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Appendix B
3. What kinds of phones are the subject of this update?
The term wireless phone refers here to hand-held wireless phones with built-in antennas, often
called cell mobile or PCS phones. These types of wireless phones can expose the user to
measurable radio frequency energy (RF) because of the short distance between the phone and
the user’s head. These RF exposures are limited by Federal Communications Commission safety
guidelines that were developed with the advice of FDA and other federal health and safety
agencies. When the phone is located at greater distances from the user, the exposure to RF is
drastically lower because a person's RF exposure decreases rapidly with increasing distance
from the source. The so-called cordless phones; which have a base unit connected to the
telephone wiring in a house, typically operate at far lower power levels, and thus produce RF
exposures far below the FCC safety limits.
4. 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 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).