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E-Cigarettes & HTPs

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E-cigarettes heat a liquid—typically composed of a base chemical (e.g., propylene glycol) plus nicotine, flavoring, and other chemicals—to generate an aerosol that users inhale. HTPs are related products, but they heat sticks of processed tobacco just short of combustion (called “pyrolysis”), and users inhale the resulting aerosol.

These products have gained market share in several countries, but a significant share in only a handful (see countries in dark red on Map). Dramatic increases in initiation among young people, strong evidence of aggressive industry marketing of these products to youth and nonsmokers, and use of child-friendly flavors (e.g., fruit, candy, mint, etc.)—often in contexts where youth smoking was declining—have generated enormous concern and controversy. In the US, youth use peaked shortly before the COVID-19 pandemic at 27% among high school students (reporting any use in the previous 30 days).

The evidence continues to mount regarding the health harms of e-cigarettes, and there is near total scientific consensus that these products are harmful to human health. Most comprehensive reviews suggest that when smokers quit to use e-cigarettes exclusively it is very likely to be less harmful than smoking, though the precise level of harm remains unknown. E-cigarette use causes negative pulmonary and cardiovascular effects, and the exposure to high levels of nicotine is particularly worrisome for brain development in youth. Studies based on biomarkers consistently reveal that e-cigarette users are exposed to fewer toxicants and carcinogens than from tobacco smoke, though recent research suggests that the harm is likely greater than initially thought. The harms of HTPs are even less clear, though most experts place the level of harm between that of cigarettes and e-cigarettes.

The three main e-cigarette device types and a HTP (e.g., IQOS)
Three main e-cigarette devices

The evidence strongly suggests that dual use of e-cigarettes and combustible products continues to be very common. The gains for public health in terms of dual use appear to be extremely low or nonexistent, as the damage from continuing to smoke even a few cigarettes each day is high. There is also some evidence that under some conditions dual use is more harmful than smoking alone, particularly for the respiratory system.

Almost all tobacco control experts agree that a strong regulatory framework is required to promote population health and reduce the harms of tobacco. Currently, the types and levels of regulation for e-cigarettes and HTPs vary widely across the world. Key considerations for developing e-cigarette regulations that promote population health include the inherent harms and addictiveness of e-cigarettes, the continuous and rapid evolution of products, the emerging evidence on long-term health impacts, evidence around youth initiation, ongoing regulatory and monitoring capacity, and the availability of support for cessation and/or these products as a harm reduction product for smokers unwilling or unable to quit. The broad pathways include regulating e-cigarettes and HTPs: 1) similarly to other tobacco products, 2) more lightly than other tobacco products, 3) like cessation products, or 4) more heavily including outright banning them. Notably, regulatory capacity is very low in many countries, and, for the sake of population health, governments will have to choose a path that best suits optimal public health within their capacity to regulate.

E-cigarette advertising aimed at children
Picture of an e-cigarette advertisement aimed at children.
Picture of an e-cigarette advertisement aimed at children.
E-cigarette pathways


Maps (adult and youth):

Various national surveys – list available upon request.

Review of overall e-cigarette harms:

National Academies of Sciences, Engineering, and Medicine. Public health consequences of e-cigarettes. Washington, DC. 2018.

E-cigarettes and cessation:

Hartmann-Boyce J, McRobbie H, Butler AR, Lindson N, Bullen C, Begh R, Theodoulou A, Notley C, Rigotti NA, Turner T, Fanshawe TR. Electronic cigarettes for smoking cessation. Cochrane database of systematic reviews. 2021(9).

Kaplan B, Galiatsatos P, Breland A, et alEffectiveness of ENDS, NRT and medication for smoking cessation among cigarette-only users: a longitudinal analysis of PATH Study wave 3 (2015–2016) and 4 (2016–2017), adult dataTobacco Control Published Online First: 15 September 2021. doi: 10.1136/tobaccocontrol-2020-056448.

E-cigarette advertisements

Jackler R. Research into the Impact of Tobacco Advertising. Palo Alto: Stanford University. Website:


Chan GC, Stjepanović D, Lim C, Sun T, Shanmuga Anandan A, Connor JP, Gartner C, Hall WD, Leung J. Gateway or common liability? A systematic review and meta‐analysis of studies of adolescent e‐cigarette use and future smoking initiation. Addiction. 2021 Apr;116(4):743-56.

Harms of dual use:

Reddy KP, Schwamm E, Kalkhoran S, Noubary F, Walensky RP, Rigotti NA. Respiratory Symptom Incidence among People Using Electronic Cigarettes, Combustible Tobacco, or Both. Am J Respir Crit Care Med. 2021 Jul 15;204(2):231-234. doi: 10.1164/rccm.202012-4441LE. PMID: 33857396.


Tehrani, Mina W.; Newmeyer, Matthew N.; Rule, Ana M.; Prasse, Carsten (2021): Characterizing the Chemical Landscape in Commercial E‑Cigarette Liquids and Aerosols by Liquid Chromatography–High-Resolution Mass Spectrometry. ACS Publications. Collection.

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