HEALTH -- February 22, 2011 at 5:39 PM EDT
Study: Cell Phone Radiation Stirs Brain Activity, but Health Effects Unknown
A PET scan shows activation in the part of the brain nearest a cell phone antenna when the phone is turned on (left) and off (right)
Talking on a cell phone increases the activity in the parts of your brain near the phone's antenna, according to researchers who scanned the brains of a small group of people making 50-minute cell phone calls.
The study provides perhaps the strongest evidence yet that the weak electromagnetic energy emitted from cell phones can affect the brain. But the researchers, and other experts in the field, caution that we still don't know whether the kinds of changes seen in the study could harm people's health.
The research shows "that the human brain is sensitive to electromagnetic radiation even if it's very weak," says neuroscientist Nora Volkow, the head of the National Institute on Drug Abuse and a lead author of the new study. "It is crucial that we now assess whether there are long-lasting effects from these exposures."
Watch Volkow discuss the findings below, in a video from the Journal of the American Medical Association.
The findings, published Tuesday in JAMA, are the latest turn in an ongoing debate over the potential dangers of cell phone radiation.
For more than a decade, researchers have tried to decipher whether heavy cell-phone users are more likely to develop brain cancer or other problems. They haven't found any clear answers. One of the largest studies, for example, the European Interphone study, found that overall there was no link between cell phone use and brain tumors, but noted that among the longest-term and heaviest cell phone users, there was a possible increased incidence of a type of tumor called a glioma.
Another study, released just last week by the journal Bioelectromagnetics, looked at the number of cases of brain cancer in the U.K. between 1998 and 2007 -- a time cell phone use was skyrocketing -- and found that the number of cases didn't go up during that time. But other researchers argue that those results don't mean much, because brain cancer can take 20 to 30 years to develop.
The new study does not address the question of cancer. Instead, it simply looks at a measure of brain activity called brain glucose metabolism. Cells in the brain use glucose as their energy source, so increased glucose metabolism means the brain is more active.
Volkow and her colleagues used PET (positron emission tomography) scans to look at glucose metabolism in the brains of 47 people during 50-minute cell phone calls. They found that the parts of the brain nearest the phone's antenna were about 7 percent more active when the phone was on and receiving a call then when it was off. That's roughly equivalent, Volkow said, to the amount of activity seen in the language areas of your brain while you're speaking.
David Carpenter, the director of the Institute for Health and Environment at the University of Albany, has testified before Congress that more research is needed on the health effects of cell phone radiation. He was not involved in the new study, but said that it provides a crucial piece of evidence.
"One of the big arguments used to discount the epidemiological studies [that showed a link between cancer and cell phone use] is that nobody has demonstrated a mechanism whereby radiofrequency fields affect the brain," he said. "And this is such a clear demonstration of an alteration of nervous tissue."
But the researchers caution that their study does not prove anything about whether cell phones cause cancer or other health issues.
"Results of this study provide evidence that acute cell phone exposure affects brain metabolic activity. However, these results provide no information as to their relevance regarding potential carcinogenic effects (or lack of such effects) from chronic cell phone use," they wrote.
In fact, said Volkow, much more research needs to be done to figure out whether the brain activity changes she showed are harmful. And if they're not, she said, it's even possible that the type of radiation emitted by cell phones could be used therapeutically (like transcranial magnetic stimulation, used to treat depression.)
Still, for her own part, Volkow said that she uses the speakerphone option or an earpiece when she talks on a cell phone -- a simple change that keeps the antenna far away from the head. "I am conservative when it comes to my brain," she said.