User's Manual

44
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 predisposed 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 neu-roma, 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 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 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