Epidemiological and animal studies undertaken by the U.S. cell phone industry and others have yielded mixed results:
- In a study published in 1999, investigators at the Orebro Medical Centre in Sweden compared the past mobile phone use of 209 Swedish brain tumor patients and 425 healthy people. Conclusion: The study found no mobile phone/brain cancer link "in virtually all respects," cancer researcher John E. Moulder, Ph.D., says in the August 2000 issue of IEEE Spectrum, the official magazine of the Institute of Electrical and Electronics Engineers. Investigators did find that mobile phone users who got certain types of brain tumors tended to report using the phone on the side of the head where they developed the tumor. The study's limitations, according to Moulder, include a weak association between cell phone use and tumor development, as well as a possibility that the cancer patients' recollections were biased by already knowing on which side of their head the brain cancer developed.
- In a yet-unpublished study presented at a 1999 scientific meeting, researcher Joshua Muscat looked for an association between mobile phone use and a type of brain cancer called glioma. Muscat did not find evidence that cell phone use increased people's risk of this type of brain cancer generally. He did, however, observe an increase in one rare kind of glioma, which FDA scientists say might have occurred by chance. Interestingly, with increased hours of mobile phone use, the risk tended to decrease rather than increase as might be expected.
- A few animal studies have suggested that low levels of RF exposure could speed up development of cancer in laboratory animals. In one recent Australian study, for example, mice genetically altered to be predisposed to developing lymphoma got more than twice as many of these cancers when exposed to RF energy compared to mice not exposed to the radiation.
- A large number of laboratory tests have been conducted to assess RF's effects on genetic material, looking for mutations, chromosomal changes, DNA strand breaks, and structural changes in blood cells' genetic material. One kind of test, called a micronucleus assay, showed structural changes in genetic material after exposure to simulated cell phone radiation. The changes occurred only after 24 hours of continuous exposure, which experts say raises questions about this test's sensitivity to heating effects and whether that sensitivity could be solely responsible for the results.
In one study of brain function and RF exposure, two groups of 18 people were given cognitive function tests while being exposed to simulated mobile phone signals. No changes were seen in the ability to recall words, numbers, or pictures, or in spatial memory, but among the 20 variables compared, there was one standout observation: The participants were actually able to make choices more quickly in one visual test when they were exposed to the signals.
Adapted from the November-December, 2000 issue of FDA Consumer.
For more information on cell phone safety, visit www.fda.gov/cellphones.