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those they can get from wireless phones. Base stations are thus not the subjects of the safety questions discussed
in this document.
3. What kinds of phones are the subjects 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 radiofrequency 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 radiofrequency 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 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
