Two New Studies Find Potential Harmful Effects of E-Cigarettes

Two new studies look at the effect of e-cigarette use. Dan Kitwood/Getty Images
Two new studies look at the effect of e-cigarette use. Dan Kitwood/Getty Images

While the deleterious effects of smoking cigarettes is no longer in question, e-cigarettes remain in a gray zone, primarily because enough research hasn't been done to make definitive claims. Things may be getting less gray, though.

A new study from the University of North Carolina shows that e-cigarette use, which delivers nicotine via vapor rather than tobacco smoke, may not be safe simply because it does not contain the same known carcinogens as tobacco cigarette smoke. The study showed e-cigarette smoke flavored with chemical additives has a negative impact on the immune system. A University of Louisville study also showed that nicotine alone, independent of tobacco, can speed up artherosclerosis.


Ilona Jaspers is a professor of pediatrics and the deputy director of UNC's Center for Environmental Medicine, Asthma and Lung Biology. Jaspers and her team looked at nearly 600 genes related to the immune system and its responses to stimuli. They examined smokers, non-smokers and e-cigarette users, investigating nasal cavity tissue samples, nasal fluid, urine and blood.

E-cig supporters point to the fact that the U.S. Food and Drug Administration (FDA) has designated many liquid flavorings as "Generally Recognized as Safe." Jaspers says that the designation, though, applies only to oral consumption – swallowing in liquid form, in this case – of the flavoring additives, and the potential for toxicity due to inhalation is unstudied.

"The digestive systems and respiratory systems are very different," says Jaspers, the deputy director of the UNC Center for Environmental Medicine, Asthma and Lung Biology. "Our stomachs are full of acids and enzymes that break down food and deal with chemicals; this environment is very different than our respiratory systems. We simply don't know what effects, if any, e-cigarettes have on our lungs."

The research, funded by the National Institutes of Health, showed that cigarette smoking suppresses immune genes in the nose's mucous membrane; not only did smokers of e-cigarettes show suppression of the same genes, but in some cases an ever wider number of immune genes were suppressed. The research suggests that it's not just tobacco in cigarettes, but the act of inhaling smoke or vapor that contains nicotine, irrespective of tobacco, that affects the body.

The team also conducted separate experiments on cinnamon-flavor additives. "We found that cinnamaldehyde e-liquids have a significant negative effect on epithelial cell physiology," Jaspers said. "The chemicals compromise the immune function of key respiratory immune cells, such as macrophages, natural killer cells and neutrophils."

Jaspers aims to continue her research and will look into how long-term exposure to e-cigarette vapor and flavor additives can affect the body and potentially impair the immune system from properly functioning. The research was announced on Thursday, Feb. 11, at the annual American Association for the Advancement of Science (AAAS) meeting in Washington, D.C.

Another study into e-cigarettes will be presented on Friday, Feb. 12, at the same conference. Daniel J. Conklin, a professor of medicine at the Unversity of Louisville's Division of Cardiovascular Medicine, conducted a study on mice that found the nicotine in e-cigarettes can accelerate atherosclerosis, a disease that causes plaque and can lead to heart attack, stroke and peripheral arterial disease.

"Currently, we do not know whether e-cigarettes are harmful," Conklin, whose research was not involved with the UNC work, said in a press release preceding the presentation. "They do not generate smoke as do conventional cigarettes but they do generate an aerosol – the vapor – that alters indoor air quality and contains toxic aldehydes. We investigated the direct effects of these toxins on cardiovascular disease in the laboratory."

"Somewhat surprising," he said, "was the finding that either nicotine alone or acrolein [the substance responsible for much of the non-cancerous health detriments in cigarette smoke] alone at levels equivalent to those present in smokeless tobacco or mainstream smoke also increased atherosclerosis in mice."