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development used animals that had been genetically
engineered or treated with cancer-causing chemicals so
as to be pre-disposed to develop cancer in the absence
of RF exposure. Other studies exposed the animals to RF
for up to 22 hours per day. These conditions are not
similar to the conditions under which people use wireless
phones, so we don't know with certainty what the results
of such studies mean for human health.
Three large epidemiology studies have been published
since December 2000. Between them, the studies
investigated any possible association between the use of
wireless phones and primary brain cancer, glioma,
meningioma, or acoustic neuroma, tumors of the brain or
salivary gland, leukemia, or other cancers. None of the
studies demonstrated the existence of any harmful health
effects from wireless phone RF exposures. However,
none of the studies can answer questions about long-
term exposures, since the average period of phone use
in these studies was around three years.
What research is needed to decide whether RF
exposure from wireless phones poses a health
risk?
A combination of laboratory studies and epidemiological
studies of people actually using wireless phones would
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provide some of the data that are needed. Lifetime
animal exposure studies could be completed in a few
years. However, very large numbers of animals would be
needed to provide reliable proof of a cancer promoting
effect if one exists. Epidemiological studies can provide
data that is directly applicable to human populations, but
10 or more years' follow-up may be needed to provide
answers about some health effects, such as cancer. This
is because the interval between the time of exposure to a
cancer-causing agent and the time tumors develop - if
they do - may be many, many years. The interpretation of
epidemiological studies is hampered by difficulties in
measuring actual RF exposure during day-to-day use of
wireless phones. Many factors affect this measurement,
such as the angle at which the phone is held, or which
model of phone is used.
What is FDA doing to find out more about the
possible health effects of wireless phone RF?
FDA is working with the U.S. National Toxicology
Program and with groups of investigators around the
world to ensure that high priority animal studies are
conducted to address important questions about the
effects of exposure to radiofrequency energy (RF).
FDA has been a leading participant in the World Health
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