107
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 the FDA doing to find out more
about the possible health effects of
wireless phone RF?
The 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
106
What are the results of the research done
already?
The research done thus far has produced conflicting
results, and many studies have suffered from flaws
in their research methods. Animal experiments
investigating the effects of radio frequency energy
(RF) exposures characteristic of wireless phones
have yielded conflicting results that often cannot
be 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 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 phones RF exposures. However,
none of the studies can answer questions about
long-term exposures, since the average period
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