E-Cigarette Vapor Found to Damage Human Cells

As the popularity of electronic cigarettes (e-cigarettes) continues to grow, so too have concerns about possible adverse health effects associated with their use. A study published in the Journal of Oral Oncology now suggests e-cigarette vapor—with or without nicotine—may be damaging to the cells that line the throat and neck.

“Right now many clinicians are unsure about what to say to their patients about the safety of e-cigarettes,” said Douglas Ziedonis, M.D., M.P.H., a substance abuse expert and chair of the Department of Psychiatry at the University of Massachusetts Medical School, who was not involved with this study. “This study provides additional, yet concerning, information to consider given that the clinical implications involving the health risks of e-cigarette use are not fully known at this time,” he told Psychiatric News.

Since the introduction of e-cigarettes in the United States in 2007, the popularity of the mechanical devices has grown. According to the Centers for Disease Control and Prevention, overall use increased from 3.3 percent in 2010 to 8.5 percent in 2013; from 2011 to 2012, usage doubled among adolescents (Psychiatric News, April 18, 2014).

The products—which allow users to inhale an aerosolized “e-liquid” in place of traditional tobacco smoke—have been portrayed by manufacturers as a safe alternative to traditional smoking and a smoking cessation aid. However, there is little scientific evidence to back these claims.

In the current study, a research team led by Jessica Wang-Rodriguez, M.D., chief of the Pathology and Laboratory Medicine Service Line at the VA San Diego Healthcare System, exposed a panel of normal human epithelial cell lines and head and neck squamous cell carcinoma lines to nicotine-containing (12mg /mL) and nicotine-free vapor extract from two popular e-cigarette brands for periods ranging from 48 hours to eight weeks. For comparison, cells were also treated with conventional cigarette smoke or with 0.5 mM nicotine, with both nicotine concentrations equivalent to that of the treatment media for nicotine-containing e-cigarettes.

The researchers found that cells exposed to e-cigarette vapor—with or without nicotine—were significantly more likely to show signs of cellular damage, including breaks in DNA strands, compared with cells that were not exposed to the vapors. In addition, cells exposed to the vapors were significantly less likely to sustain viability and more likely to experience cell death than unexposed cells.

Cells that were exposed to smoke extract from conventional cigarettes had the highest number of DNA strand breaks, but did not significantly differ in the number of strand breaks compared with cells exposed to the nicotine-containing e-cigarette vapor.

“Our study strongly suggests that electronic cigarettes are not as safe as their marketing makes them appear to the public,” the study authors wrote. “We have shown that the cytotoxic effects of e-cig vapor are mediated through nicotine as well as non-nicotine components of the e-liquid.”

During an interview with Psychiatric News, Wang-Rodriguez added, “This paper raises awareness and encourages additional investigations on various ingredients in e-cigarettes that are currently unknown to users and that may be harmful to human cells and tissues.”

Wang-Rodriguez said that she and her colleagues are working to identify the e-liquid contents that may have contributed to the cellular damage observed in cells that were exposed to nicotine-free e-cigarette vapor and plan to examine the effects of e-cigarette vapor on tissues and organs in animal models.

The study was supported by the National Institutes of Health. ■

An abstract of “Electronic Cigarettes Induce DNA Strand Breaks and Cell Death Independently of Nicotine in Cell Lines” can be accessed here.