the primary source of the RF—and the person's head. The exposure to
RF from mobile phones in which the antenna is located at greater
distances from the user (on the outside of a car, for example) is drastically
lower than that from hand-held phones, because a person's RF exposure
decreases rapidly with distance from the source. The safety of so-called
"cordless phones," which have a base unit connected to the telephone
wiring in a house and which operate at far lower power levels and
frequencies, has not been questioned.
How much evidence is there that hand-held
mobile phones might be harmful?
Brieﬂy, there is not enough evidence to know for sure, either way;
however, research efforts are on-going. The existing scientiﬁc evidence is
conﬂicting and many of the studies that have been done to date have
suffered from ﬂaws in their research methods. Animal experiments
investigating the effects of RF exposures characteristic of mobile phones
have yielded conﬂicting results. A few animal studies, however, have
suggested that low levels of RF could accelerate the development of
cancer in laboratory animals. In one study, mice genetically altered to be
predisposed to developing one type of cancer developed more than twice
as many such cancers when they were exposed to RF energy compared
to controls. There is much uncertainty among scientists about whether
results obtained from animal studies apply to the use of mobile phones.
First, it is uncertain how to apply the results obtained in rats and mice to
humans. Second, many of the studies that showed increased tumor
development used animals that had already been treated with cancer-
causing chemicals, and other studies exposed the animals to the RF
virtually continuously—up to 22 hours per day.
For the past ﬁve years in the United States, the mobile phone industry has
supported research into the safety of mobile phones. This research has
resulted in two ﬁndings in particular that merit additional study:
1 In a hospital-based, case-control study, researchers looked for an
association between mobile phone use and either glioma (a type of
brain cancer) or acoustic neuroma (a benign tumor of the nerve