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base stations are typically thousands of times lower than those they can
get from wireless phones. Base stations are thus not the primary subject
of the safety questions discussed in this document.
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 well within the
FCC's compliance limits.
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 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.
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.
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 driven the establishment of
new research programs around the world. The Project has also helped
develop a series of public information documents on EMF issues.
FDA and the Cellular Telecommunications & Internet Association (CTIA)
have a formal Cooperative Research and Development Agreement
(CRADA) to do research on wireless phone safety. FDA provides the
scientific oversight, obtaining input from experts in government, industry,
and academic organizations. CTIA-funded research is conducted through
contracts to independent investigators. The initial research will include
both laboratory studies and studies of wireless phone users. The CRADA
will also include a broad assessment of additional research needs in the
context of the latest research developments around the world.
What steps can I take to reduce my exposure to radiofrequency
energy from my wireless phone?
If there is a risk from these products--and at this point we do not know that
there is--it is probably very small. But if you are concerned about avoiding
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