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mobile phones are of concern because of the short distance
between the phone’s antenna—the primary source of the RF—and
the person’s head. The exposure to RF from mobile phones in
which the antenna is located at greater distances from the user (on
the outside of a car, for example) is drastically lower than that from
hand-held phones, because a person’s RF exposure decreases
rapidly with distance from the source. The safety of so-called
“cordless phones,” which have a base unit connected to 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 sure, either 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
uncertainty 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:
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 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. Researchers conducted a large battery of laboratory tests to
assess the effects of exposure to mobile phone RF on genetic
material. These included tests for several kinds of abnormalities,
including mutations, chromosomal aberrations, DNA strand breaks,
and structural changes in the genetic material of blood cells called
lymphocytes. None of the tests showed any effect of the RF except
for the micronucleus assay, which detects structural effects on the
genetic material. The cells in this assay showed changes after
exposure to simulated cell phone radiation, but only after 24 hours
of exposure. It is possible that exposing the test cells to radiation
for this long resulted in heating. Since this assay is known to be
sensitive to heating, heat alone could have caused the
abnormalities to occur. The data already in the literature on the
response of the micronucleus assay to RF are conflicting. Thus,
follow-up research is necessary.
2. FDA is currently working with government, industry, and
academic groups to ensure the proper follow-up to these industry-
funded research findings. Collaboration with the Cellular
Telecommunications Industry Association (CTIA) in particular is
expected to lead to FDA providing research recommendations and
scientific oversight of new CTIA-funded research based on such
recommendations.
Two other studies of interest have been reported recently in the
literature:
Two groups of 18 people were exposed to simulated mobile phone
signals under laboratory conditions while they performed cognitive
function tests. There were no changes in the subjects’ ability to
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