brain tumor, neuroma, tumorigenesis, cell phone use
Cell phones came to the United States in 1984, and they're here to stay. By 1999, 86 million of them were in use; by 2000, 92 million were; and by 2005, nearly 195 million were in use, according to the Washington, DC-based Cellular Telecommunication Industry Association. A half billion of the gadgets are used worldwide.With such pervasive use of a radiation-emitting device-and considering the length of time some people spend with phone to ear-it isn't surprising that health concerns that focus on the impact of cell phones on the brain have arisen. Cell phone safety has become a field unto itself and has generated many published studies. "To my mind, it was clear from the very beginning that the introduction of a new technology has to be accompanied by research to identify potential health risks," said Joachim Schuz, PhD, head of the Department of Biostatistics and Epidemiology at the Institute of Cancer Epidemiology in Copenhagen.Cell phones emit radiofrequency signals of 850 to 1900 megahertz, which does not damage DNA or other cellular structures because it is not ionizing radiation. Although high-powered radiofrequency waves can heat tissue, as they do in microwave ovens with 600 to 1100 watts of power, the 0.6 wattage of the average cell phone poses little danger. Still, the hypothesis that extended cell phone use increases the risk of a brain tumor has been extensively examined.A prominent example of research into cell phone safety is the Interphone Project. This project, of international scope and including 13 nations that are conducting large-scale population-based case-control studies that follow the same design, is comparing cell phone use among people who have malignant or benign brain tumors with matched controls. Odds ratios are being examined to see whether a relationship exists between cell phone use and tumorigenesis.A CNN report on a 1993 lawsuit catalyzed current concern over cell phone use. "The initial event was a Larry King interview with a Florida man named David Reynard, who alleged that his wife's brain tumor was due to cell phone use," said Joshua E. Muscat, PhD, MPH, an associate professor in the Department of Health Evaluation Sciences at the Pennsylvania State Cancer Institute. Reynard sued several phone companies but could not amass enough evidence to win. Three years later, the first large study of cell phone safety emerged, finding no increase in overall mortality.1 As cell phone use became pervasive, investigations continued.Studies show no elevated risks for glioma or meningioma among cell phone users,2,3 but risk of acoustic neuroma is slightly higher among such persons.4,5 However, researchers urge caution in interpreting data. "Acoustic neuromas and gliomas and meningiomas are different histopathologically and anatomically and are likely to have different causes. Therefore, it is not remarkable that the risk patterns differ for the different tumor types," said Patricia McKinney, PhD, a professor of pediatric epidemiology at the Leeds Institute of Genetics, Health, and Therapeutics, University of Leeds, United Kingdom. In addition, acoustic neuromas are closer to the radiation source than the other types of tumors, she added. Peter Inskip, ScD, senior investigator at the National Cancer Institute's Division of Cancer Epidemiology and Genetics, agrees. "I am not convinced of an increase in risk for acoustic neuroma. Because the radiofrequency energy drops off very quickly with depth in tissue, the deeper parts of the brain receive very little exposure."Some of the studies also stratified participants by duration of cell phone use because of the long latency for cancer. The already-published German Interphone investigation3 indicates an elevated risk for glioma and meningioma after 10 years of cell phone use but found no overall increase in risk. The researchers, therefore, are calling for confirmation of their findings. Nevertheless, ongoing investigations may be required to uncover long-term effects of cell phone use and cancer risk. "There is no biological basis to predict how long it takes for a hypothetical effect of cell phone radiation to cause brain cancer. So studies with limited exposure periods-less than 10 years-provide empirical data that limited exposures do not increase the risk," said Muscat. "I think it is justified to establish a monitoring system for long-term effects for a technology that is used by virtually everyone in most developed countries," Schuz agreed.RICKI LEWIS, PHD, a geneticist, textbook author, and freelance writer in Scotia, NY, is a contributing editor for Applied Neurology.REFERENCES1. Rothman KJ, Loughlin JE, Furch DP, Dreyer NA. Overall mortality of cellular telephone customers. Epidemiology. 1996;7:302-305.2. Hepworth SJ, Schoemaker MJ, Muir KR, et al. Mobile phone use and risk of glioma in adults: case-control study. BMJ. 2006 Jan 20; [Epub ahead of print].3. Schuz J, Bohler E, Berg G, et al. Cellular phones, cordless phones, and the risks of glioma and meningioma (Interphone Study Group, Germany). Am J Epidemiol. 2006;163:512-520.4. Inskip PD, Tarone RE, Hatch EE, et al. Cellular-telephone use and brain tumors. N Engl J Med. 2006;344:79-86.5. Lonn S, Ahlbom A, Hall P, et al. Long-term mobile phone use and brain tumor risk. Am J Epidemiol. 2006;161:526-535.