||WHO Mobile Phone Fact Sheet
Mobile Telephones and Their Base Stations
Mobile telephones, sometimes called cellular phones
or handies, are now an integral part of modern telecommunications. In
some parts of the world, they are the most reliable or only phones
available. In others, mobile phones are very popular because they allow
people to maintain continuous communication without hampering freedom of
This fact sheet has been updated in the light of
recent reviews of the effects on human beings of exposure to
radiofrequency (RF) fields conducted by the World Health Organization
(WHO) in November 1999, the Royal Society of Canada (1999), and a review
on mobile phones and health by an expert committee in the United Kingdom
Use of mobile phones
In many countries, over half the population already
use mobile phones and the market is still growing rapidly. The industry
predicts that there will be as many as 1.6 billion mobile phone
subscribers worldwide in the year 2005. Because of this, increasing
numbers of mobile base stations have had to be installed. Base stations
are low-powered radio antennae that communicate with users’ handsets.
In early 2000 there were about 20,000 base stations in operation the
United Kingdom and about 82,000 cell sites in the United States, with
each cell site holding one or more base stations.
Concerns for health
Given the immense numbers of users of mobile phones,
even small adverse effects on health could have major public health
implications. This fact sheet addresses these concerns.
Several important considerations must be kept in mind
when evaluating possible health effects of RF fields. One is the
frequency of operation. Current mobile phone systems operate at
frequencies between 800 and 1800 MHz. It is important not to confuse
such RF fields with ionizing radiation, such as X-rays or gamma rays.
Unlike ionizing radiation, RF fields cannot cause ionization or
radioactivity in the body. Because of this, RF fields are called
Mobile phone handsets and base stations present quite
different exposure situations. RF exposure to a user of a mobile phone
is far higher than to a person living near a cellular base station.
However, apart from infrequent signals used to maintain links with
nearby base stations, the handset transmits RF energy only while a call
is being made, whereas base stations are continuously transmitting
Handsets: Mobile phone handsets are
low-powered RF transmitters, emitting maximum powers in the range of 0.2
to 0.6 watts. Other types of hand held transmitter, such as "walkie
talkies", may emit 10 watts or more. The RF field strength (and
hence RF exposure to a user) falls off rapidly with distance from the
handset. Therefore, the RF exposure to a user of a mobile phone located
10s of centimetres from the head (using a "hands free"
appliance) is far lower than to a user who places the headset against
the head. RF exposures to nearby people are very low.
Base stations: Base stations transmit power
levels from a few watts to 100 watts or more, depending on the size of
the region or "cell" that they are designed to service. Base
station antennae are typically about 20-30 cm in width and a metre in
length, mounted on buildings or towers at a height of from 15 to 50
metres above ground. These antennae emit RF beams that are typically
very narrow in the vertical direction but quite broad in the horizontal
direction. Because of the narrow vertical spread of the beam, the RF
field intensity at the ground directly below the antenna is low. The RF
field intensity increases slightly as one moves away from the base
station and then decreases at greater distances from the antenna.
Typically within 2-5 metres of some antennae mounted
on rooftops, fences keep people away from places where the RF fields
exceed exposure limits. Since antennae direct their power outward, and
do not radiate significant amounts of energy from their back surfaces or
towards the top or bottom of the antenna, the levels of RF energy inside
or to the sides of the building are normally very low.
Other RF sources in the community: Paging and
other communications antennae such as those used by fire, police and
emergency services, operate at similar power levels as cellular base
stations, and often at a similar frequency. In many urban areas
television and radio broadcast antennae commonly transmit higher RF
levels than do mobile base stations.
RF fields penetrate exposed tissues to depths that
depend on the frequency - up to a centimetre at the frequencies used by
mobile phones. RF energy is absorbed in the body and produces heat, but
the body's normal thermoregulatory processes carry this heat away. All
established health effects of RF exposure are clearly related to
heating. While RF energy can interact with body tissues at levels too
low to cause any significant heating, no study has shown adverse health
effects at exposure levels below international guideline limits.
Most studies have examined the results of short-term,
whole body exposure to RF fields at levels far higher than those
normally associated with wireless communications. With the advent of
such devices as walkie-talkies and mobile phones, it has become apparent
that few studies address the consequences of localised exposures to RF
fields to the head.
WHO has identified research needs to make better
health risk assessment and promoted the research to funding agencies.
Briefly, at present time this research indicates:
International guidelines developed by the
International Commission on Non-Ionizing Radiation Protection (ICNIRP)
are based on a careful analysis of all scientific literature (both
thermal and non-thermal effects) and offer protection against all
identified hazards of RF energy with large safety margins. Both
measurements and calculations show that RF signal levels in areas of
public access from base stations are far below international guidelines,
typically by a factor of 100 or more. RF exposure levels to a user from
mobile handsets are considerably larger but below international
What WHO is doing
In response to public concerns, WHO established the
International Electromagnetic Fields (EMF) Project to assess the
scientific evidence of possible health effects of EMF. Specific studies
have been identified to address the problem of localised exposure. The
project has established a formal mechanism for reviewing the research
results and conducting risk assessments of RF exposure. It is also
developing public information materials, and bringing together standards
groups worldwide in an attempt to harmonise international exposure
WHO is also conducting RF research. A large
epidemiology study is being co-ordinated in over 10 countries by the
International Agency for Research on Cancer (IARC) – a specialised
cancer research agency of WHO – to identify if there are links between
use of mobile phones and head and neck cancers. The study is anticipated
to be completed in 2003.
Conclusions and recommendations
None of the recent reviews have concluded that
exposure to the RF fields from mobile phones or their base stations
causes any adverse health consequence. However, there are gaps in
knowledge that have been identified for further research to make better
assess health risks. It will take about 3-4 years for the required RF
research to be completed, evaluated and to publish the final results of
any health risks. In the meantime, WHO recommends:
- Cancer: Current scientific evidence indicates that exposure
to RF fields, such as those emitted by mobile phones and their base
stations, is unlikely to induce or promote cancers. Several studies
of animals exposed to RF fields similar to those emitted by mobile
phones found no evidence that RF causes or promotes brain cancer.
While one 1997 study found that RF fields increased the rate at
which genetically engineered mice developed lymphoma, the health
implications of this result is unclear. Several studies are underway
to confirm this finding and determine any relevance of these results
to cancer in human beings. Three recent epidemiological studies
found no convincing evidence of increase in risk of cancer or any
other disease with use of mobile phones.
- Other health risks: Scientists have reported other effects
of using mobile phones including changes in brain activity, reaction
times, and sleep patterns. These effects are small and have no
apparent health significance. More studies are in progress to try to
confirm these findings.
- Driving: Research has clearly shown an increased risk of
traffic accidents when mobile phones (either handheld or with a
"hands-free" kit) are used while driving.
- Electromagnetic Interference: When mobile phones are used
close to some medical devices (including pacemakers, implantable
defibrillators, and certain hearing aids) there is the possibility
of causing interference. There is also the potential of interference
between mobile phones and aircraft electronics.
IEGMP (2000) Independent Expert Group on Mobile
Phones, Mobile Phones and Health, National Radiological
Protection Board (UK) 2000. See http://www.iegmp.org.uk/IEGMPtxt.htm
- Strict adherence to health-based guidelines: International
guidelines have been developed to protect everyone in the
population: mobile phone users, those who work near or live around
base stations, as well as people who do not use mobile phones.
- Precautionary measures
If regulatory authorities have adopted
health-based guidelines but, because of public concerns, would
like to introduce additional precautionary measures to reduce
exposure to RF fields, they should not undermine the science base
of the guidelines by incorporating arbitrary additional safety
factors into the exposure limits. Precautionary measures should be
introduced as a separate policy that encourages, through voluntary
means, the reduction of RF fields by equipment manufacturers and
the public. Details of such measures are given in a separate WHO
- Individuals: Present scientific information does not
indicate the need for any special precautions for use of mobile
phones. If individuals are concerned, they might choose to limit
their own or their children’s’ RF exposure by limiting the
length of calls, or using "hands-free" devices to keep
mobile phones away from the head and body.
- Obey local restrictions on mobile phone use to avoid EMF
interference: Mobile phones may interfere with certain
electromedical devices, such as cardiac pacemakers and hearing
aids. In hospital intensive care departments mobile phone use can
be a danger to patients and should not be used in these areas.
Similarly mobile phones should not be used in aircraft as they may
interfere with its navigation systems.
- Driving safety: In moving vehicles there is a well
established increase in the risk of traffic accidents while the
driver is using a mobile phone, either a conventional handset or
one fitted with a "hands free" device. Motorists should
be strongly discouraged from using mobile phones while driving.
- Simple protective measures: Fences or barriers or other
protective measures are needed for some base stations
(principally, those located on building rooftops) to preclude
unauthorised access to areas where exposure limits may be
- RF absorbing devices: Scientific evidence does not
indicate any need for RF-absorbing covers or other "absorbing
devices" on mobile phones. They cannot be justified on health
grounds and the effectiveness of many such devices in reducing RF
exposure is unproven.
- Consultations with the community in siting base stations:
Base station sites must offer good signal coverage and be
accessible for maintenance. While RF field levels around base
stations are not considered a health risk, siting decisions should
take into account aesthetics and public sensibilities. Siting base
stations near kindergartens, schools and playgrounds may need
special consideration. Open communication and discussion between
the mobile phone operator, local council and the public during the
planning stages for a new antenna can help create public
understanding and greater acceptance of a new facility.
- Providing information: An effective system of health
information and communications among scientists, governments,
industry and the public is needed to raise the level of general
understanding about mobile phone technology and reduce any
mistrust and fears, both real and perceived. This information
should be accurate, and at the same time be appropriate in its
level of discussion and understandable to the intended audience.
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Editor: Susan K. Boyer, RN
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