Following my recent critique here of the book Disconnect by Devra Davis, about the purported dangers of cell phones to health, David Gorski asked me to comment on a recently published “review article” on the same subject. The article is entitled “Risk of Brain Tumors from Wireless Phone Use” by Dubey et al [1] published in the J. Comput Assist Tomography. At the outset, the same question occurred to both of us: what is a “review article” about cell phones and brain tumors doing in a highly technical journal dedicated to CT scans and CT imaging? While we are both still guessing about the answer to this question, we agreed that the article itself is a hodge-podge of irrational analysis.
As you might surmise, Dubey and his Indian co-authors come to the conclusion that “that the current standard of exposure to microwave during mobile phone use is not safe for long-term exposure and needs to be revised.” But within the conclusion there is also the following: “There is no credible evidence from the Environmental Health and Safety Office (I presume in India) about the cause of cancer or brain tumors with the use of cell phones. It is illogical to believe that evidence of unusual brain tumors is only because of hundred’s of millions of people using cell phones worldwide.” What?! These are opposite and contradictory statements. The main body of the article includes a lot more instances of such inconsistency.
Dubious Sources, References, & Studies
Another highly dubious feature of this review article is the nature of its sources. Many of its references are merely news reports, not scientific articles and some even come from pseudo-scientific web sites. For example, figure 1 purports to illustrate cell phone radiation penetrating a 5 year old, 10 year old, and adult head. It purports to show that cell phone radiation penetrates a child’s head much more deeply than an adult’s. The source given for this image is www.environmentalhealthtrust.org — the web site of none other than Devra Davis! The main feature on this web site is the promotion of her book Disconnect!
This particular image is one that is frequently used by alarmists. The original source is a 1996 paper by Gandhi et al [2]. This paper has long been discredited and the image is simply wrong. Gandhi himself published an update in another paper in 2002 [3] with quite different results. Numerous papers have been published examining the issue of cell phone penetration of the head. The consensus is that RF absorption in children’s heads is not greater than adults and is well within exposure limits [4].
One particularly dubious reference is to a book by the notorious industry gadfly George Carlo that even Devra Davis treats with caution. A number of the scientific papers that are listed are of dubious quality and/or have failed to be reproduced in follow up studies. For example one of the sections is entitled “Male fertility damaged by radiation.” Orac has written a critique on this hypothesis in which he takes apart one of the studies cited by Dubey et al. Male fertility is also one of the principle subjects in the book Disconnect, which I rebutted in my review on SBM. To summarize the three papers cited by Dubey et al. are of poor quality and/or have failed attempts at replication. The authors do not list or comment on the negative studies that contradict the one’s they listed.
Other statements and references that have been contradicted by follow up studies include claims that:
- “The RF emissions from cell phones have been shown to damage genetic material in blood cells”
- “Long-term cell phone use can increase the likelihood of being hospitalized for migraines and vertigo by 10% to 20%”
- “Cell phone radiation damages DNA, an undisputed cause of cancer”
- “Cell phone radiation has been shown to cause the blood-brain barrier to leak”
The fact that each one of these “findings” has failed replication attempts in rigorous follow up studies is not even mentioned.
In the conclusion, Dubey et al. makes the bold claim that: “Moreover it was repeatedly confirmed that the radiation from base stations is harmful to health. The existing ICNIRP and FCC exposure limits are based on a false premise that only thermal effects cause harm.” Here they are referring to cellular telephone base stations. But no references are provided to support either of these assertions.
Industry Funding
Figure 2 in the article is a chart that purports to show industry bias in brain tumor research. This establishes the principle theme of this article: the claim that most of the studies on brain cancer and cell phones with negative results have been funded by industry. This is not a scientific argument, it is a conspiracy theory. Other posts on SBM have observed that conspiracy theories are a favorite tactic of purveyors of pseudo-science. This “industry funding” theory is also the main thesis of the book Disconnect and alarmist cell phone web sites. The source given for this “industry funding bias” chart is the web site www.psrast.org/mobileng/mobilstarteng.htm. The organization behind this web site is a group called: “Physicians and Scientists for Responsible Application of Science and Technology (PSRAST).” This web page is full of references to the usual unscientific alarmist material found throughout the Internet.
Dubey et al. do not mention the generally accepted alternative explanation for the dichotomy in positive vs. negative studies. First there is the issue of publication bias [5]. If a researcher makes an initial positive finding, he is more likely to rush his results to publication. An initial negative finding is less likely to ever be published. Rigorous studies with all necessary controls and a large number of trials are more expensive to conduct. It is important to note that virtually all such follow-up replication studies have been negative.
An extremely important fact that is not discussed by Dubey et al. is that expert reviews by virtually all of the industrialized world’s public health organizations have come to the same conclusion as the World Health Organization “that current evidence does not confirm the existence of any health consequences from exposure to low level electromagnetic fields.” One presumes that they have also been either co-opted or duped by this industry funded conspiracy.
Hardell vs. Interphone
By far the largest and most important case control study on the possible link between cell phones and brain cancer was the Interphone study [6]. The Interphone study was an international collaboration involving 13 countries which was coordinated by the International Agency for Research on Cancer (IRAC) which is part of the WHO. The conclusion of Interphone was “Overall, no increase in risk of glioma or meningioma was observed with use of mobile phones. There were suggestions of an increased risk of glioma at the highest exposure levels, but biases and error prevent a causal interpretation. The possible effects of long-term heavy use of mobile phones require further investigation.”
Dubey et al. characterize the important Interphone study as follows: “This nonblinded, interview-based, substantially wireless industry-funded case-control study….” They are clearly discounting Interphone with the “industry funding” conspiracy theory. They compare the Interphone studies with another set of case control studies conducted by the Swedish researcher Lennart Hardell. “The 2 sets are the industry-funded Interphone studies and the independently funded Swedish studies reported by Hardell team.” Dubey et al. make a number of additional dubious criticisms of Interphone. To support these criticisms they list a number of letters to a journal including a couple by Hardell. Much of this criticism boils down to splitting hairs over who did a better job of controlling for “recall bias.”
Those of you who are regular readers of SBM may have seen a post by David Gorski commenting on another cell phone cancer review article in which the work of Hardell was given prominence. Gorski had this to say about Hardell: “Whenever one group of researchers keeps finding a result that no other group seems able to replicate or that otherwise disagrees with what everyone else is finding, that’s a huge red flag for me. Remove those studies, and even the wisp of a hint of a shadow of the association between cell phone use and cancer found in this study disappears. I’d have a lot more confidence in this seeming association in “high quality” studies if the association didn’t depend upon a single researcher and if this researcher was not also known for being an expert witness in lawsuits against mobile phone companies.” It would appear the Hardell himself has a conflict of interest.
A pair of review articles on cell phone brain cancer studies in the journal Epidemiology [7, 8] had this to say about Hardell: “One notable feature of the literature to date is that authorship by Lennart Hardell is associated with finding an adverse effect of mobile telephone use for several different endpoints. The discrepancy between the findings of Hardell and those of other scientists was striking enough that Ahlbom et al presented some of their summary findings in 2 forms, including and excluding the studies by Hardell and colleagues.”
Case control studies such as those conducted by Hardell and Interphone involve recruiting subjects who have been diagnosed with brain cancer. The subjects respond to a questionnaire in which they are asked to recall – purely from memory – how much they had used their cell phones over the years. The cancer patients are matched with a healthy control group who respond to the same questionnaire. If the study shows that people who have brain cancer used cell phones more that the controls, the conclusion is that cell phone use increases the risk of brain cancer.
But case control studies such as this suffer from a number of limitations, the most serious being “recall bias.” Brain cancer patients are certainly aware of the theory that cell phone use may lead to brain cancer. This theory has been in the news for years. Such patients are likely to over report past cell phone use when completing a questionnaire. Memory is notoriously unreliable, and it becomes more so over time. I don’t know about you, but I could only make a wild guess about how much I used my cell phone 10 years ago. This simple fact alone makes it hard to interpret conflicting studies.
Dubey et al. seem to acknowledge the issue of recall bias, but their treatment of the issue is inconsistent and contradictory. The authors even discount one of Hardell’s studies with the following: “this finding is probably explained by recall bias, with patients with glioma systematically overreporting use on the same side as their tumor and consequently underreporting use on the opposite side.” Yet despite this admission, Dubey et al. accept all of the Hardell studies and include them in their meta-analysis. They give greater credence to Hardell than Interphone and conclude: “The meta-analysis shows that long-term cell phone use can approximately double the risk of developing a glioma or an AN (acoustic neuroma) in the more exposed brain hemisphere.” This opposite to the conclusion of mainstream scientists as reflected in papers such as Ahlbom et al. [8].
What about incidence rates?
Perhaps the simplest and most compelling argument against any possible cell phone brain cancer association is the fact that brain cancer incidence rates have remained unchanged since the introduction of cell phones. Dubey et al. dismiss this evidence with a one sentence section entitled: “Outdated Central Brain Tumor Registry of the United States Tumor Data” and the statement that “the most recent data are already at least 4 years outdated.” The authors reference only a couple of older studies, and ignore the most recent ones from Europe, the US, and the UK that show no increase in brain cancer incidence up to 2003, 2006, and 2007 respectively [9, 10 11]. Furthermore, the data in the US & UK studies are more recent than any of Hardell’s studies!
Conclusion
The Dubey et al. review article is sprinkled with statements such as:
- “Most studies have not found any association between cell phone use and the development of head tumors”
- “There is generally a lack of convincing and consistent evidence of any effect of exposure to RF field on risk of cancer”
- “Although some positive findings have been reported, so far the totality of epidemiological evidence (meningioma) does not demonstrate an increase in risk of meningiomas related to mobile phone use”
- “There was no association between the use of cellular or cordless phones and salivary gland tumors found, although few studies reported for long-term heavy use”
As I wrote at the beginning of this review: these statements are opposite and contradictory to the overall conclusion of Dubrey et al. One supposes that the authors are trying to give the appearance of “balance.” However they reconcile these contradictory findings not with a scientific weight of evidence approach, but with their “industry funding” conspiracy theory. This brings me to add an additional question on top of our original query about what an article about cell phones is doing in a specialized journal on CT imaging. How did an article that promotes Internet conspiracy theories with a hodge-podge of irrational analysis even get published at all?
About the Author
Lorne Trottier is a co-founder of Matrox Ltd. and holds B. Eng., M. Eng., and Doctorate (honoris causa) degrees from McGill University. He has had a lifelong passion for science and technology and believes in the importance of combating pseudoscience. He is President of the Board of the Montreal Science Center Foundation, and is also a board member of a number of science outreach organizations including the NCSE, CFI Canada, and The Planetary Society. Trottier sponsors the annual Trottier Symposium at McGill University that deals with a variety of science topics of interest to the public, such as Confronting Pseudoscience. Trottier also maintains a web site on the subject of EMF and Health.
References
- Risk of Brain Tumors from Wireless Phone Use J Comput Assist Tomogr Vol 4 No 6,Nov/Dec 10. doi: 10.1097/RCT.0b013e3181ed9b54
- Gandhi O P, Lazzi G and Furse CM. Electromagnetic absorption in the human head and neck for mobile telephones at 835 and 1900 MHz IEEE Trans. Microw. Theory Tech. 44:1884–97, 1996. doi: 10.1109/22.539947
- Gandhi O and Kang G. Some present problems and a proposed experimental phantom for SAR compliance testing for cellular telephones at 835 and 1900 MHz Phys. Med. Biol. 47:1501–18, 2002. doi: 10.1088/0031-9155/47/9/306
- Beard et al. Comparisons of Computed Mobile Phone Induced SAR in the SAM Phantom to That in Anatomically Correct Models of the Human Head, IEEE Trans. Electro Comp, Vol. 48, No. 2, May 2006. doi: 10.1109/TEMC.2006.873870
- Vijayalaxmi et al. Genetic Damage in Mammalian Somatic Cells Exposed to Radiofrequency Radiation: A Meta-analysis of Data from 63 Publications Radiation Research 169, 561–574, 2008 doi: 10.1667/RR0987.1
- Cardis et al. Brain tumour risk in relation to mobile telephone use: results of the INTERPHONE international case-control study Int’l Journal of Epidemiology 2010; 1–20. doi: 10.1093/ije/dyq079
- Rothman. Health Effects of Mobile Phones Epidemiology Vol 20 No 5, Sept 2009. doi: 10.1097/EDE.0b013e3181aff1f7
- Ahlbom et al. Epidemiologic Evidence on Mobile Phones and Tumor Risk Epidemiology Vol 20 No 5, Sept 2009. doi: 10.1097/EDE.0b013e3181b0927d
- Inskip et al. Brain cancer incidence trends in relation to cellular telephone use in the United States, Neuro Oncol 12(11): 1147-1151 , 2010. doi: 10.1093/neuonc/noq077
- Deltour et al. Time Trends in Brain Tumor Incidence Rates in Denmark, Finland, Norway, and Sweden, 1974–2003, J Natl Cancer Inst,101(24):1721–4, . 2009 Dec 16. doi: 10.1093/jnci/djp415
- Vocht et al. Time Trends (1998–2007) in Brain Cancer Incidence Rates in Relation to Mobile Phone Use in England Article first published in Bioelectromagnetics online 28 Jan 2011. doi: 10.1002/bem.20648