Health risks of e-cigarettes emerge

Electronic cigarettes, marketed as safer than regular cigarettes, deliver a cocktail of toxic chemicals including carcinogens into the lungs, new studies show. Using e-cigarettes may even make bacterial infections resistant to antibiotics, according to one study.

Engineers developed e-cigarettes several years ago to provide tobacco users a smoke-free source of nicotine. The devices heat up a liquid that a user inhales, or “vapes.” Because e-cigarettes burn nothing, they release no smoke.

“There’s no question that a puff on an e-cigarette is less toxic than a puff on a regular cigarette,” says Stanton Glantz, director of the Center for Tobacco Control Research and Education at the University of California, San Francisco. But few studies have looked at the toxicity of their vapors. As a result, scientists have been circumspect about describing e-cigarettes as safe.

For a May 13 review in Circulation, Glantz and his team pored over emerging data on what vapers are inhaling and found, he says, greater risk than scientists had thought. E-cigarettes deliver high levels of nanoparticles, the researchers found, which can trigger inflammation and have been linked to asthma, stroke, heart disease, and diabetes (SN: 7/18/09, p. 26). The levels “really raise concerns about heart disease and other chronic conditions where inflammation is involved,” he says.

Those people may think vaping is safe, but FDA has seen no data establishing anything like that, writes the agency’s Priscilla Callahan-Lyon in the same journal. She reviewed data from 18 studies on e-cigarettes’ vapors and found that most contain at least traces of the solvents in which nicotine and flavorings had been dissolved. Those solvents, she reports, are known as lung irritants.

And the solvents can transform into something even more worrisome: carbonyls. This group includes known cancer-causing chemicals, such as formaldehyde, and suspected carcinogens, such as acetaldehyde. Because early e-cigarettes didn’t deliver the same powerful hit of nicotine that burning tobacco does, engineers developed second-generation technology that allows users to increase an e-cigarette’s voltage, and thus temperature, to atomize more nicotine per puff.

But the higher temperatures also can trigger a thermal breakdown of the solvents, producing the carbonyls, explains Maciej Goniewicz of the Roswell Park Cancer Institute in Buffalo, N.Y. If users of second-generation e-cigarettes maximize the power on their devices while using vaping liquids containing a solvent mix of glycerin and propylene glycol, formaldehyde levels can reach that found in tobacco smoke, his team reports May 15 in Nicotine & Tobacco Research.

Such compounds in smoke are mainly a concern if they make it all the way into the lungs. Many biologists think particle size and count are key, says Glantz. Vapers can inhale huge numbers of very small aerosols — the most toxic size — that can then deposit into the lung’s tiniest airways, which are pivotal to moving air into the body.

The median diameter of vaping particles falls around 200 to 300 nanometers, based on unpublished data from Jonathan Thornburg and others at RTI International in Research Triangle Park, N.C. That size “is right in line with conventional tobacco smoke,” Thornburg says.

The mass of particles in the vapors is about 3 milligrams per cubic meter of air, he says, or about 100 times as high as the Environmental Protection Agency’s 24-hour exposure limit for levels of fine air particles. Thornburg’s group’s analyses predict that some 40 percent of these inhaled particles would deposit in the lungs’ smallest, deepest airways.

In addition to nicotine and solvents, vapors also contain chemical flavorings and food preservatives from the vaping liquid. Although they may be GRAS, or “generally recognized as safe” by FDA, Thornburg says, the designation is based on tests of the compounds when they are ingested. “No one has considered their safety when it comes to inhalation,” he says.

And e-cigarette vapors can even make dangerous germs harder to kill, Laura Crotty Alexander reported May 18 at an American Thoracic Society meeting in San Diego. A pulmonary and critical care physician and scientist with the VA San Diego Healthcare System, she exposed methicillin-resistant Staphylococcus aureus, better known as MRSA, to e-cigarette vapors.

In a lab dish, these antibiotic-resistant bacteria, which can cause pneumonia, proved harder to kill using a germ-killing protein fragment — a natural antibiotic that people’s bodies make. One reason: Germs exposed to nicotine-rich vapors secreted a thicker biofilm coating that protected them.

Crotty Alexander also allowed mice to breathe in air containing MRSA that had been exposed to e-cigarette vapors. One day later, mice getting vapor-exposed germs had three times as many bacteria growing in their lungs as did mice that got unexposed germs.

“We started these studies so that we could advise our smoking patients on whether they should try switching to e-cigarettes,” she says. “My data now indicate they might be the lesser of the two evils. But e-cigarettes are definitely not benign.”