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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 conflict-
ing 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 ani-
mals. 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
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.
16
is
much
uncertainty
When 20 types of glioma were considered separately, how-
ever, 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.
2. 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 abnormali-
ties, 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 pos-
sible 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
2
research is necessary.
FDA is currently working with govern-
ment, industry, and academic groups to
ensure the proper follow-up to these
industry-funded research findings. Collab-
oration with the Cellular Telecommunica-
tions
Industry
Association
particular is expected to lead to FDA pro-
viding research recommendations and sci-
entific oversight of new CTIA-funded
research based on such recommendations.
Two other studies of interest have been
reported recently in the literature:
1. 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 recall words, numbers, or pictures, or in
their spatial memory, but they were able to make choices
more quickly in one visual test when they were exposed to
simulated mobile phone signals. This was the only change
noted among more than 20 variables compared.
2. In a study of 209 brain tumor cases and 425 matched
controls, there was no increased risk of brain tumors
associated with mobile phone use. When tumors did exist in
certain locations, however, they were more likely to be on the
side of the head where the mobile phone was used. Because
this occurred in only a small number of cases, the increased
likelihood was too small to be statistically significant.
In summary, we do not have enough
information at this point to assure the
public that there are, or are not, any low
incident health problems associated with
1
(CTIA)
in
3
4
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