Are Mobile Phones
Safe?
IEEE Spectrum
By Kenneth R. Foster, University of Pennsylvania & John E.
Moulder, Medical College of Wisconsin
A motorist using a wireless telephone might be worried about
having an accident, even while being reassured that if one were
to happen, he or she could call for help. Recently some scientists
and lay people have expressed alarm at another possible danger--that
the use of mobile phones itself may harm the user's health, perhaps
even causing cancer.
There is good reason to be concerned. The widespread use of hand-held
mobile phones means that many people routinely place radio frequency
(RF) transmitters against their heads--in some European and Asian
countries, a majority of the adult population does so. That fact
alone would warrant examination of the safety of this form of
radiant energy.
Concern about the possibility of mobile phone's ill effects on
health took shape in mid-1992 in a U.S. court. A lawsuit filed
in Florida by David Reynard alleged that the use of a cell phone
had caused his wife's fatal brain cancer. The suit was dismissed
by a Federal court in 1995 for lack of valid scientific evidence,
and similar suits since have been no more successful. But they
have raised questions for which no entirely satisfactory answers
existed at the time they were filed. Driven in part by these disturbing
allegations, a new wave of research in the United States and elsewhere
is exploring possible links between cell phone radiation and cancer.
Brain cancer, the topic of this article, is not the only health
concern, but it dominates public discussion. Now, nearly eight
years after the Reynard suit, a substantial body exists of pertinent
scientific evidence.
Fields and frequency
Wireless communication systems operate at several frequencies
in the electromagnetic spectrum. In the United States, cell phones
operate in two main frequency ranges--the older systems near 850
MHz, and the newer personal communications services, or PCS, near
1900 MHz. European mobile phones use the Global System for Mobile
Communications (GSM), a different technology than most U.S. phones,
and operate at slightly different frequencies, near 900 MHz and
1800 MHz. Many other applications transmit energy in nearby frequency
bands.
Energy in this frequency range is called non-ionizing because
the photon energy is insufficient to knock electrons from atoms
in living tissue, a source of serious biological damage from radiation
such as X-rays. The most apparent biological effects of RF energy
at cell phone frequencies are due to heating. Many mechanisms
not due to heating have been demonstrated, too; but those well
enough understood to be analyzed quantitatively are found to produce
observable effects only at very high exposure levels.
Exposure standards in the United States and most Western countries
are designed to give protection against all identified hazards
of RF energy. At present, these are associated only with excessive
tissue heating, which is hardly a likely problem with low-powered
mobile phones. Analog hand-held phones radiate 600 mW or less
of time averaged power, and many digital models produce 125 mW.
However, most modern phones' output is adaptively controlled by
the base station: the handset constantly adjusts its power to
provide the minimum signal needed to communicate reliably with
the base station.
Research, Old and New
Since World War II, there has been a massive amount of research
on the biological effects of RF energy, nearly all of it funded
by governments. Most of this research has involved fields at 915
and 2450 MHz, close to the frequencies used by mobile phones.
But, despite early claims by cell phone makers, little of this
research proves that mobile phones are safe. Few of the studies
on whether RF exposure is dangerous to animal tissue have involved
standard toxicology work--the sort that a chemical or a pharmaceutical
company would do to gain regulatory approval for a new product.
In addition, little of the research deals specifically with the
kinds of pulse-modulated energy transmitted by newer generations
of digital phones or with the exposure conditions typical of those
produced by cell phones.
The body of research is controversial in several respects. It
includes many reports of biological effects of RF fields on cells
and animals, sometimes at low exposure levels, which are poorly
understood and often not reproducible. It also includes a scattering
of reports of human health effects from low-level exposure to
RF fields. Standards-setting committees, while acknowledging this
research, have concluded that it provides insufficient basis for
exposure guidelines.
Spurred by the Reynard lawsuit and its attendant publicity, a
new round of studies began in the mid-'90s, largely funded by
mobile phone makers and mainly focused on carcinogenesis and mobile
phones. One notable effort was the US $27 million Wireless Technology
Research (WTR) program based in Washington, D.C. It was funded
mostly by U.S. phone manufacturers but operated at arm's length
from industry. That effort came to an end in December 1999 with
no official pronouncement and only a handful of published studies,
some of which are discussed below.
Many other research programs in other countries are under way,
sponsored by either industry or government. One review of the
issue, presented at a meeting in Erice, Sicily in November 1999,
identified more than 200 ongoing and recently completed studies
related to possible health hazards of RF energy.
Looking for a Link
Identifying links between cancer and environmental exposure of
any kind is surprisingly difficult because of the absence of a
single cause of cancer and for a variety of other reasons. Even
if mobile phones had no connection to cancer, thousands of users
would develop brain cancer every year, given the hundreds of millions
of mobile phone users around the world and given so-called background
rates of brain cancer (in the United States, it strikes about
six in 100 000 people per year). Identifying an effect of cell
phones against this background of the disease requires carefully
designed studies.
When investigating suspected carcinogens, health agencies rely
mostly on two sorts of studies: epidemiology studies, which involve
statistical analyses of health records, and standardized tests,
made on animals. On neither front does recent evidence support
links between mobile phones and brain cancer.
In 1996, in the first follow-up study to Reynard's brain cancer
allegations, the health records of more than 250 000 mobile phone
users were reviewed by Kenneth Rothman, a senior epidemiologist
at Epidemiology Research Institute, in Newton Lower Falls, Mass.
This industry-sponsored WTR study reported no difference in mortality
between the users of hand-held portable phones, where the antenna
is placed close to the head, and mobile cellular phones, where
the antenna is mounted on the vehicle, resulting in lower RF exposure.
In a later, follow-up study, the same investigators examined the
causes of death among nearly 300,000 mobile phone users (including
some from the previous study) in several U.S. cities. "The
only category of cause of death for which there was an indication
of increasing risk with increasing minutes of use," the investigators
reported in a November 1999 letter in the Journal of the American
Medical Association, "was motor vehicle collisions."
Other epidemiology studies have been mostly or entirely negative.
In a study that received extensive press coverage even before
it was published, Lennart Hardell and his colleagues at the Örebro
Medical Centre in Örebro, Sweden, assessed mobile phone use
by 209 Swedish brain tumor patients in comparison to 425 healthy
controls. The study, funded by the Swedish Medical Research Council,
was negative in virtually all respects.
In reporting the study, the lay media focused on one finding:
users of mobile phones who had developed certain types of brain
tumors were more likely to report having used the phone on the
side of the head with the tumor than on the other side. But the
association was weak. It was not statistically significant and
might easily have been a result of recall bias--a well-established
tendency of subjects to remember exposures to something more readily
if they developed a disease. The brain cancer patients in Hardell's
study knew their diagnosis before they were asked about their
use of mobile phones.
Brain cancer takes years or decades to develop, and these studies
say nothing about future risks. Detecting small or long-term cancer
risks is not an easy task. Detecting small increases in risk would
require large studies that are hard to control and usually are
controversial in their interpretation. Any valid study would also
have to assess an individual's use of mobile phones over a decade
or more, an assessment complicated by the rapid technological
developments in this industry.
Answers from animal studies
Animal studies, the other main source of information used in cancer
risk assessment, also have not supported a link between mobile
phones and cancer.
Exposing rats to pulse-modulated 837 MHz RF energy, similar to
that emitted by some digital cell phones, does not cause or promote
brain cancer. That was the finding of a Motorola-funded study
designed specifically to look for brain cancer and reported in
a 1999 paper by W. R. "Ross" Adey, now at the University
of California at Riverside. More recently, in April 2000, Adey
reported the same finding for continuous wave RF, such as that
emitted by analog cell phones. And in a 1999 meeting report, Bernard
Zook of George Washington University in Washington, D.C., confirmed
all of Adey's findings. The other studies in the table were not
focused on brain cancer, but they evaluated the animals for the
disease and would have noted a pronounced increase in this disease
had it occurred.
Animal studies, while easier to control than epidemiology studies,
have uncertain relevance to human health. For example, former
WTR chief George Carlo pointed out to IEEE Spectrum that none
of the animal studies done to date has adequately mimicked the
head-only exposure of a user of a mobile telephone; rather, the
animals are exposed to whole-body radiation. A countervailing
argument is that whole-body exposures are more likely to produce
toxic effects than partial body exposures. Issues of this nature
involve professional judgment about which experts routinely disagree.
Exceeding the limits
The focus on mobile phones' health effects has intensified the
scrutiny of exposure to RF energy in the United States. The FCC
limits peak exposure to 1.6 W/kg of tissue averaged over any single
gram of tissue (or 1.6 mW/g). European limits are less restrictive,
specifying 1.6 W/kg averaged over 10 grams.
Mobile telephone handsets operate at low power levels, but the
antenna, which radiates about 600 mW for an analog mobile phone
and 125 mW for a digital unit, is placed very close to the head,
which can push exposure levels close to the regulatory limits.
A complicating factor is that the exposure depends greatly on
the exact position of the handset with respect to the head and
on the exact shape and electrical characteristics of the head--all
variable quantities. Moreover, the exposure cannot be measured
directly in the head of the user, but has to be estimated by computer
models or measurements in tanks of liquids in the shape of the
head.
Manufacturers can reduce exposure by tweaking handset design,
up to a point. Significant reductions in power create the need
for more closely spaced base stations, which are unpopular with
residents in many areas. Moving antennas and other circuit elements
farther from the user's head might enlarge the handset, which
would work against consumer demands for small phones.
Industry and academic investigators have reported data showing
that mobile phones on the market meet regulatory limits, by and
large. There have been some exceptions, though. In 1998, the FCC
announced that Sony Electronics Inc. would recall 60 000 cell
phones that exceeded FCC exposure limits.
Controversy continues
Many areas of contention remain. For instance, in a 1995 study
that received wide media attention, Henry Lai and colleagues at
the University of Washington in Seattle reported exposing rats
to RF radiation at an average whole-body exposure of 1 W/kg of
body weight. The result: breaks in their brain cells' DNA--an
indicator of potential cancer causing effects.
But more recent studies have cast doubts on this finding. Attempts
to confirm Lai's results, by a Motorola-funded group led by Joseph
Roti Roti at Washington University in St. Louis, were unsuccessful.
A Belgian government-funded group led by Luc Vershaeve has reported
that similar RF exposure to rats does not cause DNA strand breaks
in other types of cells. Moreover, the Washington University group
has identified an experimental artifact that might have accounted
for Lai's positive results. Lai continues to defend his original
studies.
Scientific data can spark public controversies even before they
are published, let alone digested by health agencies. Take the
recent epidemiological study by Joshua Muscat, a research scientist
at the American Health Foundation in New York City. Results of
this WTR funded study were presented at a scientific meeting in
June 1999 but so far they have not been published in any detail.
In a Canadian TV interview four months later, former WTR chief
Carlo, referring to the Muscat study, said that "those who
use wireless phones have a higher chance of dying from brain cancer"
and pointed to "statistically significant" increases
in some rare subtypes of the disease.
Muscat's own conclusions, though, were more guarded. In his conference
paper abstract, he wrote that his study "did not find evidence
that cell phone use increases the risk of brain cancer..."
though "there remains some ambiguity" in how to interpret
an apparent increase in one kind of brain cancer. Muscat told
IEEE Spectrum that his research has been submitted for publication.
Until it has been published, his results cannot be independently
evaluated.
Are mobile phones safe?
The epidemiological results, so far, are certainly inconsistent
with any large increase in risk (a doubling or more) of brain
cancer from use of cell phones--the implication of the original
Reynard lawsuit. Nor do the animal studies show clear-cut carcinogenic
effects. However, the epidemiological studies lack the sensitivity
to detect small increases in risk, and the relevance of animal
studies to human health is uncertain--both familiar problems with
carcinogen risk assessment.
In a document posted on the Web in February 2000, the U.S. Food
and Drug Administration noted that "There is currently insufficient
scientific basis for concluding either that wireless communication
technologies are safe or that they pose a [health] risk to millions
of users."
The term "safe" brims with legal, regulatory, and ethical
implications. Health agencies on the whole shy away from pronouncing
technologies safe, but instead evaluate evidence for possible
hazards. For example, the International Agency for Research on
Cancer (IARC), in Lyon, France, has received about 8 million euros
from the European Commission for a large epidemiological study
of cell phone use in relation to head and neck cancers. Ten countries
will participate in the study, which is foreseen as including
1500 cases and 1500 healthy controls. The research is in its pilot
phase and is expected to be completed within three years. But
even with extensive data, IARC virtually never pronounces an agent
to be a "noncarcinogen," and therefore is unlikely to
do so with RF energy.
In contrast, mobile phone manufacturers must prove, not that
their products are safe, but that they meet exposure limits--a
different matter entirely. The standards that set limits on exposure
to energy from phones were developed largely on the basis of whole-body
exposure data and engineering considerations.
More research is clearly needed on the biological and biophysical
effects of near-field exposure. A better-defined threshold for
hazard might even lead to relaxed exposure limits for handsets.
Most current research is going on outside the United States. Michael
Repacholi, director of a project on health effects of electromagnetic
fields at the World Health Organization in Geneva, estimates that
there is about $100 million in ongoing research on possible health
effects of mobile telephones, very little of which is being done
within the United States.
But U.S. industry and government have not given up. In June 2000,
the Cellular Telephone Industry Association (CTIA) and the U.
S. Food and Drug Administration announced an agreement, under
which the CTIA would fund a $1 million research program, with
FDA input, on mobile phones and health. This funding is dwarfed
by the huge costs of toxicology and epidemiology studies; it will
pay for limited follow-up studies to address issues raised by
the WTR program.
Whatever the outcome of the latest generation of studies, debate
over the health effects of mobile phones will continue. Mobile
phones will join other forms of electrical technology, such as
police radar sets, computer display terminals, and power lines,
that have triggered public fears because of their electromagnetic
fields. Such issues are very difficult and time-consuming to resolve.
How to respond appropriately to public fears, identifying any
real hazard while avoiding unproductive controversy, is not a
purely scientific matter but a question with deep social aspects.
In a bid to stay ahead of the public debate CTIA recently revealed
that by the end of 2000 its members would begin including SAR
information with new models of phones. The data and some explanatory
language will appear as a pamphlet inside boxes of new phones,
a CTIA spokesperson told IEEE Spectrum. SAR data is already available
at an FCC website [www.fcc.gov/oet/rfsafety], but that site is
very difficult to navigate. Even if the CTIA initiative makes
SAR data more easily accessible, it is is unclear how consumers
can make use of the data.
Meanwhile, a mobile phone user with health concerns has simple
remedies: use an external earpiece that keeps the phone away from
the head, decrease phone use, or avoid using the phones in areas
where the signal is poor--a weak signal from the base station
causes modern handsets to increase their broadcast power. Neither
of us would recommend such measures on health grounds, but people
can decide for themselves whether to take such precautions.
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