Editor's note: The following is an unabridged version of an exchange that appears in the Letters pages of the the February 2011 print issue of Scientific American

In his column “Can You Hear Me Now?” [Skeptic], Michael Shermer argues correctly that cell phones lack the power to directly break the ionic bonds that hold together the complex structure of DNA. But Shermer is completely wrong to assert that cell-phone radiation cannot cause damage to DNA through other means or that cancer only arises after such damage occurs.

Frank Barnes, a member of the National Academy of Engineering, reports that radiofrequency energy can disrupt metabolic processes or cause other biologic changes such as a shift in the direction of neutrophils which may lead to a host of other alterations. Tuft University’s Michael Levin has found that electrical properties of one type of cell can induce other, distant cells to change their behavior, and might be "a key switch that mediates the stem cell-cancer cell distinction."

In fact, cell phones are small two-way microwave radios that rely on relatively low energy to send and receive signals. The nature of their pulsed digital signal may explain why their radiation induces DNA damage and also impairs sperm morphology, motility and count. Twelve different European laboratories working as part of the European Union sponsored REFLEX project have found significant evidence of DNA damage from signals from modern 3G phones. Split samples of human sperm studied in six different national laboratories indicate poorer morphology, motility and increased pathology for cell phone-exposed samples.

Shermer claims that the latest World Health Organization (WHO) epidemiological studies of this problem confirm that there is no overall increased risk in brain cancer tied with cell phone use. But, in fact, this project is continuing precisely because its leaders understand the need for continued surveillance. (A user in this study was defined as someone who made one cell-phone call a week for six months. No Americans were included in this analysis.) Shermer may be unaware that those who had used a phone for ten years for half an hour a day—as most of us do nowadays—had a significantly increased risk of malignant brain tumors. In fact, most studies of cell phone users have not followed people for who have used cell phones for more than a few years and every study of heavy cell phone users finds the same thing a decade later. Studies in Sweden have found that those who started using cell phones as teenagers have four to five times more brain cancer as adults. (The current WHO chief of this work, Joachim Schutz, and the distinguished American epidemiologist Jonathan Samet do not share in Shermer’s conviction, noting that more studies are needed over a longer time period before reaching any firm conclusion based solely on human evidence).

Have we really learned nothing from the history of tobacco and asbestos? Studies of these agents found no increased risk of cancer ten years after people began to use these known carcinogens, which only showed up twenty to thirty years later. In fact, the ways we use phones and the people who use them nowadays have changed radically since cell phones were first introduced.

No major research and training programs are underway in bioelectromagnetics in this nation and no major studies are planned on human impacts of these now ubiquitous devices. The last national survey of exposure to microwave and other electromagnetic radiation took place in 1980. If cell phones are in fact safe, why have all the major manufacturers of smart phones issued fine print warnings saying that phones cannot be used directly next to the head or body without violating Federal Communications Commission standards? Why are secondary insurers no longer providing coverage for health related damages from cell phones?

As a matter of public policy, we must ask: should we rely solely on the limited epidemiological studies of this now ubiquitous modern device and ignore the growing body of experimental findings? When should we have acted against tobacco and asbestos? The French, Finnish and British governments have looked at all the information on cell phone impacts and have issued advisories to use headsets and speakerphones. In France it is now illegal to sell a cell phone without a headset or warnings about safe use and advertising to children is banned.

Shermer has his physics right, but his biology all wrong. Taking precautions now in the ways we use two-way microwave radios makes a great deal of sense and may spare our grandchildren a tremendous burden.

Devra Davis
Environmental Health Trust
[Editor’s note: When the February issue went to print Davis was at the University of Pittsburgh but has left that university as of December 2010.]

Although I agree with Shermer’s overall conclusion, there are inaccuracies present on the scientific basis of why there should or should not be concern from cell phone radiation. He is correct that there is not enough energy in microwaves or radio frequency (RF) produced by cell phones for communication to cause the breakage of chemical bonds and particular, DNA (which is the source of mutations that lead to cancer). The electromagnetic radiation from cell phones is similar to that found in a microwave oven, though with much less energy, and the main concern should be from thermal heating of the tissue. And those of us that use microwave/RF energy for medical purposes (treatment of tumors to cause local hyperthermia for the improvement of chemo/radiation therapy) know that the temperature rise caused by cell phones is very modest and generally considered to below that necessary to cause tissue damage. Hence my general agreement with the overall statement of the article.   Research does exist, however--I am a co-author on a review article relating to it—discussing the carcinogenic effect of elevated tissue temperature with and without coexisting DNA damage from other causes. To my knowledge, no research exists yet on the low-temperature rises that cell phone radiation causes, the increased neurological sensitivity of young individuals, or the unlikely situation where there is known carcinogenic exposure combined with thermal exposure below thermal levels that can cause damage. Consequently, I am hesitant in this case to completely ignore the precautionary principle.

Benjamin L. Viglianti
Department of Radiology
University of Michigan at Ann Arbor

SHERMER REPLIES: Many readers have noted that cancer has many causes, such as epigenetic mechanisms, that do not require the breaking of DNA chemical bonds, but these other causes are not what Davis and others claim for the alleged connection between cell phone use and brain cancer. Davis agrees with me that “cell phones cannot directly break DNA,” but then, oddly, she cites an E.U.-sponsored study allegedly linking DNA damage to 3G phones. According to Harriet Hall and David Gorski, two physicians who on medical controversies for sciencebasedmedicine.org (where you can read much more on cell phones and cancer), the E.U. study has been discredited, the Swedish studies have not been replicated, and the sperm motility research was a pilot study that has also not been replicated. (And in any case, what does sperm cell motility have to do with brain cells becoming cancerous?) Furthermore, Hall pointed out to me that the Interphone study that I cited in my column actually found an apparent protective effect against brain tumors from cell phone use, except for the highest use groups, and that in any case the fact that they are conducting further research is not an endorsement of a causal link. Gorski informs me that, in fact, “the Nazis knew about the link between cigarette smoking and cancer more than two decades before the Surgeon General's report,” thereby gainsaying Davis’ final claim. Finally, I cannot help but wonder in this scenario why no one seems concerned about skin cancers caused by holding cell phones in one’s hand and pressed against one’s ear?

Viglianti makes a good point that should, in principle, be a testable hypothesis that could lead to a fuller understanding of cancer and its causes. In the meantime, I cannot help but wonder why no one seems concerned about skin cancers caused by holding cell phones in one’s hand and pressed against one’s ear.