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E-Cigarettes: What the Research Shows

By Stephanie Watson
WebMD Health News

Reviewed by Arefa Cassoobhoy, MD, MPH

March 26, 2014 -- Teens usually start smoking cigarettes to be cool or rebellious, or because their friends are doing it. These days, though, the cigarettes they smoke are more and more of the electronic variety -- not tobacco.

The number of middle school and high school students who'd tried the candy-like flavors of e-cigarettes doubled between 2011 and 2012. About 1.78 million U.S. students had tried e-cigarettes as of 2012.

A study published earlier this month shows that middle school and high school students who smoke e-cigarettes also are more likely to smoke tobacco cigarettes. While the study didn't prove cause and effect, it does show a strong link between the two habits.

Further research shows that 70% of adult smokers start before age 18.

The growing popularity of e-cigarettes -- among adults as an aid to quit smoking and among teens -- has turned them into a $1.5 billion-a-year industry. Revenue could grow to $3 billion in 5 years.

Research into their potential effects on health, though, is still in the early phases. There's enough concern that the FDA is considering regulations.

For teens who have never smoked, e-cigarettes are an introduction to nicotine, which is highly addictive. Public health officials are worried this could lead to tobacco use.

For adults who smoke tobacco cigarettes, e-cigarettes may not be as dangerous, because they don't have the same toxins as the tobacco kind, except for the nicotine.

"There's enough data to conclude that they are much safer than regular cigarettes, and for smokers who are having trouble quitting using other methods, they're much better off switching to electronic cigarettes," says Michael B. Siegel, MD. He's a professor at the Boston University School of Public Health.

The data don't explore the long-terms health effects of e-cigarettes, though. "We don't know the absolute risks -- whether, over a very long period of time, the e-cigarette might have harms associated with it," Siegel says. "They haven't been on the market long enough to understand if they may have long-term side effects."

And it's still unclear whether they help people kick the habit. One recent study concludes e-cigarettes didn't lead to quitting or less smoking.

E-Cigarettes vs. Tobacco Cigarettes

Tobacco contributes to 5 million deaths worldwide a year. For centuries, cigarettes have remained basically the same: tobacco rolled in paper. What makes them so deadly are the estimated 4,000 chemicals they give off when lit. Some of those chemicals, like arsenic, formaldehyde, and lead, can cause cancer and a long list of other deadly diseases.

An e-cigarette is a battery-powered tube about the size and shape of a cigarette. A heating device warms a liquid inside the cartridge, creating a vapor you breathe in. Puffing on an e-cigarette is called "vaping" instead of "smoking." E-cigarettes also make chemicals, but in much smaller numbers and amounts than tobacco cigarettes.

What's in E-Cigarettes?

The nicotine in e-cigarettes goes to your brain quickly. It can cause a brief feeling of relaxation and can lift your mood. As the nicotine leaves your system, your body craves another cigarette. Some research links nicotine to a higher risk of heart disease.

While the amount of nicotine in e-cigarettes is far lower than in regular cigarettes, the doses can vary greatly by e-cig brand.

The other main chemicals in e-cigarettes are propylene glycol and vegetable glycerin. They are used either separately or together as liquids to make the vapor.

Propylene glycol is a food additive and an ingredient in the fog machines used in clubs and theater shows. It has been through a lot of testing, and the FDA considers it safe for use in food and medicine. It's an ingredient in many food flavorings, toothpastes, and cough syrups. It has been linked to minor skin and lung irritation.

The FDA also considers vegetable glycerin safe for people to use, but there's not a lot of research to confirm its effects on health.

There's also a lack of research into what's produced when you "light up." The heat can create potentially harmful chemicals, although in amounts 9 to 450 times lower than in real cigarettes. The evidence isn't clear on the health effects of these lower amounts of chemicals.

Also worrisome is the rainbow of flavors added to make e-cigarettes taste like everything from mint to bubblegum. Although the FDA says these additives are safe enough to be eaten in food, "we don't have enough data showing the potential risk from inhaling these flavors," says Maciej Goniewicz, PhD, PharmD. He's an assistant professor at Roswell Park Cancer Institute in Buffalo, N.Y.

The sheer number of e-cig varieties on the market adds to the problem. "There are different models, different types, different brands," Goniewicz says.

The chemicals in them can vary, too. That makes it hard to draw any conclusions about their safety.

Secondhand Vaping

Smoking doesn't affect just the people who light up. Everyone around you also breathes in chemicals released in the smoke. Secondhand cigarette smoke has been linked to cancer, heart disease, and many other conditions. So researchers want to know whether secondhand vaping is dangerous, too.

Goniewicz and his research team have measured the amount of chemicals in e-cigarette vapors. They found nicotine in the vapor, but levels of other toxic chemicals were too low to cause concern.

But he says more research is needed to look at the effects of secondhand vapor on people who spend a lot of time with long-term users, especially children. Research is also needed on secondhand e-cigarette vapor outside of the lab, in the real world. "I think there need to be more studies that measure the levels of real settings like restaurants and bars where people would really be using them," Siegel says.

Next Steps

Because there are so many unknowns about the possible health risks of e-cigarettes, the FDA is looking to regulate these products as it does tobacco cigarettes and smokeless tobacco products. It's not clear when these proposed regulations would go into effect.

Siegel says regulation is a good idea, because it will encourage more studies into the health effects of e-cigarettes. "I think with research we'll be able to find a way of delivering nicotine that's as safe as possible," he says.

For now, a lot of unanswered questions remain about electronic cigarettes, Goniewicz says. And though they are a safer option than regular cigarettes if you're a smoker trying to quit, they're not necessarily risk-free.

SOURCES: Business Week: "L.A. Council Approves Restriction of E-Cigarette Industry." American Lung Association: "What's in a Cigarette?" Maciej Goniewicz, PhD, PharmD, assistant professor of oncology, department of health behavior, Roswell Park Cancer Institute, Buffalo, NY. Michael B. Siegel, MD, professor, Boston University School of Public Health. Caponnetto, P. Expert Review of Respiratory Medicine, February 2012. Schripp, T. Indoor Air, July 2, 2012. Bullen, C. Lancet, November 2013. Dawkins, L. Addictive Behaviors, August 2012. Czogala, J. Nicotine & Tobacco Research, Dec. 11, 2013. King, B. Nicotine & Tobacco Research, September 2013. Vansickel, A. Addiction, August 2012. American Caner Society: "Secondhand Smoke." CDC: "Notes from the field: electronic cigarette use among middle and high school students -- United States, 2011 - 2012," "Fact Sheet--Fast Facts--Smoking & Tobacco Use." Dutra, L. JAMA Pediatrics, March 2014. FDA: "Electronic Cigarettes (e-cigarettes)." Caponnetto, P. Expert Review of Respiratory Medicine, February 2012. Goniewicz, M. Tobacco Control, March 2013. American Lung Association: "Why Kids Start."

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