American Journal of Public Health: The Claim That E-Cigarettes Are 95% Less Harmful Than Cigarettes

January 10, 2011 - A recent article published in the American Journal of Public Health (AJPH) questioned the study that e-cigarettes are 95% safer than combustible cigarettes; the original study concluded that e-cigarettes are 95% safer than combustible cigarettes.

This research comes from a 2013 study that evaluated the relative harms of 12 nicotine products using 14 criteria.The authors of the 2013 study concluded that e-cigarettes are far less harmful than combustible cigarettes.

Widely quoted in the media is the view that e-cigarettes are 95% less risky than tobacco cigarettes.

The authors of the AJPH article write that even if the 2013 estimates were valid, they cannot be applied today, and current vapor products are very different from those of 2013. These devices are now more powerful, produce more aerosols and expose users to more toxins.

Despite the fact that the researchers of the original study acknowledged the flaws in their work (i.e., the lack of conclusive evidence that most products are hazardous by most standards), the UK's Public Health and the Royal College of Physicians endorsed the claim and gave it credibility.

The authors of the AJPH's skeptical article say the claim that public health practitioners, scientists and physicians are exposing a 95% reduction in risk by emphasizing its unreliable provenance and lack of validity is weak.

Here are some of the points made in the challenge article:

In July 2013, a panel of 12 experts in decision sciences, medicine, pharmacology, psychology, public health policy, and toxicology evaluated the relative harms of 12 nicotine-containing products by using 14 criteria for harm to self and others.

The panel concluded that combustible cigarettes were the most harmful, while electronic nicotine delivery systems (e-cigarettes or e-cigarettes) were far less harmful than combustible cigarettes. These results have been repeatedly cited in the popular press as being 95% less dangerous or 95% less harmful than combustible cigarettes. However, as the authors point out in a brief statement about the shortcomings of their work, the limitation of this study is the lack of conclusive evidence that most products are harmful to most people.

Despite the lack of hard evidence, the Department of Public Health and the Royal College of Physicians in the United Kingdom have recognized and promoted the claim of a 95% reduction in harm.

Senior Public Health England staff highlighted the evidence behind the 95% figure, despite the lack of evidence. There is very little research on the dubious nature of the 95% reduction in hazardous substances estimate between 2014 and 2016, particularly on the health impacts of e-cigarettes available in 2013, which have now been well reported.

After six years of research focused on e-cigarettes, which has produced a growing body of hard evidence about harm, the time has come to re-examine that estimate.

Today's e-cigarettes are different

There is ample evidence that the range of e-cigarettes offered today is significantly different from what was available in July 2013
. These differences make it so that even if the 2013 estimates were valid at the time, they no longer apply today. For example, in addition to using different materials and more heating coils, many of today's e-cigarettes also have power outputs that are 10 to 20 times higher (i.e., sometimes more than 200 times higher) than most over-the-counter 2013 models. More power increases the potential harms of using e-cigarettes because more aerosol is produced, exposing users to more nicotine and other toxic substances. It also increases the risk of bystanders being exposed to any harmful aerosol components as the user exhales more aerosol. In addition, greater power increases the likelihood of malfunctions (e.g., device explosions),

Additionally, e-cigarette liquids have changed considerably since 2013, with thousands of flavors widely available that use chemicals typically considered safe for consumption but have unknown lung toxicity. Perhaps the most dramatic change has been the general popularity of protonated nicotine liquids. Protonated nicotine (nicotine salts) are made by adding an acid to free base nicotine, thus introducing another potentially toxic substance that is rarely seen in 2013. Aerosolized protonated liquids are less inhalable than free base nicotine, allowing users to increase the concentration of nicotine in the liquid and potentially increase their own dependence on nicotine. Today, the concentration of protonated nicotine e-cigarette liquids exceeds 60 milligrams per milliliter, and these liquids have become very popular, sparking a nicotine arms race.

E-cigarettes harm cells

There is substantial evidence (unavailable in 2013) that e-cigarette aerosols contain toxic substances and that these aerosols are harmful to living cells both in vitro and in vivo. For example, thermal degradation of e-cigarette liquid components can produce volatile aldehydes, which exhibit a variety of cardiorespiratory toxic effects at the concentrations produced by e-cigarettes. E-cigarettes can produce carcinogenic substances in addition to other toxic substances (e.g., chloropropanols). Even at room temperature, e-cigarette liquids may be unstable, producing irritating acetal compounds that are carried into the aerosol. Numerous studies have shown that cellular function is impaired after exposure to e-cigarette aerosols. Similarly, animals exposed to e-cigarette aerosols have clearly shown adverse effects,#p#Page Break #e#

E-cigarettes harm users

Recent evidence suggests that e-cigarette users show evidence of harm. For example, in a sample of healthy young occasional smokers who used e-cigarettes with or without nicotine, airway epithelial damage was observed in both cases, and the authors concluded that, therefore, e-cigarette aerosol components may damage the respiratory system or worsen pre-existing lung disease through multiple mechanisms. Consistent with this report, asthma is a symptom of underlying respiratory disease and is associated with e-cigarette use. E-cigarette use increases heart rate, blood pressure, and platelet activation and reduces blood flow-mediated dilation and heart rate variability, effects that portend long-term cardiovascular risk. In fact, a preliminary report suggests that e-cigarette users may be at increased risk for myocardial infarction and coronary artery disease.

E-Cigarettes Increase Smoking Risk

Since 2013, numerous surveys have shown that the use of e-cigarettes by previously nicotine-naïve people is increasing, and that the risk of these people starting to smoke is also increasing. With the National Academies of Sciences, Engineering and Medicine concluding that there is substantial evidence that e-cigarette use increases the risk of combustible tobacco cigarette use among young people. E-cigarette use may be considered as harmful as smoking for that individual.

E-cigarette smoke is harmless

The difference in toxic content between e-cigarette aerosol and cigarette smoke cannot by itself convey less lethality, as toxicity depends on the extent and manner of use. For example, propylene glycol (PG), one of the main ingredients in e-cigarette aerosols, is usually considered safe when consumed, but is toxic when injected intravenously over a period of several days. E-cigarette aerosols containing propylene glycol and vegetable glycerin (another common ingredient) cause inflammation of the lungs, suggesting that inhalation of propylene glycol and vegetable glycerin have different safety profiles. In addition, since the toxic substances in e-cigarette aerosols are sometimes different from cigarette smoke, the same may be true of any disease states caused by e-cigarettes. There is no doubt that proprietary users of e-cigarettes are unlikely to die from lung cancer caused by nitrosamines or polycyclic aromatic hydrocarbons (PAHs), which are characteristic of cancer-causing tobacco (and which are largely absent from e-cigarette aerosols). What they are likely to die from, and if their deaths are hastened by e-cigarette use, will form part of the much-needed evidence base upon which valid risk estimates can be built.

In summary, the 2013 assessment of the lack of evidence on the harms of e-cigarettes relative to combustible cigarettes is often cited. However, e-cigarette devices and liquids have changed since 2013. Evidence of potential harm has accumulated. Therefore, the lack-of-evidence estimates derived in 2013 remain invalid today and should not be cited further. Future estimates of the harms of e-cigarettes should be based on the available evidence and revised accordingly as more evidence becomes available.

Call to Action

Safer 95% of estimates are factual: unreliable information is repeated so often that it is accepted as fact. Public health practitioners, scientists, and physicians should highlight the fragile state, emphasize its unreliable provenance and validity today, and point to the many changes in e-cigarette devices and liquids, the accumulation of evidence of potential harms, the rise in smoking prevalence, and the growing evidence linking e-cigarette use to subsequent smoking.

Acknowledgments: this work was supported by the National Institutes of Health and the Center for Tobacco Products of the U.S. Food and Drug Administration.

NOTES. This content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health or the Food and Drug Administration.