Oct 10 2007

Do Cell Phones Cause Brain Tumors?

Gee, I really hope not. That would be tragic. Brain tumors are no fun and the idea that something as useful and commonplace as cellphones is increasing the risk of brain tumors is very disturbing. But my personal preferences aside (even if they are likely to be representative) this is one of those important questions that can and should be answered by a dispassionate, careful, and systematic look at all the evidence.

So far the answer appears to be – probably not, but we’re not sure. More study is needed.

But science is not easy, and a seemingly simple question such as – “do cell phones cause cancer?” turns out to be very complex. Exploring this complexity (much of which is common to any such question) is a good place to start, and also can provide a guide to thinking about such questions in the future – and such questions are likely to be endless in our increasingly technological society.

There are two types of scientific studies we can do to answer this question. The first is biological and looks at the effects of radiation, and specifically the type and strength of radiation emitted by cell phones, on cells in a test tube and on animals. This will tell us if a risk from cell phones is plausible, if there is a mechanism, and what, if any, the effects are likely to be. But this kind of data will not tell us if cell phones in fact have caused or are causing brain tumors.

The second kind of scientific evidence is epidemiological, which looks for a correlation between cell phone use and brain tumors. Epidemiological studies look more directly at the actual question, but have their own complexities and limitations. It is difficult to impossible to perfectly isolate the variable of interest (cell phone use) an measure its correlation to another variable (brain tumors). Further, as soon as you start asking the question a miriad of sub-questions emerge:

How much cell phone use is necessary to cause a brain tumor? This further breaks down to the variable of intensity of the radiation, frequency and duration of exposure, and duration of total exposure. And further, is there an apparent dose-response – does a higher does of cell phone radiation cause an increased risk of tumors?

What kind of tumors are we talking about? Does use correlate with an increased risk of benign tumors, all tumors, only malignant tumors? Does is correlate with tumors on the side of preferred cell phone use, or anywhere in the brain? What if cell phone use increases the risk of getting cancer from other causes, but is not a risk by itself. In other words, maybe smokers get more smoking-related cancers if they also use cell phones.

Then there is the issue of sub-populations. Are children more at risk? What about men vs women, those with compromised immune systems, and short-statured albinos?

There are also different ways to look at the data. We can begin with a population of cell phone users and another population of non-cell phone users, follow them over time and keep track of who gets what kind of brain and other tumors. (This is called a cohort study). Or, we can look at 100 people with brain tumors and then quiz them about their prior cell phone use. Or you can do a population study by surveying a large population for a number of variables, like cell phone use and brain tumors, and then do a statistical analysis to look for correlations.

And here we begin to see the problem with epidemiological studies. They provide very useful information, but variables can multiply endlessly forever muddying the waters. A pattern can emerge, however, after multiple different types of epidemiological studies are completed on different populations with varying methods. A consistent pattern favoring a lack of correlation, or a positive correlation, can emerge and become highly reliable. Although it must be pointed out that such studies cannot prove, by definition, the absence of any correlation. They can only set statistical limits on the probable maximum size of any such correlation. A correlation smaller than the power of the studies to detect is always possible. It may seem pedantic to point this out, but often researchers have couched their conclusions in such terms leading true-believers to declare, “Aha, they are admitting they cannot rule out that watching reruns of Law and Order causes POF (particularly objectionable flatulence).”

So what does all this science stuff say about cell phone use. The biological studies hare largely been negative, although some studies have shown changes in cells or their genes after prolonged exposure to cell phone radiation. However, the exposures were greater than what would occur with even frequent cell phone use, so the utility of these studies are questions.

The epidemiological evidence can best be described as “mixed.” In other words, there is no strong signal, no strong correlation between cell phones and brain tumors. Neither, however, has any correlation been adequately ruled out. We are still in that pesky “we need more data” phase. Here is the FDA summary of the evidence so far.

A recent meta-analysis suggested that there may be a small increase in risk for certain kinds of tumors only in those with exposure for greater than 10 years. I do not put a great deal of faith in meta-analyses. They have their own problems. I prefer systematic reviews. But sometimes they give a snap shot of the current literature on a specific question.

This meta-analysis also, however, was published before an even more recent, and very large, UK study that found no association between cell phones and tumors. That’s reassuring, but the literature is likely to go back and forth like this for a while. Eventually, all of the criticisms and short comings of prior studies will be used to design a few very large and fairly definitive studies, and then a firmer consensus will likely emerge.

For now, we remain hopeful but cautious. For those who want to err on the side of caution, there are some reasonable recommendations (these come from multiple organizations, so they seem to represent a consensus, or at least plagiarism).

- Limit your cell phone use (duh.)

- Do not allow small children to begin using cell phones.

- Use a head set to increase the distance from the antenna to your head.

Why not allow kids to use cell phones? This is purely speculative at this point, but the fear is that their thinner skulls will allow more radiation to pass through, their smaller brains will not dissipate the heat as well, and their immature development stage will make them more susceptible to any biological effects. All plausible, but unproven. Studies specifically looking at kids are on the way, but no data yet.

Of course, like any scientific or health issues these days, there is a layer of pseudoscience piled on top of this question. There is one notable crank, Arthur Firstenberg, who has been ranting for years about the evils of cell phones and other wireless technology. His writing reads like classic conspiracy-based fear mongering, with a distinct aftertaste of crank. He quotes numerous dubious scientific claims about cell phones without ever providing proper references, but of course because big industry is hiding what they have all known for nearly a century. Bottom line – don’t believe the hysteria.

There is also a cottage industry of entrepreneurs who would love to cell you a device that protects you from the cell phone radiation. These devices tend to fall into one of three categories: 1) pure magic, like crystals; 2) sound technological but do nothing; or 3) they actually shield cell phone radiation, but at the expense of the wireless signal that makes them work. So far no one has figured out a way to shield against cell phone radiation without shielding against cell phone radiation.

But just because there are some fear-mongering or greedy pseudoscientists out there does not mean that the claims can be dismissed. What the evidence shows is that there is biological plausibility for a negative effect; the epidemiological evidence for any correlation with <10 years of exposure is mixed but leaning negative, and for >10 years of exposure is mixed but leaning weakly positive. I think we can rule out a strong correlation (meaning a large risk), but not a small one. It is reasonable to caution about cell phone use in kids until we get some data either way. An we need more data all around before the question can be put to bed.

I hope you weren’t expecting a yes or no answer.

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14 responses so far

14 Responses to “Do Cell Phones Cause Brain Tumors?”

  1. JFlavon 10 Oct 2007 at 10:18 pm

    “Use a head set to increase the distance from the antenna to your head.”

    Now you’re just opening up the lines of crankery for “Bluetooth devices cause cancer!” attacks.

    Unless you were talking about wired headsets, in which case we can’t even predict what nonsense will ensue.

  2. Adam Lon 11 Oct 2007 at 12:56 am

    Quackwatch has a pretty good article about power lines and cancer:

    http://www.quackwatch.org/01QuackeryRelatedTopics/emf.html

    The short answer: the electromagnetic frequency makes a BIG difference. There is no evidence that the 60Hz magnetic fields from power lines are in any way dangerous. Apart from an early, flawed study every attempt to link power lines and cancer has been negative.

  3. ellazimmon 11 Oct 2007 at 1:48 am

    Thank you for discussing this so thoroughly. There will always be some people who are incapable of understanding the way science works and the statistics involved but there are quite a few people who can be taught given time and patience. I suspect it is evolutionarily beneficial to avoid situations that MIGHT cause harm but just because we are hardwired to seek out patterns doesn’t mean that correlation is causation. And has been mentioned before, if the study is large enough and long enough to be meaningful some participants will develop malign tumours but if that number matches the background rate that helps to confirm non-causation.

    Keep fighting the good fight.

  4. daedalus2uon 11 Oct 2007 at 12:17 pm

    You forgot to mention the readily available shielding, the aluminum foil hat. As a good conductor, aluminum foil is essentially opaque to the RF radio waves that are generated by cell phones. A layer of aluminum foil that covered the entire head would be pretty effective at shielding the brain inside from exposure to cell phone radiation. Of course you would need holes for your eyes, and to breathe, but these can be small and if much smaller than the wavelength of the radiation don’t allow much in. The hole for your neck is more problematic. At these wavelengths, each side of a piece of aluminum foil is equally reflective, there is no “shiny side” at RF.

    The ELF from power lines is quite different. Exposure to very high magnitude ELF is unavoidable simply by moving. The Earth has a magnetic field of about 50 microTesla. When you stand in one place and spin around, the field goes from +50 microTesla to -50 microTesla and back, a change of 100 microTesla over each half rotation.

    This level has not changed over evolutionary time, so presumably organisms have evolved to accommodate it. ELF from power lines is much lower in magnitude (typically less than 1 microTesla). A “toxic” effect from something 2 orders of magnitude smaller than an omnipresent natural exposure seems unlikely. It is at a different frequency, and is always present. ELF from the Earth’s field stops (mostly) when the organism is motionless (as during sleep). There continues to be some natural ELF, but that is variable.

    Some organisms are sensitive to the Earth’s magnetic field and use it for navigation. Perhaps there is some “signal” from the Earth’s magnetic field that organisms use for “something”, and ELF disrupts what ever that “something” is. Perhaps akin to how photoperiod helps to set biological time cycles. If so, artificial light likely disrupts those cycles more and distinguishing between the known effect of photoperiod and the speculative effect of ELF without controlling for photoperiod would not be possible.

  5. kilroyon 11 Oct 2007 at 12:54 pm

    Just 2 small comments:

    First I’ve heard that using a head set may actually be worse than not using one. The explanation being that the head set wires can actually act as an antenna. This would mean that you are broadcasting directly into your ear. I do not know how valid this argument is though.

    Another way to reduce the radiation to which you are exposed, comes directly from a manufacturer (Nokia):
    Many models of cell phones have internal antennae, usually in the upper rear of the device. It is advisable to keep your hands clear of this part of the phone (don’t press it to your ear with your index finger for instance, a common way of holding a phone). The reason is not obvious though. It turns out that if you partially block the transmission, the phone automatically increases the intensity of transmission to make up for the impedance, thereby exposing you to a stronger dose of radiation.

  6. Joshuaon 11 Oct 2007 at 5:27 pm

    johnny: Well, in Steve’s case, it’s no doubt because the studies that have been done have all (or mostly) come back negative, unlike the cell phone studies which tend to be mixed.

    I’m not a doctor, though. I’m an electrical engineer. So for me, it’s a matter of frequency. AC power is typically run at very low frequency (50-60Hz). These frequencies are biologically harmless.

    Cell phones, on the other hand, run at much higher frequencies that could have plausible biological action, particularly the newer technologies that run in the microwave range.

    (Of course, it’s not a simple matter of high frequency = bad, but rather that the frequency ranges that actually cause damage to tissue are all much higher than the frequencies used in power transmission.)

  7. edyong209on 12 Oct 2007 at 4:56 am

    The thing about that recent meta-analysis is that they found that, overall, mobile phone use (even long-term use) had no significant effect on the risk of glioma or acoustic neuroma. That very simple and very key negative result was not reported in the abstract or in any of the subsequent press coverage.

    The analysis also found that mobile phone use was linked to a significantly increased risk of a tumour on the same side of the head that people reported holding their phones too. That could well be due to recall bias i.e. people with brain tumours mis-reporting the side-of-head they held their phones on. Especially since a few of the studies included in the meta-analysis also found a reduced risk of cancer in the opposite side of the head.

  8. dougsmithon 22 Oct 2007 at 4:54 pm

    Just noticed this thread. I was at a talk on this very subject given last summer in Bilbao, Spain by two professors from the University of País Vasco. It was organized by the spanish Círculo Escéptico and the Center for Inquiry as well as a few other local organizations. There is a short writeup about this, in spanish unfortunately, here:

    http://blogs.elcorreodigital.com/index.php/magonia/2007/07/03/dos_cientificos_valientes_contra_la_sinr

    I also started a thread about it on the CFI web forum here:

    http://www.centerforinquiry.net/forums/viewthread/2652/

    The long and short of their conclusion is that there is no credible evidence that cellphone radiation is of any danger. Cellphone radiation lacks the energy necessary to break chemical bonds, which is the only known method of action for cancer-causing radiation. All it can do is to heat tissue. The maximum allowed heating capacity of a cellphone tower is on the order of a half of a degree centigrade in a human body, which is something less than you’d get on a sunny day.

    This dovetails nicely with physicist Robert Park’s treatment of microwave and powerline radiation in his book Voodoo Science. It also fits nicely with the World Health Organization’s take on the possibility of cancer from cellphones:

    http://www.who.int/mediacentre/factsheets/fs193/en/

    “Current scientific evidence indicates that exposure to RF fields, such as those emitted by mobile phones and their base stations, is unlikely to induce or promote cancers.”

  9. TheBlackCaton 06 Nov 2007 at 12:46 pm

    There is a common thread here including homeopathy, vaccine autism, aspartame. There is no strong evidence supporting the conclusion and no plausible mechanism by which it could work, yet people still hold to it. Meta studies that include potentially or outright flawed regular studies in their analysis find an effect, but the larger and better-controlled the study the less effect is found. This is, of course, the correct way to look at it. These are all pseudoscience. What I fail to see is any difference with the current cell phone controversy. The arguments you make for not concluding that the effect is bogus could just as easily apply to homeopathy or vaccines causing autism. Your suggestion that people do certain things to be careful because the jury is still out could apply just as well to autism or aspartame. What makes cell phones causing cancer any more plausible than vaccines causing autism or homeopathy curing people?

    I don’t think any of those things are plausible myself, but neither do I think cell phones causing cancer is plausible. It all looks the same to me. If any effect is found there are either possible flaws in the study or the effects are at the edge of statistical significance. Meta-analyses can show an effect but large-scale, well-controlled studies do not. There is no plausible physiological mechanism by which the effect could be caused. Where does the difference lie that leads you to think this is plausible while all the other effects you criticize are not?

  10. [...] George Carlo is a legitimate researcher, and has been involved with research into the health effects of cell phones for years. He is at one end of the spectrum of this debate, however, claiming that the evidence [...]

  11. andrewon 02 Jun 2008 at 2:45 pm

    Arthur Firstenberg is making another news round, claiming allergies to WIFI in public buildings:

    http://kob.com/article/stories/S451152.shtml?cat=517 and http://www.crn.com/networking/208400676

    “I get chest pain,” Arthur Firstenberg told the TV station. “It doesn’t go away right away. I suffer for a couple of days.”

    Firstenberg, 57, added: “If I walk into a room of a building that has Wi-Fi, my most immediate sign is that the front of my right thigh goes numb. If I don’t leave, I’ll get short of breath, chest pains and the numbness will spread.”

  12. [...] fearless leader Steve Novella also summarized the state of the evidence regarding cell phone use and the risk of cancer and [...]

  13. [...] year I wrote an entry summarizing the evidence concerning the association of cell phone use and brain tumors. The bottom [...]

  14. justeron 12 Nov 2008 at 10:08 pm

    I’m pretty convinced that cell phones do emit enough radiation to cause problems and that it makes sense to protect oneself. There’s a great research article found here:

    http://www.mthr.org.uk/research_projects/documents/PorteretalEindhoven_000.pdf

    One of the recommendations is to use a ferrite bead attached to a wired headset to reduce the radiation that travels up the wire. I bought mine from http://www.brainbeads.com, and they also have them at http://www.mercola.com

    Even if the jury is still out, that doesn’t mean the verdict is innocent.

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