Neuroscientists at the National Institutes of Health published puzzling research in the Journal of the American Medical Association (JAMA) in February 2011. Though many have speculated on the effects of cell phone signals on the brain, studies have found no increased risk of cancer associated with cell phone use according to both the American Cancer Society and National Cancer Institute. However, the use of radiofrequency so close to the head may still have other effects. These yet unknown effects appear to include energy use by brain cells.
Using positron emission tomography (PET) brain scans, the research group led by Nora Volkow examined the effect of cell phone proximity on the brains of 47 volunteers (the study abstract is available here. They measured glucose consumption, a sign of energy expenditure activity, with acute use. Specifically, the cell phone was on for 50 minutes. What they found was that the brain as a whole was not affected. However, the orbitofrontal cortex and temporal pole (i.e. above the eye around to the ear) on the side of the head where the cell phone was placed (i.e. the region closest to the antenna) exhibited significantly higher metabolism levels, equivalent to a 7 percent boost in sugar consumption. In addition, the increased metabolism correlated with the amplitude of the electromagnetic field generated by the phone.
The findings are based on statistical comparisons and averaging computer generated voxels to represent activity, so there are definitely some limitations to interpreting the findings. However, most previous studies used much fewer people and examined use over a matter of seconds, so it is currently the best look at cell phone radiation on the brain to date. As the researchers and others have pointed out, it is now obvious that cell phone signals do affect the brain in some way, though the increase in activity is very little compared to changes seen with other activities. How and whether there are any long-term effects is just not yet known.
Cell phone manufacturers are required to estimate how much radiation any particular model might cause the body to absorb, called the specific absorption rate (SAR), due to speculation about health concerns. The Samsung used in Volkow’s study peaks at 1 Watt per kg of tissue for the head, which Wired noted is one-fifth the average SAR for the whole body when sunbathing. Though the small effects found in the study may end up meaning nothing, some researchers urge the use of wireless and hands-free devices to decrease any potential effects they may uncover later. The signal dissipates with distance, allowing such devices to eliminate exposure of the brain to the electromagnetic waves.