Fears concerning the possible dangers of prolonged cell phone use won't go away, despite numerous studies showing no conclusive link between cell phones and brain tumors or cancer.
Now new data from the National Institutes of Health suggesting that cell phone radiation boosts brain activity is poised to stir the debate even further.
Researchers used PET scans to measure brain activity in 47 participants when they had cell phones held to their ears in both off and on but muted positions and found that exposure to an in-use cell phone for more than 50 minutes increased brain activity by about 7 percent in the regions closes to the antenna.
This suggests that while no link has been proven between adverse health effects and cell phone radiation, the human brain is sensitive in some way to the electromagnetic waves coming off of a cell phone.
Whereas past studies have looked at cerebral blood flow to measure changes in brain activity, this study measured the brain's consumption of glucose -- the fuel of the brain -- in order to measure localized activity near the antenna.
"There have been several studies since the late 1990s trying to address whether the human brain is affected by the electromagnetic radiation from cell phones because it's very, very weak," said the lead author on the study, Dr. Nora Volkow of the National Institute on Drug Abuse. "The studies were very inconsistent, but we designed this study so it would be powered to detect small activity.
"This shows that the human brain is sensitive to these weak magnetic impulses."
But sensitivity does not equal harm or an increased risk of cancer, Volkow says, and it may even turn out that the ability of this radiation to boost brain activity could have therapeutic effects. Further study is needed, however, to explore the potential detrimental or beneficial effects of such an increase in activity.
Although the research on this topic has been mixed and inconclusive, Volkow says, their findings reopen the debate about cell phone concerns and make it impossible to ignore that prolonged use over many years might have some kind of unknown effect on the brain.
This study, published today in the Journal of the American Medical Association, does not speak to the possible cancer risks supposedly associated with cell phone use, but its findings may stir up past debates concerning the health hazards of America's cell phone habit.
The cell phone-cancer debate began in the late '90s as increasing use of cell phones both for work and play stirred interest in the potential effects of the small amounts of radiation emitted from any phone in use.
"Our bodies are exposed to electromagnetic radiation all the time, and it is relatively harmless in the low doses we receive," Dr. Jennifer Smullen of the Department of Otology and Laryngology at Harvard Medical School said.
"But cell phone antennas are associated with strong electromagnetic fields and are placed close to our body."
The largest-ever study of cell phones, known as the Interphone study, released its long-term results in May of 2010 and found no increased risk for benign or cancerous brain tumors, except at its highest level of use, a level deemed "implausible" as a comparison to real-life by the investigators. Even this link was only seen with benign tumors, not with cancer.