E-cigarettes damage cells in ways that could lead to cancer

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."

She says her team is now trying to sort out those other substances and their specific effects.

Scientists already know of some troubling chemicals in the products. One is formaldehyde, a known carcinogen. Using the products at a low voltage setting may minimize the production of formaldehyde, research suggests. Another possible culprit is diacetyl, a flavoring agent that has been linked to lung disease. A Harvard study found it in more than three-quarters of flavored e-cigarettes and refill liquids, or "e-juice."

There are nearly 500 brands of e-cigarettes on the market, in more than 7,000 flavors. So scientists have their work cut out for them identifying all the potential problems.

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

She notes that cells in the lab are not completely comparable to cells within a living person. The cells lines that scientists work with have been "immortalized because of certain cell changes," she says. So it could be that e-cigarette vapor has different effects than those seen in the lab.

Also, her team didn't seek to mimic the actual dose of vapor that an e-cigarette user would get.

"In this particular study, it was similar to someone smoking continuously for hours on end, so it's a higher amount than would normally be delivered," she says. "What we're looking at now is to dose-control these. We want to know at what dose it causes that critical switch-over to where we see the damage."

The overarching question is whether the battery-operated products are really any safer than the conventional tobacco cigarettes they are designed to replace.

Wang-Rodriquez doesn't think they are.

"Based on the evidence to date," she says, "I believe they are no better than smoking regular cigarettes."


Veterans Affairs Research Communications


  1. Paul Barnes Paul Barnes United Kingdom says:

    So, stick some cells in a petri dish so they swim about in e-liquid “extract” and see if the cells “die”, which they will do in pretty much any scenario.

    Key points missing:
    - the non-treated cells also showed signs of cell death.
    - exposure was for 24/7 for up to eight weeks
    - the cells used in the experiment are technically human, but you don’t have any like them in your body
    - cell cultures were specifically chosen from cancerous cell lines

    Drowning near-human cells in anything will have an effect, but you cannot specifically claim that it is “cancer causing”. You can say they have similar effects as some things that cause cancer – and some things that don’t. (HNSCC), a disease for which traditional cigarette smoking is a well-established risk factor yet the potential role of e-cigs has remained entirely unexplored.

  2. Júlio Cesar Darvas Júlio Cesar Darvas Brazil says:

    Making the statement "I believe they are no better than smoking regular cigarettes" without comparing the results of the same test with tobacco is only junk science.

    Shame on you Dr.

  3. pamela gorman pamela gorman United States says:

    Anyone capable of minimal critical thought can see this is not just "junk science" but over-the-top such that one would wonder if the whole study was designed to engineer a desired outcome.  Not-normal cells being treated for not-real exposure times and not-real concentrations of a substance is bad scientific method.  

    But, drawing conclusions (as this researcher has) and pushing out the results into the press with propaganda style demonstrates a level of brazen unethical practice that is at once shocking and sad.  There was a day when no researcher would sink this low and be taken seriously by her peers in her field.  But, modern "science" is an unhinged broken system wrought with corporate interest service and perverse incentives by funding which has seemingly tapped into the most base of human tendencies to survive.  

    This study shows nothing about the true effects of e-cigarettes on humans. What it does show is that the scientific community, as a whole, is desperately in need of correction.  No researcher should feel confident doing and saying what this one has without fear of public humiliation and career ruining blowback.  Sadly, I believe this is now the "norm" and not the exception.  Ethics be damned, I guess?

    But, when people literally will be making life and death decisions based on the outcomes of research, saying "I believe they are no better than smoking regular cigarettes," is a dangerous and unethical new low.  Congratulations, Jessica, you have now equated yourself with the now infamous crew of tobacco-paid scientists who used to twist their junk science results and tell the world that smoking was safe.  People believed them. And people died.

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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