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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 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 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