Cell Phone Brain Glucose Study Challenged
May 26, 2011
In February a study showing RF from cell phones had a measurable impact on brain glucose metabolism was widely reported in the media. I found few, if any, articles criticizing the study, although one knowledgeable RF Report reader said the exposure estimate and correlation calculations cannot be correct.
Recently the Journal of the American Media Association published reply letters questioning the study by Dr. Nora Volkow and associates. One letter was from Dr. Christopher Davis and Quirino Balzano, PhD, Department of Electrical and Computer Engineering at the University of Maryland in College Park, It says:
"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. The highest temperature elevations that occur in the brain during cell phone use as a result of the radiofrequency fields from the cell phone are on the order of 0.1°C to 0.2°C, temperature elevations that are smaller than those resulting from physical activity. The photon energy from the cell phone is too small to break even the weakest bonds, and the frequency of the fields is too high to affect ion transport. The study did not evaluate the exposure of the brain to the fields from the cell phone correctly."
The study was criticized by Dr. Carl-Heprik Nordstrom, MD, PhD, at the Department of Neurosurgery, University of Southern Denmark, in Odense, Denmark. Dr. Nordstrom reported that:
"A high degree of correlation between absolute and normalized glucose metabolism and estimated RF-EMF amplitudes and increase in measures was demonstrated. However, these data are difficult to reconcile with the regional glucose metabolism in a representative participant."
He further noted that in the participant in the study such an "increase in glucose metabolism in the orbitofrontal cortex…was outside the cerebral areas exposed to the highest amplitude of RF-EMFs."
He also observed that the temporal portion of the brain nearest the cell phone did not show "a corresponding increase" in glucose metabolism. He said it would appear that the cerebral areas further away from the phone showed "a more pronounced increase in glucose metabolism than that observed in the right temporal lobe."
Dr. Volkow and her associates responded to these and other letters stating, "Our study showed that cell phone activation was associated with metabolic increases in brain regions closest to the antenna, and that the increases showed a negative linear correlation with distance from the antenna.
She noted that Dr. Kosowsky and his colleagues, in their letter, pointed out that "realistic RF-EMF models are likely more complex than the model we used." She said that such assumptions about the model would only be relevant in interpreting "the spatial distribution of the observed effect, but they have no impact on the significance of the effect itself." She added that the narrow range of subject to antenna distances (9 to 11 cm.) in the study would suggest "that a first-order Taylor approximation for any potential RF-EMF model might be sufficiently accurate."
She concluded that such a linear decrease in metabolic effect with distance would be consistent with such an approximation.
Full text of the letters and reply is available for a fee from the JAMA links above.