User's Manual

70
Safety Guidelines
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 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.
5. 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 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.
6. 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