that the use of iQOS impacts lung health. One study reviewed the data on pulmonary and immune toxicities associated with IQOS from PMI’s MRTP application to the US FDA, to assess PMI’s reduced harm claims.22 Researchers found no evidence of improvement in pulmonary inflammation or pulmonary function in cigarette smokers who switched to IQOS. These researchers concluded that IQOS use was associated with significant pulmonary and immunomodulatory toxicities with no detectable differences between conventional cigarette smokers and those who were switched to IQOS in PMI’s studies.
Another study evaluated and compared the biological effects of exposure to total particulate matter (TPM) from the aerosol of a candidate modified-risk tobacco product (cMRTP) on the lungs, in comparison with exposure to TPM from conventional cigarettes.23 Endpoints linked to lung carcinogenesis were assessed following a twelve-week period. The study findings demonstrated that exposure to TPM from the cMRTP did have a biological impact on lung cells but that this impact was lower than that of exposure to TPM from the conventional cigarette.
Two independent studies examined the effects of inhaling emissions from heated tobacco products in comparison with electronic and conventional cigarettes. 24, 25 In the first study, 23 researchers analysed and compared carbonyl emissions from PMI’s IQOS, (both regular and menthol variants), the Nautilis Mini e-cigarette , and a Marlboro Red cigarette. The IQOS emitted substantially lower levels of carbonyls than a regular cigarette (Marlboro Red) but higher levels than a Nautilus Mini e-cigarette. In the second study, 24 researchers used limited cytotoxic measures and found that the heated tobacco product showed reduced cytotoxicity relative to the conventional cigarette but higher toxicity than an e-cigarette.
Early independent research suggests that heat-not-burn tobacco products may exert a lower impact on oral health than conventional cigarettes. A group of researchers used a systems toxicology assessment framework to compare the effects of exposure to heat not burn aerosol on oral cavity tissue with that of conventional cigarette smoke.26 The findings demonstrated an absence of cytotoxicity, reduction in pathophysiological alterations, toxicological marker proteins, and inflammatory mediators following exposure to the heated tobacco product aerosol compared with the conventional cigarette. Another study27 suggests that the vapour from heat-not-burn tobacco products have less impact on tooth discolouration compared to conventional cigarette smoke. Two groups of teeth, both comprising composite resin restorations and dental hard tissue, were exposed to either conventional smoke or aerosol from tobacco heated products over three weeks. At the end of the study period, the group of teeth exposed to the conventional cigarette smoke had colour mismatch between the composite resin restorations and dental hard tissues. The group of teeth exposed to the heated tobacco product vapour had minimum discolouration in the enamel, dentin, and composite resin restorations exposed to the heated tobacco product. Further, no colour mismatch was observed between the composite resin restorations and the dental tissue of that group.
In terms of bystanders, an independent study concluded that despite emissions being lower than from combustible cigarettes, exposure to submicronic particles when heated tobacco products are used indoors does occur, and it is likely that a high proportion of the inhaled particles reach the alveolar region.28 A study in Japan found that more than one-third (37%) of participants who had been exposed to others’ heated tobacco aerosol, had reported at least one symptom because of it.29 Limited evidence comparing environmental emissions from heated tobacco products with those from e-cigarettes suggests that exposure from heated tobacco products poses a greater health risk.14, 30
Additional independent studies are needed to understand the health risks of heat-not-burn tobacco products and to assess industry claims of reduced risk/harm.11
Relevant news and research
For recent news items and research on this topic, click here. ( Last updated November 2022)
1. World Health Organization, Tobacco industry interference with tobacco control. Geneva: WHO; 2009. Available from: http://www.who.int/tobacco/publications/industry/interference/en/.
2. Haziza C, de La Bourdonnaye G, Merlet S, Benzimra M, Ancerewicz J, et al. Assessment of the reduction in levels of exposure to harmful and potentially harmful constituents in Japanese subjects using a novel tobacco heating system compared with conventional cigarettes and smoking abstinence: A randomized controlled study in confinement. Regulatory Toxicology and Pharmacology, 2016; 81:489–99. Available from: http://www.ncbi.nlm.nih.gov/pubmed/27693654
3. Haziza C, de La Bourdonnaye G, Skiada D, Ancerewicz J, Baker G, et al. Evaluation of the tobacco heating system 2.2. Part 8: 5-day randomized reduced exposure clinical study in poland. Regulatory Toxicology and Pharmacology, 2016. Available from: https://www.ncbi.nlm.nih.gov/pubmed/27816672
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8. No authors listed. Clinical study reveals smokers who switch to glo had significantly reduced exposure to toxicants. British American Tobacco, 2018. Available from: http://bat-science.com/groupms/sites/BAT_9GVJXS.nsf/vwPagesWebLive/DOAW6FS2?opendocument
9. Haswell LE, Corke S, Verrastro I, Baxter A, Banerjee A, et al. In vitro rna-seq-based toxicogenomics assessment shows reduced biological effect of tobacco heating products when compared to cigarette smoke. Scientific Reports, 2018; 8(1):1145. Available from: https://www.ncbi.nlm.nih.gov/pubmed/29402904
10. Gale N, McEwan M, Eldridge AC, Fearon IM, Sherwood N, et al. Changes in biomarkers of exposure on switching from a conventional cigarette to tobacco heating products: A randomized, controlled study in healthy Japanese subjects. Nicotine & Tobacco Research, 2018. Available from: https://www.ncbi.nlm.nih.gov/pubmed/29912406
11. World Health Organization. Heated tobacco products information sheet. 2017. Available from: http://www.who.int/tobacco/publications/prod_regulation/heated-tobacco-products/en/
12. Bekki K, Inaba Y, Uchiyama S, and Kunugita N. Comparison of chemicals in mainstream smoke in heat-not-burn tobacco and combustion cigarettes. Journal of UOEH, 2017; 39(3):201–7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/28904270
13. Auer R, Concha-Lozano N, Jacot-Sadowski I, Cornuz J, and Berthet A. Heat-not-burn tobacco cigarettes: Smoke by any other name. JAMA Internal Medicine, 2017; 177(7):1050–2. Available from: https://www.ncbi.nlm.nih.gov/pubmed/28531246
14. Ruprecht AA, De Marco C, Saffari A, Pozzi P, Mazza R, et al. Environmental pollution and emission factors of electronic cigarettes, heat-not-burn tobacco products, and conventional cigarettes. Aerosol Science and Technology, 2017; 51(6):674–84. Available from: https://doi.org/10.1080/02786826.2017.1300231
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16. Salman R, Talih S, El-Hage R, Haddad C, Karaoghlanian N, et al. Free-base and total nicotine, reactive oxygen species, and carbonyl emissions from IQOS, a heated tobacco product. Nicotine & Tobacco Research, 2018. Available from: https://www.ncbi.nlm.nih.gov/pubmed/30476301
17. Mallock N, Boss L, Burk R, Danziger M, Welsch T, et al. Levels of selected analytes in the emissions of "heat not burn" tobacco products that are relevant to assess human health risks. Arch Toxicol, 2018; 92(6):2145–9. Available from: https://www.ncbi.nlm.nih.gov/pubmed/29730817
18. Food and Drug Administration (FDA). 2019 premarket tobacco product marketing orders. 2019. Available from: https://www.fda.gov/tobacco-products/premarket-tobacco-product-applications/premarket-tobacco-product-marketing-orders.
19. Food and Drug Administration (FDA). FDA permits sale of IQOS tobacco heating system through premarket tobacco product application pathway. 2019. Available from: https://www.fda.gov/news-events/press-announcements/fda-permits-sale-iqos-tobacco-heating-system-through-premarket-tobacco-product-application-pathway.
20. Kaplan S. F.D.A. Permits the sale of IQOS, a new tobacco device. NY Times, 2019. Available from: https://www.nytimes.com/2019/04/30/health/iqos-tobacco-device-fda.html
21. US Department of Health and Human Services. E-cigarette use among youth and young adults. A report of the surgeon general. Atlanta, GA: US Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2016. Available from: https://www.cdc.gov/tobacco/data_statistics/sgr/e-cigarettes/index.htm.
22. Moazed F, Chun L, Matthay MA, Calfee CS, and Gotts J. Assessment of industry data on pulmonary and immunosuppressive effects of IQOS. Tobacco Control, 2018; 27(Suppl 1):s20–s5. Available from: https://www.ncbi.nlm.nih.gov/pubmed/30158203
23. van der Toorn M, Sewer A, Marescotti D, Johne S, Baumer K, et al. The biological effects of long-term exposure of human bronchial epithelial cells to total particulate matter from a candidate modified-risk tobacco product. Toxicol In Vitro, 2018; 50:95–108. Available from: https://www.ncbi.nlm.nih.gov/pubmed/29524472
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26. Zanetti F, Sewer A, Scotti E, Titz B, Schlage WK, et al. Assessment of the impact of aerosol from a potential modified risk tobacco product compared with cigarette smoke on human organotypic oral epithelial cultures under different exposure regimens. Food Chem Toxicol, 2018; 115:148–69. Available from: https://www.ncbi.nlm.nih.gov/pubmed/29505817
27. Zanetti F, Zhao X, Pan J, Peitsch MC, Hoeng J, et al. Effects of cigarette smoke and tobacco heating aerosol on color stability of dental enamel, dentin, and composite resin restorations. Quintessence Int, 2019; 50(2):156–66. Available from: https://www.ncbi.nlm.nih.gov/pubmed/30564805
28. Protano C, Manigrasso M, Avino P, Sernia S, and Vitali M. Second-hand smoke exposure generated by new electronic devices (IQOS(r) and e-cigs) and traditional cigarettes: Submicron particle behaviour in human respiratory system. Annali Di Igiene, 2016; 28(2):109–12. Available from: http://www.ncbi.nlm.nih.gov/pubmed/27071321
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