Fact sheet N°304
May 2006
Electromagnetic fields and public health
Base stations and wireless technologies
Mobile telephony is now commonplace around the world. This wireless technology relies upon an extensive network of fixed
antennas, or base stations, relaying information with radiofrequency (RF) signals. Over 1.4 million base stations exist
worldwide and the number is increasing significantly with the introduction of third generation technology.
Other wireless networks that allow high-speed internet access and services, such as wireless local area networks (WLANs),
are also increasingly common in homes, offices, and many public areas (airports, schools, residential and urban areas). As the
number of base stations and local wireless networks increases, so does the RF exposure of the population. Recent surveys
have shown that the RF exposures from base stations range from 0.002% to 2% of the levels of international exposure
guidelines, depending on a variety of factors such as the proximity to the antenna and the surrounding environment. This is
lower or comparable to RF exposures from radio or television broadcast transmitters.
There has been concern about possible health consequences from exposure to the RF fields produced by wireless
technologies. This fact sheet reviews the scientific evidence on the health effects from continuous low-level human exposure
to base stations and other local wireless networks.
Health concerns
A common concern about base station and local wireless network antennas relates to the possible long-term health effects that
whole-body exposure to the RF signals may have. To date, the only health effect from RF fields identified in scientific
reviews has been related to an increase in body temperature (> 1 °C) from exposure at very high field intensity found only
in certain industrial facilities, such as RF heaters. The levels of RF exposure from base stations and wireless networks are so
low that the temperature increases are insignificant and do not affect human health.
The strength of RF fields is greatest at its source, and diminishes quickly with distance. Access near base station antennas is
restricted where RF signals may exceed international exposure limits. Recent surveys have indicated that RF exposures from
base stations and wireless technologies in publicly accessible areas (including schools and hospitals) are normally thousands
of times below international standards.
In fact, due to their lower frequency, at similar RF exposure levels, the body absorbs up to five times more of the signal from
FM radio and television than from base stations. This is because the frequencies used in FM radio (around 100 MHz) and in
TV broadcasting (around 300 to 400 MHz) are lower than those employed in mobile telephony (900 MHz and 1800 MHz)
and because a person's height makes the body an efficient receiving antenna. Further, radio and television broadcast stations
have been in operation for the past 50 or more years without any adverse health consequence being established.
While most radio technologies have used analog signals, modern wireless telecommunications are using digital transmissions.
Detailed reviews conducted so far have not revealed any hazard specific to different RF modulations.
Cancer: Media or anecdotal reports of cancer clusters around mobile phone base stations have heightened public concern. It
should be noted that geographically, cancers are unevenly distributed among any population. Given the widespread presence
of base stations in the environment, it is expected that possible cancer clusters will occur near base stations merely by chance.
Moreover, the reported cancers in these clusters are often a collection of different types of cancer with no common
characteristics and hence unlikely to have a common cause.
Scientific evidence on the distribution of cancer in the population can be obtained through carefully planned and executed
epidemiological studies. Over the past 15 years, studies examining a potential relationship between RF transmitters and
cancer have been published. These studies have not provided evidence that RF exposure from the transmitters increases the
risk of cancer. Likewise, long-term animal studies have not established an increased risk of cancer from exposure to RF
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fields, even at levels that are much higher than produced by base stations and wireless networks.
Other effects: Few studies have investigated general health effects in individuals exposed to RF fields from base stations.
This is because of the difficulty in distinguishing possible health effects from the very low signals emitted by base stations
from other higher strength RF signals in the environment. Most studies have focused on the RF exposures of mobile phone
users. Human and animal studies examining brain wave patterns, cognition and behaviour after exposure to RF fields, such as
those generated by mobile phones, have not identified adverse effects. RF exposures used in these studies were about 1000
times higher than those associated with general public exposure from base stations or wireless networks. No consistent
evidence of altered sleep or cardiovascular function has been reported.
Some individuals have reported that they experience non-specific symptoms upon exposure to RF fields emitted from base
stations and other EMF devices. As recognized in a recent WHO fact sheet "Electromagnetic Hypersensitivity", EMF has not
been shown to cause such symptoms. Nonetheless, it is important to recognize the plight of people suffering from these
symptoms.
From all evidence accumulated so far, no adverse short- or long-term health effects have been shown to occur from the RF
signals produced by base stations. Since wireless networks produce generally lower RF signals than base stations, no adverse
health effects are expected from exposure to them.
Protection standards
International exposure guidelines have been developed to provide protection against established effects from RF fields by the
International Commission on Non-Ionizing Radiation Protection (ICNIRP, 1998) and the Institute of Electrical and Electronic
Engineers (IEEE, 2005).
National authorities should adopt international standards to protect their citizens against adverse levels of RF fields. They
should restrict access to areas where exposure limits may be exceeded.
Public perception of risk
Some people perceive risks from RF exposure as likely and even possibly severe. Several reasons for public fear include
media announcements of new and unconfirmed scientific studies, leading to a feeling of uncertainty and a perception that
there may be unknown or undiscovered hazards. Other factors are aesthetic concerns and a feeling of a lack of control or
input to the process of determining the location of new base stations. Experience shows that education programmes as well as
effective communications and involvement of the public and other stakeholders at appropriate stages of the decision process
before installing RF sources can enhance public confidence and acceptability.
Conclusions
Considering the very low exposure levels and research results collected to date, there is no convincing scientific evidence that
the weak RF signals from base stations and wireless networks cause adverse health effects.
WHO Initiatives
WHO, through the International EMF Project, has established a programme to monitor the EMF scientific literature, to
evaluate the health effects from exposure to EMF in the range from 0 to 300 GHz, to provide advice about possible EMF
hazards and to identify suitable mitigation measures. Following extensive international reviews, the International EMF
Project has promoted research to fill gaps in knowledge. In response national governments and research institutes have
funded over 250ドル million on EMF research over the past 10 years.
While no health effects are expected from exposure to RF fields from base stations and wireless networks, research is still
being promoted by WHO to determine whether there are any health consequences from the higher RF exposures from mobile
phones.
The International Agency for Research on Cancer (IARC), a WHO specialized agency, is expected to conduct a review of
cancer risk from RF fields in 2006-2007 and the International EMF Project will then undertake an overall health risk
assessment for RF fields in 2007-2008.
Further Reading
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http://www.who.int/mediacentre/factsheets/fs304/en/print.html
ICNIRP (1998) www.icnirp.org/documents/emfgdl.pdf
IEEE (2006) IEEE C95.1-2005 "IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency
Electromagnetic Fields, 3 kHz to 300 GHz"
Related links
- Base stations & wireless networks: Exposures & health consequences
- Fact sheet: Electromagnetic fields and public health: Electromagnetic Hypersensitivity
- WHO handbook on "Establishing a Dialogue on Risks from Electromagnetic Fields"
- 2006 WHO Research Agenda for Radio Frequency Fields [pdf 100kb]
For more information contact:
WHO Media centre
Telephone: +41 22 791 2222
E-mail: mediainquiries@who.int
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