100

U.S. FDA

How much evidence is there that hand- held mobile phones might be harmful?

Briefly, there is not enough evidence to know for sure, either way; howev- er, research efforts are on-going.

The existing scientific evidence is conflicting and many of the studies that have been done to date have suffered from flaws in their research methods. Animal experiments inves- tigating the effects of RF exposures characteristic of mobile phones have yielded conflicting results. A few ani- mal studies, however, have suggest- ed that low levels of RF could accel- erate the development of cancer in laboratory animals. In one study, mice genetically altered to be predis- posed to developing one type of can- cer developed more than twice as many such cancers when they were exposed to RF energy compared to controls. There is much uncertainty among scientists about whether re- sults obtained from animal studies apply to the use of mobile phones. First, it is uncertain how to apply the results obtained in rats and mice to humans. Second, many of the stud- ies showed increased tumor devel- opment used animals that had al- ready been treated with cancer- causing chemicals, and other studies exposed the animals to the RF virtu- ally continuously — up to 22 hours per day.

For the past five years in the United States, the mobile phone industry has supported research into the safe-

ty of mobile phones. This research has resulted in two findings in partic- ular that merit additional study:

1.In a hospital-based, case-control study, researchers looked for an as- sociation between mobile phone use and either glioma (a type of brain cancer) or acoustic neuroma (a be- nign tumor of the nerve sheath). No statistically significant association was found between mobile phone use and acoustic neuroma. There was also no association between mobile phone use and gliomas when all types of gliomas were considered together. It should be noted that the average length of mobile phone ex- posure in this study was less than three years.

When 20 types of glioma were con- sidered separately, however, an as- sociation was found between mobile phone use and one rare type of glio- ma, neuroepithelliomatous tumors. It is possible with multiple compari- sons of the same sample that this as- sociation occurred by chance. More- over, the risk did not increase with how often the mobile phone was used, or the length of the calls. In fact, the risk actually decreased with cumulative hours of mobile phone use. Most cancer causing agents in- crease risk with increased exposure. An ongoing study of brain cancers by the National Cancer Institute is ex- pected to bear on the accuracy and repeatability of these results.1