Sharp R520_CJ16_MM_111009_F4 - Manual (Page 142)

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repeated in other laboratories. A few animal studies, however,
have suggested that low levels of RF could accelerate the
development of cancer in laboratory animals. However, many of
the studies that showed increased tumor development used
animals that had been genetically engineered or treated with
cancer-causing chemicals so as to be pre-disposed to develop
cancer in 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 phones 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 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 ten 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