Evidence of the potential health risks of electronic cigarettes is growing. A California laboratory team tested two electronic cigarette products and found both products, and their nicotine-free versions, caused cell damage that could lead to cancer. These findings were published in Oral Oncology (doi:10.1016/j.oraloncology.2015.10.018).

“Our study strongly suggests that electronic cigarettes are not as safe as their marketing makes them appear to the public,” wrote the researchers, who work at the Veterans Affairs (VA) San Diego Healthcare System in California.

The US Food and Drug Administration does not regulate e-cigarettes the same as it does conventional tobacco products. However, it has issued warnings of possible health risks. So far, though, the evidence on what exactly e-cigarettes contain and whether those chemicals are safe, particularly in terms of cancer, is limited.

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“There haven’t been many good lab studies on the effects of these products on actual human cells,” said Jessica Wang-Rodriquez, MD, a specialist in studies of head and neck cancer and one of the lead researchers on the new study. She is a professor of pathology at the University of California San Diego, and chief of pathology and laboratory medicine at the San Diego VA.

Her team created an extract from the vapor of 2 popular brands of e-cigarettes and exposed human epithelial cells to the extract in Petri dishes. Compared with unexposed cells, the exposed cells were more likely to suffer DNA damage and die.

The exposed cells showed several forms of damage, including DNA strand breaks. The familiar double helix that makes up DNA has 2 long strands of intertwining molecules. When one or both of the strands break apart and the cellular repair process is not working correctly, the stage is set for cancer. The affected cells were also more likely to launch into apoptosis and necrosis, leading to cell death.

The scientists tested both nicotine and nicotine-free versions of each e-cigarette. Nicotine is the compound that makes smoking addictive. There is also some evidence that it damages cells. Although the San Diego team found the damage was worse with the nicotine versions, even the nicotine-free vapor altered cells.

“There have been many studies showing that nicotine can damage cells,” said Wang-Rodriguez. “But we found that other variables can do damage as well. It’s not that the nicotine is completely innocent in the mix, but it looks like the amount of nicotine that the cells are exposed to by e-cigarettes is not sufficient by itself to cause these changes. There must be other components in the e-cigarettes that are doing this damage. So we may be identifying other carcinogenic components that are previously undescribed.”

Wang-Rodriguez’ team is now trying to sort out those other substances and their specific effects. With nearly 500 brands of e-cigarettes in more than 7000 flavors, scientists have their work cut out for them identifying all the potential troublemakers.

“For now, we were able to at least identify that e-cigarettes on the whole have something to do with increased cell death,” said Wang-Rodriguez. “We hope to identify the individual components that are contributing to the effect.”