95
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
questions about the effects of exposure to radio frequency
energy (RF). FDA has been a leading participant in the World
Health Organization international Electromagnetic Fields (EMF)
Project since its inception in 1996. An influential result of this
work has been the development of a detailed agenda of research
needs that has driven the establishment of new research
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