Appendix C
90
the telephone wiring in a house and which operate at far lower
power levels and frequencies, has not been questioned.
How much evidence is there that hand-held mobile phones
might be harmful?
Briefly, there is not enough evidence to know for su re, eith er way;
however, 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 investigating the effects of RF exposures
characteristic of mobile phones have yielded conflicting results. A
few animal studies, however, have suggested that low levels of
RF could accelerate the development of cancer in laboratory
animals. In one study, mice genetically altered to be predisposed
to developing one type of cancer developed more than twice as
many such cancers when they were exposed to RF energy
compared to controls. There is much un certainty among
scientists about whether results 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 studies that showed increased tumor development
used animals that had already been treated with cancer-causing
chemicals, and other studies exposed the animals to the RF
virtually 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 safety of mobile phones.
This research has resulted in two findings in particular that merit
additional study:
1 In a hospital-based, case-control study, researchers looked for an
association between mobile phone use and either glioma (a type of
brain cancer) or acoustic neuroma (a benign 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 exposure in this study was less than
three years.
When 20 types of glioma were considered separately, however, an
association was found between mobile phone use and one rare type
of glioma, neuroepithelliomatous tumors. It is possible with multiple
comparisons of the same sample that this association occurred by
chance. Moreover, 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 increase risk with increased exposure. An
ongoing study of brain cancers by the National Cancer Institute is
expected to bear on the accuracy and repeatability of these results.1