ELECTROMAGNETIC FIELDS AND PUBLIC HEALTH: Health Effects of Radiofrequency Fields

Fact Sheet N183
Reviewed May 1998

ELECTROMAGNETIC FIELDS AND PUBLIC HEALTH
Health Effects of Radiofrequency Fields
This Fact Sheet is based on the Environmental Health Criteria 137 "ElectromagneticFields (300 Hz to 300 GHz), World Health Organization, Geneva, 1993, and the reportof the Scientific Review under the auspices of the International EMF Project of theWorld Health Organization, Munich, Germany, November 1996.

Radiofrequency (RF) fields are part of the electromagnetic spectrum. For the purpose ofthe International EMF Project, such fields are defined as those within the frequency range
10 MHz (or 10 000 kHz) and 300 GHz. Natural and human-made sources generate RF
fields of different frequency.
Common sources of RF fields include: FM radio (30 - 300 MHz), mobile telephones,
television broadcast, microwave ovens, medical diathermy (0.3 - 3 GHz), radar, satellitelinks, microwave communications (3 -30 GHz) and the sun (3 -300 GHz).
RF fields are non-ionizing radiations (NIR). Unlike X-rays and gamma rays, they aremuch too weak to break the bonds that hold molecules in cells together and, therefore,produce ionization. RF fields may, however, produce different effects on biologicalsystems such as cells, plants, animals, or human beings. These effects depend on
frequency and intensity of the RF field. By no means, will all of these effects result inadverse health effects.
RF fields above 10 GHz are absorbed at the skin surface, with very little of the energy
penetrating into the underlying tissues.
The basic dosimetric quantity for RF fields above 10 GHz is the intensity of thefield measured as power density in watts per square metre (W/m2 ) or for weak
fields in milliwatts per square metre (mW/m 2 ) or microwatts per square metre(mW/m2 ).
For adverse health effects, such as eye cataracts and skin burns, to occur fromexposure to RF fields above 10 GHz, power densities above 1000 W/m2 areneeded. Such densities are not found in everyday life. They do exist in very close
proximity to powerful radars. Current exposure standards preclude human presencein this areas.
RF fields between 10 MHz and 10 GHz penetrate exposed tissues and produce heatingdue to energy absorption in these tissues. The depth of penetration of the RF field into
the tissue depends on the frequency of the field and is greater for lower frequencies.
Energy absorption from RF fields in tissues is measured as a specific absorption
rate (SAR) within a given tissue mass. The unit of SAR is watts per kilogram(W/kg). SAR is the basic dosimetric quantity for RF fields between about 1 MHz
and 10 GHz.

ELECTROMAGNETIC FIELDS AND PUBLIC HEALTH: Health Effects of Radiofrequency Fields

An SAR of at least 4 W/kg is needed to produce adverse health effects in people
exposed to RF fields in this frequency range. Such energies are found tens ofmeters away from powerful FM antennas at the top of high towers, which makesthese areas inaccessible.
Most adverse health effects that could occur from exposure to RF fields between 1
MHz and 10 GHz are consistent with responses to induced heating, resulting inrises in tissue or body temperatures higher than 1C.
Induced heating in body tissues may provoke various physiological andthermoregulatory responses, including a decreased ability to perform mental or
physical tasks as body temperature increases. Similar effects have been reported inpeople subject to heat stress: for example, those working in hot environments orsuffering a prolonged fever.
Induced heating may affect the development of a fetus. Birth defects would occur
only if the temperature of the fetus is raised by 2-3C for hours. Induced heating canalso affect male fertility and lead to the induction of eye opacities (cataracts).
It is important to emphasize that most RF studies conducted at frequencies
exceeding 1 MHz, examined the results of acute exposure to high levels of RFfields - an exposure that is not normally found in everyday life.
Other effects on the body from exposure to low-intensity RF fields, present in the living
environment, have been reported. But, either they have not been confirmed by otherlaboratory studies, or their health implications are unknown. However, these studies haveraised important health concerns about an increased risk of cancer. It is for this reason
that they are being monitored and evaluated under the International EMF Project.
Exposure to RF fields and cancer: Current scientific evidence indicates that
exposure to RF fields is unlikely to induce or promote cancers.
Cancer studies using animals have not provided convincing evidence for aneffect on tumour incidence. A recent study found that RF fields, similar to thoseused in mobile telecommunications, increased the incidence of cancer among
genetically engineered mice that were exposed near (0.65m) an RF transmitting
antenna. Further studies will be carried out to determine the relevance of theseresults to cancer in human beings.
Many epidemiological (human health) studies have addressed possible links
between exposure to RF fields and excess risk of cancer. To date these studies do
not provide enough information to allow a proper evaluation of human cancer risk
from RF exposure because the results of these studies are inconsistent. This can beexplained by differences in the design, execution and interpretation of these studies,including the identification of populations with substantial RF exposure andretrospective assessment of such exposure. The International EMF Project isencouraging coordinated research in this area.
Exposure to low-levels of RF fields, too low to produce heating, has been reported toalter the electrical activity of the brain in cats and rabbits by changing calcium ionmobility. This effect has also been reported in isolated tissues and cells. Other studies
have suggested that RF fields change the proliferation rate of cells, alter enzyme activity
or affect the genes in the DNA of cells. However, these effects are not well established,
nor are their implications for human health sufficiently well understood to provide a basis
for restricting human exposure.
Electromagnetic interference and other effects: Mobile telephones, as well as manyother electronic devices in common use, can cause electromagnetic interference in otherelectrical equipment. Therefore, caution should be exercised when using mobiletelephones around sensitive electromedical equipment used in hospital intensive careunits. Mobile telephones can, in rare instances, also cause interference in certain othermedical devices, such as cardiac pacemakers and hearing aids. Individuals using suchdevices should contact their doctor to determine the susceptibility of their products tohttp://www.who.int/docstore/peh-emf/publications/facts_press/efact/efs183.html[2011/04/26 16:06:26]

ELECTROMAGNETIC FIELDS AND PUBLIC HEALTH: Health Effects of Radiofrequency Fields

these effects.
RF fields from natural sources have very low power densities. RF intensity from thesun - the primary natural source - is less than 0.01 mW/m 2 . Human-made sources,
which emit the majority of RF fields found in the immediate environment, can be divided
into those found in the community, home, and workplace:
Community: Most RF fields found in the environment are due to commercial
radio and TV broadcasting, and from telecommunications facilities. RF exposure
from telecommunications facilities is generally less than from radio or TV
broadcasting. A study conducted in the Unites States found that, in large cities, theaverage background RF levels were about 50 µ W/m2 . About 1% of people
living in large cities are exposed to RF fields exceeding 10 mW/m 2 . Higher RF
field levels can occur in areas located close to transmitter sites or radar systems.
Home: RF sources in the home include microwave ovens, mobile telephones,
burglar alarms, video display units and TV sets. Microwave ovens that could
potentially be the source of very high RF levels, are covered by productperformance standards which limit the amount of microwave leakage. Overall, theRF field background from household appliances is low, and of the order of a few
tens of µ W/m2 .
Workplace: Relatively high levels of exposure to RF fields can occur to workers
in the broadcasting, transport and communications industries when they workin close proximity to RF transmitting antennas and radar systems. An important
subset of these workers are military personnel. Stringent regulations controllingthe civil and military use of RF fields exist in most countries.
Safety Standards: To ensure that devices emitting RF are safe and their use does notinterfere with other devices, international standards are adopted. Exposure limits for RF
fields have been developed by the International Commission on Non-Ionizing
Radiation Protection (ICNIRP) - a nongovernmental organization formally recognizedby WHO. ICNIRP guidelines were developed following reviews of all the peer-reviewed
scientific literature, including thermal and non-thermal effects. The RF field limits arewell above the levels found in the living environment. The standards are based on
evaluations of biological effects that have been established to have health consequences.
The objective of the International EMF Project is to determine if the biological effects
reported from exposure to RF fields at low levels have any adverse health consequences.
If such consequences were found, this may result in a reevaluation of the limits of human
exposure.
Exposure to RF fields may cause heating in body tissues. Heating is the primaryinteraction of RF fields at high frequencies, above about 10 MHz.
A scientific review by WHO, held under the International EMF Project (Munich,November, 1996), concluded that, from the current scientific literature, there is noconvincing evidence that exposure to RF shortens the life span of humans, induces
or promotes cancer.
However, the same review also stressed that further studies are needed to draw amore complete picture of health risks, especially about possible cancer risk fromexposure to low-levels of RF exposure.
_________________________________________________________________________For further information, please contact the Office of Press and Public Relations, WHO,Geneva. Telephone (41 22) 791 2599. Fax (41 22) 791 4858. Email: info@who.int

ELECTROMAGNETIC FIELDS AND PUBLIC HEALTH: Health Effects of Radiofrequency Fields

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