Activity rises near the ear where a phone is located.
Talking on a cell phone pressed to the ear changes activity in the brain.
Many variables have prevented scientists from getting good epidemiological evidence about the potential health risks of cell phones.
Power-talkers with cell phones glued to their ears may be getting more than conversation. A 50-minute call boosts activity in brain regions near the ear where a phone is located, a brain-scanning study published February 22 in the Journal of the American Medical Association shows.
"This is the first paper that really shows there are changes in the brain," says bioengineer Henry Lai of the University of Washington in Seattle, who coauthored an editorial published in the same issue of JAMA. Talking on a cell phone pressed to the ear, he says, "is not really safe."
In the study, researchers measured the brain activity of 47 participants who had pairs of Samsung cell phones strapped to their heads, one on each side. The phone on the left ear was turned off, while the one on the right received a 50-minute recorded message. This phone was kept muted so that the subject didn't know which phone was on, and also to prevent stimulation of the brain's hearing center.
A few minutes after the call, a PET scan revealed that brain regions next to the working phone had higher levels of glucose metabolism. The left side of the brain and other areas, even those quite close to the phone, showed no changes. Since active brain cells require glucose, the increase suggests that cell phone radiation is boosting brain activity. "The human brain is sensitive to the electromagnetic radiation that is emitted from cell phones," says study coauthor Nora Volkow of the National Institute on Drug Abuse in Bethesda, Md.
The particular brain regions affected would probably change depending on a phone's design and how a person held it, Volkow says. On the phones used in the study the antennas are near the bottom, so the brain areas involved were the orbitofrontal region, which sits right behind the eyes, and the temporal pole below it.
Glucose metabolism rose in these areas by about 7 percent — an increase typically seen when brain regions become active. For instance, glucose metabolism in the language centers of the brain rises by about 10 percent when a person is talking, Volkow says.
The increase in brain metabolism observed in the experiment may be an underestimate, because cell phones emit more radiation when a person is talking, Lai says. Radiation levels also change depending on the phone type, the distance to the nearest cell phone tower and the number of people using phones in the same area. These variables have prevented scientists from getting good epidemiological evidence about potential health risks of cell phone usage.