Electronic cigarettes are handheld nicotine-delivery devices that, despite a devoted following, are currently swirling in controversy.
New York is pushing to become the first state to ban the devices, which so far remain unregulated and mostly unstudied. With cutesy colors, fruity flavors, clever designs and other options, e-cigarettes may hold too much appeal for young people, critics warn, offering an easy gateway to nicotine addiction.
But those criticisms clash with equally strong arguments for the value of e-cigarettes. The devices, which are tobacco-free, may be a safer alternative to cigarettes, say advocates, who point to testimonials from thousands of smokers who say they have used e-cigarettes to help them quit.
As the U.S. Food and Drug Administration struggles to gain regulatory control, and as safety studies remain works in progress, the debate continues.
"There really are a lot of unknowns with respect to health," said Prue Talbot, a toxicologist at the University California, Riverside. "I don't know of any studies in the literature which are peer-reviewed. Almost all of the studies have been paid for by the e-cigarette companies.
"E-cigarettes are often sold as safe, which is probably not true," Talbot added. "They may not be as dangerous as real cigarettes, but on the other hand, they could be. We just don't know."
Electronic cigarettes typically use a rechargeable battery-operated heating element to vaporize the nicotine in a replaceable cartridge. Nicotine is usually dissolved in propylene glycol, a clear and colorless liquid that is commonly found in inhalers, cough medicines and other products.
Some e-cigarettes are made to look like real cigarettes, cigars or pipes. Others look like pens or USB memory devices. There is no tobacco involved, and no smoke either. Instead, users do what's called "vaping." As they inhale, they take in nicotine-filled vapor.
By isolating nicotine, e-cigarettes should carry far fewer chemical risks than regular cigarettes, said Michael Siegel, a tobacco researcher at Boston University. Tobacco contains about 5,000 known chemicals, he said, with as many as 100,000 more that haven't yet been identified. E-cigarettes eliminate many of those ingredients.
Siegel and a colleague reviewed 16 studies that analyzed the contents of electronic cigarettes. In a paper just published in the Journal of Public Health Policy, they reported that levels of certain harmful chemicals were on par with levels found in nicotine patches and hundreds of times lower than what's found in cigarettes.
The researchers also found evidence that vaping reduces cravings among smokers, not just for nicotine but also for the need to hold something in their hands and put something in their mouths -- making the devices more appealing to them than patches or gum.
As a cigarette-quitting strategy, Siegel compared e-cigarettes to heroin needle exchange programs. It's not that the devices are good for anyone, he said. They are just better than what they're meant to replace.
"The relevant question is not, 'Are these things safe?'" he said. "But are these things much safer than real cigarettes, and do they help people quit smoking? The answer to both of those questions we know is yes."