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Reflections on the INTERPHONE Study of Cell Phones and Brain Cancer

Posted on by Joseph D. Bowman, PhD, CIH

lady holding cell phone near earMany people cannot imagine life without a cell phone. Since commercial cell phone networks were first introduced in the 1980s, over half the world’s population now uses them. While becoming a way of life and work, the radio frequency (RF) waves from cell phones have also been depositing energy into users’ brains. With billions of people exposed to more RF energy than ever before, scientists and the public have asked if a lifetime of cell phone use might be a health risk.

Cell phones are carefully designed and tested so that their RF emissions comply with all current health standards. However, the research upon which these safety guidelines are based cannot rule out the possibility of phone RF causing tumors in the head after 10 to 20 years of use. Since many people use cell phones and other RF devices at their work, potential hazards from cell phones are also of interest to the occupational safety and health community.

To answer these questions, an epidemiologic study called INTERPHONE was funded by the European Union and health agencies in 13 countries. From 2000 to 2005, INTERPHONE interviewed 14,000 adults about their cell phone use, other exposures to RF radiation, and other factors conceivably related to brain cancer. With this information, the INTERPHONE epidemiologists have been testing whether indicators of the phone’s RF radiation correlate with increased cancers in the head.

After five years of debate, the INTERPHONE epidemiologists recently published their findings on brain cancer, but their paper raise more questions than it answers. Its conclusions are:

Overall, no increase in risk of [brain cancer] was observed with use of mobile phones. There were suggestions of an increased risk… at the highest exposure levels… However, biases and errors limit the strength of the conclusions we can draw from these analyses and prevent a causal interpretation… The possible effects of long-term heavy use of mobile phones require further investigation.

Conflicting Interpretations

The journal’s commentary on the INTERPHONE paper likened this conclusion to the Delphic oracle in ancient Greece, whose advice to generals and emperors was famously difficult to decipher. In explaining their oracular conclusions to reporters, INTERPHONE epidemiologists offered several conflicting interpretations of the study results. Emphasizing the conclusion’s first sentence, Swedish researcher Maria Feychting said: “The use of mobile phones for over ten years shows no increased risk of brain tumors.”

Others emphasized the “increased risk” in the conclusion’s second sentence. Dr. Siegal Sadetzki from the Israeli INTERPHONE study said: “What worried me was that, in my study, I saw consistent positive results and they always appeared where there is biological plausibility… [The tumors] appeared in the more than ten years [group], they appeared on the same side where the phone was held, they appeared for the heavy users… So the fact that all of these indications appeared where they should have appeared told me that it was really a red light.”

In rebuttal, the first camp cite the “biases and errors” from the third quoted sentence. “The entire association [seen in INTERPHONE] can be explained by bias,” said Joachim Schz from the German study. “We have identified implausible values of [phone] use in the main data set.”

A middle position was expressed by Jack Siemiatycki of the Canadian INTERPHONE group who called the results “genuinely perplexing, enigmatic and paradoxical.” Siemiatycki said his perception of the phone’s risks have gone “from implausible to something higher.”

When asked to advise cell phone users, the differences of opinion became sharper. Principal investigator Elisabeth Cardis said, “Overall, my opinion is that the results show a real effect… It is too early to make strong recommendations to adults and children concerning the use of phones… But there are ways to limit exposure to the brain from mobile telephones, through the use of [text messaging], speakers or other hands-free devices. This may be a reasonable course of action until stronger conclusions can be drawn about risks from mobile phone use.” But Anthony Swerdlow from the British study disagreed: “This study does not give reason for precautionary measures.”

As the only U.S. citizen who was part of INTERPHONE, I have been reflecting on its contradictory findings. After years of collaboration, why are the INTERPHONE epidemiologists now giving conflicting advice on cell phone use? What can people conclude about the safety of cell phone use?

I was not directly involved in the epidemiologists’ discussions since my role in INTERPHONE was to assess RF exposure in workplaces. However, my research on electromagnetic fields (EMF) and cancer has given me some insight into how environmental health researchers draw conclusions from conflicting epidemiologic findings. From a careful reading of the INTERPHONE paper and the epidemiologists’ public statements, I can offer a few observations:

Indirect Evidence

As a fan of the TV show Law and Order, this INTERPHONE paper reminds me of a missing person case without a body to autopsy. To decide whether this is murder, the detectives can only gather circumstantial evidence. INTERPHONE also lacks a “smoking gun”—measurements of the RF energy absorbed from cell phones in the subjects’ brains. So the epidemiologists are analyzing indirect exposure evidence that can be obtained from interviews and medical records: years of use, time spent on the phone, the tumors’ proximity to the ear, and whether subjects used their phone on the side of the head where the tumors appeared. This approach resulted in calculations of cell phone risks from many different perspectives but little certainty.

Biases

When INTERPHONE’s conclusions speak of “biases,” the scientists are not referring to their personal state of mind, but to well-known flaws in epidemiology. When studies collect data on the past behaviors of people in everyday life, these flaws inherent to observational epidemiology can tilt the results one way or the other. With INTERPHONE, this problem was compounded by several factors. First, they recruited subjects without cancer by phone, but their requests were refused by 47% of those called, an indication of the public’s growing resistance to telemarketers. Even worse, controls who refused were less likely to use cell phones. This unrepresentative sample tilted INTERPHONE’s risk estimates downward, often giving the appearance that cell phones protected their users against brain cancer. Some argued that the large number of data points with no cancer risk was reassuring. Others said that many were due to the tilted sample from the phone solicitations. So INTERPHONE re-analyzed the risks without the subjects who never used cell phones and found a smoothly increasing risk with the time spent on the phone. The two camps could not agree on what this re-analysis meant, so it was consigned to an online appendix.

Other Studies

In order to evaluate this complex array of evidence, some epidemiologists based their interpretation solely on INTERPHONE, but others took earlier research on RFs health effects into account. For example, Microwave News reported:

“If there were a stronger effect, we would have seen it.” … [Joachim] Schz said that his outlook on long-term risk is largely based, not on INTERPHONE, but on his … Danish cohort studies and … a more recent analysis of the incidence of brain tumors in the Nordic countries…. Neither points to an increase in brain tumors among the general population.

Dr. Swerdlow cast his net even wider to include animal cancer assays and previous epidemiologic studies. “The balance of evidence from this study, and in the previously existing scientific literature, does not suggest a causal link between mobile phone use and risk of brain tumours,” he concluded.

Keeping Score

How do epidemiologists add up all this statistical data with their pluses and minuses to decide whether cell phones cause cancer? Unfortunately, the INTERPHONE epidemiologists and scientists in general have not agreed on how to keep score.

Should risks tainted by possible “biases and errors” be rejected or thoughtfully interpreted? Should the pattern of elevated risks from several “biologically plausible” conditions suggesting RF exposures be seen as a “red light,” as Dr. Sadetzki argued? Or do the study’s complexities make any patterns illusory?

Is the re-analysis in the online appendix a valid method for adjusting for the study’s control selection problems? Should its pattern of a growing risk with increasing phone use be taken as evidence of a cancer risk? Or is this an invalid change of the rules after the cards were dealt?

Should past studies that found no cell phone risks raise the bar for INTERPHONE’s evidence? Or should each study be analyzed on its own merits before comparing its findings with other studies done under different conditions?

The INTERPHONE experience shows that epidemiologists do not have universally-accepted answers to these questions, especially for this complex study with multiple lines of indirect evidence and imperfect data.

Cell Phones and Public Health

After five years of debate over the conclusions, the epidemiologists could only agree that the “possible effects of long-term heavy use of mobile phones require further investigation.” While waiting for these new studies, should people change how they use cell phones? There again, the INTERPHONE investigators disagree.

Prof. Swerdlow concluded no changes are needed. On the other hand, Drs. Cardis and Sadetzki suggest spending less time speaking on the phone and moving the phone away from the head by using text messaging, ear pieces and the speaker phone option. This advice is based on the elevated cancer rates associated with the total time spent talking on phones and with the older “analog” cell phones that direct more RF energy to the brain.

These contradictory interpretations of the INTERPHONE evidence are rooted in two philosophies held by epidemiologists and other public health scientists. One philosophy holds that an agent like RF radiation has no effect unless data clearly shows otherwise. This cautious approach to drawing conclusions is a cornerstone for sciences of all kinds and has been a key to its many successes over the past 300 years.

In opposition is the precautionary principle that endorses action when research findings are suggestive but not conclusive. From a scientific viewpoint, the precautionary approach can be justified for questions of public health because the errors in a study can also obscure risks.

Dr. Sadetzki suggests how these two philosophies can be balanced when she said, “As a scientist, this is not enough [evidence] … for causality, but an indication that, according to my judgment, it is enough in order to advise the precautionary principle.”

Judge for Yourself

In all these reflections on the INTERPHONE paper, the common thread is that its interpretation depends as much on judgment as on the data. Since the experts disagree, each person must now judge whether to reduce his or her RF exposure from cell phones based on these controversial reports of brain cancer.

Here are a few facts that can be helpful in making these judgments:

  • The contested INTERPHONE finding is a doubling of brain cancers in people who used cell phones for over a half-hour a day over ten or more years.
  • The type of brain cancer that reportedly increased is called “glioma.” It is a relatively rare cancer which strikes 6 to 8 people per 100,000 every year. This incidence is far lower than the 68 cases of lung cancer per 100,000. Thirty-three percent of brain cancer patients are alive five years after diagnosis compared to 15% of the lung cancer patients.
  • The radiation received from a cell phone can be greatly reduced by using it away from the head. Texting, the speaker phone option, ear buds and Bluetooth® all lower the radiation received from the phone.
  • People absorb far more RF radiation from a cell phone held to the ear than from Wi-Fi, portable phones, wireless computer networks, cell phone towers, and all other wireless devices (outside of a few workplace sources).
  • Cell phones and all other wireless consumer devices comply with all safety standards which protect against RF’s proven health hazards.
  • The greatest risks from cell phones are their distractions while people are driving cars or doing other potentially hazardous activities.

Final Reflections

Other data collected by INTERPHONE may eventually provide more clarity on RF cancer risks. Papers on tumors of the acoustic nerves and salivary glands are scheduled. INTERPHONE investigators have been using the detailed interviews of cell phone usage to estimate the RF energy absorbed at the tumor’s location. By combining all of the collected information into a single measure of RF exposure, this approach may provide more direct evidence on the phone’s brain cancer risk.

In addition, NIOSH has been collaborating with some INTERPHONE investigators to analyze its data on occupational RF exposure in a new study called INTEROCC. Funded by a research grant from the National Institutes of Health, INTEROCC is using the INTERPHONE interviews to test whether brain cancer risks are associated with occupational exposures to RF radiation and chemicals. NIOSH heads the evaluation of the subjects’ exposures to occupational RF and other electromagnetic fields.

Although INTERPHONE and other health research have not yet given a clear answer on the cancer risks from cell phones, the data collected and the supporting studies by engineers, physicists, and biologists have greatly increased our understanding of people’s exposures to RF radiation from these new wireless technologies. If this additional research firmly establishes any health risks from cell phones, NIOSH and other public health agencies will have much of the information needed to make science-based recommendations to protect people’s health.

Dr. Bowman is a certified industrial hygienist in the NIOSH Division of Applied Research and Technology. He thanks Bob Park, Louis Slesin, and Greg Lotz for helpful discussions.

All quotes from the INTERPHONE investigators are from Interphone Resources and U.S. Senate Hearing on Cell Phones and Health: A Recap by Microwave News.

Posted on by Joseph D. Bowman, PhD, CIH

32 comments on “Reflections on the INTERPHONE Study of Cell Phones and Brain Cancer”

Comments listed below are posted by individuals not associated with CDC, unless otherwise stated. These comments do not represent the official views of CDC, and CDC does not guarantee that any information posted by individuals on this site is correct, and disclaims any liability for any loss or damage resulting from reliance on any such information. Read more about our comment policy ».

    I don’t think I learned anything from this other than “more research is needed”. However, it is refreshing when researchers provide insight into problems with a studies data and conclusions. This blog would make a nice appendix to the end of the study.

    Finally a reasearch on brain cancer related to cellphones! Will you put out a whitepaper on this subject? Would you mind if i add your information to my blog and site as i want my readers to know (finally) to watchout for their mobile phones.

    Does it makes sense to say:
    Keeping the cellular as far as 9meters from the body helps reduce the waves?

    Thank you for your comment. NIOSH is not planning further publications on cell phones until more definitive research has been published, but you are welcome to distribute this blog further.

    On the cell phone’s distance from the head, a relationship with cancer risks cannot be determined because no epidemiologic study has so far examined the RF energy absorbed by the brain. We only know that less energy is absorbed as the distance increases. With typical older phones, the absorbed power is cut in half by moving the phone away by 1.5 centimeters (0.6 inches). At all distances, RF emissions from cell phones are within the safety standards set by the U.S. government on the basis of earlier research studies.

    I find studies like this one so frustrating! Why can’t they be more specific. I am dying to know (excuse the pun) if cellphones result in increased risks of brain cancer. You know we all speculate it.

    It is another study that does not answer the question and just raises more. With the electric that close to the cells, you know damage is happening.

    More information about the biological effects of non-ionizing radiation from wireless technology is coming out every day. Enough is not being done by cities, counties, states and the Federal Government to protect us from the potentially devastating health and environmental effects. Through the 1996 telecommunications act the telecoms are shielded from liability and oversight. Initially cell phones were released with no pre-market safety testing despite the fact the Government and the Military have known for over 50 years that radio frequency is harmful to all biological systems (inthesenewtimes dot com/2009/05/02/6458/.). Health studies were suppressed and the 4 trillion dollar a year industry was given what amounts to a license to kill. On it’s face, the 1996 telecommunications act is unconstitutional and a cover-up. Within the fine print city governments are not allowed to consider “environmental” effects from cell towers. They should anyway!

    It is the moral and legal obligation of our government to protect our health and welfare? Or is it? When did this become an obsolete concept? A cell tower is a microwave weapon capable of causing cancer, genetic damage & other biological problems. Bees, bats, humans, plants and trees are all affected by RF & EMF. Communities fight to keep cell towers away from schools yet they allow the school boards to install wi fi in all of our schools thereby irradiating our kids for 6-7 hours each day. Kids go home and the genetic assault continues with DECT portable phones, cell phones, wi fi and Wii’s. A tsunami of cancers and early alzheimer’s await our kids. Young people under the age of 20 are 420% more at risk of forming brain tumors (Swedish study, Dr. Lennart Hardell) because of their soft skulls, brain size and cell turn over time. Instead of teaching “safer” cell phone use and the dangers of wireless technology our schools mindlessly rush to wireless bending to industry pressure rather than informed decision making. We teach about alcohol, tobacco, drugs and safe sex but not about “safer” cell phone use. We are in a wireless trance, scientists are panicking while young brains, ovaries and sperm burns.

    I just came here to say this is the dumbest study on the planet, and honestly, was it necessary to spend tax payer money on stock photos? Especially when you could just have an employee take out their phone, and have another employee with a camera phone snap a picture.

    NIOSH is a careful steward of tax payer dollars. The image used in the blog is available to us under a CDC-wide licensing agreement. There are no individual image charges involved with its use. The use of stock photos under this agreement is a cost-savings mechanism, eliminating the time and cost associated with taking photos, cropping and editing images, and acquiring proper releases.

    Glenn Doyle is the NIOSH Web Team Lead

    I find it disturbing that the information from the study is inconclusive.

    This is important to me because at (company name removed) we are dealing with the same form of problem with the high tension power lines that crackle with energy in certain neighborhoods. So far, all I have every been able to find in official studies is that there is no proven correlation or results are inconclusive. However, the anecdotal evidence suggests otherwise. I would hate for us to have to wait another 20 years do discover we have been dosing ourselves with massive opportunities for brain cancer.

    The inconclusive nature of the INTERPHONE study has disappointed many who were hoping that the study would provide definitive answers on the risks from cellular phone exposures. Research on environmental health risks goes that way sometimes. Nevertheless, even without a conclusive outcome, people can still use these research findings to gain insights on the possible health risks of cellular phone use. That was one of my goals for this blog on INTERPHONE.

    People who are following this research need to understand the difference between cell phones and high-voltage power lines. Both give off electromagnetic fields (EMF). However, the radio frequency (RF) EMF from cell phones oscillate about a billion times per second (which scientists call a “gigahertz” or GHz). In contrast, the EMF from power lines have the 60 Hz frequency of AC electricity. This billion-fold difference in the EMF’s frequency makes their interactions with our bodies totally different. For example, gigahertz EMF decrease rapidly as they penetrate the body, while 60 Hz magnetic fields pass through unabated.

    So health studies on RF sources like cell phones have little relevance to power line EMFs (which are called “extremely low frequency” or ELF fields). NIOSH’s EMF Topic Page has links to reviews of possible health risks from ELF EMF.

    It seems insurance companies would do more studies on the effects of heavy cell phone use. Most people probably do not use a cell phone enough to be a problem, but it seems studies should be done on people who use a cell phone for 4-5 hours a day or more, every year. It would be interesting to see the results.

    There has been so much bogus hype surrounding cell phones and health that it would nice to actually have some viable research to bring the discussion to a close. Or at least, close the unsupported assertions and move forward with viable, data driven research.

    I hope this goes forward.

    It seems unlikely that further epidemiology will change the picture. While much of the population are exposed to cell phones, the issue remains alive because higher social class people are included, unlike other environmental exposures. So, there will be more epidemiology, while other agents with more plausible associations remain understudied.

    The metaphorical connection between brain electrical activity (neurons), EMF and brain cancer is flawed. CNS cancers arise from glial cells, not neurons. Of course, there are electrical potentials across membranes in glial cells, like all tissues, but they are not the source of “brain waves.”

    Dr. Mirer raises an important point about the $25 million cost of the INTERPHONE study and the additional millions being spent on new epidemiologic studies of cell phones and brain cancer. Since brain cancers and other head tumors are relatively rare, other possible causes of cancer in our environment and workplaces might be better targets for public health research funds.

    Despite these legitimate concerns, the U.S. government had several reasons for participating in the INTERPHONE and INTEROCC studies. With over half the world’s population now using cell phones, even a small risk of brain cancer would lead to greater health costs than many well-known occupational carcinogens like ionizing radiation and benzene. Second, other wireless technologies with RF emissions similar to cell phones are constantly appearing in workplaces. By studying cell phones and the other RF sources in the INTEREPHONE questionnaire, public health agencies will also be learning about the possible health risks from these wireless innovations. Third, the occupational RF safety standards are more lenient than those for cell phones, so industrial RF from plastics heating, telecommunication antennas, etc. might be inflicting greater cancer risks on blue collar workers. Finally, INTERPHONE’s interview data allows the INTEROCC study to study brain cancer risks from workplace chemicals as well as RF. For all those reasons, NIOSH and our partners have continued a small research effort on the cancer risks of RF energy.

    Note: I’m sorry if the term “RF waves” in my blog created any confusion. I was referring to the electromagnetic waves from the cell phone’s antenna, not the “brain waves” from neuron’s electrical activity.

    Dr. Bowman, I found your article very interesting and objective in nature. Although the study is inconclusive and more sutdy is needed, you give us useful advise on precautionary measures that can be taken by individuals and employers.

    I appreciate your HONEST assessment.

    The concern about cellphones is quite popular, actually, as it has been emailed to & by others many times since a few years ago. Maybe excessive usage is the culprit. However, we should not wait until it is proven hazardous before we start raising the alarm. What about the dangers of synthetic perfumes? I think we should be cautious about everything that affects us, though they make life easier.

    If you tune to your body, you will feel the effects during conversation on mobile or cordless phone it has on the site of your head, I do so I try ot cut the conversations short or use speaker on my phone. Remember, the damage is irreversable!

    Is there any risk to your body of keeping a cell phone, turned on, in your pocket all day? Isn’t the cell phone creating RF emissions all the time that it is turned on?

    You are right that cell phones emit RF radiation when they are in standby mode. The phone sends out short signals so that its cellular network knows were to send an incoming call. However, these emissions are so brief and infrequent that they are a small fraction of the phone’s total RF emissions for most users. To equal the energy from a minute of talking, the phone has to be in standby mode for days. None of the research has examined whether such small RF exposures would have any adverse effects on the body.

    What basis do these studies have in conjunction with study done by Dr. George Carlo several years ago alerting the public to the dangers of cell phones? Does his study merit any recognition or response with respect to the newest international studies? Thanks.

    Dr. Carlo led an industry-funded program of research related to cell phone health effects in the 1990’s. Based on his experiences, he raised concerns about cell phones and brain cancer in a book published in 2001. The few epidemiological studies from that program that were published in the peer-reviewed scientific literature are part of the overall literature that forms the background for the INTERPHONE study, but were much smaller in design and duration of cell-phone use. Thus, the studies funded by the Carlo-directed program contribute to the overall literature, but do not help clarify the findings of the INTERPHONE study.

    Greg Lotz, Ph.D., is Director of the NIOSH Division of Applied Research and Technology

    Terrific work! This is the type of information that should be shared around the web. Shame on the search engines for not positioning this post higher!

    Hi i just want to add that i come from a local FD that uses cell towers to make money for their coffers and all these towers are built nearby to the station. in the past several years many of our firefighters have come up with some sort of cancer (all have been from the same fire station)i bilieve that the cell towers are a direct link to these cancers being seen. I believe that NIOSH is scheduled to evaluate this site and I hope you post the finding to ease the fear that not only the stress of saving lives but living directly under these cell towers might just be worse than any fire we can go on. Thanks

    I am looking into renting commercial space that is quite close to a cell phone tower.

    A distance of 1500 ft has been widely quoted as the minimum safe distance and has been bandied about in various public hearings about local cell towers planned near schools and other residential locations.

    What is the CDC position, if any, on live/work proximity to towers?
    If one owns or rents property close to one, are their ways to “shield” the
    interior to protect the occupants. For example is a metal roof better than shingles?
    Is cinderblock better than wood and sheetrock?

    Please advise. Thanks,

    Thanks for your great information, the contents are quiet interesting.I will be waiting for your next post.

    We heard a lot of things about cell phone and brain cancer but no one in my opinion cares about it, cause cell phones are part of our lifestyle

    I think cell phones are absolutely horrible and a complete disaster. If we must have them then they need to somehow be made environmentally safe. It has gotten to the point where an individual who is sensitive to this can get inundated with cell phone and wireless radiation. If people want to make themselves pests with cell phones, cell phones compounded with other EMF creating entities, people can actually make you sick and cause cognitive dysfunction, nausea etc. especially if there are enough of them. This, in so far as I am concerned, is ultimately an epidemic and a complete outrageous disaster. It has gotten to the point that EMF concentrations can get so high they can cause complete insomnia if not a myriad of other problems. At least in Europe and other countries they are more aware of the dangers and are at least more aggressively researching it. As usual America is one step behind and captive to the embraces of an aggressive cell phone corporate lobby. I think I read somewhere that at one time the defense department was interested in how to weaponize EMF’s I think the ultimate question here is how could something that could be weaponized not be insidiously dangerous and extremely harmful?

    We heard a lot of things about cell phone and brain cancer but no one in my opinion cares about it, cause cell phones are part of our lifestyle.

    In 2016, there is now a body of literature to respond to Mary Green’s question (#15) about cell phones in pockets that was not available when Dr. Bowman responded. The following link discusses this: http://www.saferemr.com/2015/09/effect-of-mobile-phones-on-sperm.html
    In this review, you will read that ten studies were examined including 1,492 human sperm samples. Exposure to mobile phones was found to be associated with a significant eight per cent average reduction in sperm motility and a significant nine per cent average reduction in sperm viability. The effects on sperm concentration were more equivocal. The results were consistent across experimental laboratory studies and correlational observational studies…The authors concluded that the overall results suggest that mobile phone exposure negatively affects sperm quality in humans. From this have come advisories not to store phones in pockets or clothing.

    Re pregnancy, the following link lists studies on humans and animals exposed to cell phone radiation during prenatal development. In many studies, the brain and behavior of the offspring were impacted, leading many researchers to advise pregnant women to limit exposure when possible. This would include not using or storing the phone near the abdomen. http://www.saferemr.com/2014/06/joint-statement-on-pregnancy-and.html

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