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New Data on Cell Phones and Cancer

This is a science and medicine story we have been following for a while – out of personal and scientific interest, and the need to correct confused or misleading new reporting on the topic. Are cell phones linked to an increased risk of brain cancer or other tumors? New data is reassuring.

David Gorski and I have both written on this topic. To give a quick summary, there is no convincing data to link cell phone use and brain cancer. Epidemiological studies have not found an increase in the incidence of brain cancer following the widespread adoption of cell phones in the mid 1990s – as one would expect if there were a causal relationship. Further, large scale studies have not found any consistent correlation between cell phone use and brain cancer.

It is clear from the literature that there is no measurable increased risk from short term cell phone use – less than 10 years. There is no evidence to conclude that there is a risk from long term use (> 10 years) but we do not yet have sufficient long-term data to rule out a small risk. Further, the data is somewhat ambiguous when it comes to children – still no convincing evidence of a link, but we cannot confidently rule out a link.

Further, the plausibility of a connection is quite low. While electromagnetic radiation from cell phones is a physical mechanism that can potentially have an effect, it is generally too weak to have any plausible biological effect. This by itself is very reassuring, but still cannot rule out a possible effect from cell phones through some as yet undiscovered biological effect of cell phone radiation.

So the claim for a link between cell phones and brain cancer has low plausibility, good epidemiological evidence for a lack of association for less than 10 years of exposure in adults, and equivocal but generally negative evidence for children and greater than 10 years of exposure in adults. Longer term studies will hopefully address these latter issues more definitively.

With that as background, we have the newly published results of the Interphone study. This is an epidemiological study involving 13 different countries looking for any correlation between cell phone use and two common types of brain tumors – glioma and meningioma. Parts of this data have been previously published, but this is now the first time data from all 13 participants has been published – including “2,708 people with glioma, 2,409 with meningioma and 7,658 matched controls.”

The overall findings of the study were negative – no clear association between cell phone use and gliomas or meningiomas. However, there were two interesting subgroup findings. For those with regular use of cell phones there was a 20% decrease in risk of tumors compared to those without any use of cell phones.

As implausible as it is that cell phones cause brain cancer, it is even more implausible that they protect against cancer. So, it’s possible this is just noise in the data. However, epidemiologist Anthony Swerdlow, who was involved in the UK arm of the study, gives another explanation:

“We have evidence that the people who refused to be controls are people who didn’t use phones. This meant that the control group, consisting of people without cancer, was rather skewed, appearing to have more mobile-phone use than would be found in a representative sample from the general population. “The controls were over-represented with phone users.”

These results, therefore, were very likely due to a systematic bias in the data – such are the perils of epidemiology.

The other correlation found was a 40% increase in risk of brain tumor among the top 10% of mobile phone users. This is an interesting result, because it suggests a dose response effect. However, this result is also questionable and may be due to methodology. It turns out that many of the people answering the survey used in the study reported improbable amounts of cell phone use – such as 12 hours per day. It was therefore considered to be an unreliable method of determining cell phone use. Number of calls made per day gave more realistic results, and therefore may be easier for people to understand or remember. When the data is viewed with number of calls made instead of time per day, the correlation with brain tumors disappears.

So at the end of all this, we are pretty much where we started. There is still no evidence to link cell phone use and cancer. This data has a few quirks in it, but in the final analysis is probably negative. So we can be a bit more confident in the lack of correlation – or we can think of it as shrinking a bit further the upper limit of any possible effect from cell phone use.

The study does extend the duration of our data somewhat as well – to about 15 years. But we still lack long term data for exposure greater than 15 years.

Unfortunately, the wrinkles in this study lead to some confusion among the media. While reporting this study it is possible to emphasize the increased risk among the highest cell phone users, while either missing or glossing over the fact that further analysis shows this correlation is probably not real. For example, Science News reports: “Interphone study finds hints of brain cancer risk in heavy cell-phone users.” Many other outlets repeated the headline that the study was “inconclusive.”

Conclusion:

Cell phones are an increasingly common tool of modern society. It is certainly necessary and valid to carefully study their safety and monitor for possible adverse health outcomes from their regular use. I am reassured by the current evidence, however, that there is no large risk from cell phones. There is either no risk or a very small long term risk.

Consider, however, that you are probably at greater risk of premature death from using your cell phone while driving, or from driving at all. So as individuals we always need to balance a small risk against the convenience of new technology. The better data we have and the better we understand that data – the better we will be able to make informed decisions for ourselves.

Posted in: Cancer, Public Health

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41 thoughts on “New Data on Cell Phones and Cancer

  1. BillyJoe says:

    The whole cellphone/cancer fiasco started with an interview by a well known american talk show host with the husband of a woman who died of a brain tumour. This person decided that her use of a cellphone was the cause of his wife’s brain tumour just because she happened to use the phone on the same side of the head. Or so he remembered. He was, I think, suing the cellphone manufacturers.

    (I have unsccessfully tried to verify this story so this is as I remember it)

    15 years and millions of dollars and wasted man hours later, and, despite lots of evidence to the contrary and very little in support, in the eyes of the public there is still a link between cellphones and brain cancer. This is mostly the result of a combination of media misreporting and exaggeration and “experts” providing inexpert or misguided commentary.

    Meanwhile cellphone use continues to rise. Apparently they are just too convenient to use. The public’s false belief in the cellphone/cancer link and their continued use of cellphones forming a sort of stable cognitive dissonance.

  2. qetzal says:

    My comments:

    1) Why is it even less likely that cell phones might reduce brain cancers? If cell phones affect brain cancer risk at all, they must be having some effect on the brain. I agree that’s highly unlikely, and there’s no obvious mechanism for such an effect. But if we assume an effect might nevertheless exist, why is a positive effect obviously less plausible than a negative one? Especially since any effect is clearly very small.

    IMO, if we’re willing to entertain a possible small negative effect of cell phones, despite the absence of a scientific basis, we should be equally willing to entertain a possible small positive effect.

    2) I wonder if language such as this may confuse many lay readers:

    The other correlation found was a 40% increase in risk of brain tumor among the top 10% of mobile phone users.

    To me, this sounds like it’s saying that high mobile phone use actually increases brain tumor risk. But what the study actually found was that brain cancers were more common among people in the study who reported high mobile phone use. I wonder if the latter phrasing (or something similar) would help at least some reporters and lay readers realize that such findings don’t necessarily show a true risk.

    Of course, I’m aware that such risk statements are a common way of stating such results, and that experts understand what they actually mean. But even experts are human and prone to inappropriate interpretations. Just a thought.

  3. “It turns out that many of the people answering the survey used in the study reported improbable amounts of cell phone use – such as 12 hours per day. It was therefore considered to be an unreliable method of determining cell phone use. Number of calls made per day gave more realistic results, and therefore may be easier for people to understand or remember. When the data is looked at with number of calls made instead of time per day, the correlation with brain tumors disappears.”

    Why were they relying on self-reporting for amount of time spent on the phone? Wouldn’t it be better to look at the cellphone call records?

  4. windriven says:

    FDA/CDRH released this today under the headline, “No Evidence Linking Cell Phone Use to Risk of Brain Tumors”:

    http://www.fda.gov/downloads/ForConsumers/ConsumerUpdates/UCM212306.pdf

    Clearly this establishes beyond doubt a conspiracy between the US government and Nokia to protect Nokia’s profits at the expense of Americans’ health.

    Get a rope…

  5. Scott says:

    Why were they relying on self-reporting for amount of time spent on the phone? Wouldn’t it be better to look at the cellphone call records?

    One might suspect that people would be sufficiently hesitant about giving out those records to pose a significant recruitment problem.

  6. superdave says:

    If we are really just trying to determine cell phone safety, we should look at all possible risks not just the most scary sounding. I am glad you mentioned the cell phone car bit.

  7. scott – “One might suspect that people would be sufficiently hesitant about giving out those records to pose a significant recruitment problem.”

    I suppose that could be true, but it just seems like a waste when I’m sure there are perfectly good ways to collect the data accurately and still maintain privacy.

  8. Scott says:

    In principle, sure. But *trusting* the methods used is a different matter than whether they work.

  9. superdave
    “If we are really just trying to determine cell phone safety, we should look at all possible risks not just the most scary sounding. I am glad you mentioned the cell phone car bit.”

    I agree – But I feel compelled to point out, having been a pedestrian in a car where my (past) boss was talking on his cell phone, checking his schedule and driving 90 miles an hour in heavy traffic, I can assure you that cell phone driving is REALLY scary. ;)

  10. #
    # Scotton 19 May 2010 at 1:05 pm

    In principle, sure. But *trusting* the methods used is a different matter than whether they work.

    True – but the people have cell phone accounts that can be hacked into, they probably communicate online, which can be hacked into. Is there a reason to trust the researchers methods will work less than verizons, comcasts or googles?

  11. BenAlbert says:

    In reply to QETZAL: (sorry I’m not sure how to quote properly)

    “IMO, if we’re willing to entertain a possible small negative effect of cell phones, despite the absence of a scientific basis, we should be equally willing to entertain a possible small positive effect.”

    Not equally willing. There are many more ways to damage an intricate system than to improve it.

    To apply this to the complex system of growth factors, receptors, second messengers and the genes they interact with and encode those growth factors, receptors etc and control the cell cycle, it is easy to imagine ways to disrupt this system.

    At least it is easy to imagine ways to disrupt it with ionising radiation such as xrays. With microwave range radiation it is less easy but not implausible that there could be effects on the system that lead to perturbations of the system, ultimately leading to genetic change and loss of cell cycle regulation. Maybe for example heat causes mild tissue damage and resultant inflammation and repair, this proliferation carries with it a small chance of a genetic error and repeated cycles over time add up to eventually lead to a tumour in some people. We of course have not seen convincing evidence that this occurs – I made it up.

    To imagine that microwave radiation improves the workings of this delicate system is harder, less plausible and so while not impossible (hey maybe the heat effects preferentially damage very early and shallow brain tumours), I do not think we should be equally willing to believe the two propositions.

    -Ben

  12. David Gorski says:

    Exactly. It is always easier to damage a system than to repair it, particularly in biology.

  13. trrll says:

    Biologists are more cautious that physicists in making blanket assertions as to what biological systems can and cannot do. There is evidence that birds can sense the magnetic field of the earth. This is a very low energy interaction, well below the ionization energy threshold. That implies that there is some molecular system capable of responding to very small magnetic fields and amplifying that signal. In principle, one could imagine similar amplification mediating a pathological response.

    Likely? No. But not something that can be dismissed out of hand.

  14. David Gorski says:

    Precisely. Biological systems constantly surprise us, and over the last couple of decades we’ve learned that there are multiple mechanisms that don’t require direct DNA damage by the inciting agent that can predispose or result in cancer.

    As I’ve said elsewhere, the hypothesis that cell phone radiation causes cancer is very, very implausible, but it’s not homeopathy-level implausible by a long shot and it’s not impossible.

  15. Maybe cost was the issue. Unless there is a system already in place that collects the data in a way that is sensitive to privacy concerns, it is probably cheaper to use self reporting. Also, it’s hard to think of a way that you could reuse your cellphone use data collection application once the research is concluded, so you can’t spread the cost out over many projects.

    But it would have been cooler to use the real cellphone hours…

  16. cervantes says:

    Unfortunately, this is one of those questions that’s never going to be answered to the satisfaction of true believers by means of observational studies. You can always find objections to them. And there’s basically no way to do an experiment on humans.

    The whole thing might fade away just because these cancers are rare and there isn’t a big constituency for the proposition, but if somebody wants to believe it, they’ll keep on believing it.

  17. qetzal says:

    It is always easier to damage a system than to repair it, particularly in biology.

    Sure, if you’re heating it to 45C or blasting it with ionizing radiation. But if anything is going on re cell phones and cancer, it’s much more subtle. IMO, that makes it harder to argue that small positive effects are substantially less likely than small negative ones.

    Less likely – sure. But much less likely – to the point that we should entertain possible negative effects but not possible postive ones? I don’t think so.

  18. BillyJoe says:

    “As I’ve said elsewhere, the hypothesis that cell phone radiation causes cancer is very, very implausible, but it’s not homeopathy-level implausible by a long shot and it’s not impossible.”

    I would have been inclined to leave out the “by a long shot”.

    Also, as yest undiscovered mechanisms would very likely have a very small effect perhaps almost to the level of being undetectable. For example, the heat effect of cellphones is much smaller by far than the heat effect of walking in the sun. And, although a synergistic microwave/heat effect might possibly have a greater effect than heat alone, we are multiplying unknowns.

  19. BillyJoe says:

    …oh $#!+ the moderation dragon had hit.

  20. Charon says:

    “[We] still cannot rule out a possible effect from cell phones through some as yet undiscovered biological effect of cell phone radiation”

    I’m sorry, as a physicist, I just don’t agree. The question is not whether or not there is some undiscovered biological effect. You need an undiscovered interaction between light and matter to induce cancer, and I have to tell you, the interaction of light and matter is understood really well. Unless you can get cancer without breaking any chemical bonds, we can definitively say cell phones can’t cause cancer. SBM, not EBM.

  21. Charon says:

    And if you’re relying on there being some unlikely but not impossible mechanism that has no evidence for it, theoretical or experimental, then you can’t stop with cell phones. WiFi, power lines, radio broadcasts, GPS, cosmic rays… any radio astronomer can tell you in great detail how damn hard it is to get away from electromagnetic interference. Until you have some sort of plausible mechanism, how can you justify looking at cell phones instead of any of these other sources? With no mechanism, you can’t even justify assuming a dose-response relationship.

    Physicists aren’t telling the biologists that we know everything about how to cause cancer. What we are saying is that there is no mechanism even proposed for how cell phones might do it, and when you’ve got no mechanism, you can’t justify spending any more time thinking about cell phones than about solar neutrinos, when looking at cancer etiology.

  22. David Gorski says:

    Charon,

    Actually, you can get cancer “without breaking chemical bonds”–with an important qualification. You see, you make a big assumption, namely that it is the inciting agent that has to break chemical bonds directly. Such is not the case. There are epigenetic, metabolic, immune, and stromal contributors to and causes of cancer that do not require the direct breaking of chemical bonds, and carcinogenesis is a multistep process. Although mutations do ultimately occur later, they may be a downstream effect, with multiple steps between their appearnce and the inciting exposure. Low grade chronic inflammation, for instance, can cause cancer; that’s been well known for decades. Asbestos, for instance, definitely causes cancer, and we still don’t know why, as asbestos fibers do not, as far as we know, break any chemical bonds within the cell.

    You see, when I see physicists argue that the hypothesis that cell phones cause cancer is impossible on a strictly physical basis, as a cancer researcher I cringe inside. The reason is that I know they are they almost always making such arguments based on an understanding of cancer that is simplistic at best and at least a decade out of date. For an idea of how complex cancer is, check out:

    http://www.sciencebasedmedicine.org/?p=4832

    In any case, again, I’m not arguing that it is a plausible hypothesis that cell phones cause cancer. I’m simply arguing that it is not impossible based on what we know now and that it is not even homeopathy-level improbable. In fact, my own personal opinion on the data is that cell phone radiation doesn’t cause cancer. However, I’m not so confident that I don’t leave a tiny crack in the door.

  23. addisontree says:

    What are the mechanisms for radiation to effect living tissue? It can heat the tissue or break chemical bounds in the cells in the tissue. Are there other mechanisms? (I really don’t know; I’m embarrassingly ignorant when it comes to biology.)

    I think the physicists may have a point. Sure cancer can be caused by many things. For example, holding your empty hand over your ear for 10 hours a day every day might slightly increase your risk for cancer. The extra heat could cause irritation or increase the rate of chemical processes or trigger an immune effect and could result in increased rates of cancer. There are probably several theoretically possible mechanisms that can’t be completely ruled out. But really, how likely is it that holding your hand to your ear for 10 hours every day would increase cancer rates?

    I think the physics tell us that the radiation coming off a cell phone is no more likely to affect biological processes than holding a hand to your ear without a cell phone.

    Or am I missing something?

  24. addisontree says:

    Just thought of one more subtle effect.

    What is the effect on cancer rates of simply engaging in normal conversation for 10 hours every day with your social group? Talking coherently is a complicated process and causes specific types of brain activity. Further, emotional conversations (and for some people all conversations are emotional) can cause mood swings resulting in changes to brain chemistry (like maybe adrenaline when a conversation makes you angry).

    This mechanism, a priori, seems just as likely a mechanism as radiation from the cell phone. And yet recommending less socializing to reduce risk of cancer would be recognized as absurd. (I think…)

  25. Wolfy says:

    If science based medicine eventually discovers that cell phones cause cancer, hopefully Apple will be able to quickly come up with “an app for that.” ;)

  26. weing says:

    I hope it doesn’t cause cancer. But I read recently that it seems to protect against Alzheimer’s, at least in mice.
    http://www.j-alz.com/press/2010/20100106.html

  27. trrll says:

    “Unless you can get cancer without breaking any chemical bonds, we can definitively say cell phones can’t cause cancer. SBM, not EBM.”

    Keep in mind that there are energy sources already present in the cell that are fully capable of breaking covalent bonds. ATP, ion gradients, free radicals. Bonds are being broken all the time just in the normal course of cellular metabolism. The very fact that you can feel your phone warm up when you are using it means that that little bit of thermal energy is sufficient to alter the firing patterns of neurons, a process involving large numbers of ions traveling down electrical gradients of a hundred millivolts or so.

  28. JMB says:

    I guess I may have been confused by my education, but I thought microwave radiation produced free radicals. While a free radical chemical reaction won’t directly change the sequence of the DNA, it may have indirect effects such as producing reactive oxygen species that can damage the DNA. But I have only an undergraduate education in chemistry.

    I am not arguing that cell phone use causes brain tumors. I would accept the author’s arguments. But I would think there is a plausible reason to worry about a link.

  29. Matlatzinca says:

    Given the preponderance of negative data, as well as the lack of a proposed causative mechanism, I was surprised to see that the President’s Council report released last week on Cancer Prevention included a section detailing decreasing use of cell phones. Clearly this was a mostly political document, though, and not the only nit I had to pick with their “recommendations”

  30. Harriet Hall says:

    weing, I wrote about the protection from Alzheimer’s in mice at http://www.sciencebasedmedicine.org/?p=3666 You may have missed it.

  31. weing says:

    Harriet,

    So that’s where I must have read about it and couldn’t remember where. (Gotta use the cellphone more) I had to search out the reference. I thought the picture was cute.

  32. “# addisontreeon 19 May 2010 at 10:00 pm

    Just thought of one more subtle effect.

    What is the effect on cancer rates of simply engaging in normal conversation for 10 hours every day with your social group? Talking coherently is a complicated process and causes specific types of brain activity.”

    Well, I’ve overheard a lot of cellphone conversations and I’m not sure “talking coherently” is actually the activity. :)

  33. David Gorski says:

    Given the preponderance of negative data, as well as the lack of a proposed causative mechanism, I was surprised to see that the President’s Council report released last week on Cancer Prevention included a section detailing decreasing use of cell phones. Clearly this was a mostly political document, though, and not the only nit I had to pick with their “recommendations”

    Agreed, and I pointed that out in my analysis of the report:

    http://www.sciencebasedmedicine.org/?p=5045

  34. trrll says:

    The energy of microwave photons is inadequate to generate free radicals directly. There is no physical way the microwaves themselves at the low intensity of a cell phone can directly cause harm to any component of a cell. Basically, your cells would have to work at being harmed by microwaves–i.e. the cell would somehow have to respond to the microwaves in such a way as to use the cell’s own energy stores to harm it. This is quite far-fetched, but not quite impossible.

  35. desta says:

    A few things:
    1. Self reported minutes? And who really cares about privacy? Have you been on facebook? Seems like a study design flaw to me, and there could have been work-around ways to get the actual number of minutes on the phone without ruining privacy. I can view my minutes online any time I want. If you want a dose(or non-dose, in the case of cell phones IMO)-response type curve, this seems like the easy way to go.

    2. Even if the highest levels of cell phone use are accurately self-reported (given that 12 hrs a day is even possible), two words: confounding factors. Seems like you’ve got one stressful, complicated life if you’re on the phone that much, and considering lifestyle issues would certainly be high on my list for those unusually high volume users.

    3. Type I error: Suppose you do a bunch of studies looking for the correlation between two things that you know are not correlated. Even with no relationship, some of the time, it is quite likely that a few of the studies will show significance. So a little positive effect here for cell phone, a whole bunch of no effects, and a little negative effect in a study here or there, means that cell phone use and cancer rates are behaving a lot like they would if they had little to nothing to do with each other. I can’t speak to the biological plausibility, but from a statistical standpoint, whew, beneficial effect of cell phone use sure seems like a stretch to me. And that’s not even considering the biases in the study that Dr. Novella pointed out.

  36. desta says:

    OH, and I haven’t been able to listen to Living on Earth (npr) since they did a completely credulous report of cell phone use/cancer with nary a skeptical peep.

    http://www.loe.org/shows/segments.htm?programID=10-P13-00012&segmentID=1

    From the intro “the science is inconclusive”——soooo misleading. Then listen to the piece. I was so disappointed.

    Looks like no matter how many studies are done, they will be ‘inconclusive.’Sound familiar?

  37. anoopbal says:

    What do you think about his Steve: http://www.ted.com/talks/william_li.html

    He talks about angiogeneisis and cancer. Had a some good pics and case studies which says nothing.. i think it’s too early to say anything.

  38. I feel compelled to point out, having been a pedestrian in a car where my (past) boss was talking on his cell phone…

    micheleinmichigan, that must have been one very big car! ;-)

  39. DrBombay says:

    It doesn’t matter now what science proves, the people who have already heard that cell phones cause cancer and believe it are never going to change their minds.

    Partly because most people have no idea what radiation is or that there are different kinds, etc, and partly because people old enough not to have grown up with cell phones still maintain a vague fear and hatred of them (probably from the days when someone using a “car phone” was obviously a wealthy, arrogant, egotistical ass). A lot of people just plain hate cell phones and love to think “those idiots with cell phones are killing themselves, serves ‘em right!”

    Look how many people believe a cell phone can cause a fire at a gas station, even though it’s never happened and pretty much couldn’t happen. Even the oil companies pay to print up and distribute warning stickers to put on all their pumps saying so; some places have laws requiring them! And meanwhile, it’s just plain false.

  40. DrBombay says:

    @KimballAtwood:

    Maybe michelleinmichigan was crossing the road and landed in the car when her boss hit her because he was talking on his cell phone?

  41. BillyJoe says:

    “A lot of people just plain hate cell phones and love to think “those idiots with cell phones are killing themselves, serves ‘em right!””

    I just plain hate cellphones but, unfortunately, I have to admit (because that’s where the evidence lies) they are not killing people. :(

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