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E-Cigarettes: The Science

E-cigarettes: An Overview
E-cigarettes: The Basics
E-cigarettes: The Science
E-cigarettes: Battery Safety
E-cigarettes: FAQS
E-cigarettes: Facts About Vaping Video
Historical Timeline of Electronic Cigarettes

General Overviews

Millions of long-term smokers have developed diseases that have caused them to die early. It is well understood that these diseases are caused almost exclusively by inhaling smoke. E-cigarettes do not burn tobacco or any other material, and so do not produce the smoke that causes smoking related diseases. This video explains that important difference, as well as the implications for using e-cigarettes as a tool to dramatically reduce smoking related harms:

Facts about vaping

Clive Bates of Counterfactual Consulting and Advocacy, in his E-cigarettes, vaping and public health. A summary for policy-makers covers a range of issues including the case for tobacco harm reduction, exposure risks for e-cigarette users, and policy recommendations:

Briefing on the science and policy of e-cigarettes and vaping

The landmark report E-cigarettes: an evidence update. A report commissioned by Public Health England was the first major health agency in the world to conclude there is overwhelming evidence that using e-cigarettes is dramatically less risky than smoking:

E-cigarettes: an evidence update A report commissioned by Public Health England

The prestigious Royal College of Physicians, founded in 1518, is the oldest medical college in England. This organization has been at the forefront of medical advances and health related knowledge for hundreds of years. Their report, Smoking and Health, in 1962, outlined the considerable dangers of cigarette smoking two years ahead of the 1964 U.S. Surgeon General’s report on the same topic. With this report, Nicotine without smoke: Tobacco harm reduction. A report by the Tobacco Advisory Group of the Royal College of Physicians, they outline the evidence and assert the “huge potential” of e-cigarettes to prevent smoking related death and disability:

Nicotine without smoke: Tobacco harm reduction

Surveys of who is using e-cigarettes

The overwhelming majority of e-cigarette users are smokers or ex-smokers, while very few non-smokers or never smokers use them.

In the United States:

How Many Americans Vape? CDC Data Show Fewer Vapers & Smokers in 2015

In the United Kingdom:

Population impact of e-cigarettes: recent evidence from the UK

In the European Union:

Electronic cigarette use in the European Union: analysis of a representative sample of 27 460 Europeans from 28 countries

Risks to users and bystanders

Igor Burstyn of Drexel University reviewed over 9000 different measurements of the chemicals in e-cigarettes from a wide variety of sources. He specifically looked at contaminants associated with a risk to health, and compared the values observed to the standards set for occupational workplace safety. The results analyzed the amount of these contaminants an e-cigarette user is deliberately exposed to through vaping. The conclusion: if these were an involuntary exposure in a workplace, taking place over decades, they would not justify any attention. Indeed, the values obtained were between 1% and 5% of the levels needed to cause a health concern in a workplace. Because vapor expelled by the user is immediately diluted by the ambient air, the risk to bystanders is 1/100th to 1/1000th compared to smoke. That is, essentially zero:

Peering through the mist: systematic review of what the chemistry of contaminants in electronic cigarettes tells us about health risks

Dainius Martuzevicius and colleagues, in a presentation given at the 2016 Global Forum on Nicotine in Warsaw, Poland, compared the characteristics of e-cigarette vapor and cigarette smoke. They found that the particles in e-cigarette vapor are made of liquid (water) and evaporate quickly, within 10-15 seconds. In contrast, cigarette smoke is made of solid particles which do not dissipate quickly and accumulate in the room. It is well understood that the solid particles of smoke cause a variety of health harms, whereas liquid particles generally do not:

Characterisation of the dynamic properties of exhaled aerosol particles following use of electronic and conventional cigarettes

Health risks of using nicotine

The health risks of using nicotine stem mainly from its stimulant effects. Although in healthy adults this presents little concern, for those with cardiovascular disease all stimulants that temporarily raise blood pressure and heart rate should be used with caution. As the following studies make clear, smoking presents a substantial risk to cardiovascular health compared to nicotine:

Cardiovascular toxicity of nicotine: Implications for electronic cigarette use

Cigarette smoke but not electronic cigarette aerosol activates a stress response in human coronary artery endothelial cells in culture

There is no established link between nicotine use and cancer. This study by Murray and colleagues is fairly typical of the results from studies investigating this possible relationship:

Does nicotine replacement therapy cause cancer? Evidence from the Lung Health Study

Perhaps the best evidence of nicotine’s overall safety is that the FDA has modified the longstanding guidelines for nicotine replacement product use. Previously limited to 12 weeks, the FDA now recommends, in consultation with a physician, that nicotine replacement products can be used indefinitely.

Modifications To Labeling of Nicotine Replacement Therapy Products for Over-the-Counter Human Use

Smoking cessation

Adult smoking rates in the U.S. continue their rapid decline, which began in 2010. This followed six years (2004-2009) of virtually no decline. Although the latest decline in smoking rates coincides with the expansion of e-cigarette use, it is unclear how much e-cigarettes have contributed to this decline. Data on smoking rates year by year comes from the 2015 National Health Interview Survey (See page 55):

Early Release of Selected Estimates Based on Data  From the 2015 National Health Interview Survey

Farsalinos and colleagues surveyed over 27,000 people from all 28 of the European Union member states concerning their e-cigarette use. The authors estimate that 6.1 million EU citizens have quit smoking with the use of e-cigarettes:

Electronic cigarette use in the European Union: analysis of a representative sample of 27,460 Europeans from 28 countries

A number of surveys have polled current e-cigarette users about their motivation to use e-cigarettes. Large majorities in these surveys report using e-cigarettes with the express intention to quit smoking. CASAA surveyed its members in late 2015 about their e-cigarette use.  Among the findings are that 64% said they started using e-cigarettes with the intention to quit, while 25% intended to reduce their smoking, but wound up quitting entirely. 11% of members said they first used e-cigarettes with no intention of quitting or reducing their smoking, but wound up quitting entirely:

Working paper: Phillips – Preferences, practices, and intentions of a population of U.S. adult enthusiast vapers (CASAA member survey)

Youth e-cigarette use

Youth smoking continues to hit all-time lows. The 2015 nationwide Monitoring the Future Survey of over 40,000 8th, 10th, and 12th grade students across the U.S. shows that the youth smoking rate has fallen to approximately 7%:  

Teen cigarette smoking drops to historic low in 2015

However, this survey used the highly unreliable “used in past month” response to count who “uses” tobacco cigarettes. A more reliable measure of who is a smoker, in the traditional sense, is daily use. When this question is asked, the smoking rates for 8th, 10th, and 12th grade students are 1.3%, 3%, and 5.5% respectively.

Concerning e-cigarette “use,” a more recent Monitoring the Future Survey reports that 8% of 8th graders, 14% of 10th graders, and 16% of 12th graders reported using e-cigarettes at least once in the past month. When the results are broken down by how often an e-cigarette was used in the past month (1 to 5 times vs. 6+ times) we have a fairly rough measure of who is actually using e-cigarettes in the traditional sense, versus those who are likely just experimenting with them.  Approximately 4% of students surveyed reported using an e-cigarette 6+ times per month.  However, when asked if they vaped nicotine, only around 40% of this group reported using nicotine.  This means that nationwide, only about 1.5% of 8th to 12th grade students are using an e-cigarette with nicotine 6 or more times per month.  

What are kids vaping? Results from a survey of US adolescents.

There has been considerable consternation in public health circles that e-cigarettes may be serving as a significant route to nicotine addiction among youth.  The results of this survey strongly suggest this fear is unfounded. Indeed, these results are entirely consistent with the 2015 survey asking students the most important reasons for using an e-cigarette.  A majority indicated they were just experimenting or they liked the flavors, whereas barely 1% said they were “hooked” or “have to have it.”

[Table] Reasons for Use of Electronic Vaporizers

The majority of students report using e-cigarettes “to experiment–to see what it’s like” and “because it tastes good.” In contrast, approximately 1% of students report using e-cigarettes “because I am ‘hooked’–have to have it.” This response indicates an answer to the true area of concern, that is, whether e-cigarettes are providing a rapid route to nicotine dependence. This answer appear to be “no.” Also, the less publicized result of this study determined that only about 22% of students report using nicotine in their e-cigarettes.

The 2015 Monitoring the Future Survey was sponsored by the National Institute on Drug Abuse, and a more complete summary of these and other findings are below:

Monitoring the Future Survey, Overview of Findings 2015

E-cigarettes as a gateway to smoking

The claim that e-cigarettes are causing youth to smoke who otherwise wouldn’t is perhaps the most extraordinary claim made about e-cigarettes. This claim is even more extraordinary considering a total lack of evidence. Clive Bates of Counterfactual Consulting and Advocacy offers a summary of this claim and the logical fallacies behind it:

How not to be duped by gateway effect claims

For a science-based view of the gateway claim, and the evidence needed to support it, Carl Phillips has published an excellent paper on the topic:

Gateway Effects: Why the Cited Evidence Does Not Support Their Existence for Low-Risk Tobacco Products (and What Evidence Would)

E-cigarette flavors attracting youth

Hardly a day goes by without some public health official claiming that the variety of flavors used in e-cigarettes (candy, cake, fruit, etc.) are a deliberate effort to attract youth users. The potentially nefarious motivation of e-cigarette manufacturers aside, the pertinent question is, How enticing are e-cigarette flavor descriptions to non-smoking youth? Shiffman and colleagues used a basic survey to help answer this question:

The Impact of Flavor Descriptors on Nonsmoking Teens’ and Adult Smokers’ Interest in Electronic Cigarettes