Using a cellular telephone while driving or walking clearly causes accidents, yet some people may be more worried about getting brain cancer from cell phones—a concern that has been largely dispelled by public health authorities.
The U.S. National Cancer Institute has concluded that “studies thus far have not shown a consistent link between cell phone use and cancers of the brain, nerves, or other tissues of the head or neck.” Similarly, the Food and Drug Administration has found “no increased health risk due to radiofrequency energy, a form of electromagnetic radiation that is emitted by cell phones.”
But fears of cell phone-caused brain cancer have persisted for at least two reasons, risk science expert George M. Gray said 7 September during a Capitol Hill briefing organized by AAAS with support from the Dana Foundation. First, public health messages have at times been mixed. The International Agency for Research on Cancer, part of the World Health Organization, recently classified radiofrequency electromagnetic fields as “possibly carcinogenic to humans.” That group pointed to human evidence showing an increased incidence of glioma, a malignant form of brain cancer, said Gray, a professor and director of the Center for Risk Science and Public Health at George Washington University.
“Cell Phones: How Do They Affect the Brain?”
A public luncheon briefing hosted by AAAS in Washington, D.C., on 7 September 2011.
At the same time, he said, people seem to be inherently fearful of unfamiliar, unseen or “man-made” risks, as well as risks beyond their control. Electromagnetic energy may thus trigger more dread than, say, a handgun. People using cell phones while driving may fear other drivers without fully recognizing that they have put themselves in harm’s way.
“People are much more concerned about radiation from nuclear power plants than they are about radiation from the sun,” Gray said. “More people die of sun-induced radiation in one year than have died in all of history from nuclear power plants.”
Scientific uncertainty obviously complicates risk communication, too. Radiofrequency energy, such as the waves emitted by cell phones, clearly does not cause damage to DNA in cells, which can in turn cause cancer. But different types of studies have offered conflicting results, said Nora Volkow, director of the National Institute on Drug Abuse at the National Institutes of Health. Some researchers have reported changes in people’s cognitive abilities before and after cell phone use, for example, while others have found no such effect. Studies based on cerebral blood flow as well as electroencephalography (EEG), a technology for measuring electrical brain signals, have been similarly inconsistent, she said.
“When we have a ‘risk,’ something that could cause harm, it automatically means we have uncertainty,” Gray noted. “If we knew exactly what happened, we would not talk about it as a ‘risk.’ It would be a ‘cause.’” In grappling with scientific uncertainty, he said, the public inevitably will want to understand both the cause of the risk and “how big a problem” they are facing.
Gray has investigated using numbers to communicate levels of risks since the public may at times be confused about terms such as “probably carcinogenic” versus “possibly carcinogenic to humans.” When the International Agency for Research on Cancer said that cell phones are “possibly carcinogenic,” that classification represented “the weakest result they could come to,” in the absence of evidence to clearly disprove a connection, Gray said.
But he added that risk assessment is highly subjective, varying significantly across cultures, and from person to person. It is well-known, for instance, that white males generally tend to worry about risks much less than women, or men or women of color.
In an effort to reconcile conflicting information, NIDA researchers recently analyzed increases in glucose metabolism within the brain following cell phone use (Journal of the American Medical Association, February 2011). Fluorescent glucose was injected into 47 research subjects who took part in the randomized study, and positron emission tomography was used to measure glucose activity after 50 minutes of exposure to cell phones that were either on or off, Volkow explained.
NIDA researchers found that when the phones were on, there was “a significant increase in brain glucose metabolism in the areas of the brain that were receiving the greatest exposure to electromagnetic radiation,” Volkow said. But she emphasized that scientists don’t know whether this increased activity is harmful in any way. Many activities, including speaking, can increase brain glucose metabolism.
Further research is needed. “If cell phones are carcinogenic, the effect is not going to be immediate, and it will require long-term exposure,” Volkow said, in conclusion. “If they do have carcinogenic effects, the effects are likely to be small.”
Meanwhile, she added, simple, common-sense steps may help to minimize or eliminate any possible risks associated with using cell phones: Take advantage of hands-free technology whenever possible, select phones with antennas located at the bottom rather than at the top of the device, send text messages rather than making calls when feasible, and limit the use of cell phones by children.
“I am very worried about cell phone use and accidents. Those are real injuries and real deaths and yet that’s not high on our national risk worry list,” Gray said. “There are real public health consequences to having a gap between the way we perceive risks and what the risks really are.”
Read about the first briefing in this fall’s neuroscience series, on neurotechnology and the military.