Electronic cigarettes, or e-cigs, have been on the market in the U.S. since 2008 and have gained wider use in recent years. Now, evidence is beginning to emerge on e-cigs' short-term effects, and their positive and negative impact on people's health.
E-cigarettes are battery-powered devices that heat a liquid — usually containing nicotine mixed with the chemicals propylene glycol and glycerin, and often flavorings ranging from bubble gum to watermelon — into a vapor that users can inhale. They deliver nicotine, a highly addictive drug, to the body without producing any smoke.
This month, the U.S. Food and Drug Administration announced that its authority to regulate tobacco products will now extend to include e-cigarettes. The devices — along with cigars, hookah and pipe tobacco — will now be regulated in a similar way to conventional cigarettes. The new rules, which take effect on Aug. 8, also banned the sale of these products to people under age 18 both in stores and online. [4 Myths About E-Cigarettes]
But because e-cigs are relatively new nicotine-delivery products, there are many unanswered questions about their safety and health impacts, including questions about their long-term use and effectiveness in helping traditional smokers to quit. What, exactly, is in an e-cigarette, and how do these chemicals affect the heart and lungs as well as a person's overall health? Live Science asked two tobacco experts for their insight into these questions, and here is what they said.
What's known about e-cigs
"There is no question that a puff on an e-cigarette is less dangerous than a puff on a conventional cigarette," said Stanton Glantz, a professor of medicine and the director of the Center for Tobacco Control Research and Education at the University of California, San Francisco.
Because e-cigarettes create a vapor rather than produce a tobacco smoke, they generally deliver less nicotine to users than cigarettes do, Glantz said. [Infographic: How E-Ciggs Work]
However, this doesn't mean the devices always represent a safer step down from cigarettes. In fact, one of the most dangerous things about e-cigarettes is that they may keep people smoking conventional cigarettes longer, rather than encourage them to attempt to quit, he said. Although estimates vary, anywhere from 70 to 90 percent of e-cigarette users are "dual users," meaning they continue to smoke regular cigarettes after they begin vaping, Glantz said.
But regardless of how the nicotine is delivered — whether through e-cigs or conventional cigarettes — it still has effects on the body. The drug is a cardiovascular stimulant, and can potentially worsen heart disease in people who already have severe heart conditions. However, it's not known whether nicotine alone can cause heart disease in people who don't have heart problems, said Dr. Michael Siegel, a tobacco researcher and professor of community health sciences at the Boston University School of Public Health.
But there's some evidence that e-cigarettes can have a substantial effect on blood vessels, and may increase people's heart attack risk in that way, Glantz said.
What's more, nicotine is poisonous in its concentrated, e-liquid form, and there have been an increasing number of cases of infants and young children accidentally ingesting it, Siegel said.
Nicotine also has effects on reproductive health, and exposure to nicotine during pregnancy, regardless of its delivery method, can harm the developing fetus and lead to babies born with low birth weights, he said.
The use of e-cigarettes by kids of high school age has soared – CDC statistics show that 1.5 percent of high school teens had tried e-cigs in 2011, compared with 16 percent in 2015. The rise has occurred even as researchers are finding more evidence that nicotine can be toxic to a young person's still-developing brain and body systems, Glantz said. Studies have also shown that kids who use e-cigarettes have more respiratory problems and take more days off from school, he said.
In addition to the nicotine, e-cigs' other chemicals may also affect health. Research on the vapors emitted and inhaled from e-cigarettes has shown they deliver particles small enough to reach deep into the lungs and that they are not the "harmless water vapor" that marketers may claim, Glantz told Live Science.
Propylene glycol, a chemical found in e-liquids, can irritate the eyes and airways, Siegel said. Early studies have also revealed that when propylene glycol or glycerin are heated and vaporized, they can degrade into formaldehyde and acetaldehyde, he said. Both of these chemicals are considered carcinogens, although it's not yet clear how repeated exposure to them may cause cancer, he said. [10 Scientific Quit-Smoking Tips]
One of the biggest safety risks of e-cigarettes is the potential for their lithium-ion batteries to explode, sometimes into a person's face or eyes, Siegel said. There is clearly a need for standards to make these batteries safer, he said.
But all in all, even if e-cigarettes involve some health risks, they are not more toxic than smoking cigarettes, and so anything that can get people away from tobacco is moving them in the right direction, Siegel said. He believes that vaping gives people a safer alternative because although users are still getting nicotine, they are getting lower levels of some of the toxic substances and carcinogens found in cigarette smoke, he said.
Eventually, the goal is to get people off vaping and to quit completely, but people have to start somewhere, Siegel said. He also acknowledged that many of his colleagues in public health don't share his opinion. Rather, they view e-cigarettes as a gateway to smoking conventional cigarettes, especially for young people, or as a method of getting nicotine that actually diminishes people's interest in quitting.
Glantz falls into this latter category. In an analysis he and a colleague published earlier this year, they found that adult smokers who use e-cigarettes are about 30 percent less likely to stop smoking than people who attempt to quit smoking without turning to vaping, he said. One possible explanation is that people may generally use e-cigarettes as part of a "taper-down" strategy, which is less effective than quitting cold turkey, he suggested.
The unknowns about e-cigs
Studies evaluating whether e-cigarettes are less harmful than cigarettes have been inconclusive, according to a review of studies published in the journal Tobacco Control in May 2014.
Moreover, the long-term health effects in people who get nicotine in a vaporized form over time are not known, Siegel said. It's also unclear whether propylene glycol, a known irritant to the respiratory tract, could result in lung problems after decades of vaping, he said.
And because e-cigarettes have been on the market for only about 10 years, there have been no long-term studies of people who have used them for 30 to 40 years. Therefore, the full extent of e-cigs' effects on heart and lung health, as well as their cancer-causing potential, over time is not known, Glantz told Live Science.
Another unanswered question is how the flavorings used in the devices may affect people's health. Nearly 500 brands and 7,700 flavors of e-cigarettes are currently on sale, according to the American Lung Association. This wide variety of flavors has helped make vaping appealing to young people.
It's not yet known whether these flavorings have any respiratory effects when they are vaporized and inhaled, Siegel said. More research is needed to identify any hazards associated with the potential inhalation of flavoring agents, he said.
In addition, little is known about how the flavoring agents in e-cigarettes may influence nicotine's addictive qualities, Glantz said.
More work needs to be done to understand the dynamics between smoking traditional cigarettes and also using e-cigarettes in people who are dual users, he said. Future research also needs to look at whether using both traditional cigarettes and e-cigs interferes with the desire to quit, and whether using e-cigarettes is an effective strategy for quitting smoking compared with other methods, such as the nicotine patch and behavioral counseling, Glantz said.
The FDA has not approved e-cigarettes as a smoking cessation aid, he added.