International EMF Project
Information Sheet

February 2005

ELECTROMAGNETIC FIELDS AND PUBLIC HEALTHIntermediate Frequencies (IF)Exposure to human-made electromagnetic fields (EMF) has increased over the pastcentury. The widespread use of EMF sources has been accompanied by public debate
about possible adverse effects on human health. As part of its charter to protect publichealth and in response to these concerns, the World Health Organization (WHO)established the International EMF Project to assess the scientific evidence of possible
health effects of EMF in the frequency range from 0 to 300 GHz. The EMF Projectencourages focused research to fill important gaps in knowledge and to facilitate thedevelopment of internationally acceptable standards limiting EMF exposure.
Public concerns have ranged from possible effects of exposure to extremely low frequency(ELF) electric and magnetic fields (e.g. electricity supply including power lines) having
frequencies between 0 and 300 Hz to possible effects of exposure to radiofrequency (RF)fields (e.g. microwave ovens and broadcast and other radio-transmission devices includingmobile phones) having frequencies in the range 10 MHz - 300 GHz. A large body ofscientific research in these two frequency ranges now exists. For the purpose of thisdocument, the intermediate frequency (IF) region of the EMF spectrum is defined as being
between the ELF and RF ranges; 300 Hz to 10 MHz. A relatively small number of studies
has been conducted on the biological effects or health risks of IF fields. This is due, in part,to the fact that fewer types of devices produce fields in this frequency range. But because
these devices now have a high consumer and industrial market penetration, it is important toevaluate their impact on human health. This information sheet addresses the known healtheffects of IF fields, and offers recommendations for further study.
SourcesCommon sources of IF fields can be found in the following settings:••••

Industry: Dielectric heater sealers, induction and plasma heaters, broadcast andcommunications transmitters,
General public: Domestic induction cookers, proximity readers, electronic article
surveillance systems and other anti-theft devices, computer monitors and television sets,
Hospitals: MRI systems, electromagnetic nerve stimulators, electro-surgical units, andother devices for medical treatment,
Military: Power units, submarine communication transmitters and high frequency (HF)
transmitters.

Except for medical diagnostic and treatment devices, levels of human exposure from IF
devices normally fall below limits recommended by the International Commission on NonIonizing Radiation Protection (ICNIRP). However, workers in a few categories (e.g.
operators of dielectric heater sealers and induction heaters, some military personnel andInformation sheet: Intermediate frequencies1technicians working near high powered broadcast equipment) may be exposed toconsiderably higher levels of IF fields.
How EMF Affects the Human Body
Several mechanisms, both thermal and non-thermal, by which electromagnetic (primarily,electric) fields can interact with biological systems are well established. The limiting hazard
will arise from the adverse effect (thermal or non-thermal) that has the lowest thresholdunder given exposure conditions. While strong fields in the upper IF range may cause
thermal damage (a relatively slow process that requires tissue to be maintained at hightemperatures for a given period of time), some of the most obvious hazards from acuteexposure to electric currents in the body may occur through membrane excitation. This nonthermal mechanism results from changes in membrane potential induced by external fields
and occurs, for example, in the stimulation of peripheral nerves and muscle cells. Anothermechanism is electroporation, which is the reversible or irreversible disruption of cell
membranes when a field induces excessive electrical potentials across them. This can
provoke tissue injury through electric shock, but is also being investigated for therapeutic
purposes by using short electric field pulses to make human tissues more permeable todrugs.
External IF fields can induce these effects inside the human body but only at field strengths
many times higher than typical environmental levels.
Reported Biological and Health Effects
Health benefits from electric and magnetic fields have been claimed since the 18th century,and pulsed EMFs in the IF range have found a place in modern medical practice for thetreatment of bone healing and nerve stimulation and regeneration. However, concern has
been expressed about possible health hazards associated with technology, both at home
and in the workplace. These concerns include worker complaints of disturbances (e.g.
swelling, prickling of fingers, headaches) and public anxiety about possible adverse healtheffects of IF fields from computer monitors and televisions. Types of research conducted sofar have included:•Human studies: Until now, most epidemiological studies concerning IF exposure havefocused on reproductive and ocular effects from the use of computer monitors. Several
major reviews have concluded that these, with their extremely weak IF fields, do notconstitute a threat to human health and that they do not interfere with reproductive
processes or pregnancy outcomes. Also, no association between such exposure andeye abnormalities has been established. A large study on female radio and telegraphoperators showed a slight increased risk of breast cancer. However, this group ofworkers is also exposed to many other factors that could explain this increased risk.
The high degree of biological variability and the multitude of EMF parameters make it
difficult to reach firm conclusions about the significance of any of these studies forhuman health. Some of the most important health hazards due to IF sources relate toindirect action of EMF. For example, EMF produced by electronic anti-theft systems
may interfere with implanted electronic medical devices (e.g. pacemakers, neurologicalstimulators).

•Laboratory studies: Few reported cellular studies using IF fields have shown
independently-confirmed biological effects. Studies on mice have shown no morbidity,change in behaviour or lymphoma development with exposure to low-strength magnetic
field signals in the kHz range. Although a few studies of effects on reproduction anddevelopment of mice, rats, and chick embryos and a few other studies suggest thepossibility of minor skeletal anomalies; overall there is no clear evidence for increased
malformations.

Information sheet: Intermediate frequencies

2Compared to extremely low frequency fields (ELF, which includes AC power frequencies)and radio frequency fields (RF, which includes mobile phone communications), little
research has been done of the effects of IF fields. The scientific evidence is not convincingthat adverse health effects occur from exposure to IF fields normally found in the living andworking environment. This conclusion is partly based on the studies conducted with IF fields
but also on the fact that IF fields act on the body in a way similar to ELF and RF fields,
depending on the frequency of the IF field.
International Standards
ICNIRP is an independent scientific commission formally recognized by WHO that has
published guidelines on exposure limits for all EMF in the 0 to 300 GHz frequency range.
Exposure guidelines in the IF range have been established from rigorous review of thescientific literature on possible adverse health effects and by extrapolating limits from theELF and RF ranges, based on coupling of external fields with the body and assumptions
about the frequency dependence of biological effects.
What Should Be Done?
The scientific evidence does not suggest any health risk from IF fields at exposures below
the ICNIRP guideline levels. However, there is a need for more high quality research toaddress uncertainties in current knowledge. The following key areas have been identified
for further research:
••

•

•
•

Epidemiological studies: It is recommended that epidemiological studies beconsidered only if pilot studies demonstrate the feasibility of gathering high quality
exposure data in appropriate highly exposed populations, thereby achieving adequate
statistical power and identifying relevant health outcomes.
Exposure evaluation: The degree and type of EMF exposure currently encountered in
occupational and domestic settings need to be better characterized. Periodic checks
must be made and documented in industrial and other occupational settings where IFfields are used, to ensure that the equipment is operating properly and that exposure
guidelines are not exceeded.
Animal studies: Future animal studies should attempt to use exposure conditions thatare similar to human exposures from industrial and other sources, and also should
explore higher exposure levels. If specific suspect pathways are identified, these studies
could be supplemented by cell or tissue studies to clarify how IF fields affect organisms.
Biological interaction: More comprehensive understanding of the biological interaction
and hazard thresholds is required to refine exposure guidelines, particularly for pulsed
fields or fields with complex waveforms.
Dosimetry: Computer modelling techniques exist that enable the calculation of fields
induced inside the bodies of people exposed to IF fields. The most advanced of thesetechniques employ anatomically realistic computational phantoms. Such methods are
particularly appropriate in risk assessment and testing compliance of measured IF fields
with exposure limits in a consistent manner. It is important that, where appropriate,
female and child phantoms are also considered for use in such assessments.

What is the World Health Organization doing about the issue?
The WHO's International EMF Project has established a programme to review research
results and conduct risk assessments of EMF exposure. It is developing public informationmaterials, and bringing together standards groups world-wide in an attempt to harmonize
approaches to the development of EMF exposure standards. Health risks from EMF
exposure, including cancer, are being evaluated by WHO in collaboration with theInternational Agency for Research on Cancer (IARC) – the specialized cancer research
agency of WHO – and by ICNIRP.

Information sheet: Intermediate frequencies3Further Reading
Bernhardt JH, McKinlay AF and Matthes R, editors: Possible health risk to the generalpublic from the use of security and similar devices. Report to the European Commission
Concerted Action QLK4-1999-01214, ICNIRP, 2002 (ICNIRP 12/2002).
Matthes R., van Rongen E., Repacholi M., editors: Proceedings of the International Seminaron Health Effects of Exposure to Electromagnetic Fields in the Frequency Range 300 Hz to
10 MHz, Maastricht, The Netherlands, ICNIRP, 1999 (ICNIRP 8/99).
Litvak E, Foster K R and Repacholi M H (2002): Health and safety implications of exposure
to electromagnetic fields in the frequency range 300 Hz to 10 MHz. Bioelectromagnetics
23(1): 68-82.
Matthes R., Bernhardt J., McKinlay A., editors: Guidelines on Limiting Exposure to NonIonizing Radiation, ICNIRP, 1999 (ICNIRP 7/99 ) http://www.icnirp.org.

Information sheet: Intermediate frequencies4