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FDA Update
94
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.
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 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.
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:
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 use of mobile phones. FDA continues to work with all
parties, including other federal agencies and industry, to assure that
research is undertaken to provide the necessary answers to the
outstanding questions about the safety of mobile phones.
What is known about cases of human cancer that have been
reported in users of hand-held mobile phones?
Some people who have used mobile phones have been diagnosed with
brain cancer. But it is important to understand that this type of cancer
also occurs among people who have not used mobile phones. In fact,
brain cancer occurs in the U.S. population at a rate of about 6 new cases
per 100,000 people each year. At that rate, assuming 80 million users of
mobile phones (a number increasing at a rate of about 1 million per
month), about 4800 cases of brain cancer would be expected each year
among those 80 million people, whether or not they used their phones.
Thus it is not possible to tell whether any individual's cancer arose
because of the phone, or whether it would have happened anyway. A
key question is whether the risk of getting a particular form of cancer is
greater among people who use mobile phones than among the rest of
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