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U.S. FDA
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24
velopment used animals that had already
been treated with cancer-causing chemi-
cals, and other studies exposed the ani-
mals 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 mo-
bile phones. This research has resulted in
two findings in particular that merit addi-
tional study:
1. In a hospital-based, case-control study,
researchers looked for an association be-
tween mobile phone use and either glio-
ma (a type of brain cancer) or acoustic
neuroma (a benign tumor of the nerve
sheath). No statistically significant associ-
ation 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, neuroepithel-
liomatous tumors. It is possible with mul-
tiple 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 ac-
tually decreased with cumulative hours of
mobile phone use. Most cancer causing
agents increase risk with increased expo-
sure. An ongoing study of brain cancers
by the National Cancer Institute is expect-
ed to bear on the accuracy and repeat-
ability of these results.
1
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 abnormalities, including muta-
tions, 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 micro-
nucleus assay, which detects structural ef-
fects 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 radia-
tion 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 al-
ready in the literature on the response of
the micronucleus assay to RF are conflict-
ing. Thus follow-up research is
necessary.
2
FDA is currently working with govern-
ment, industry, and academic groups to
ensure the proper follow-up to these in-
dustry-funded research findings. Collabo-
ration with the Cellular Telecommunica-
tions Industry Association (CTIA) in
particular is expected to lead to FDA pro-
viding research recommendations and sci-
entific oversight of new CTIA-funded re-
search 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 un-
der laboratory conditions while they
performed cognitive function tests.
There were no changes in the subjects'
ability to recall words, numbers, or pic-
tures, 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.
3
• In a study of 209 brain tumor cases and
425 matched controls, there was no in-
creased risk of brain tumors associated
with mobile phone use. When tumors
did exist in certain locations, however,
