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Clinical Review State of the Art Review

What are the respiratory effects of e-cigarettes?

BMJ 2019; 366 doi: (Published 30 September 2019) Cite this as: BMJ 2019;366:l5275
  1. Jeffrey E Gotts, assistant professor of medicine1,
  2. Sven-Eric Jordt, associate professor2 3,
  3. Rob McConnell, professor of preventive medicine4,
  4. Robert Tarran, professor of cell biology and physiology5 6
  1. 1Department of Medicine, University of California San Francisco, San Francisco, CA, USA
  2. 2Department of Anesthesiology, Duke University, Durham, NC, USA
  3. 3Yale Center for the Study of Tobacco Products and Addiction, Department of Psychiatry, Yale School of Medicine, New Haven, CT, USA
  4. 4Department of Preventive Medicine, University of Southern California, CA, USA
  5. 5Marsico Lung Institute, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 USA
  6. 6Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 USA
  1. Correspondence to: R Tarran robert_tarran{at}


Electronic cigarettes (e-cigarettes) are alternative, non-combustible tobacco products that generate an inhalable aerosol containing nicotine, flavors, propylene glycol, and vegetable glycerin. Vaping is now a multibillion dollar industry that appeals to current smokers, former smokers, and young people who have never smoked. E-cigarettes reached the market without either extensive preclinical toxicology testing or long term safety trials that would be required of conventional therapeutics or medical devices. Their effectiveness as a smoking cessation intervention, their impact at a population level, and whether they are less harmful than combustible tobacco products are highly controversial. Here, we review the evidence on the effects of e-cigarettes on respiratory health. Studies show measurable adverse biologic effects on organ and cellular health in humans, in animals, and in vitro. The effects of e-cigarettes have similarities to and important differences from those of cigarettes. Decades of chronic smoking are needed for development of lung diseases such as lung cancer or chronic obstructive pulmonary disease, so the population effects of e-cigarette use may not be apparent until the middle of this century. We conclude that current knowledge of these effects is insufficient to determine whether the respiratory health effects of e-cigarette are less than those of combustible tobacco products.


  • Series explanation: State of the Art Reviews are commissioned on the basis of their relevance to academics and specialists in the US and internationally. For this reason they are written predominantly by US authors

  • Contributors: All the authors jointly conceived of, researched, and wrote this article.

  • Funding: This work was funded by NIH/FDA HL120100 and NIH/NHLBI R01 HL135642 (RT), U54DA036151 and R01ES029435 (SEJ), NHLBI U54 HL147127 (JG), and NIH/FDA P50CA180905 and NIH/NICHD R21HD084812 (RM). Research reported in this publication was in part supported by NIH and the FDA Center for Tobacco Products (CTP). The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH or the Food and Drug Administration.

  • Competing interests: We have read and understood the BMJ policy on the declaration of interests and declare that we have no conflicts of interest; SEJ has receiving personal fees from Hydra Biosciences LLC and Sanofi SA and non-financial support from GlaxoSmithKline Pharmaceuticals outside the submitted work.

  • Provenance and peer review: Commissioned; externally peer reviewed.

  • Patient involvement: No patients were involved in the drafting or review of this manuscript.

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