In recent years, people have been divided by conflicting studies about the risk of cancer posed by cell phone radiation. Does the current conflicting research eradicate or support the cell phone-cancer controversy?
Cell phone use has shown a dramatic increase in the world during the 1990s. The heated controversy today is about whether there is a relationship between cell phone use and the risk of developing malignant and benign brain tumors. This controversy did not exist—at least in the eyes of the public—until accumulating anecdotal evidence began suggesting a link between cell phone use and cancer. Since the first pieces of anecdotal evidence, numerous studies have investigated the cell phone-brain cancer link and a general summary of the findings is, at best, confusing. The substantial room for improvement in the experimental designs of these studies, the appearance of brain cancer after a long period of exposure, and some conflicts of interest among researchers prevented the results from being conclusive. More recent studies provide growing evidence for the link, suggesting there is reason to be suspicious about the studies that refute the relationship between cell phone use and brain cancer.
Possible health issues regarding exposure to radio frequency (RF) energy were described in a previous Fountain article (Tombak, 2002). This article also stated that proving or disproving the existence of RF exposure’s biological hazards remains an issue for epidemiology due to relatively low exposure levels, relatively small populations, and a lack of reliable dose estimates. The National Cancer Institute (NCI) is now maintaining an up-to-date web page to inform the public on key points that can be drawn from epidemiological studies investigating the cell phone-brain cancer link. It would be advisable that individuals concerned about this potential link become familiar with this web page and visit frequently to check the updates. A regular visitor will notice that the language on this page is evolving in every update in a way that the most recent version is less likely than the previous one to discredit the link as “out of the question”. This is because we are starting to see—albeit still opposed as weak—stronger signs of the alleged link as there is an increase in both the sheer number and the experimental design quality of relevant studies.
The first two key points that NCI draws on concern the type of electromagnetic energy emitted by cell phones, and the factors that determine a users energy exposure level. It would not be surprising if this train of thought followed with a third key point that stated that the cancer risk depended on the amount of energy that each individual was exposed to. However, the third key point quickly draws the conclusion that “studies thus far have not shown a consistent link between cell phone use and cancers of the brain, nerves, or other tissues of the head and the neck.” It further states “more research is needed because cell phone technology and how people use cell phones have been changing rapidly”.
Regardless of what type of general message one gets from these three key points, I want to emphasize that there is benefit in avoiding a lump-sum conclusion, and in making oneself aware of the results of individual studies. Before I move on to individual studies, however, I will point out how scientifically sound interpretations of statistical power and significance may lead to categorizations as ‘non-existent’ or ‘weak’, but how this scientific reasoning can potentially be misleading for the population at large. In this manner, one would better be able to make sense of why cell phone companies are, on one hand, highlighting the studies that have failed to find a causal link between cell phone use and brain cancer, but on the other hand, are taking all legal precautions necessary to prevent a future litigation by inserting a warning slip in fine print that cautions users not to hold the phone closer than a certain distance against one’s head or body.
The null vs. the alternative
A statistical hypothesis test involves two hypotheses: the null and the alternative hypothesis. The null hypothesis represents the status quo; it assumes that there is no real difference between the two groups under study and the observed difference can be attributed to random chance. Drawing a parallel with legal systems, the presumption that a defendant is innocent until proven guilty can be interpreted as saying that his or her innocence is the null hypothesis. There has to be sufficient evidence on the contrary, i.e showing the guilt, in order to be able to convict the defendant. In a similar fashion, an epidemiological study investigating the presence of a link between cell phone use and brain cancer would have a null hypothesis that states the absence of such a link. The cell phone technology is assumed to be innocent unless the data prove otherwise.
The alternative hypothesis, the latter of the two, represents the claim that there actually is a statistically significant link between cell phone use and brain cancer, and the observed link cannot be attributed to random chance. In our legal analogy, the alternative hypothesis is laying the charges against cell phone technology, thus as the Latin maxim “semper necessitas probandi incumbit ei qui agit” states, the burden of proof lies with the alternative hypothesis.
As a consequence of this construction, a hypothesis test can have only one of two conclusions. If the data shows results that are beyond some predetermined significance level, the null hypothesis is rejected and the researchers believe that there is sufficient evidence to say that the alternative is true. Such a conclusion would establish a link between cell phone use and brain tumors. On the other hand, if the results do not reach the desired significance level, the conclusion is not the confirmation of the null hypothesis, but a failure to conclude that the alternative is true. In other words, when the desired significance level is not reached, the only outcome is a lack of conclusion; the test would not falsify the null hypothesis but would not declare it to be true either. The accused would be vindicated on the basis of insufficient evidence.
News on the innocence of cell phone technology, or any technology for that matter, should be read primarily with this perspective in mind. The conclusions of research studies are reported on the basis of whether the results “reach or fail to reach significance”. However, a more meaningful statistic to report from the study would be the deviation of the results from significance, if they were not significant. Results that are close to statistical significance can still be “meaningful”. After all, the significance level chosen for most studies relies more on traditional scientific habits than anything else. In this perspective, it can even be called arbitrary. In reality, we may not have expertise in today’s world to determine whether a 5% significance level is more meaningful than a 10% when it comes to studying the link between cell phone use and brain cancer. So when the NCI officials mention “lack of a consistent link,” all of what they mean is that the desired significance level has not been reached in most credible and up-to-date studies. Yet, the public is not informed about how significant the results were. Furthermore, as we see in the much-acclaimed Interphone study, failure to reach significance in the entire study may be overshadowing the fact that significance was attained for a subgroup of people, for instance, the top 10% of the population with highest cell phone use (The Interphone study group, 2010).
Perspectives on brain cancer risk
News regarding cell phone tumor risks is plainly confusing because a battle continues among different international panels and interest groups over how to analyze and interpret cell phone tumor data. An article (July 6, 2011) on Microwave News explains why there is no overlap in the conclusions made by the International Commission for Non-Ionizing Radiation Protection (ICNIRP) and the International Agency for Research on Cancer (IARC), the two panels that are supposed to work together, but fell into deep disagreement as the data started showing some link between cell phone use and brain cancer. This piece is a highly suggested read for anyone who would like to be able to make more sense of the past and potentially future news on cell phone tumor risks.
The Interphone study
Much of the current debate on cell phone tumor risks actually revolve around the Interphone study, which was conducted by a consortium of researchers from 13 countries, and is the largest health related case control study of the use of cell phones and head and neck tumors. According to NCI’s summary, “most published analyses from this study have shown no statistically significant increases in brain or central nervous system cancers related to higher amounts of cell phone use. One recent analysis showed a statistically significant, albeit modest, increase in the risk of glioma among the small proportion of study participants who spent the most total time on cell phone calls. However, the researchers considered this finding inconclusive because they felt that the amount of use reported by some respondents was unlikely and because the participants who reported lower levels of use appeared to have a reduced risk of brain cancer.”1
The general message that comes across in NCI’s summary of Interphone results is that we do not have enough reason to believe that cell phones are dangerous. However, it is very important to remember that one can never accept the null hypothesis that “cell phones are safe.” The only conclusion that can be drawn is on the basis of insufficient evidence, which is to say that cell phones are dangerous since the desired significance level has not been reached.
As the Interphone study is the largest of its kind, it has drawn substantial attention from concerned parties, and a significant part of this attention has been in the form of harsh criticisms for the experimental design, data analysis, and stated conclusions. For instance, one of Interphone’s biggest critics, the International Electromagnetic Field (EMF) Collaborative, published a paper in May 2010 detailing the flaws of the study. Among other things, these flaws included using data from 2004 and before when cell phone use was much less common, categorizing subjects who used cordless phones (which emit the same microwave radiation as cell phones,) as ‘unexposed’; exclusion of many types of brain tumors; exclusion of people who had died, or were too ill to be interviewed, as a consequence of their brain tumor; and exclusion of children and young adults who are more vulnerable.
In August 2009, more than forty leading independent scientists, physicians and other experts from fourteen countries endorsed the white paper “Cell-phones and Brain Tumors: 15 Reasons for Concern, Science, Spin and the Truth Behind Interphone” by US researcher Lloyd Morgan. Investigating the research on cell phone tumor risks including the Interphone study, this paper concluded that “there is a risk of brain tumors from cell phone use; telecom funded studies underestimate the risk of brain tumors; and children have larger risks than adults for brain tumors”. Unlike the Interphone study, some industry funded research also accepts the risks associated with cell phone use. In 1999, Dr. George Carlo, head of a $25m research body funded by the mobile phone industry in the US, said his study showed an increased risk of getting a type of rare brain tumor from using mobile phones. This early in the debate, he was probably one of the first researchers with links to industry who stopped ruling out the tumor risks of cell phones.
A review of other main studies
Hardell et al.
Dr. Lennart Hardell, from Örebro University in Sweden, is one of the most adamant leaders in cautioning the world about cell phone tumor risks. In 2007, he and his team reported that cell phone users were at an increased risk of malignant glioma, and that a daily one-hour exposure significantly increased the risk for developing a brain tumor after 10 years (Hardell et al., 2007). In a more recent study also cited by NCI, they found statistically significant trends of increasing brain cancer risk for the total amount of cell phone use and the years of use among people who began using cell phones before the age of 20 (Hardell et al., 2011). They also published a number of other papers in epidemiological journals pointing to the risks associated with cell phone and cordless phone usage.
The Danish cohort study
A 2011 cohort study in Denmark linked billing information from more than 420,000 cell phone subscribers with brain tumor incidence data from the Danish Cancer Registry (Frei et al., 2011). This study was an update on the 2006-update of a 2001 cohort study (Schüz et al., 2006; Johansen et al., 2001) that has been dogged by controversy and political suspicions since the first results were published ten years ago. NCI cites the study and states that the analyses found no association between cell phone use and the incidence of glioma, meningioma, or acoustic neuroma, even among people who had been cell phone subscribers for 10 or more years. However, there is no mention of the published or vocal criticisms of the study.
The main criticism for the study is that more than 200,000 corporate mobile subscribers were excluded from the cohort as cell phone bills were not in users’ names. Microwave News states, “In the time period covered in the Danish project—from 1987 through 1995—cell phones were expensive and it’s no stretch to assume that those who did not have to pay their own bills racked up the most talk time.”2 Thus, the study designers effectively removed one-third of the population with the heaviest cell phone use. Dr. Lennart Hardell had also criticized the original 2001 paper by publishing on the shortcomings that make the conclusions premature (Hardell and Mild, 2001). Concerning the 2011 update, the Microwave News bluntly suggests, “Don’t believe a word of it”.
It is also interesting to note that the results came just five months after a panel of experts from the World Health Organization’s International Agency for Research on Cancer (IARC) deemed cell phones a possible cause of cancer—a statement that sparked fear in many of the world’s 5 billion cell phone users.
While there is still no established causal link between cell phone use and cancer, we know as a fact that different research groups have found an increased risk of a rare type of brain cancer among heavy users. Even though children are known to be at a greater risk because of being in earlier stages of neural development, it is unfortunate that data from children were not included in studies until very recently. Concerned citizens of the world need to raise awareness about the behind-the-scenes battle taking place between different international panels and interest groups. This will make a reliable interpretation of conflicting news more possible. Further corroboration for both statistical and anecdotal evidence on the relationship between cell phone use and brain cancer may be necessary to “prove” a link, but this should, by no means, be interpreted as a vindication of cell phones. In the meantime, it is only safe to take precautions oneself, and encourage loved ones to reduce exposure to electromagnetic energy from cell phones by using a hands-free device and by reserving the use of cell phones for shorter conversations.
- Frei P, Poulsen AH, Johansen C, et al. 2011. “Use of mobile phones and risk of brain tumours: update of Danish cohort study.” British Medical Journal; DOI: 10.1136/bmj.d6387.
- Hardell, L., Walker, M. J., Walhjalt, B., Friedman, L. S. and Richter, E. D. 2007. “Secret ties to industry and conflicting interests in cancer research.” American Journal of Industrial Medicine,; 50: 227–233. doi: 10.1002/ajim.20357.
- Hardell L, Carlberg M, Soderqvist F, Hansson-Mild K, Morgan LL. 2007. “Long-term use of cellular phones and brain tumours: Increased risk associated with use for > or = 10 years.” Occup Environ Med. 64:626–632.
- Hardell L, Carlberg M, Hansson Mild K. 2011. “Pooled analysis of case-control studies on malignant brain tumours and the use of mobile and cordless phones including living and deceased subjects.” International Journal of Oncology; 38(5):1465–1474.
- Hardell L, Mild KH. 2001. “Re: Cellular Telephones and Cancer—a Nationwide Cohort Study in Denmark”; JNCI J Natl Cancer Inst. 93(12): 952.
- Johansen C, Boice Jr. JD, McLaughlin JK, Olsen JH. 2001. “Cellular telephones and cancer: a nationwide cohort study in Denmark.” Journal of the National Cancer Institute; 93(3):203–207.
- Schüz J, Jacobsen R, Olsen JH, et al. 2006. “Cellular telephone use and cancer risk: update of a nationwide Danish cohort.” Journal of the National Cancer Institute; 98(23):1707–1713.
- Tombak, Ali. 2002. “Biological Effects of Cellular Phones.” The Fountain, 37 (1).
- The Interphone Study Group. 2010. “Brain tumour risk in relation to mobile telephone use: results of the Interphone international case-control study.” International Journal of Epidemiology; 39(3):675–694.