Cell harm seen in lab tests of e-cigarettes

Adding to growing evidence on the possible health risks of electronic cigarettes, a lab team at the Veterans Affairs San Diego Healthcare System tested two products and found they damaged cells in ways that could lead to cancer. The damage occurred even with nicotine-free versions of the products.

"Our study strongly suggests that electronic cigarettes are not as safe as their marketing makes them appear to the public," wrote the researchers, who published their findings in the journal Oral Oncology.

The U.S. Food and Drug Administration does not regulate e-cigarettes like it does conventional tobacco products. But it has warned of possible health risks. So far, though, evidence is limited on what exactly e-cigarettes contain and whether those chemicals are safe, particularly in terms of cancer.

"There haven't been many good lab studies on the effects of these products on actual human cells," says Dr. Jessica Wang-Rodriquez, 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. She specializes in studying head and neck cancer.

Her team created an extract from the vapor of two popular brands of e-cigarettes and used it to treat human cells in Petri dishes. Compared with untreated cells, the treated cells were more likely to show 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 two long strands of molecules that intertwine. When one or both of these strands break apart and the cellular repair process doesn't work right, the stage is set for cancer.

The affected cells were also more likely to launch into apoptosis and necrosis, which lead to cell death.

In the main part of the experiment, the team used normal epithelial cells, which line organs, glands, and cavities throughout the body, including the mouth and lungs.

The scientists tested two types of each e-cigarette: a nicotine and nicotine-free version. Nicotine is what makes smoking addictive. There is also some evidence it can damage cells. The San Diego team found that the nicotine versions caused worse damage, but even the nicotine-free vapor was enough to alter cells.

"There have been many studies showing that nicotine can damage cells," says 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."