When the Journal of the American Medical Association published a study a few months ago that suggested cell phone radiation might increase blood flow in certain brain areas, it madeheadlines. Now that a World Health Organization panel has classified cellphones as possible carcinogens, the JAMA study is making the rounds again. But this time when readers look up the study online they will find three letters from physicists and other experts pointing out what they believe to be significant flaws with the research.
In one of the letters, physicists at the University of Pittsburgh argue that the study authors oversimplified the physics of radiation.
"The authors assumed that the radiofrequency-modulated electromagnetic fields (RF-EMFs) deposited in the brain had an amplitude equal to the electric field of a near-field dipole in a vacuum," they write. "Cell phone antennas are often fractal instead of dipole, significant angular dependence is ignored, and the brain has complicated dielectric properties, which may lead to large differences from the assumed field and invalidate the claimed correlation."
There are also concerns that the results may have been biased--the test subjects were blinded to whether the phones they used were turned off or on, but the researchers were not.
But the critics' biggest complaint seems to be that the effects on brain activity that the researchers observed could have been caused by heat from the phones rather than by radiofrequency fields. In their response to the letters, the study authors argue that the cellphones wouldn't have gotten hot enough during the experiment to affect brain activity. They claim that the temperature increase in the brain would be on the order of 0.1 degrees Celsius at most, citing a 2001 study in IEEE Transactions on Microwave Theory and Techniques. They also argue that the pattern of brain activity would be in different areas if thermal sensation had been the cause.
Christopher Davis and Quirino Balzaro, both researchers at the University of Maryland, College Park's department of electrical and computer engineering, disagree. In their letter, they cite a 2005 study that found thermal heat from active cellphones significantly increased skin temperature on users' faces.
"We believe this study is flawed, as there is no mechanism other than heating by which the radiofrequency fields from a cell phone could affect human tissue," they write, adding, "the authors should have controlled for this temperature difference between the 2 sides of the face to determine whether the heat from the cell phone was the cause of the glucose metabolism changes."
The debate is only bound to intensify as more studies on this subject come out. For journalists and concerned citizens trying to keep track of all the research on cellphones and the brain, it's worth checking the Letters sections of scientific and medical journals to see how these studies are being received by the scientific community. And perhaps the editors of these journals could consider making these dialogues more available to the public, given how much public concern over this issue has grown in recent years.
PHOTO: Vicky TGAW, via Flickr