This report contains the collective views of an international group of
    experts and does not necessarily represent the decisions or the stated
    policy of the United Nations Environment Programme, the International
    Labour Organisation, or the World Health Organization.

    Published under the joint sponsorship of
    the United Nations Environment Programme,
    the, World Health Organization, and the
    International Radiation Protection Association

    World Health Orgnization
    Geneva, 1984

        Reprinted 1992

        ISBN 92 4 154095 8  

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    (c) World Health Organization 1984

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    1.1. Purpose and scope
    1.2. Sources of exposure
    1.3. Clinical applications
    1.4. Field measurement and dosimetry
    1.5. Characteristics of biophysical interactions
    1.6.  In vitro studies
    1.7. Experimental animal studies
    1.8. Effects on man
    1.9. Exposure standards
    1.10. Conclusions and recommendations


    2.1. Quantities and units
    2.2. Computational methods and measurements of ELF
         electric fields
    2.3. Field polarization and homogeneity
    2.4. Energy carried by the field
    2.5. Determination of ELF field exposure
    2.6. The physical interaction of man and laboratory
         animals with electric fields
         2.6.1. Surface fields and internal current
         2.6.2. Capacitive coupling of the electric
                field to man and laboratory animals
         2.6.3. Shock currents
    2.7. Dosimetry and scaling between laboratory animals
         and man
    2.8. Magnetic induction of electric fields


    3.1. Natural electric fields
    3.2. Natural magnetic fields
    3.3. Man-made sources of ELF
         3.3.1. High-voltage transmission lines
         3.3.2. Electric fields near transmission lines and substations
         3.3.3. Magnetic fields near transmission lines
         3.3.4. Man-made ELF fields in the home, workplace,
                and public premises
    3.4. Corona and noise effects of transmission lines
    3.5. Electric shock
    3.6. Interference of ELF fields with implanted
         cardiac pacemakers


    4.1. Biophysical mechanisms of electric field
    4.2. Biophysical mechanisms of magnetic field


    5.1. Cellular and membrane studies
    5.2. Neurophysiological studies in animals
         and animals tissues
    5.3. Behavioural studies
    5.4. Sensory phenomena
    5.5. Effects on the haematopoietic system in animals
    5.6. Cardiovascular effects
    5.7. Effects on endocrinology and blood chemistry
    5.8. Effects on the immune system
    5.9. Growth and development studies
    5.10. Reproduction and fertility
    5.11. Mutagenesis
    5.12. Circadian rhythms in animals
    5.13. Bone growth and repair
    5.14. The problems of extrapolating animal exposure
         data to human beings


    6.1. Sources of information
    6.2. Study design
    6.3. Health status of occupationally-exposed
         human beings
    6.4. Studies on the general population
         6.4.1. Studies on inhabitants of areas in the
                vicinity of HV-lines
    6.5. Studies on human volunteers
    6.6. Summary




    9.1. Goals
    9.2. Groups to be protected
    9.3. Protection rationale






    While every effort has been made to present information in
the criteria documents as accurately as possible without
unduly delaying their publication, mistakes might have
occurred and are likely to occur in the future.  In the
interest of all users of the environmental health criteria
documents, readers are kindly requested to communicate any
errors found to the Manager of the International Programme on
Chemical Safety, World Health Organization, Geneva,
Switzerland, in order that they may be included in corrigenda,
which will appear in subsequent volumes.
     In addition, experts in any particular field dealt with in
the criteria documents are kindly requested to make available
to the WHO Secretariat any important published information
that may have inadvertently been omitted and which may change
the evaluation of health risks from exposure to the
environmental agent under examination, so that the information
may be considered in the event of updating and re-evaluation
of the conclusions contained in the criteria documents.



Dr J. Bonnell, Central Electricity Generating Board, London,

Dr B. Bosnjakovic, Ministry of Housing, Physical Planning, and
   Environment, Rijswijk, The Netherlandsa

Dr J. Cabanes, Medical Committee, Electricité de France - Gaz
   de France, Paris, France

Dr M. Grandolfo, Laboratory of Radiation, Institute of Public
   Health, Rome, Italy

Dr B. Knave, Research Department, National Board of
   Occupational Safety and Health, Solna, Sweden

Dr J. Kupfer, Occupational Hygiene Standardization, Central
   Institute of Occupational Medicine, Berlin, German
   Democratic Republic  (Vice-Chairman)

Dr R. Phillips, Biology Department, Pacific Northwest
   Laboratory, Richland, Washington, USA

Dr A. Portela, Institute of Biophysical Research, National
   Council of Scientific and Technical Research (CONICET),
   Buenos Aires, Argentina

Dr M. Repacholi, Royal Adelaide Hospital, Adelaide, South
   Australia  (Chairman)a

Dr A. Sheppard, J.L. Pettis Memorial Hospital, Loma Linda,
   California, USA (Rapporteur)

 IRPA Secretariat

Mrs A. Duchęne, Commissariat ŕ l'Energie Atomique, Déparement
   de Protection Sanitaire, Fontenay-aux-Roses, Franceb

 WHO Secretariat

Mr G. Ozolins, Manager, Environmental Hazards and Food
   Protection, Division of Environmental Health, WHO, Geneva,
   Switzerland  (Secretary)

Dr M. Shore, National Center for Devices and Radiological
   Health, Food and Drug Administration, Rockville, Maryland,
   USA  (Temporary Adviser)

a  Members of the International Non-Ionizing Radiation
   Committee of IRPA.
b  Scientific Secretary of the International Non-Ionizing
   Radiation Committee of IRPA.

Electric and magnetic field quantities and units in the SI system
Quantity                 Symbol     Unit
Frequency                f          hertz (Hz)

Electric field strength  E          volt per metre (V/m)

Electric flux density    D          coulomb per square metre (C/m2)

Capacitance              C          farad (F)

Current                  I          ampere (A)

Current density          J          ampere per square metre (A/m2)

Electric charge          Q          coulomb (C = A x s)

Impedance                Z          ohm (omega)

Volume charge density    p          coulomb per cubic metre (C/m3)

Magnetic field strength  H          ampere per metre (A/m)

Magnetic flux density    B          teslaa (1 T = 1 Wb/m2)
                                    (weber per square metre)
Permittivity             epsilonb   farad per metre (F/m)

Permittivity of vacuum   epsilono   epsilono  = 8.854 x 10-12 F/m

Permeability             µ          henry per metre (H/m)

Permeability of vacuum   µo         µo =  12.57 x 10-7 H/m

Time                     t          seconds (s)
a  1 T = 104 Gauss (G), a unit in the CGS unit system.
b  Designates a complex number.


    Following the recommendations of the United Nations Conference 
on the Human Environment held in Stockholm in 1972, and in response 
to a number of World Health Resolutions (WHA23.60, WHA24.47, 
WHA25.58, WHA26.68), and the recommendation of the Governing 
Council of the United Nations Environment Programme, (UNEP/GC/10, 3 
July 1973), a programme on the integrated assessment of the health 
effects of environmental pollution was initiated in 1973.  The 
programme, known as the WHO Environmental Health Criteria 
Programme, has been implemented with the support of the Environment 
Fund of the United Nations Environment Programme.  In 1980, the 
Environmental Health Criteria Programme was incorporated into the 
International Programme on Chemical Safety (IPCS).  The result of 
the Environmental Health Criteria Programme is a series of criteria 

    A joint WHO/IRPA Task Group on Environmental Health Criteria 
for Extremely Low Frequency Fields met in Geneva from 5 to 9 March 
1984.  Mr. G. Ozolins, Manager, Environmental Hazards and Food 
Protection, opened the meeting on behalf of the Director-General.  
The Task Group reviewed and revised the draft criteria document, 
made an evaluation of the health risks of exposure to extremely low 
frequency electromagnetic fields, and considered rationales for the 
development of human exposure limits. 

    The International Radiation Protection Association (IRPA) 
initiated activities concerned with non-ionizing radiation by 
forming a Working Group on Non-Ionizing Radiation in 1974.  This 
Working Group later became the International Non-Ionizing Radiation 
Committee (IRPA/INIRC) at the IRPA meeting in Paris in 1977.  The 
IRPA/INIRC reviews the scientific literature on non-ionizing 
radiation and makes assessments of the health risks of human 
exposure to such radiation.  Based on the Environmental Health 
Criteria documents developed in conjunction with WHO, the 
IRPA/INIRC recommends guidelines on exposure limits, drafts codes 
of safe practice, and works in conjunction with other international 
organizations to promote safety and standardization in the non-
ionizing radiation field. 

    This document is a combination of drafts prepared by Dr A. 
Sheppard and Dr W.R. Adey (J.L. Pettis Memorial Veterans 
Administration Hospital, Loma Linda, California), Dr M.G. Shandala, 
Dr V. Akimenko and colleagues (A.N. Marzeev Institute of General 
and Community Hygiene, Kiev, USSR), and Dr P. Czerski and Mr J.C. 
Villforth (National Center for Devices and Radiological Health, US 
Department of Health and Human Services, Rockville, Maryland).  The 
drafts were integrated at working group meetings in Grenoble 
(1980), and Paris (1982).  A subsequent draft of the document was 
prepared by Dr P. Czerski, Dr B. Bosnjakovic, Dr M. Repacholi, Dr 
V. Akimenko, Dr M. Grandolfo, Dr J. Cabanes, and Mrs A. S. Duchęne 
at the WHO/IRPA working group in Paris in March 1983.  A final 
draft, incorporating the comments of reviewers from WHO National 
Focal Points and many international experts, was prepared by Dr M. 

Repacholi and Dr A. Sheppard in Geneva in December 1983.  
Scientific editing of the draft, approved by the WHO/IRPA Task 
Group in March 1984, was completed by Dr M. Repacholi and Dr A. 
Sheppard.  The efforts of all who helped in the preparation and 
finalization of the document are gratefully acknowledged. 

    Subjects briefly reviewed, with particular reference to power 
frequency (50 and 60 Hz) electric fields, include:  the physical 
characteristics of ELF fields; measurement techniques and 
dosimetry; sources and applications of ELF; levels of exposure from 
devices in common use; mechanisms of interaction; biological 
effects in animals and animal tissues; human studies; health risk 
evaluation and guidance on the development of protective measures 
such as regulations or safe-use guidelines. 

    Although the emphasis of this document is on the effects of ELF 
electric fields at 50 and 60 Hz, effects of ELF magnetic fields are 
briefly mentioned since they always exist when electric current 
flows.  However, the specific problems related to static and time-
varying magnetic fields will be the subject of a separate 
environmental health criteria document. 

    Health agencies and regulatory authorities are encouraged to 
set up and develop programmes to ensure that the lowest exposure 
occurs with the maximum benefit.  It is hoped that this criteria 
document will provide useful information for the development of 
national protection measures against ELF fields. 


1.1.  Purpose and Scope

    This document comprises a review of data on the effects of ELF 
fields, predominantly ELF electric fields at 50 and 60 Hz, on 
biological systems pertinent to the evaluation of health risks for 
man.  The purpose of the document is to provide information for 
health authorities and regulatory agencies on the possible effects 
of ELF field exposure on human health, and to give guidance on the 
assessment of risks from occupational and general population 
exposure.  Areas in which uncertainties exist and further research 
is needed are also indicated. 

    The document includes a review of the data on the biological 
effects on human beings and animals of exposure to low frequency 
electric and magnetic fields in the frequency range of zero to 300 
hertz (Hz) (ELF).a  Data on the biological effects of exposure to 
sinusoidally varying fields are mainly concerned with effects in 
the range of 5 - 20 Hz or at 50 and 60 Hz, while limited data are 
available on effects scattered throughout the ELF spectrum.  Data 
on studies with non-sinusoidal waveforms in this range have also 
been considered.  Effects of electrostatic and magnetostatic fields 
are not included. 

    As the document mainly concerns effects directly attributed to 
ELF electric fields, the effects of co-generated ozone, noise, 
ultraviolet radiation (UVR) and X-rays from corona discharges, 
induced short-circuit currents, etc., which may be important 
factors in the overall transmission line environment, are discussed 
only briefly. 

    In general, the effects of contact currents have not been 
considered in detail since restriction of leakage currents from, 
for example, household appliances and electromedical devices, is 
already treated by national and international standards. 

1.2.  Sources of Exposure                         
    Natural electric fields at extremely low frequencies are very 
weak, while those of man-made origin are much stronger.  The      
strongest of the man-made electric fields are those surrounding   
high voltage transmission lines b at 50 or 60 Hz, distribution    
lines, and traction (transportation) systems that may operate at  
16.67, 25, or 30 Hz.  Within the home, the proximity of appliances
a  According to generally accepted usage in Europe, the region
from 30 Hz to 300 Hz is designated as extremely low frequency;
the region below this ELF band is unnamed.  In the USA, the
ELF region is sometimes designated as 0 - 100 Hz (Polk, 1974).

b These fields range up to about 10 kV/m within transmission  
line corridors, and decrease to a background level of 10-4 V/m
at approximately 103 m.                                       

and low voltage wiring produces ambient electric fields of 10-1 - 
102 volt/metre (V/m), depending on the mains voltage and the      

    The natural 60 Hz magnetic field is approximately 10-9
millitesla (mT), which is low compared with the average fields (up 
to 0.01 mT) found in private homes.  Under the centre line at the 
midspan of 1100 kV transmission lines, the 60 Hz magnetic field at 
1 m above the ground is less than 0.035 mT.  This is weaker than the 
magnetic fields of up to 1 mT that occur close to common household 

    It has become common practice to specify fields in terms of 
their electric and magnetic field strength (E and H).  The electric 
field strength is specified in units of volts per metre (V/m).  The 
magnetic field is given by the field strength H in ampere/metre 
(A/m) or the magnetic flux density B in weber/square metre (Wb/m2), 
where 1 Wb/m2 = 1 tesla. 

1.3.  Clinical Applications

    The growth of bone tissue can be stimulated by electric 
currents, and pulsed ELF fields are being used successfully in 
clinical applications with patients suffering from intractable bone 
disease or fractures.  In the latter technique, electric currents 
at ELF and higher frequencies are induced by pulsed magnetic 

1.4.  Field Measurement and Dosimetry

    To characterize ELF fields, the strength, frequency, and 
orientation of the electric and magnetic fields have to be 
determined.  Under power lines, the electric field has its major 
component oriented vertically (perpendicular to the Earth's 
surface), while the main magnetic field component is horizontal 
(parallel to the Earth's surface).  Principles of calculation and 
measurements of these fields are outlined in section 2 of this 

    A human or animal body located in an ELF electric field causes 
perturbation of the field, resulting in an uneven distribution of 
the field around the body.  Both the electric and magnetic fields  
induce electric currents in the exposed body.  The electric fields 
at the body surface and currents induced in man (a biped) and 
quadruped animals are quite different, even at the same unperturbed 
field strengths.  The factors affecting the magnitude and 
distribution of fields at the surface of the body and currents 
induced inside the body are discussed below. 

1.5.  Characteristics of Biophysical Interactions

    In regions of strong alternating electric fields, three 
interactions occur: 

    (a) large surface fields exist, particularly at highly
        curved regions, and may stimulate surface body
        receptors, producing sensations;

    (b) small currents flow within the body due to the large
        surface fields; their magnitude is very small in
        comparison with the currents that flow when contact
        is made with charged conductors.  The associated
        internal electric field is some 105 - 107 times
        smaller than the applied external electric field;

    (c) spark discharges occur when objects with significantly 
        different potentials approach contact.

    In most experimental situations with whole animals or in human 
studies, the complex interrelationship between surface field 
effects and possible internal electric field effects makes it 
impossible to reach a clear conclusion on the importance of each 

    Although the non-magnetic nature of most biological materials 
strongly suggests exclusion of magnetic field interactions, 
alternating magnetic fields can induce electric currents similar to 
the type of currents induced by coupling to electric fields.  However, 
in the transmission line context, the magnetically-coupled electric 
currents are generally smaller, but within an order of magnitude of 
the electric field-coupled currents.  For exposures of prolonged 
duration, currents produced by pulsed magnetic fields (peak 
intensities of the order of 1 mT) are effective in modifying cell 
functions (e.g., in the repair of bone fractures in human beings).  
In laboratory studies with these same fields, changes have been 
reported in bone growth, amphibian nucleated erythrocyte 
dedifferentiation, nerve regeneration, and initiation and 
alteration of DNA transcription, at current densities in fluid 
bathing body cells of about 1 - 10 µA/cm2 and electric gradients of 
the order of 0.1 - 1 V/m. 

    The mechanisms by which a weak ELF field may interact with 
biomolecular systems and tissues are incompletely understood. 
However, from  in vitro studies, there is now evidence of 
field-induced interactions, including the phenomena of ionic 
interactions with membrane surface macromolecules, which appear to 
involve coupling of the cell interior to signals from neurotransmitters, 
hormones, and antibodies. 

1.6.   In vitro Studies

     In vitro studies are conducted for two main reasons:

    (a) to elucidate mechanisms of interaction of ELF fields
        with biological materials; and

    (b) to provide information on end-points to search for  in vivo.

    These studies have included examination of interactions with 
excised and cultured tissues, cell biochemistry, neurophysiology, 
and growth of bone tissue.  Electric fields were reported to affect 
endocrine gland secretion, response to hormonal stimulation, brain 
calcium ion exchange, immunoreactivity of lymphocytes, electrical 
excitability of neuronal tissue, and tissue growth rates. 

    Some of these studies have revealed ELF field effects occurring 
within certain "windows" in frequency and amplitude. 

1.7.  Experimental Animal Studies

    The majority of ELF research has focused on effects directly or 
indirectly involved with the central nervous system including 
physiological, ultrastructural, and biochemical alterations, changes 
in blood composition, behaviour, reproduction, and development.  
Studies have been conducted almost exclusively on small laboratory 
animals, except for a few studies carried out with miniature swine 
and non-human primates. 

    Although some experimental data exist, one of the most serious 
shortcomings of the studies on small animals results from an 
inability to make extrapolations to human beings because of 
uncertainty about applying the mechanisms proposed for the effects 
seen so far.  In particular, it is difficult to cite equivalent 
human exposure because of vast differences in the distribution of 
surface electric field strengths and internal current densities 
between human beings and animals, and because there are no data on 
the species dependency of effects. 

    Studies with small animals exposed to electric fields up to 
100 kV/m have revealed effects on components of the nervous system, 
including synaptic transmission, on circadian rhythms, and on the 
biochemical properties of brain tissue.  Results of behavioural 
studies suggest that the nervous system may be affected by an ELF 
electric field that is far too weak to stimulate synaptic function 
or cell firing, although  in vivo studies often do not exclude the 
possible role of tactile sensory phenomena. 

    Field effects on peripheral blood composition and biochemistry 
have been studied by numerous investigators with inconsistent 
results.  Generally, the changes in blood picture involve small 
deviations from individual norms, but the values usually remain 
within physiological norms.  Results of studies on the influence of 
ELF fields on immunocompetence in whole animals appear to be 

    Studies on swine exposed to 30 kV/m and rodents exposed to 65 
kV/m for up to 18 months have revealed evidence of teratological 
effects.  These data are not conclusive and do not prove the 
teratogenic potential of ELF fields in general. 

    Many studies on genetic effects and effects on cardiovascular 
function have been reviewed and the conclusion reached that such 
effects have not been convincingly demonstrated. 

1.8.  Effects on Man

    Existing surveys of the state of health of high voltage (HV) 
substation workers and HV line maintenance crews have been based on 
small populations and have produced conflicting results.  Soviet 
authors noted an increased incidence of subjective complaints 
attributable to effects on the nervous system and shifts in blood 
biochemistry, but other authors have not reported such observations.
Differences in method often make comparison difficult, if not 
impossible.  Field strengths to which personnel were exposed were 
only estimated, and only approximate data on the duration of 
exposure to fields in a given strength range were available. 

    Some studies on volunteers exposed to electric fields up to 20 
kV/m for short periods (days), under laboratory conditions, 
confirmed the existence of slight changes (within the normal 
physiological range) in populations of peripheral blood cells and 
biochemistry, similar to those observed in experimental animal 

    Several recent epidemiological reports have presented 
preliminary data suggesting an increase in the incidence of cancer 
among children and adults exposed to magnetic fields through living 
close to various types of electrical power lines or devices (e.g., 
power lines coming into the home, transformers, or other electrical 
wiring configurations), and among workers in electrotechnical 

    Slight increases in genetic defects or abnormal pregnancies 
have been reported in one study.  Epidemiological studies have been 
performed on linemen and switch-yard workers, the groups considered 
to be subjected to the highest electric-field exposure levels.  
However, the exposure levels to which these people are subjected 
have been found to be remarkably low.  The preliminary nature of 
the epidemiological findings, the low levels of exposure, and the 
relatively small increment in the reported incidence of any 
effects, suggest that, though the epidemiological data cannot be

dismissed, there must be considerable study before they can serve 
as useful inputs for risk assessment. 

    No pathological effects resulting from ELF field exposure have 
been established. However, thresholds for perception, startle, let-
go, respiratory tetany, and fibrillation due to contact currents 
(electric shocks) have been quantified. 

1.9.  Exposure Standards

    The few instances where countries have developed standards 
limiting human occupational or environmental exposure to ELF fields 
are discussed and compared in section 9 of the document. 

1.10.  Conclusions and Recommendations

1.  In order to relate biological findings from  in vitro and  in 
     vivo studies on experimental animals to human beings, it is 
    recommended that dosimetry studies should be continued to 
    measure and relate external electric field strengths and 
    internal current density distributions in the whole body of 
    both animals and human beings. 

2.  From studies on man and animals, observed sensitivities are 
    consistent with two proposed models, one on the basis of 
    stimulation of peripheral sensory receptors in strong local 
    electric fields at the body surface, and the other on the basis 
    of current densities induced in the extracellular fluid.  It is 
    recommended that models be devised that correlate exposure and 
    biological effects in terms of physical factors, such as 
    surface electric field, tissue current density, spark 
    discharges, and waveform. 

3.  The continuation of basic research on electric and magnetic 
    field interaction mechanisms is strongly recommended. 
    Investigations should be conducted on the possible synergism or 
    antagonism of field influences with physical and chemical 
    agents, since such data are not available. 

4.  In some studies, restriction of ELF effects to certain "windows" 
    in frequency and amplitude has been reported.  It is recommended 
    that the window concept be further investigated to determine the
    applicability of data obtained with various frequencies and
    waveforms, and to relate the findings to potential health
    detriment in human beings. 

5.  Studies have been performed on workers with long-term exposure 
    to electric and magnetic fields, but no adverse health effects 
    have been identified.  However, these studies were not designed 
    to evaluate effects on reproductive functions, or long-term 
    carcinogenic risks.  In two of the studies, electric field 
    exposure was carefully evaluated, and it was found that average 
    exposures in the occupationally-exposed groups were remarkably 

    A suggestion of increased cancer incidence has been reported by 
    a number of investigators who have examined occupational and 
    general population groups exposed to electric and magnetic 
    fields.  The studies performed have serious deficiencies in 
    epidemiological design and do not adequately characterize 
    levels and duration of exposure. 

    The limited knowledge of the potential human health risk 
    associated with exposure to electric and magnetic fields makes 
    it imperative that well-designed epidemiological studies should 
    continue to be undertaken to provide a firmer basis for risk 

6.  Occupational exposure to strong electric fields is generally 
    intermittent and of short duration; exposed populations have 
    been identified, and there are some limited data based on 
    practical experience.  At field strengths where spark 
    discharges are prevalent, prolonged exposures may impair 
    performance.  Such exposures should be avoided, where possible. 

7.  Linemen working on energized extra- or ultra-high-voltage 
    conductors experience extreme electric field conditions, and 
    the use of appropriate protective clothing or devices is 

8.  Whilst it would be prudent in the present state of scientific 
    knowledge not to make unqualified statements about the safety 
    of intermittent exposure to electric fields, there is no need 
    to limit access to regions where the field strength is below 
    about 10 kV/m.  Even at this field strength, some individuals 
    may experience uncomfortable secondary physical phenomena such 
    as spark discharge, shocks, or stimulation of the tactile 

9.  It is not possible from present knowledge to make a definitive 
    statement about the safety or hazard associated with long-term 
    exposure to sinusoidal electric fields in the range of 1 - 10 
    kV/m.  In the absence of specific evidence of particular risk 
    or disease syndromes associated with such exposure, and in view 
    of experimental findings on the biological effects of exposure, 
    it is recommended that efforts be made to limit exposure, 
    particularly for members of the general population, to levels 
    as low as can be reasonably achieved. 

10. In principle, electric and magnetic field interference with 
    implanted cardiac pacemakers can lead to reversion to a fixed 
    rate, but cessation of stimulation is possible.  Direct 
    interference has not been reported in fields below 2.5 kV/m. 
    Although body currents produced by contact with a vehicle in a 
    weaker field may cause interference, the risk of pacemaker 
    reversion is believed to be slight. 

    It is recommended that pacemaker designers and manufacturers of 
    other similar electronic equipment ensure that their devices 
    are resistant to failures caused by electric or magnetic field-
    induced currents. 


2.1.  Quantities and Units

    The electric (E) and magnetic (H) fields that exist near sources 
of ELF electromagnetic fields must be considered separately, because 
the very long wavelengths (thousands of kilometres) characteristic 
of extremely low frequencies means that measurements are made in the 
non-radiating near field.  The E and H fields do not have the same 
constant relationship that exists in the far field of a radiating 

    In the vicinity of high-voltage transmission lines, the E and H 
fields are typically of the order of a few kilovolts per metre 
(kV/m) and a few tens of amperes per metre (A/m), respectively.  
Persons standing under HV-transmission lines or in the vicinity of 
charged conductors will have currents induced in their bodies as a 
result of the interactions of these fields with the body tissues.  
To fully assess the health implications of these ELF fields on man, 
the fields must be measured accurately and interactions with the 
body described quantitatively.  The human body has a complex 
geometrical structure making it difficult to obtain precise 
theoretical or experimental descriptions of these interactions. 

    The quantities and units used in describing ELF electric and 
magnetic fields are given on page 8. 

    The electric and magnetic fields are each described by a vector 
defined by space components along three orthogonal axes.  For 
steady-state sinusoidal fields, each space component can be 
represented as a phasor, i.e., a complex number having a magnitude 
and phase.  The magnitude is expressed as the root mean square 
(rms) value of the field strength in volts per metre or amperes per 
metre, respectively.  The electric field strength is defined in 
terms of a force exerted by the electric field on a unit charge and 
the magnetic field by the force on a unit current in a unit length 
of wire. 

    The flow of charge is the electric current measured in amperes 
(A).  The electric charge is the integral of electric current over 
time and is expressed in ampere-seconds (A x s) or coulombs (C).  
Derived quantities are surface charge density (A x s/m2) and volume 
charge density (A x s/m3).  The current density is defined as the 
current flowing through a unit area perpendicular to the current 
direction and is expressed in amperes per square metre (A/m2). 

    The electric flux density D is a vector quantity, the divergence 
of which is equal to the volume charge density.  The unit of the 
electric flux density is A x s/m2, and it is related to the 
electric field strength by the equation D = epsilonE, epsilon being 
the permittivity.  Permittivity of the vacuum is epsilono = 8.854 
x 10-12 A x s/Vm.  The relative permittivity, epsilonr, a 
dimensionless quantity, is defined as epsilonr = epsilon/epsilono. 
In free space, epsilonr = 1, but in tissues, the values of epsilonr 
are significantly greater than 1.  The capacitance between two 

objects, measured in farads (1 F = 1 A x s/V), is defined as the 
charge acquired by an object divided by the potential difference 
existing between them. 

    The magnetic field can be described by the magnetic field 
strength H and by the magnetic flux density B, where B = µH, µ 
being the permeability.  In free space, µo = 12.566 x 10-7 
V x s/Am.  The relative permeability µr, a dimensionless quantity, is defined 
as µr = µ/µo, µr = 1 in air, by definition, and also, for all practical 
purposes, in biological tissues as well.  The magnetic field is an axial 
vector quantity, the curl (rotation) of which is equal to the total current 
density, including the displacement current.  Magnetic flux density, sometimes 
called magnetic induction, is expressed in tesla, where 1 T = 1 V x s/m2 = 1 

    When describing exposure conditions, the electric and magnetic 
field strengths and orientations should be indicated together with 
the frequency.  In the case of AC transmission lines, electric and 
magnetic field components have a fundamental frequency equal to 60 
Hz in North America and 50 Hz elsewhere. 

    Harmonic content is due to the distortion of sinusoidal wave-
form of the fundamental frequencies by waveforms of other frequencies, 
and can be characterized by a Fourier series.  The harmonic content 
may be of importance at points near large industrial loads or in 
laboratory installations. 

    Three-phase transmission lines generate fields, the space 
components of which are not in phase.  The field at any point close 
to line current conductors can be described by the field ellipse, 
i.e., the field vector describes an ellipse in any full cycle.  At 
distances of about 15 m or more away from the outer conductor, the 
electric field of transmission lines can be considered practically 
a single phase field. 

    The vertical component of the electric field under a 
transmission line is the rms value of the component of the electric 
field along the line perpendicular to the ground and passing through 
the point of measurement.  This quantity is often used to characterize 
induction effects in objects close to ground level. 

    The space potential of a point is a phasor representing the 
voltage difference between the point and the ground.  The space 
potential is perturbed by the introduction of an object into the 
field.  The "unperturbed space potential" that would exist if the 
object were removed is often used in describing the field.  This is 
the induction field potential. 

    It is important to consider the action of an electric field on 
the human body.  Within the body, the low frequency electric field 
is attenuated by about 105 - 107 from the value of the external 
field.  This is in contrast with a magnetic field.  Because of the 
high conductivity of the human body, the electric field is distorted
and localized at the surface of the body.  In an alternating field, 
a current is produced within the body, that has the same frequency 
as the external field. 

    The human body acts as a conductor at ground potential, when a 
person is in good electrical contact with earth, as when wearing 
conducting shoes.  A person wearing well-insulated shoes assumes a 
free or floating potential above ground.  However, the resistance 
to earth of a person wearing shoes with leather soles is about 
15 k ohms and with plastic shoes about 100 M ohms (Deno, 1977).  
When the body is earthed, a current flows through the body to 
ground.  This current is approximately 14 µA (for 50 Hz) and 17 µA 
(for 60 Hz) for each 1 kV/m of undisturbed field strength 
(depending on the body size and shape).  Of this current, about 
one-third flows into the head (Hauf, 1982). 

    Kaune & Gillis (1981) formalized a number of concepts that 
simplify the description of the interaction between an animal and 
an ELF electric field.  These authors showed that the electric-
field intensity at the surface of the body and induced currents 
passing through various segments of the body are determined by:  
(a) the characteristics of the applied electric field, i.e., field 
strength, spatial structure, and frequency; (b) the shape of the 
body; (c) the location of the body relative to ground and other 
conductors; and (d) any conduction currents from the body to ground 
or other conductors.  Because these quantities do not depend on the 
internal structures of the body, they can be measured using 
conducting models, which may be hollow.  The authors showed that 
the electric field outside the body and the induced charge density 
on the surface of the body are independent of frequency in the ELF 
range for both grounded and ungrounded exposure conditions.  They 
also showed that the electric field outside and inside a body will 
be unchanged by a scaled change in the size of the body.  Finally, 
these authors proved that the electric charge induced inside the 
body of an exposed human being or animal is small compared with 
that induced on the surface of the body. 

    The magnetic field is not perturbed by objects that are free of 
magnetic materials.  Magnetic field induction in objects causes two 
types of electric currents (Zaffanella & Deno, 1978): 

    -   a circulating current inside the object (eddy
        current) induced by the magnetic flux density; and

    -   a current entering and leaving the object which may
        be induced by the magnetic flux density through some
        large loop external to, but including, the object.

2.2.  Computational Methods and Measurements of ELF Electric Fields

    Computational methods for the determination of electric and 
magnetic fields are presented in standard textbooks on engineering 
and physics.  Detailed data on computational methods for in case of 
HV transmission lines are presented in The Transmission Line 
Reference Book (1975) and Zaffanella & Deno (1978). 

    There are basically two different approaches to the measurement 
of 50 or 60 Hz E fields: 

    (a) free-body probes that measure fields at points remote
        from the ground (Transmission Line Reference Book,
        1975; Bracken 1976); and

    (b) ground-reference instruments that measure the current
        to ground that is collected by a metallic surface
        (Miller, 1967).

    The principles of operation of both types of instruments are 
closely related.  A free-body instrument consists of a hollow 
metallic shell that is cut in half and the two halves insulated 
from each other.  The displacement current intercepted by a half-
shell is the time derivative of the surface unit charge, and for a 
sinusoidal field: 

     I = dQ/dt = k omega epsilonoE cos omega t       Equation (1)

where E is the E-field strength, Q is the charge induced on one of 
the half-shells, omega is the angular frequency, epsilono is the 
permitivity of free space, and k is a constant. 

    The theory of operation for the ground-reference instrument is 
quite similar to the above.  A flat reference plate is placed on 
the ground in electrical contact with the ground.  A second plate 
is placed a small distance above the reference plate and insulated 
from it.  The displacement current is again given by Equation (1). 

    The free-body approach is recommended for outdoor measurements 
near power lines, since it does not require a known ground reference
for measurements anywhere above ground.  The ground-reference probes 
can be used only under special conditions as discussed in the 
Transmission Line Reference Book (1975). 

    The electric field is perturbed (in some circumstances 
significantly) by the presence of human beings, vegetation, or 
other structures.  Data presented in the literature show that, as 
a general rule, in the presence of each perturbing influence, the 
measured values are somewhat less than the unperturbed ones. 

    Three main procedures are used for the calibration of E-field 

    (a) parallel plate techniques (usually with guard rings);

    (b) single ground plate;

    (c) current injection (Miller, 1967).

    These three techniques have been reviewed by Kotter & Misakian 
(1977).  The first method is the best as it provides an accuracy of 
1% or better for calibration of the field. 

    The electric field strength meter should be calibrated 
periodically at intervals determined by the stability of the meter.  
The instrument on a long (at least 2.5 m) handle is held between 
the plates at the centre of the structure to take the appropriate 
measurements while the plates are at a known voltage. 

    For some instruments, a correction for temperature and humidity 
may be required.  Therefore, these parameters should always be 
recorded at the time of calibration and at the time measurements 
are made. 

    In 1978, IEEE presented a technique using parallel plates to 
calibrate power-line field survey meters.  Two parallel, square 
metallic plates separated by a distance d are supplied by an 
alternating voltage source.  The electric field strength E at the 
midplane of the setting is given by: 

                     E = V/d

where V is the voltage difference existing between the plates.  
Fringing field effects at the periphery of the plates tend to 
modify the field that would be expected to occur at the centre 
point of the plates.  It was found that for a pair of parallel 
plates 1 m2 each and spaced 0.5 m apart, the variation in field 
magnitude was less than 1% from the simply computed value at the 
centre in the midplane.  This system constitutes a simple method of 
evaluating survey meters. 

    For additional data, see the IEEE Standard for Recommended 
Practices for the Measurements of Electric and Magnetic Fields from 
Power Lines (IEEE 1978, 1979) and Tell (1983). 

2.3.  Field Polarization and Homogeneity 

    At ground level, beneath the transmission line, the electric 
field is essentially a vertical homogeneous field with a horizontal 
component that is about 20% of the vertical component (Poznaniak et 
al., 1979).  At distances of more than 15 m from the outer conductor,
this horizontal field drops to less than 10% of that of the vertical 
field (Zaffanella & Deno, 1978). 

    Most experimental arrangements for the exposure of animals 
involve a pair of horizontal parallel electrodes to produce a 
vertical electric field that is quite homogeneous, if the electrode 
spacing is adequate.  Calculations (Ware, 1975; Shih & DiPlacido, 
1980) indicate that the unperturbed electric field strength between 
parallel plates is quite uniform in both the horizontal and vertical
directions, when the horizontal dimensions are two or more times 
greater than the distance between the plates. 

2.4.  Energy Carried by the Field 

    A 10 kV/m electric field has an energy density of 4.42 x 10-4 
J/m3 producing an average power density in the body of man of about 
10 µW/m3, which is about 10-8 times the metabolic rate of the human 
body (Sheppard & Eisenbud, 1977).  Thus heating of a body by an ELF 
field is completely negligible. 

2.5.  Determination of ELF Field Exposure

    There are no universally accepted and clearly defined concepts 
relating ELF field "dose" to biological effects, comparable with 
ionizing or radiofrequency dosimetry in terms of exposure and 
absorbed doses.  Deno (1977), for example, suggests that exposure 
to the electric field can be expressed as the product of electric 
field strength and the duration of exposure.  The current dose 
(charge) on the various body surfaces and inside the body is a 
constant ratio in the unperturbed field, if a person stays erect.  
An "equivalent" E field is the vertical field at ground level (0.5 
m), which would cause the same induction space potential at each 
body position.  The fields induced inside the body depend only on 
the charges at the body surface (Deno 1979). 

    A "dose monitor" to measure the electric field exposure in 
terms of the time integral of the unperturbed field in the ranges 
of 0 - 5 kV/m, 5 - 10 kV/m, and above 10 kV/m has been constructed.  
A separate device discharges the integrator monitors and gives a 
reading of the doses after the exposure period.  The actual 
exposures were shown to be lower than those obtained by multiplying 
the electric field strength in the area of work by the total time 
spent in these areas.  A similar device, constructed by Lövstrand 
et al. (1979), was used to measure the exposure of workers in 50 Hz 
EHV-substations.  Lövstrand et al. (1979) stressed, however, that 
the relationship between the unperturbed electric field strength 
and the biological effect was by no means clearly established.  
They maintained that further work was needed to develop dosimetric 
concepts and to establish the relative significance of surface 
charge densities, internal electric field strength, current, and 
current densities for the "dose"-biological effect relationship. 

2.6.  The Physical Interaction of Man and Laboratory Animals with 
Electric Fields 

    The exposure of intact organisms to ELF electric fields is 
conventionally specified in terms of the unperturbed field 
strength, in V/m or kV/m, which is measured or calculated before 
the subject enters the field.  The unperturbed field is not, 
however, the field that acts directly on an exposed subject.  The 
fields to which a subject is actually exposed can be categorized as 

    (a) Electric fields acting on the outer surface of the
        body.  These fields can cause hairs to vibrate and
        can thereby be perceived; they may also be able to
        stimulate other sensory receptors in the skin.

    (b) Electric fields induced inside the body.  These
        fields act at the level of the living cell, and their
        presence is accompanied by electric currents because
        of the conductivity of living tissues.

    It has been shown that electric fields at the surface of a 
conducting object are enhanced relative to the unperturbed field, 
while induced fields inside the body are attenuated by about 106 
(Barnes et al., 1967; Deno, 1977; Kaune & Phillips, 1980). 

2.6.1   Surface fields and internal current density

    The electric field lines (the directions along which a charge 
is moved by the force imposed by the field) are perpendicular to 
the surface of the body.  A greater concentration of electric field 
lines (i.e., higher field strength) exists at a curved surface, 
such as the human head, than on less curved surfaces of the body.  
For this reason, it is useful to specify the surface electric field 
that exists on various parts of the body. 

    A conducting object placed in an electric field carries a 
current that is directly related to these surface fields.  Thus, 
the internal currents are greatest at the areas of the most intense 
surface electric field.  The current carried within the body (or a 
portion thereof) can be calculated from the capacitance of the 
body, a quantity that takes into account the size and shape of the 
body and its proximity to other conducting objects such as the 
ground and high voltage electrodes or wires, or perhaps other 
animals, fences, trees, etc. (Deno, 1974, 1975, 1976, 1977; 
Bracken, 1976; Zaffanella & Deno, 1978; Kaune & Phillips, 1980). 

    Within the body, the two quantities of interest are the current 
and the current density.  The total current is more easily measured 
or calculated, but the current density is more directly relevant in 
discussion of electric field effects in a particular tissue or 
organ.  The electrical complexity of the interior of the human 
body, due to the presence of insulating membranes and tissues of 
various impedances, has so far frustrated confident analysis of 
precise interior current densities (Kaune & Phillips, 1980; 
Spiegel, 1981). 

2.6.2   Capacitive coupling of the electric field to man and 
laboratory animals

    A body is coupled to an electric field in proportion to its 
capacitance such that the greater the capacitance the greater the 
current flow in the body.  For example, the capacitance of a rat is 
about 5 picofarad (pF), while human beings have capacitances of 
about 125 pF, when in close proximity with ground (Deno, 1974; Deno 
& Zaffanella, 1975). 

    In many laboratory exposures of small animals, the distance 
between the animal and the lower electrode is small or nonexistent 
so that the animal's capacitance to this lower (usually earthed) 
electrode represents a substantial portion of the total 

    By definition, in capacitive coupling, the body, according to 
its capacitance C, "acquires" a certain amount of surface charge Q 
and attains a potential V = Q/C.  This view finds formal expression 
in models that express any arbitrarily complex body as an equivalent
plate at an equivalent height, such that the total current collected 
by the plate is the same as that for the actual body (Deno, 1974).  
The capacitance, and thus the induced current, decrease for a body 
separated from the ground and not close to the energized electrode.  
The capacitance is dependent on the size, especially on the surface 
area, shape, and orientation of the body, so that internal currents 
will differ between fat and thin persons, between persons standing 
and reclining, and between persons walking barefoot and those 
wearing thick rubber-soled shoes or standing on a platform.  It 
would be useful, in all cases, to define the conditions under which 
the capacitance has been measured. 

    A short-circuit current Isc flows in a body placed in an
electric field and connected to the ground through a low resistance 
path (paws, bare feet, a hand grasping an earthed pole).  This 
current is the sum of all the displacement currents collected over 
the surface of the body.  The only place on the body where a 
current of the magnitude of the short-circuit current flows is 
where there is connection with the ground. 

2.6.3  Shock currents 

    In contrast with capacitive coupling to the field, a person 
touching a conductor carries a "shock current", the magnitude of 
which is determined by the total circuit impedance including the 
electrical impedance of the skin and body.  Exposure to an 
extremely strong electric field would be needed to produce 
displacement currents of several milliamperes, which would 
represent a hazard similar to that of touching a live wire (Schwan, 

2.7.  Dosimetry and Scaling Between Laboratory Animals and Man 

    The surface and induced fields to which quadrupeds (e.g., 
laboratory animals) and bipeds (e.g., human beings) are exposed are 
markedly different at the same unperturbed field strength.  Hence, 
it is necessary to scale exposures across species to compare 
biological responses. 

    At present, there are several ways in which electric-field 
exposure effects found in animals might be scaled to possible 
effects in human beings.  One way is to scale on the basis of 
equivalent surface electric fields.  Alternatively, the induced 
currents or electric fields in corresponding tissues and organs 
could be determined. 

    When scaling of exposure is made on the basis of equivalent 
surface electric fields, it is assumed that the mechanism by which 
biological effects are produced involves stimulation of receptors 
on the surface of the body or currents at the surface of the body.  
Stimulation of peripheral somatosensory receptors has been 
demonstrated by Jaffe (1982, in press).  Also, electric fields at 
the surface of the body can produce oscillation of hairs on the 
surface with a resultant stimulatory effect. 

    Classical neurophysiology suggests that induced current       
densities could produce changes in cell physiology when 
transmembrane current densities are of the order of 0.1 mA/cm2 
(Schwan, 1982b).  Large current densities are not normally possible 
because such high E fields would be needed that electrical break-
down of the air would occur long before these current densities 
could be induced.  Novel mechanisms of interaction of the E field 
with various biological systems would be needed to explain any 
effects at the current densities of 10-6 - 10-9 A/cm2 that may 
be caused by fields found in the environment. 

    An erect grounded human being (biped) couples more strongly to 
an ELF electric field than laboratory animals (quadrupeds).  
Surface electric fields and axial current densities have been 
measured in models of man, pig, and rat by Kaune & Phillips (1980) 
(Fig. 1).  At the tops of the bodies, surface electric fields are 
enhanced over the unperturbed field strength present before the 
subjects entered the field by factors of 18, 6.7, and 3.7 for human 
beings, swine, and rats, respectively.  For an unperturbed field 
strength of 10 kV/m, average induced axial current densities in the 
neck, chest, abdomen, and lower part of the legs are, respectively: 
550, 190, 250, and 2000 nA/cm2 for human beings; 40, 13, 20, and 
1100 nA/cm2 for swine; and 28, 16, 2, and 1400 nA/cm2 for rats. 

    Recently an attempt has been made to determine human exposure 
conditions simulated by animal exposures to 60-Hz electric fields 
(Guy et al., 1982).  A thermographic method for determining the 
specific absorption rate (SAR) was used to quantify the electric 
current distributions in homogeneous models of animals and human 
beings exposed to uniform 60-Hz electric fields by exposing models
(of scaled size and conductivity) to 57.3 MHz fields.  Although the 

values of maximum current density predicted in the ankles of models 
of human beings exposed to 60-Hz fields at 1 kV/m, 200 nA/cm, 
agreed with independent measurements on full-scale models, the 
simulation of the 60-Hz field with a 57.3-MHz field may not be 
exact, when determining corresponding current densities in animals 
and man. 


    Theoretical models of biological effects of electric fields 
must distinguish between the importance of the microscopic electric 
field versus the microscopic electric current, although these two 
quantities will always be interrelated.  If the model for inter-
action depends on transport of a certain quantity of charge, then 
the microscopic electric field is not the quantity of interest, and 
various experimental results should be scaled according to the 
current density in the tissue.  On the other hand, if the tissue is 
sensitive to the electric field strength, independent of the charge 
transported by that field strength, the model would require scaling 
on the basis of internal electric field strengths.  In general terms, 
two such models would characterize the ultimate biophysical inter-
action measurement as either "voltmeter-like" or "ampmeter-like". 

    Whether an experimental result should be scaled according to 
the current or the electric field can be very important because the 
tissue conductivity that relates these two quantities varies 

signficantly among various tissues and, even more widely, among the 
tissue or subcellular components (e.g., plasma membranes) of 
different species (section 5). 

    It is clear from these data that exposures in studies with 
laboratory animals must be scaled to compare biological effects 
from such studies to possible effects in man.  Although 
considerable progress has been made in the dosimetry of ELF 
electric fields during the past several years, additional research 
is needed before data from experimental animal studies can be 
extrapolated to man.  Information is needed on: 

    (a) interaction mechanisms;

    (b) critical sites in the body that produce any effects;

    (c) species dependent sensitivies to equal electric
        fields or current densities; and

    (d) physiological differences between species.

2.8.  Magnetic Induction of Electric Fields

    An animal or human body does not appreciably affect a magnetic 
field, but the magnetic field induces currents within the body.  
The magnitude of these internal currents is determined by the 
radius of the current path, the frequency of the magnetic field, 
and its intensity at the location within the body.  Unlike the 
electric field, for which the internal field strength is many times 
less than the external field strength, the magnetic field strength 
is virtually the same outside the body as within.  The magnetically-
induced electric currents are greatest at the periphery of the body 
where the conducting paths are largest, whereas microscopic current 
loops anywhere within the body would have extremely small current 
densities.  The magnitude of the current density is also influenced 
by the conductivity of the tissues, and the exact paths of the 
current flow depend in a complicated way on the conducting 
properties of tissues. 

    The induced current density and power absorbed by a prolate 
spheroid model of a man exposed to the magnetic-field component of 
a transmission line have been calculated by Spiegel (1977). 


3.1.  Natural Electric Fields

    The electric and magnetic fields of the Earth consist of a 
static component, which is dominant, and a time-varying component, 
which is smaller than the static component by several orders of 
magnitude in the 50 - 60 Hz frequency range (Polk, 1974).  The 
fields are characterized by vertical components Ez and Hz for the 
electric and the magnetic fields, respectively, as well as by two 
horizontal components Ex,y and Hx,y. 

    The most important sources of man-made fields in the ELF range 
operate at the power frequencies of 50 Hz or 60 Hz.  The natural 
electric field strength at the power frequencies of 50 Hz or 60 Hz 
is about 10-4 V/m, which means that fields in the close vicinity of 
HV transmission lines are 108 times stronger, and the fields 
introduced into homes by wiring or appliances are still about 103 - 
106 times stronger than the natural background. 

    The natural electric field near the Earth's surface is a static 
field of about 130 V/m (Dolezalek, 1979).  This is due to a 
separation of electric charge between the atmosphere and the 
ground, so that the Earth resembles a spherical capacitor and the 
ground and upper atmosphere represent conducting surfaces.  Daily 
changes in the natural electric field are attributed to factors, 
such as thunderstorms, that affect the rate of charge transfer 
between the ground and the upper atmosphere.  According to Chalmers 
(1967), thunderstorms have electric fields of 3 - 20 kV/m. 

    The alternating fields at low frequency are related to 
thunderstorm activity and magnetic pulsations that produce currents 
within the Earth (telluric currents).  The strength of the Earth's 
electric field varies in time and over the frequency range 0.001 - 
5 Hz (Krasnogorskaja & Remizov, 1975).  Local variations occur 
depending on atmospheric conditions and variations in the magnetic 
field.  The main characteristic of the Earth's electric field are 
presented in Table 1. 

3.2.  Natural Magnetic Fields

    The natural magnetic field is composed of an internal field, 
due to the Earth acting as a permanent magnet, and to an external 
magnetic field in the environment from such components as solar 
activity, telluric currents, atmospheric activity, etc. 

    The internal magnetic field of the Earth originates from the 
electric current in the upper layer of the Earth's core.  There are 
significant local differences in the strength of this field, 
varying from about 50 A/m at the poles to about 23 A/m at the 
equator (Presman, 1971; Benkova, 1975).  These field strengths also 
vary with time. 

Table 1.  Characteristics of the Earth's electric field in the ELF range
Frequency   Nature of the field       Field strength     Reference
range (Hz)                            (V/m)
0.001 - 5   Short duration pulses     0.2 - 1000         Krasnogorskaja &
            (magnetohydrodynamic      for Ez             Remizov (1975);
            origin)                                      Vanjan (1975)

7.5 - 8.4   3 - 6 quasisinusoidal     On the average,    Beresnev et al.
and         pulses of undetermined    (0.15 - 0.6)       (1976)
26 - 27     origin during an          10-6 for
            interval of 0.04 - 1 s    Ex,y with a
                                      maximum of 10-6

5 - 1000    Related to atmospheric    10-4 - 0.5         Aleksandrov et al.
            changes (atmospherics)    for Ez, and        (1972);
            present all the time      one order of       Presman (1971);
                                      magnitude lower    Kleinmenova (1963)
                                      for Ex,y. The
                                      decreases with
    The external magnetic field consists of many components 
differing in spectral and energy characteristics (Aleksandrov et 
al., 1972; Polk, 1974; Benkova, 1975).  The variations in the 
magnetic fields are related to solar activity, particularly with 
respect to the ELF components, which change over 11-year and 27-day 
periods and also exhibit circadian variations.  Other causes of 
variations in the natural magnetic fields are thunderstorms, 
atmospheric changes, and air ionization.  About 2000 thunderstorms 
are occurring simultaneously over the globe, and lightning is 
striking the Earth's surface about 160 times per second; the 
currents involved may reach 2 x 105 A at the level of the Earth 
(Kleimenova, 1963).  Electromagnetic fields having a very broad 
frequency range (from a few Hz up to a few MHz), originate the 
moment lightning strikes and propagate over long distances, 
influencing the magnitude of magnetic fields. 

    The characteristics of the Earth's magnetic field can be 
summarized as follows: 

    (a) The amplitudes from 4 x 10-2 to 8 x 10-2 A/m are at
        pulsation frequencies ranging from 0.002 to 0.1 Hz.

    (b) The geomagnetic pulsations up to 5 Hz are of short
        duration, lasting from a few min to a few h.

    (c) The amplitude of the field decreases with increasing
        frequency from 8 x 10-6 A/m at 5 - 7 Hz to 8 x 10-9 at 3

    (d) At 50 or 60 Hz, the natural magnetic field is
        approximately 10-9 mT (Polk, 1974).

    The geomagnetic field exhibits temporal and spatial variations 
related predominantly to solar activity and local magnetic 

3.3.  Man-Made Sources of ELF

3.3.1  High-voltage transmission lines

    The principal man-made sources of ELF are HV transmission 
lines, and all devices containing current-carrying wire, including 
equipment and appliances in industry and in the home operating at 
power frequencies of 50 Hz in most countries and at 60 Hz in North 

    Electrical energy is transmitted from the power plant, where it 
is generated, along conductive, metallic transmission connections 
(overhead power lines or underground cables) to substations and 
finally to energy consumers. 

    A typical overhead line (Fig. 2) consists of supporting 
structures (transmission towers or pylons) from which the live 
conductors are suspended by sets of insulators.  Each set of 
insulators supports a single conductor or a bundle of two or more 
conductors, which carries one electrical phase of the power supply.  
The conductors of each phase are suspended far enough away from the 
other conductors and the transmission tower to prevent flashover or 
short-circuiting between one phase and another, or between the 
phases and earth (via the supporting structure).  In overhead 
lines, the conductors consist of bare metal cables.  Thus, any 
approach to a live conductor presents a lethal danger due to 
flashover and a resulting electric current flow that would precede 
actual contact with a conductor. 

    High voltage lines are operated at standard voltages up to 750 
or 765 kV and a line at 1100 kV is operating in the USSR.  The 
construction of 1000 - 1200 kV or 1500 kV lines is in progress or 
at various stages in planning. 

    Most widely used are alternating current (AC) 3-phase HV lines.  
One circuit of the 3-phase line comprises 3 single or 3 sets of 
conductors under high-voltage and 1 or 2 grounded conductors that 
protect the live conductors against lightning. 

    Typically, the unperturbed electric field at the height of an 
average man, standing at the location of the maximum field (just 
outside the outer conductor) of a high-voltage transmission line of 
750 kV, is of the order of 10 kV/m.  A lower value of about 1 kV/m 
exists where the line is highest from the ground (20 m) and about 
12 kV/m where it is lowest (13 m) (Zaffanella & Deno, 1978).  The 
electric field strength is a function of the lateral distance from 
the centre of the HV line as shown in Fig. 3. 



    Occupational exposures that occur near high voltage transmission
lines depend on the worker's location either on the ground, or at 
the conductor during live-line work at high potential.  When working 
under live-line conditions, protective clothing may be used to 
reduce the electric field strength and current density in the body 
to values similar to those that would occur for work on the ground.  
Protective clothing does not weaken the influence of the magnetic 

3.3.2.  Electric fields near transmission lines and sub-stations 

    At ground level, beneath high-voltage transmission lines, the 
electric fields created have the same frequencies as those carried 
by the power lines.  The characteristics of these fields depend on 
the line voltage, and on the geometrical dimensions and positions 
of the conductors of the transmission line.  The field intensity 
selected for reference or comparison purposes is the undisturbed 
ground level electric field strength.  To avoid the effects of 
vegetation or irregularities in the terrain, the unperturbed field 
strength is usually computed or measured at a given height above 
ground level (0.5, 1, 1.5, or 1.8 m). 

    There are several primary influences on the electric field
strength beneath an overhead transmission line.  These include:

    (a) the height of the conductors above ground (which is
        influenced considerably by the ambient temperature
        and heating caused by the current passing through the

    (b) the geometric configuration of conductors and
        earthing wires on the towers, and in the case of two
        circuits in proximity, the relative phase sequencing;

    (c) the proximity of the grounded metallic structure of
        the tower;

    (d) the proximity of other tall objects (trees, fences,

    (e) the lateral distance from the centre line of the
        transmission line;

    (f) the height above ground at the point of measurement;

    (g) the actual (rather than the nominal) voltage on the

    Inside buildings near HV transmission lines, the field 
strengths are typically lower than the unperturbed field by a 
factor of about 10 - 100, depending on the structure of the 
building and the type of materials (Manders & van Nielen, 1981). 

    Conductor height, geometric configuration, lateral distance 
from the line, and the voltage of the transmission line are by far 
the most significant factors in considering the maximum electric 
field strength at ground level.  At lateral distances of about 
twice the line height, electric field strength decreases with 
distance in an approximately linear fashion.  Reference to typical 
measured or calculated field contours in the vicinity of the line 
(Zaffanella & Deno, 1978) indicates that, for a 525 kV transmission
line (height about 10 m), the field is always less than 1 kV/m at 
distances of more than 40 m from the outer conductor, while for a 
1050 kV line, which has much higher conductors, the 1 kV/m field 
occurs at a distance of about 100 m from the outer conductor.  
Typically, where a right-of-way (RoW) is used for a transmission 
line of 500 kV or more, it varies from 35 to 70 m, so that electric 
fields at the edge of the RoW are of the order of 1 kV/m. 

    The electric field strengths at and above ground level from 
various transmission lines are shown in Fig. 4 (Gary, 1976).  The 
electric field distribution within various voltage substations is 
given in CIGRE (1980). 


3.3.3.  Magnetic fields near transmission lines

    Just as an electric field is always linked with the presence of 
charges, a magnetic field always appears when electric current 
flows.  A static magnetic field is formed in the case of direct 

current, whereas time-varying electric and magnetic fields are 
induced in the vicinity of alternating current power transmission 

    The magnetic field beneath high-voltage overhead transmission 
lines is directed mainly transversely to the line axis.  The 
maximum flux density at ground level may be either on the route 
centre line or approximately under the outer conductors, depending 
on the phase relationship between the conductors. 

    Apart from the geometry of the conductor, the maximum magnetic 
field strength is determined only by the magnitude of the current.  
The maximum magnetic flux density at ground level for the most 
common overhead transmission line systems is approximately 0.1 
mT/kA (Hylten-Cavalius, 1975). 

    In contrast to an electric field, a magnetic field is more 
penetrating and very difficult to shield.  It easily penetrates 
human beings and, in the case of an alternating or rotating field, 
induces circulating or eddy currents that are not conducted to 
ground.  The internal voltage differences induced within the body 
by a magnetic field from power lines may be as high as 1 mV, if the 
magnetic flux density reaches approximately 0.028 mT (Hauf, 1982). 

    The maximum ground level magnetic field strengths associated 
with overhead transmission lines are of the order of 0.01 - 0.05 mT 
and are also related to line height.  Unlike the electric field, 
they are also directly affected by the current carried by the line.  
The magnetic flux density decreases in an approximately linear 
fashion with distance from the conductor (Lambdin, 1978; Zaffanella 
& Deno, 1978). 

    In principle, these magnetic fields can induce electric 
currents in the body and could induce effects via the same 
mechanisms as electric field-produced currents.  However, for 
exposures near a HV transmission line, the smaller magnitude of 
these magnetically-induced currents (generally no more than 25% of 
the electric field-induced currents) has resulted in little 
emphasis on their contribution.  The largest current densities 
occur at the periphery of the body and they are lower inside.  Fig. 
5 and 6 show the magnetic field distribution near a HV-transmission 
line carrying only about 10% of the typical rated load current for 
such lines. 

3.3.4.  Man-Made ELF Fields in the Home, Workplace, and Public

    In the home or workplace, ELF electric field sources occur at 
electric wiring, appliances, and light fixtures, or industrial 
electrical machines.  Measurements of electric fields in a typical 
American home (115 V circuits) ranged from less than 1 V/m to about 
10 V/m, while fields measured at 30 cm from some appliances varied 
from 2 to 5 V/m near a light bulb to several hundred volts per 
metre near an electric broiler (Miller, 1974; Zaffanella & Deno, 
1978).  As a rule, values appear to be greater than 10 V/m near 
appliances, and will vary with the nominal voltage. 



    Typical values of electric field strengths and magnetic flux 
densities in the vicinity of home appliances and the potential 
leakage currents through the body if contact is made with these 
appliances is given in Appendix I. 

3.4.  Corona and Noise Effects of Transmission Lines

    A high-voltage electrode can create ozone (O3) by means of 
ionization of air near the high-voltage conductors.  In the vicinity 
of corona-free, high-voltage, overhead transmission lines (fair 
weather conditions), no ozone is created.  Under certain weather 
conditions causing corona discharges in the vicinity of HV 
transmission lines, formation of ozone occurs.  However, since 
ozone is a very unstable gas, it rapidly decomposes into harmless 
oxygen compounds in the open air and biological effects should 
not be expected.  Measurement and calculations of ozone near 
transmission lines show that local increments in levels of the gas 
are insignificant (Frydman et al., 1972; Roach et al., 1973). 

    Noise is of concern in regions beneath or near power lines, and 
in switch-yards.  Techniques are available to reduce corona-induced 
noise beneath power lines to acceptable levels or to standards set 
by law.  The switch-yard acoustic environment is special and can 
differ considerably from that near the overhead lines.  Both the 
frequency spectrum of the noise and intensity in different spectral 
regions should be taken into account.  Effects of noise in terms of 
annoyance, sleep disturbance, and community reaction in the case of 
HV transmission lines in the USA are discussed in detail by 
Pearsons et al. (1979).  Results of their study indicate that 
transformer and transmission line noise may create problems, 
particularly in densely-populated urban and suburban areas. 

3.5.  Electric Shock

    In regions of high electric field strength, objects, if 
insulated from ground, can assume large potential differences.  
If the human body becomes the pathway for currents between such 
objects, substantial electric currents (of the order of 1 mA) can 
flow.  Investigation of these effects has revealed two exemplary 
cases in which significant shock currents exist: 

    (a) a long unearthed metal fence running parallel to the
        line; and

    (b) a large vehicle beneath the conductors and
        effectively insulated from ground.

    It is necessary to distinguish between the transient short-
circuit current and the steady-state short-circuit current.  
Zaffanella & Deno (1978) presented data, obtained under various 
circumstances, that indicated that peak currents of up to 20 A can 
flow for a few microseconds when a person draws a spark discharge 
from an object with a hand-held metal key.  The peak currents are 
an order of magnitude smaller if the finger is used for contact.  
The energy content of spark discharges obtained from a carpet are 

found to be similar to those in a 10 kV/m electric field with the 
important exception that the AC field continually recharges the 
electrified body so that repeated frequent sparks are possible, 
whereas several steps must be taken on a carpet to recharge the 
body.  The steady-state short-circuit current that flows when the 
charged object is earthed depends on the capacitance to earth of 
the object, and the open-circuit voltage to which the object is 
charged, when disconnected from ground, according to the relation: 
Isc = omegaVoc x C, where Isc is the short circuit current, 
omega is the angular frequency of the electric field, Voc is the 
open circuit voltage, and C the capacitance to earth of the object 
(Deno, 1974). 

    For human beings standing on the ground with arms at the side 
of the body in an electric field of frequency f, the short circuit 
current Isc in amperes is given approximately by the empirical 
formula (Deno, 1974): 

    Isc = 9.0 x 10-11 h2 E x f

where f is 50 or 60 Hz, h is the person's height in metres (m), and 
E the electric field strength in volts per metre (V/m).  Thus, in a 
10 kV/m, 60 Hz electric field, a person 1.7 m tall carries a short 
circuit of about 160 µA. 

    Typical capacitances for objects range from 700 pF for a small 
vehicle to several thousand pF for buses and large trucks and about 
1000 pF for a 150 m fence (Deno, 1974).  Thus, the short-circuit 
current for a 150 m fence could be as great as 2.2 mA, if the fence 
were located in a field of 5 kV/m.  Zaffanella & Deno (1978) 
measured the short-circuit currents of a farm tractor, jeep wagon, 
and a school bus.  In a 10 kV/m electric field, these vehicles 
conducted 0.6, 1.1, and 3.9 mA of current to earth, respectively.  
Although the shock currents are of appreciable magnitude, they 
should not present a hazard if appropriate safety procedures are 
followed.  Good engineering practice to reduce the risk of shocks 
includes the carefully earthing of fences, gutters, and other long 
metallic objects in a strong electric field. 

    Data (Zaffanella & Deno, 1978) concerning human beings exposed 
to spark discharges of various intensities showed that 50% of the 
population perceived spark discharges in a field of 2.7 kV/m and 
that 50% of the population found the spark discharges annoying at 7 
kV/m.  To obtain these data, persons standing in an electric field 
touched a metallic post with a finger; it is assumed that their 
capacitance was of the order of 170 pF. 

    The sensations that result from microshocks do not appear 
hazardous (except insofar as they may produce a startle reflex that 
could result in an accident), but they may be highly significant in 
the evaluation of effects attributed to the fields.  Although the 
scope of this document does not include the possible health effects 
of such microshocks or transient spark discharges, more than 
cursory mention is given to these effects because of their 

    For the human responses, it is useful to define 3 thresholds:

    (1)  Perception:  the minimum current for perception by touch 
        is about 0.4 µA;

    (2) the  Let-Go Current:  the maximum current for which a person 
        can release the involuntary muscular contraction (Fig. 7) 
        (Dalziel & Lee, 1968);

    (3) the  Fibrillation Threshold:  the minimum body-current to 
        cause ventricular fibrillation is especially dependent on 
        the pathway of the current in the body and the duration 
        (Fig. 8) (Kupfer, 1979; Kupfer et al. 1981).  If the 
        current is directly applied to the heart, the fibrillation 
        threshold is about 5 x 102 times lower (Kupfer, 1982; 
        Weirich et al., 1983).

3.6.  Interference of ELF Fields with Implanted Cardiac Pacemakers

    An implanted pacemaker is an electromedical device that 
artificially stimulates the heart, thus making it possible for 
persons with certain heart diseases to lead relatively normal 
lives.  Although pacemakers may be susceptible to some forms of 
electrical interference, hazardous situations resulting from 
ambient electromagnetic fields have not been reported.  Results of 
a research programme reported by Bridges & Frazier (1979), who 
carried out bench studies and studies with implants in animals, 
showed a wide range in interference sensitivity among various 
devices and for different arrangements of the implanted leads. 



  Pacemaker reversion can be brought about via the following three 
mechanisms (Bridges & Frazier, 1979):

    (a) direct coupling to an ambient electric field (typical
        threshold range, 3 - 600 kV/m);

    (b) transient coupling to an ambient electric field
        through vehicle leakage current ("microshock")
        (typical threshold range, 60 V/m - 60 kV/m);

    (c) coupling to appliances having a leakage current
        (typical threshold range, 40 - 6000 µA).

    Butrous et al. (1983) studied 35 patients (fitted with 16 
different pacemaker models from 6 manufacturers) who were exposed 
to 50-Hz electric fields up to a maximum of 20 kV/m.  Current flow 
measures varied between 15 and 300 µA, depending on the field 
strength and the position of the patient in the field.  Four 
different response patterns were encountered:  (a) normal sensing 
and pacing in all conditions (one manufacturer); (b) reversion to 
the fixed (interference) rate; (c) slow and irregular pacing; and 
(d) mixed behaviour over a critical range of field strengths and 
then reversion to a fixed rate.  Their responses depended on the 
pacemaker units.  The field strengths required to induce such 
behaviour varied with unit and model.  Generally, the interference 

threshold depended on the magnitude and distribution of induced 
body current relative to the pacemaker, as well as field strength, 
and thus varied with patient height, build, and posture. 


    Several mechanisms have been proposed to explain the reported 
effects of ELF electric fields on laboratory animals, and in 
tissues and cells  in vitro including: 

    a)  stimulation of peripheral receptors in the skin;

    b)  induced electric fields and currents inside the body
        acting at the level of cells; and

    c)  non-specific stress.

4.1.  Biophysical Mechanisms of Electric Field Interactions

    Electric field coupling occurs through capacitive and 
conductive modes.  Energy is transferred to the object from the E 
field and an electric charge in the object is put into motion.  The 
amount of charge involved depends on the size and location of the 
object with respect to the E field.  When a path to ground is 
provided, the charge movement results in a current flow.  If the 
object is insulated from the ground, a potential develops with 
respect to the ground, the magnitude of which depends on the 
capacitance to ground. 

    The penetration depth of the field lines into the body is very 
shallow at low frequencies.  There is evidence that the field 
induces direct effects on skin sensors of the cat paw at a 
threshold local field strength of over 200 kV/m (Jaffe, in press).  
Some reported behavioural effects in chickens, mice, rats, and pigs 
exposed to unperturbed fields of 30 - 100 kV/m may be related to 
sensory stimulation.  These effects are presented in reports on 
field perception, arousal, avoidance, transitory activity changes, 
and transitory increases in cortecosterone levels (Moos, 1964; 
Graves et. al., 1978; Hjeresen et. al., 1980; Sagan et. al., 1981; 
Rosenberg et. al., 1983; Stern et. al., 1983). 

    With large field strengths, discharges may be detected.  Small 
currents flow within the body due to capacitive coupling to the 
fields.  In principle, an electric field of sufficient magnitude 
could have a direct effect on biological tissues by acting directly 
on the free ions in the extracellular milieu, on the charged 
portions of the biomolecules, or by interaction with electric 
moments of molecular electronic structure.  However, the very small 
internal electric fields that result from capacitive or magnetic 
coupling (Barnes et al., 1967; Sheppard & Eisenbud, 1977) could not 
affect covalent molecular structures or the electrostatic bonds 
between molecules, nor could there be direct effects on steric 

    In his consideration of ELF electric field interactions with 
neural cells, Schwan (1977) stated that, under a wide range of 
assumptions for cellular shape and cellular electrical properties, 
it was impossible that the largest electric fields in air could

significantly affect neural membrane potentials by the passage of 
transmembrane currents.  Schwan added, however, that the anomalous 
properties at frequencies below 100 Hz, though still poorly 
understood, "provide for more possibilities of subtle effects if 
there are any at all". 

    Adey (1980) suggested that it is important to take into 
account the possibility that one cell may influence another in 
brain and other tissues through modulation of their shared electro-
chemical environment.  The same author (Adey, 1981) proposed that 
amplification of the weak initial stimulus occurs by a cascade of 
intracellular processes taking place at receptor sites on the cell 
membrane surface.  This model may be supported by data on the 
coupling of the parathyroid hormone receptors to the cyclic 
adenylase and cyclic AMP responses in bone cells (Luben et al., 

    It was suggested by Cain (1981) that voltage-sensitive ion 
channels play a role at sufficiently large field strengths.  He 
proposed that an alternating potential across the cell membrane may 
change membrane conductance by interacting with the charged groups 
of the protein macromolecules that gate voltage-sensitive ion 

    Pilla (1980) developed a model for electrochemical information 
transfer at membrane surfaces that involves a minimal electrostatic 
perturbation of the molecular structure.  The essence of the model 
is that specific surface adsorption is expected to exhibit a 
significantly longer relaxation time than dielectric or electro-
static interactions, due to the number of aqueous and membrane 
steps involved, so that the characteristic time for adsorption may 
be about 10 ms.  This is in agreement with data obtained from toad 
bladder membrane (Pilla & Margules, 1977).  This mechanism would 
work in parallel with the charge transfer processes already known 
to occur, and could mediate enzymatic reactions to have significant 
effects on cellular chemistry. 

    Recently, Schwan (1982a,b) discussed the possible role of 
alternating field-induced ponderomotoric forces, i.e., forces 
exerted by electric fields on nonpolar particles.  The theory 
developed on this basis can be used to explain dielectrophoresis 
(Pohl, 1978), rotation, deformation, destruction of cells (Schwan, 
1982a), and electrical cell fusion (Pilwat et al., 1981; Richter et 
al., 1981) in cases where electric field strength greatly exceeds 
that which could be produced in tissue by an environmental ELF 

4.2.  Biophysical Mechanisms of Magnetic Field Interactions

    The eddy currents created by magnetic ELF fields in the human 
body cannot be measured directly, but they can be calculated and 
confirmed by measurements on phantom models.  The biological effects 
of such induced electric currents are discussed above, but any 
direct magnetic field effects are not well understood at present. 


    Since human volunteers cannot be used for studies that could 
potentially cause harmful effects, biological investigations are 
normally conducted using various other animal species.  Studies 
have been performed, mainly using rats and mice, but a wide variety 
of other subjects, including insects, birds, dogs, swine, and non-
human primates, have also been used.  A broad range of exposure 
levels have been employed, and an equally large number of 
biological end-points have been examined for evidence of possible 
electric-field effects.  Since all animal studies cannot be 
discussed, this review will be limited to studies having some 
bearing on health risk assessment.  Experiments not discussed will 
be summarized in the tables.  Some studies showed effects from 
exposure, and others showed no effects.  There is general consensus 
among scientists that exposure to electric fields produces 
biological effects; however, more data are still needed to 
determine whether these effects constitute a hazard. 

    Many studies have been performed based on the explicit or 
implied hypothesis that because electrochemical processes are 
involved in nervous system functioning, there might be an 
interaction of the electric field with the nervous system.  Such 
hypotheses became of greater interest when initial reports on 
linemen and switch-yard workers (Asanova & Rakov, 1966; Korobkova 
et al., 1972) suggested the occurrence of a generalized alteration 
in central nervous system function.  Other studies were based on 
generalized physiological hypotheses, such as the expectation that 
electric field exposure, continued over a long period of time, 
might induce a stress response, alter cardiovascular function, 
affect immune responses, or alter various biochemical and 
physiological variables, especially blood chemistry and blood cell 
populations.  Study areas briefly reviewed below also include 
growth and development, reproduction, fertility, and behaviour. 

    Studies on the effects of electric and magnetic fields on the 
ecosystems involving plants, invertebrates (including insects), 
birds, fish, and mammals have been summarized (Lee et al., 1979, 
1982).  As these studies do not have a direct relevance for human 
health risk assessment they are not discussed further. 

5.1.  Cellular and Membrane Studies

    The effects of electric fields on  in vitro systems have
been studied in a few laboratories.  With these studies, it is
possible to use large sample sizes and to have a high degree
of control over experimental variables.  Such studies also
provide a more direct investigation of the possible mechanisms
of interaction between a biological system and an electric
field.  However, the most serious problems with  in vitro
experiments are those of dosimetry and extrapolation.  The
dosimetric relationship between exposure in cellular systems
and in whole animals is unclear, and extrapolation of results
from less complicated systems to human beings is extremely

    Preliminary experiments using cultured Chinese hamster ovary 
(CHO) cells exposed to 3.7 V/m showed no effects on cell survival, 
growth, or mutation rate (Frazier et al., 1982).  Cell-plating 
efficiency, however (reflecting a possible alteration in the cell 
membrane), was reduced in cells exposed to 60-Hz fields at 
strengths greater than 0.7 V/m.  At the same field strength (0.7 
V/m) (Marron et al., 1975; Goodman et al., 1976, 1979), after 
several months of exposure, slime mold showed frequency-dependent 
effects on mitotic rate, cell respiration, and protoplasmic 
streaming.  These effects were observed with both electric fields 
and magnetic fields, alone or in combination. 

    Studies using a variety of models (Greenebaum et al., 1979a,b; 
Miller et al., 1979) have given contradictory results.  Effects on 
cell division, growth, and metabolism may appear at field strengths 
of the order of tenths of a V/m or tenths of a mT in the medium.  
On the other hand, electrical cell rotation and fusion (Pohl, 1978) 
appear in the range of 10 - 100 kV/m. 

    Experimental findings suggest that the principal site of 
interaction between ELF fields and the interior of living systems 
is the cell membrane (Adey, 1975, 1977, 1980, 1981; Bawin et al., 
1975, 1978; Sheppard & Adey, 1979; Adey et al., 1981).  These 
include a 10 - 20% alteration in the calcium exchange from chick or 
cat brain tissues exposed to ELF electric fields, either amplitude-
modulated radiofrequency (RF) carrier waves of 50, 147, or 450 MHz, 
or ELF sine wave fields (Bawin et al., 1975, 1978; Blackman et al., 
1979, 1980, 1982).  The calcium effect is windowed in frequency, 
where maximal effects occur for 16 Hz modulation, and in the case 
of direct ELF exposures, Blackman et al. reported several windows 
at 15 Hz and its harmonics up to 105 Hz, in fields of less than 100 
V/m in air.  A similar narrow amplitude window limits the range in 
field strength (Bawin et al., 1978; Blackman et al., 1979, 1982).  
Bawin et al. (1978) found a relationship between the observed 
effect and the ionic composition of the bathing medium. 

    In the case of the ELF modulation of a RF field, the magnitude 
of the effective ELF field (obtained by demodulation of the RF 
field envelope) that acts on the calcium-binding sites depends on 
an unknown efficiency for a demodulation process occurring at an 
unidentified site.  Assuming complete demodulation, the effective 
ELF field would correspond to an ELF-only field in air of the order 
of 100 kV/m (Adey, 1981), though by use of the RF carrier there is 
no significant heating of tissue (Tenforde, 1980) and no known 
artifact (such as spark discharges). 

    A calcium efflux effect is also reported for  in vivo studies 
on the cat (Adey, 1980).  Possible underlying biophysical mechanisms 
and a relationship to the electric properties of the brain (electro-
encephalograph waves or EEG waves) are discussed by Grodsky (1976).  
However, the physiological implication of the calcium efflux 
phenomenon is not known. 

    Electric field effects on synaptic transmission and peripheral 
nerve function in rats exposed for 30 days to a 60 Hz field of 
effective strength 65 kV/m were studied in replicate (Jaffe et al., 
1980, 1981).  The exposure apparatus was designed to eliminate the 
confounding influence of electric shock currents.  Neurons of the 
superior cervical ganglion showed significantly increased 
excitability compared with the control group, as determined from 
tests in which the amplitudes of paired compound action potentials 
were measured (conditioning test response or C-T response).  None 
of several other indices of neural function was altered to a 
significant extent.  The authors interpreted the data as evidence 
of an effect on pre- or post-synaptic mechanisms, possibly indicating
enhanced excitability, and as evidence against a significant effect 
on nerve conduction mechanisms. 

    An investigation (Wachtel, 1979) in which invertebrate
neurons from the sea hare  Aplysia were exposed  in vitro to a low-
frequency electric field indicated a strong frequency dependence in 
response to extracellular currents that included synchronization 
with the applied field.  The neuron was most sensitive at frequencies 
below 1 Hz, close to the natural firing rate of  Aplysia neurons, 
and for a particular neuronal orientation with respect to the field.  
Other data were reported by Sheppard et al. (1980) concerning the 
ELF field exposure of  Aplysia neurons, including transient changes 
in the firing rate and increased variability during exposure to
an electric field of 0.25 V/m rms.  Episodic synchronization between
the neuron and the applied field was reported at 1.4 x 10-4 A/cm2 

    In a study by Bawin et al. (in press) on rat brain tissue 
slices exposed to either 5- or 60-Hz electric fields at field 
strengths in the range of the EEG, 1 - 10 V/m, evidence was 
presented of long-lasting changes in neuronal excitability that 
differed with field frequency and exposure duration.  While 5-Hz 
fields were generally excitatory, brief 60-Hz fields either 
potentiated or depressed the tissue response following field 
exposure, and prolonged 60-Hz fields depressed the response.  
Although potentiations (believed to be due to an effect on synaptic 
mechanisms) can last indefinitely (observations have lasted for as 
long as 7 h), the depressed response after 60-Hz exposures was 
transient, lasting about 10 min. 

    In summary, the results of  in vitro studies suggest that 
time-varying ELF electric fields may change the properties of 
cell membranes and modify cell function.  Several theoretical 
explanations have been proposed (section 4), and it seems 
conceivable that several parallel mechanisms exist.  No 
comprehensive and experimentally confirmed theory has been 

proposed.  Some of the effects observed on cells and tissues  in 
 vitro can be detected  in vivo. 

5.2.  Neurophysiological Studies in Animals and Animal Tissues

    Blanchi et al. (1973) reported changes in the electroencephalo-
graph (EEG) patterns of guinea-pigs exposed for 30 min to a 100-
kV/m, 50-Hz electric field.  Gavalas et al. (1970) noted EEG 
spectral power peaks in the hippocampus, and less frequently in the 
amygdala and centrum medianum, in all three monkeys exposed in 7- 
and 10-Hz electric fields (7 V/m peak to peak).  Others failed to 
see any EEG alterations in chicks exposed at 40 kV/m (Bankoske et 
al., 1976), and cats exposed at 80 kV/m (Silney, 1979).  EEG 
effects have not been reported in other studies. 

    Hansson (1981a,b) reported that Purkinje cells of the cerebella 
of rabbits exposed to the 14-kV/m (50-Hz) field of an outdoor 
substation or exposed in the laboratory showed pathological changes 
in the cellular cytoskeleton and alterations in the concentrations 
of two glial cell proteins (S-100, GFA).  When young rabbits were 
exposed to a 50-kV/m electric field for 6 months, no ultrastructural 
changes were found in cerebellar cells, nor changes in several 
plasma hormones (Portet & et al., 1984). 

    Jaffe et al. (1981) found a significant effect of field 
exposure (30 days, 65 kV/m) on neuromuscular physiology for one 
type of muscle (slow-twitch soleus), but not for another (fast-
twitch soleus). 

    The data from neurophysiological tests  in vivo and  in vitro 
indicate that electric fields may have effects on tissues, especially 
components of the nervous system.  The physiological significance 
for human beings exposed to environmental fields has not been 
determined.  Information is needed on the relationships between 
biophysical and biological effects.  In some  in vitro studies, 
the fields or current densities clearly exceed the values estimated 
for internal fields or current densities in human beings exposed to 
environmental fields. 

5.3.  Behavioural Studies

    Among the most sensitive measures of insult to a biological 
system are tests that determine modifications in the behavioural 
patterns of animals.  This sensitivity is especially valuable in 
studying environmental agents of relatively low toxicity (Anderson 
& Phillips, 1984).  Behavioural studies in several species provide 
evidence of field perception and the possibility that the fields 
may directly alter behaviour.  In rats, the threshold of detection 
varies from subject to subject in the range of 4 - 10 kV/m with an 
average level at about 8 kV/m (Sagan et al., 1981; Stern et al., 
1983).  In mice, responses to a 35-kV/m field were reported 
(Rosenberg et al., 1983); perception was seen in pigeons at 
approximately 30 - 35 kV/m (Graves, 1977), and in pigs at 30 - 35 
kV/m (Kaune et al., 1978). 

    Hjeresen et al. (1980) reported on field avoidance among rats 
exposed at 75 - 100 kV/m (60 Hz).  Preference for shielded areas at 
night was found among pigs exposed at 30 kV/m (Hjeresen et al., 
1982).  However, at 25 kV/m, rats preferred the field region during 
the inactive phase (Hjeresen et al., 1980).  Tests of aversion in 
rats exposed to fields of 32 - 130 kV/m produced a complex pattern 
of null effects in some cases (Creim et al., 1980) or positive 
effects in others (Lovely, 1982), depending on the behavioural 

    Alterations in rat activity were noted at 1.2 kV/m by Moos 
(1964).  Other studies on activity indicated transitory 
increased response on initial exposure of rats or mice at 25 -
35 kV/m (Hjeresen et al., 1980; Rosenberg et al., 1983), 
depressed activity in chickens exposed at 26 - 40 kV/m 
(Bankoske et al., 1976; Graves et al., 1978), and increased 
activity among bees exposed at 4.2 kV/m (Greenberg & Bindokas, 

    Tests with monkeys at 7 - 100 V/m exposed to frequencies 
typical of the EEG (1 - 32 Hz) showed altered behavioural 
reponses in an operant conditioning task (Gavalas et al., 1970; 
Gavalas-Medici & Day-Magdaleno, 1976), while in other tests 
involving exposure to magnetic and electric fields, behaviour 
was unaffected (DeLorge, 1972, 1973).  Feldstone et al. (1980) 
observed minor changes in behaviour among baboons exposed to 30 
kV/m (60 Hz). 

    Tests on the behaviour of cats exposed to ELF-modulated radio-
frequency signals were reported to show evidence of long-lasting, 
frequency-specific changes in brain rhythms (EEG), and studies of 
brain rhythms in rabbits exposed to ELF-modulated radiofrequencies 
were also reported to show specific changes in the EEG (Takashima 
et al. 1979). 

    Behavioural tests which most frequently showed an effect of 
exposure were those relating to detection of the field or to 
activity.  Most other behavioural tests did not change with 
electric-field exposure at field strengths up to 100 kV/m. Table 2 
includes a summary of experimental results from nervous system and 
behavioural studies in animals. 

5.4.  Sensory Phenomena

    Strong electric fields cause hairs to oscillate.  The movement 
of hairs on the ear tips of swine was detected photographically in 
60-Hz electric fields at 50 kV/m (Kaune et al., 1980); rat 
vibrissae movement was observed in a 50 Hz, 50 kV/m field by 
Cabanes & Gary (1981).  Stern et al. (1983) attempted to examine 
field sensitivity thresholds in nude or shaved rats, but saw little 
difference from results with fur-bearing subjects. 

    Jaffe (in press) observed a direct field effect on mechanoreceptors 
of the cat paw above a threshold local electric field strength of 
220 kV/m. 

    Extraordinarily sensitive electroreceptive capabilities exist 
in some species (e.g.,  Elasmobranch fish), particularly where 
there has been evolutionary adaptation to refine sensory organs 
(Kalmijn, 1966; Bullock, 1973). 

    Cues, including magnetic field direction, seem important in 
birds (Walcott, 1974) and in several species ranging from bacteria 
and bees (where ferromagnetic materials have been found) (Gould et 
al., 1978) to dolphins and man (Blakemore et al., 1979), although 
the data in man are disputed.  These findings highlight the fact 
that extrapolation of the results of experimental amimal studies to 
man is quite complex.  Allowances must be made for differences in 
species sensitivities to ELF fields. 

5.5.  Effects on the Haematopoietic System in Animals

    Numerous studies on animals (Blanchi et al., 1973; Cerretelli & 
Malaguti, 1976; LeBars & Andre, 1976; Graves, 1977; Graves et al., 
1979; Marino & Becker, 1977; Cerretelli et al., 1979; Phillips et 
al., 1979; Conti et al., 1981; Ragan et al., 1983) concern field-
related variations in blood cell populations.  There is evidence in 
these studies of a prompt effect on neutrophilic cells and possibly 
an effect on thrombocytes and reticulocytes.  The data do not permit
determination of possible mechanisms that may involve either an 
effect of the internal fields directly on haematopoietic tissues, 
or an effect on tissues affected via the central nervous system as 
a result of peripheral sensory stimuli.  In all cases, the changes 
in peripheral leukocyte counts have been within the range of 
physiological norms.  A summary of studies on the haematopoietic 
system in animals is presented in Table 3. 

Table 2.  Nervous system and behavioural studies in animals
Exposure   Frequency   Subject   Effects examined                               Reference               
(kV/m)     (Hz)                                                                                         
0.0074     60          monkey    no effect on operant behaviour                 deLorge (1973)          
up to      45, 60,     monkey    altered behaviour (frequency specific)         Gavalas-Medici &        
0.056      75                                                                   Day-Magdaleno (1976)    
0.01 -     7, 10       monkey    changes in interresponse time, dose-           Gavalas et al. (1970)   
0.056                            dependent, EEG entrainment at field frequency                          
0.1        60          rat       no effect in preference behaviour or in        deLorge & Marr (1974)   
                                 temporal discrimination                                          
up to 0.1  45          mouse     no effect on brain and serum sertotonin        Krueger & Reed (1975)   
up to 0.1  45          rat       altered brain acetyl transferase               Noval et al. (1976)     
0.8 - 1.2  60          mouse     more active in dark periods                    Moos (1964)             
4.2        60          bees      increased activity during exposure             Greenberg & Bindokas    
up to 25   60          rat       initial startle reaction                       Stern et al. (1980)     
2 - 10     60          rat       detection threshold approximately 8 kV/m       Stern et al. (1983)     
25, 50     60          mouse     initial sterile reaction                       Graves (1977)           
25, 50     60          rat       preference for area of exposure                Hjeresen et al. (1980)  
26         60          chick     peck suppression, 28% decrease in motor        Graves et al. (1978)    
30         60          swine     perception of field, prefer shielded area      Hjeresen et al. (1982)  
                                 at night                                                 
30         60          rat       no effect in taste aversion                    Creim et al. (1980)     
30         60          baboon    small behavioural changes                      Feldstone et al. (1980) 

Table 2.  (contd.)
Exposure   Frequency   Subject   Effects examined                               Reference               
(kV/m)     (Hz)                                                                                         
32         60          pigeon    perception of field altered in exposed         Graves et al. (1978)    
10 - 75    60          mouse     transient hyperactivity in inactive phase,     Ehret et al. (1980b)    
                                 35 kV/m average threshold                      Rosenberg et al. (1983) 
40         60          chicks    decreased activity in exposed animals          Bankoske et al. (1976)  
                                                                                Graves et al. (1978)    
50         50          mouse,    no effect on behaviour                         Le Bars et al. (1983)   
10 - 75    60          mouse     hyperactivity with intermittent exposure       Rosenberg et al. (1983) 
                                 (commencing at 50 kV/m)                                                 
67         60          chicken   no effect on activity or gross behaviour       Bankoske et al. (1976)  
67         60          mouse     hyperactivity with intermittent exposure       Ehret et al. (1980a,b)  
75, 90,    60          rat       rats spend more time out of field              Hjeresen et al. (1980)  
80         60          cat       EEG changes                                    Silney (1979)           
65a        60          rat       increased excitability of sympathetic          Jaffe et al. (1980)     
65a        60          rat       no effect on peripheral nerve function         Jaffe et al. (1980)     
65a        60          rat       excitatory changes in neuromuscular            Jaffe et al. (1981)     
                                 function; slower recovery from fatigue                                 
100        60          rat       aversion behaviour                             Lovely (1982)           
a  Effective field strength.
5.6.  Cardiovascular Effects

    Cardiovascular function can be assessed by measuring blood 
pressure and heart rate and by performing ECGs.  So far, reported 
evidence of changes in cardiovascular function has been limited and 
contradictory.  In early studies, a decrease was reported in the 
heart rate and cardiac output of dogs exposed to 15 kV/m (Gann, 
1976), and an increase in heart rate in chickens exposed to 80 kV/m 
(Carter & Graves, 1975).  Comprehensive studies in rats showed no 
effects from exposure to 100 kV/m (Hilton & Phillips, 1980).  
Transient increases in blood pressure in dogs exposed to field 
strengths greater than 10 kV/m have been reported (Cerretelli & 
Malaguti, 1976). 

5.7.  Effects on Endocrinology and Blood Chemistry

    A large body of data has been collected under different 
exposure conditions on measurements of different blood plasma 
proteins, enzymes, etc.  Some of these data are summarized in Table 
4.  No consistent picture of physiological or pathological changes 
is evident. 

    Many of the major hormones have been examined for the effects 
of electric-field exposure, particularly in rats and mice (Phillips 
et al., 1979).  Possible effects have been observed in only three: 
corticosterone, testosterone, and melatonin.  Because corticosterone
is produced by the body in response to stress, blood levels of the 
hormone are extremely sensitive to the method used in obtaining 
samples.  Perhaps because of this sensitivity (rather than the 
effects of electric-field exposure), a number of laboratories have 
reported conflicting results. 

5.8.  Effects on the Immune System

    In considering the pattern of effects on white cell populations,
it is of special importance to evaluate the immunocompetence of 
electric-field-exposed animals.  Schneider & Kaune (1981) did not 
find any effects on the response to infection in chicks exposed to 
2 kV/m.  Morris & Phillips (1982, 1983) did not find any effects on 
cell-mediated or humoral immune response in rats or mice exposed to 
fields of 0.2 kV/m.  No effect was observed from electric-field 
exposure on infectivity by a leukemogenic virus in chickens (Phillips 
et al., 1981).  Lyle et al. (1983), however, observed significant 
decrements in the cytolytic capacity of lymphocytes exposed to radio-
frequency fields modulated at 60 Hz.  In an extensive study, Le Bars 
et al. (1983) found no significant effects on immune response of 
rats, mice, or guinea-pigs exposed to 50 kV/m, 50 Hz electric fields 
for 8, 14, or 18 h/day over periods varying from 1 to 6 months. 

Table 3.  Haematopoietic studies in animals
Exposure  Frequency   Subject      Effects                             Reference
(kV/m)    (Hz)
0.01      50          mouse        altered leukocyte distribution      Blanchi et al. (1973)
0.01      50          rat          altered leukocyte distribution      Blanchi et al. (1973)

0.01      45, 60      rat          all effects within normal range     Mathewson et al. (1977)

5         60          mouse        decrease in RBC concentrations      Marino & Becker (1977)

10        50          dog          no effect on haematology            Cerretelli et al. (1979)

10        50          dog          no effect on haematology            Conti et al. (1981)

25        60          mouse        higher WBC count                    Graves et al. (1979)

25        50          dog          altered leukocyte distribution,     Cerretelli & Malaguti       
                                   RBC count and haemoglobin           (1976)

50        50          rabbit       altered total leukocytes and RBC    LeBars & Andre (1976)

50        50          rat          no effect on haematology            LeBars & Andre (1976)

50        50          rat, mouse,  no effect on haematology            LeBars et al. (1983)

50        60          mouse        higher WBC count                    Graves et al. (1979)

65        60          rat          increased leukocytes in  in utero-   Phillips et al. (1979)
                                   exposed offspring

Table 3.  (contd.)
Exposure  Frequency   Subject      Effects                             Reference
(kV/m)    (Hz)
65        60          rat          no effect on haematology            Ragan et al. (1983)

65        60          mouse        WBC increased in F2                 Phillips et al. (1979)
                                   generation females

65        60          mouse        RBC increased in F2 generation      Phillips et al. (1979)

90        60          rat          no effect on polychromatic RBCs     Phillips et al. (1979)

100       50          rat          altered leukocyte distribution      Cerretelli & Malaguti (1976)

100       50          rat          significant changes in blood        Cerretelli et al. (1979)
                                   morphology and chemistry

100a      60          rat          no effect on haematology            Ragan et al. (1983)

100       50          rat          significant changes in blood        Conti et al. (1981)
                                   morphology and chemistry

100       60          rat          increased leukocytes in  in utero-   Phillips et al. (1979)
                                   exposed animals

100       60          rat          no effect on haematology or serum   Ragan et al. (1983)
a 65 kV/m effective.

Table 4.  Studies on endocrinology and blood chemistry
Exposure  Frequency  Subject   Effects                           Reference
(kV/m)    (Hz)
0.1       45         rat       altered plasma corticosterone     Noval et al. (1976)

0.1       45         rat       no effects on serum chemistry     Mathewson et al. (1977)

1.5       60         rat       lower melatonin in pineal gland   Wilson et al. (1981, 1983)

5         60         rat       no effects on serum chemistry     Marino & Becker (1977)

10        60         rat       adrenal response elevated         Lymangrover et al. (1983)

15        60         rat       lower serum corticosterone        Marino et al. (1976a)

15        60         rat       lower albumin                     Marino & Becker (1977)

15        60         dog       no effects on cortisol secretion  Gann (1976)

25        50         dog       no effects                        Cerretelli & Malaguti (1976)

25, 50    60         mouse     transient effect on steroid       Graves (1977)

Table 4.  (contd.)
Exposure  Frequency  Subject   Effects                           Reference
(kV/m)    (Hz)
50        50         rabbit    altered calcium, glucose, urea    LeBars & Andre (1976)

50        50         mouse     no effects on blood biochemistry  LeBars et al. (1983)

50        50         rat       no effects                        LeBars & Andre (1976);
                                                                 LeBars et al. (1983)

50        50         guinea-   no effects on blood biochemistry  LeBars et al. (1983)

65        60         rat       lower testosterone levels         Free et al. (1981)
                               (120-day exposures); no effects 
                               in other hormones

80        60         rat       no change in corticosterone level Seto et al. (1982)

100a      60         rat       no effects on serum chemistry     Ragan et al. (1983)

100       50         rat       no effects                        Cerretelli & Malaguti (1976)
a 65 kV/m effective.
    Evidence from many blood studies on man or laboratory animals 
shows slight changes in white cell populations, almost always 
within the range of normal values.  These shifts may, however, 
indicate some alterations involving the immune system.  Further 
research is indicated, before a conclusion can be reached.  
Overall, the evidence from many studies indicates that animal 
morbidity and mortality in long-term exposures is unaffected, 
suggesting that the immune response is generally unaffected. 

5.9.  Growth and Development Studies

    Data from many studies on rats, mice, or chickens (Knickerbocker
et al., 1967; Marino et al., 1974; Krueger et al., 1975; Bankoske et 
al., 1976; Cerretelli & Malaguti, 1976; LeBars & Andre, 1976; Noval 
et al., 1976; Mathewson et al., 1977; Cerretelli et al., 1979; 
Graves et al., 1979; Phillips et al., 1979, 1981; Fam, 1980; Conti 
et al., 1981; Greenberg & Bindokas, 1981; Le Bars et al., 1983; 
Portet, 1983) suggest that there are no effects on growth and 
development.  In particular, the data from multi-generation studies 
on mice do not indicate any pattern of an effect on these parameters. 

    Exceptions are reported in two instances.  Severe stunting was 
reported in a wild strain of rabbits reared outdoors in a 
substation electric field of 14 kV/m (50 Hz) in comparison with 
rabbits in an electric field-free cage (Hansson, 1981a,b).  The 
same author did not find any growth changes in rabbits exposed 
under indoor laboratory conditions.  Secondly, the results of 
multi-generation studies in electric-field-exposed swine (30 kV/m) 
and rats (65 kV/m) revealed developmental defects that included an 
increased incidence of fetal malformations in two successive 
generations of miniature swine exposed for 18 months and in one of 
two rat generations (Phillips, 1981, 1983; Sikov, 1982; Anderson & 
Phillips, 1984).  Because of the important implications of these 
studies, additional research should be conducted to address 
questions that, at present, preclude conclusions concerning a cause 
and effect relationship between the various fields used in these 
studies and the observed effects on development.  In particular, in 
the swine or rat studies, similar effects were not seen in all 
generations, and the influence of environmental stress in the 
rabbit study requires clarification.  A summary of some of the 
results of growth and development studies is given in Table 5. 

5.10.  Reproduction and Fertility

    Studies on reproductive function have been carried out at many 
field strengths (Knickerbocker et al., 1967; Krueger et al., 1975; 
Phillips et al., 1979; Sikov et al., 1979) with no evidence of 
consistent electric-field effects in rats or mice. 

    Effects on rat, swine, rabbit, and chicken growth and development
are described in the previous section.  Swine conceived, born, and 
then kept in the electric field for 18 months showed a deficit in 
mating performance (Phillips, 1981). 

    A summary of effects on fertility and reproduction is presented 
in Table 6. 

5.11.  Mutagenesis

    Results of studies on  Drosophila (Mittler, 1972; Bender, 
1976) did not indicate any mutagenic effects, though those of an 
earlier study (Coate & Negerbon, 1970) had suggested effects.  
Other studies (Knickerbocker et al., 1967; Krueger et al., 1975) 
did not show any effects. 

    No effects have been observed that would suggest that electric-
field exposure is mutagenic (Phillips et al., 1979; Frazier et al., 

5.12.  Circadian Rhythms in Animals

    Apart from the extensive investigations of Wever (1968) on 
alterations in circadian rhythms in human beings, only a few 
studies have been conducted to examine the effects of electric 
fields on natural biological rhythms.  Ehret et al. (1980a,b) 
measured rat metabolism but did not observe any effects on the 
circadian rhythms of metabolism in animals exposed to 8.2 kV/m, or 
on ultradian rhythm in fields up to 100 kV/m.  Wilson et al. (1981, 
1983) examined circadian rhythms in rats in a more direct fashion, 
measuring the cyclical pineal production of indolamines and 
enzymes.  A significant reduction in the normal night-time rise of 
melatonin and biosynthetic enzymes was observed in rats exposed to 
either 1.5 or 40 kV/m.  Furthermore, the change in pineal indole 
response occurred only after 3 weeks of chronic exposure (Anderson 
et al., 1982). 

5.13.  Bone Growth and Repair

    McClanahan & Phillips (1983) reported that bone growth in rats 
did not appear to be affected by exposure to 100 kV/m. Marino et 
al. (1979) and McClanahan & Phillips (1983) reported that bone-
fracture repair was retarded in rats and mice exposed to fields as 
low as 5 kV/m but not in animals exposed to very low (1 kV/m) field 
strengths.  Exposure may affect the rate of healing but not the 
strength of the healed bone (McClanahan & Phillips, 1983). 

Table 5.  Studies on growth and development
Exposure      Frequency  Subject   Effect                            Reference
(kV/m or mT)  (Hz)       
0.1           45         rat       no effect on body weight          Mathewson et al. (1977)

0.1           45         rat       altered growth                    Noval et al. (1976)

3.4           45 or 75   chick     no effect on body weight          Krueger & Reed (1975)

3.5 (0.1      45, 60,    chick     no effect on posthatching         Durfee et al. (1975)
- 3 mT)       or 75                growth and development

5 and 15      60         rat       decreased body weight             Marino et al. (1976, 1980)

7             60         bee       no effect on bee or hive weight   Greenberg et al. (1979)

10 and 15     60         mouse     decreased body weight             Marino et al. (1976)

14            50         rabbit    stunted growth (raised outdoors)  Hansson (1981a,b)

15            60         rat       increased pituitary and adrenal   Marino et al. (1976)
                                   weights in exposed

25            60         mouse     no effect on development          Phillips et al. (1981)

25            50         rat       lower growth rate                 Cerretelli et al. (1979);
                                                                     Conti et al. (1981)

30            60         swine     no effect on body weight          Phillips et al. (1979)

30            60         swine     increased rate of fetal malfor-   Phillips et al. (1981);
                                   mations (in 2 generations)        Phillips (1983)

Table 5.  (contd.)
Exposure      Frequency  Subject   Effect                            Reference
(kV/m or mT)  (Hz)       
50            50         rabbit    no effect on growth               LeBars & Andre (1976)

50            50         mouse,    no effect on growth               LeBars et al. (1983)

50            50         rat       no effect on growth               Portet (1983)

65            60         rat       increased rate of fetal malfor-   Phillips (1983)
                                   mations (1 of 2 generations)

67            50         chicken   no effect on body weight          Bankoske et al. (1976)

80            60         chick     no effect on body weight          Graves et al. (1979)

80            50         chick     no effect on growth               Bankoske et al. (1976)

100           50         rat       no effect on embryo morphology    Cerretelli & Malaguti 

100           50         rat       lower growth rate                 Cerretelli et al. (1979);
                                                                     Conti et al. (1981)

100           60         rat       no effect on growth               Phillips et al. (1979)

160           60         mouse     lower body weight in offspring    Knickerbocker et al. (1967)
                                   of exposed males

Table 6.  Studies on fertility and reproduction
Exposure  Frequency  Subject     Effect                             Reference
(kV/m)    (Hz)
1.6 (or   60         chicken     reduced egg production             Krueger et al. (1975)
1.2 G)

3.4       60         chicken     no effects on hatchability, em-    Krueger et al. (1975)
                                 bryonic morphology, or sex ratios

3.5 (or   45, 60,    chicken     no effects on hatchability,        Durfee et al. (1975)
1 - 3 G)  or 75                  embryonic survival

10 or 15  60         mouse       no effects on litters or litter    Marino et al. (1976)

30        60         swine (F0)  no effects on farrowing success    Phillips (1981)
                                 rate (1st breeding)

30        60         swine (F0)  increase in fetal abnormalities    Phillips (1981)
                                 (2nd breeding)

30        60         swine (F1)  poor breeding performance          Phillips (1981)

30        60         swine (F1)  increased fetal abnormalities      Phillips (1983)
                                 (1st breeding)

50        50         rat         no effect on estrus cycle          LeBars & Andre (1976)

67        60         chickens    no effects on hatchability or      Bankoske et al. (1976)
                                 time to hatch

Table 6.  (contd.)
Exposure  Frequency  Subject     Effect                             Reference
(kV/m)    (Hz)
100       50         rat         effect on numbers of matings and   Cerretelli & Malaguti 
                                 pregnancies                        (1976)

100       50         rat         no effect on fertility             Cerretelli et al. 
                                                                    (1979); Conti et al. 

100       60         mouse       no effects on fertility, mor-      Phillips et al. (1979)
                                 tality, size of litter, sex ratio

100       60         rat         no effects on mortality, litter    Sikov et al. (1979)
                                 size, or reproductive performance

100       60         rat         earlier development of motor       Phillips et al. (1979)

160       60         mouse       no effect on reproductive ability  Knickerbock et al. 

5.14.  The Problems of Extrapolating Animal Exposure Data to Human

    Because either the surface electric field or the internal 
current density at a particular organ varies with the size, shape, 
and orientation of the body, no single animal model can successfully 
simulate the exposure conditions of a human being.  At best, a 
single study can approximate human exposures either to the surface 
fields at a selected spot, or to the internal current density in a 
selected organ (Sheppard & Eisenbud, 1977; Kaune & Phillips, 1980). 

    Kaune & Phillips (1980) calculated the current through various 
sections of the body, and from the cross-sectional area, calculated 
the average current density for the rat, swine, or human being 
exposed to the same (unperturbed) electric field.  The data showed 
very large differences in currents as a function of animal posture.  
For example, the total neck current in a horizontal rat exposed to 
a 10-kV/m vertical E field was 1.6 µA, but, when the rat reared, 
the current increased to 3.2 µA.  The respective current densities 
were 28 and 140 nA/cm2.  An even larger ratio of about 7-fold 
occurred for the chest currents, while, in the abdomen, the resting 
rat had a current density of only 2 nA/cm2 compared with 85 nA/cm2 
in the rearing rat.  In either case, because of the larger capacitance
of the human body, the current density in the human neck will be 
greater than that in the rat. 

    According to the foregoing considerations, for example, a study 
designed to examine the effects of electric current density in the 
neck of a man exposed to 10 kV/m would, if conducted on rats, 
require an electric field of 200 kV/m, or in the case of pigs, 140 
kV/m, whereas studies involving animals that stand erect more often 
(such as primates) would require lower field strengths (Kaune & 
Phillips, 1980).  An electric field that produced a reasonable 
match between man and the test animal in one part of the body would 
tend to overexpose other parts of the animal body, for example, the 

    Another approach to the determination of relative exposures 
between man and animals considers the "enhancement factors" for the 
surface electric field.  Deno (1977) reported that, for human 
beings, the surface electric field at the top of the head was 18 
times that of the unperturbed electric field, whereas at the back 
of the head the enhancement was 15 fold.  At the upper arm, an 8-
fold enhancement occurred for the size and shape parameters given 
by Deno.  When a rat was exposed to a 10-kV/m unperturbed electric 
field, the maximum field strength of 37 kV/m occurred at the back, 
while an upright man in the same field had a maximum field of 180 
kV/m at the top of the head (Kaune & Phillips, 1980). 

    These data indicate that man's size and posture make it 
difficult to simulate in laboratory animals the current densities 
that occur when man is exposed to strong electric fields.  Because 
of the interference of artifactual shocks, hair stimulation, 
corona, and other problems of extremely high voltage, it is not 
practical to expose animals to levels much higher than 100 kV/m. 

    The species differences between man and laboratory animals 
may strongly affect the threshold for biological response, the 
magnitudeof a physiological response, and the degree of adaption.  
Biochemical differences among species may also prove significant.  
None of these species-dependency factors is understood in the 
context of ELF electric field exposures. 

    Magnetic field exposures may require scaling according to body 
size, shape, and orientation if the primary action is due to the 
induced electric field.  The magnetic field itself is not perturbed 
by either animal or human bodies and is essentially unchanged at 
points outside or inside the body. 


6.1.  Sources of Information

    Three sources of information exist concerning the effects on 
man of exposure to ELF fields: 

    (a) surveys of the state of health of high-voltage
        linemen, utility, substation, and switch-yard workers;

    (b) epidemiological studies of inhabitants near
        high-voltage transmission lines, power distribution
        lines, and substations; and

    (c) examination of volunteers exposed to ELF fields under
        controlled conditions.

    Additional information can be obtained from follow-up studies 
of patients exposed to ELF fields as a result of medical applications.
Except for a report by Bassett (1981) on the state of patient health, 
information is related to the effectiveness of the applied medical 

    Although there is no good substitute for reliable epidedmiological
data for the evaluation of general population and occupational health 
aspects of ELF exposure, data from present studies are insufficient 
to draw any firm conclusions. 

    However, other epidemiological studies are in progress which 
may provide further information needed to establish better health 
criteria (Baroncelli et al., 1984; Checcucci, 1984; Knave, 1984). 

6.2.  Study Design

    In epidemiological studies, it is difficult to obtain quantitative, 
unbiased data that can be reliably interpreted.  Two problems with 
most of the human studies to date are the failure to obtain 
measurement data on the level and duration of exposure, and the 
failure to include an appropriate control group that is comparable 
in all respects to the exposed group, except for exposure to the 
electromagnetic field.  While this does not necessarily invalidate 
the results of such studies, these shortcomings must be taken into 

    End-points can be selected to ascertain the health impact of 
ELF exposure in areas of particular public concern.  Effects on the 
nervous system, behaviour, the cardiovascular system, tumour 
incidence, reproductive success, or development are among the 
appropriate end-points.  Some authors (Utidjian, 1979) maintain 
that, because there is no basis for postulating a specific disease 
or cause of death related to ELF exposure, epidemiological studies 
need to be cross-sectional, evaluating the general state of health 
and the incidence of diseases.  A basic problem is the selection of 
appropriate matched control groups.  Other, often overlooked 
problems include those of obtaining appropriate information on 

exposure duration and levels, the occurrence of confounding 
factors, as well as the need for differentiation between the 
effects of ELF exposure and the influence of collateral phenomena 
such as noise, microshocks, ozone, or possibly the presence of 
various ions and chemical substances. 

    Finally, to prevent the introduction of bias, all studies 
should be "blind".  This means that, whenever possible, personnel 
who record data should be unaware of the subjects' exposure 

6.3.  Health Status of Occupationally-Exposed Human Beings

    A summary of studies on the health status of linemen and 
switch-yard workers is given in Table 7. 

    Asanova & Rakov (1966) examined 45 high-voltage switch-yard 
workers.  This survey indicated a variety of symptoms in the 
cardiovascular, digestive, and central nervous systems subsequent 
to prolonged exposure of switch-yard workers to electric fields (up 
to 26 kV/m).  The disturbances noted were subjective.  No control 
group was examined.  Furthermore, recent work in the USSR has 
suggested that the observed effects might be the result of exposure 
to microshocks or kerosene vapour rather than to electric fields 
(Danilin et al., 1969; Savin et al., 1978; Bourgsdorf, 1980). 

    Results from the earliest comparable studies in the USA failed 
to confirm those of the USSR studies.  Kouwenhoven et al. (1967) 
and Singewald et al. (1973) who studied 10 linemen exposed during 
their work (4-year period) to unperturbed fields of up to 25 kV/m 
did not observe any correlation between exposure and the health of 
the subjects.  However, this study included only a small number of 
subjects, and descriptions of the experimental protocol and results 
were incomplete. 

    Sazonova (1967) reported on physiological tests performed on 
400 - 500 kV substation workers divided into 2 groups according to 
the presumed extent of electric field exposure.  The high electric-
field-exposed group had significantly lower blood pressure, greater 
neuromuscular activity, and increased latent reaction times and 
higher error rates in a stimulus-response test.  The exposure 
information was not adequate to determine either electric field 
strength or duration of exposure. 

Table 7.  Studies on the health status of linemen and switch-yard workers
Reference           No. of    Comments
Kouwenhoven et al.  10        Linemen, 10-year period of observation, only general
(1967); Singewald             medical data, no effects reported, no data on exposure
et al. (1973)                 levels, no control groups; same subjects in both

Asanova & Rakov     45        Switch-yard workers (500 kV): subjective and objective
(1966)                        indications of functional neurovegetative disturb-
                              ances; exposure estimated; no control group; Danilin
                              et al. (1969) suggested that chemical pollution
                              (kerosene) may have been responsible

Sazonova (1967)     211       Switch-yard workers (400 - 500 kV): exposure
                              estimated; neurovegetative disturbances (as above);
                              increased latent reaction time and error rates; no
                              control group

Revnova et al.      114       Switch-yard workers (500 kV): findings as Asanova &
(1968)                        Rakov (1966); inadequate data on exposure; no control

Danilin et al.      12        Switch-yard workers: detailed clinical (hospital-
(1969)                        ization) study; average exposure 14 kV/m, maximum 26
                              kV/m; no effects; no control group

Fole et al.         9         Switch-yard workers transferred from a 200 kV to a 400 kV
(1974); Fole                  substation: exposures up to 15 kV/m; findings as Asanova 
(1973)                        & Rakov (1966) plus visual troubles; no control group

Malboysson (1976)   160       84 switch-yard workers and 76 HV-linemen compared to 94
                              controls (low-voltage linemen): questionnaires and medical
                              examinations; no effects, better health of HV-workers;
                              inadequate data on exposure; no statistical analysis

Roberge (1976)      160       Switch-yard workers (735 kV): inadequate data on exposure;
                              no health effects; electric shock anxiety; ratio male/
                              female offspring 17:3; no control group

Stopps &            30        Linemen compared to 30 matched controls from among the 
Janischensky                  power company employees: clinical studies, including ECG 
(1979)                        and EEG; no effects; exposed group was preselected 
                              (volunteers); exposures extrapolated from measurements

Knave et al.        53        400 kV station workers matched with 53 unexposed power
(1979)                        company employees: no differences in health status;
                              comprehensive medical and psychological study; good 
                              exposure data

Issel et al.        110       Linemen working on 110 and 380 kV lines with protective
(1977)                        clothing; no effects; control group used
Table 7.  (contd.)
Reference           No. of    Comments
Broadbent et al.    390       Questionnaires on linemen and switch-yard workers; 28
(in press)                    exposed above level of detection threshold of monitor;
                              control group; no effects found
    Revnova et al. (1968) carried out a study on 114 workers (99 
males, 15 females) in a 500 kV substation with findings similar to 
those of Asanova & Rakov (1966).  Danilin et al. (1969) did not 
report any adverse health effects in a clinical study on 12 workers 
exposed to an average field strength of 14 kV/m, which generated 
whole body currents of 130 µA (maximum 26 kV/m and 230 µA).  
Krivova et al. (1973) found no physiological changes at 10 kV/m, 
but did identify some impairment of motor skills after exposure for 
2 h to 16 kV/m. 

    To assess the health status of electricians on high voltage 
systems, an investigation was started in the German Democratic 
Republic in 1971 (Kupfer & Issel, 1975).  The subjects included 
linemen wearing protective clothing who worked bare-handed on 110 - 
380 kV lines (Jahn et al., 1978).  The men were examined according 
to clinical criteria (locomotion system, cardiovascular system, 
respiration system, haematopoietic system, kidney and liver 
function, eyes, ears, and nose) and psychological criteria (risk-
taking behaviour, motivation, sensomotor coordination, reaction 
time, intellectual abilities for technical thinking, personality). 
Examination of 110 linemen and fitters did not reveal any health 
changes or injuries attributable to the 50-Hz fields (Issel et al., 
1977).  Electric fitters exposed under similar physiological and 
psychological conditions, but at a field strength of 5 kV/m, served 
as a control group. 

    In Spain, Fole (1973) and Fole et al. (1974) reported subjective
health effects among 6 workers from a 400-kV substation; there was 
no control group.  A group of 84 substation workers and 76 linemen 
in Spain were compared with 94 linemen working on low voltage systems 
(Malboysson, 1976).  The linemen in both groups showed no apparent 
adverse effects due to work in electric fields.  No exposure 
measurements were taken, and the data were not statistically analysed. 

    Knave et al. (1979) examined 53 workers at 400 kV-substations 
in comparison with a matched reference group of 53 unexposed 
workers.  Only occasional exposures to field strengths above 5 kV/m 
occurred (Table 8).  Data on subjective complaints were collected 
using standard questionnaires and interviews.  Eight psychological 
tests were performed.  EEGs and ECGs were recorded, blood pressure 
measured, and peripheral blood cell counts were made.  No biochemical 
tests were made.  Comparison of substation workers and the reference
group generally showed no observation of a lower number of offspring.  
However, a lower rate of male offspring was observed but not 
attributed to electric field exposure. 

Table 8.  Percentage (%) of working time spent in electric fields
of different strengths by 400-kV substation workersa
Type of work             E-field strength ranges (kV/m)
                       0 - 5    5 - 10    0 - 15    15 - 20
Inspection rounds      66       37        2          1
Everyday work          34       61        4.8        0.2
Breaker work:                                     
  Revision             60       0         18         16
  Testing              95       5         0          0
a From: Knave et al. (1979).

    In an earlier study (Roberge, 1976), 56 switch-yard workers at  
735-kV substations in Quebec, Canada were examined.  A questionnaire
oriented towards nervous system complaints was used, and a clinical 
examination that included an ECG and a thorough examination of the 
peripheral blood chemistry, was conducted.  The data were compared 
with "normal" reference values rather than those of a control group.  
Differences in eosinophil number ( P < 0.05) were, however, within 
clinical norms, and of doubtful statistical value. 

    Stopps & Janischewsky (1979) studied 30 high-voltage maintenance
men and 30 matched employees not exposed to electric fields.  Clinical 
and psychological investigations were made in a hospital.  In the 
exposed group, 19 linemen had estimated exposures of 7 kV/m h per day 
(up to 8000 kV/m h over 10 years); and 11 substation workers had 
average estimated exposures of 13 kV/m h per day (up to 36 000 kV/m 
h over 10 years).  No adverse health effects were found. 

    A health-questionnaire study (Broadbent et al., in press) was 
conducted on 390 electrical power transmission and distribution 
workers employed in the electrical industry in the United Kingdom, 
of whom 28 were exposed to levels above the detection threshold of 
the dosemeter.  Actual exposure levels, measured during the two 
weeks prior to the questionnaire interview, were considerably less 
that the estimated exposures.  About 150 interview questions were 
administered by industrial nurses.  Each man was asked to assess 
his own experience of headaches in the last 6 months on a scale 0 - 
3.  Visits to doctors over six months and taking of prescribed or 
unprescribed medicines were noted.  A measure of cognitive failure, 
i.e., frequency of minor episodes of forgetfulness or inattention, 
was measured.  Although there were significant differences in the 
health effect measurements between different job categories and 
different parts of the country, no significant correlation was 
found between these effects and exposures to electric fields. 

    Five preliminary observations were reported, four published as 
"letters to the editor", of an increase in the incidence of 
leukaemia in groups of workers loosely defined as "electrical 
workers" (Milham, 1982; Wright et al., 1982; Coleman et al., 1983; 
McDowall, 1983; Vagero & Olin, 1983). 

    Milham (1982) reported on a data base of 438 000 deaths of men, 
who were 20 years of age or older and were residents of Washington 
State, USA, from 1950-79.  A proportional mortality ratio (PMR = 
observed/expected x 100) due to leukaemia, significant at the  P < 
0.01 level, was observed for "electricians", TV and radio repair-
men, power station operators, and aluminium workers.  Wright et al. 
(1982) sought to verify Milham's (1982) results by examining a 
similar statistic, the proportional incidence ratio (PIR) of a 
different and much smaller data base.  They found significant 
increases ( P < 0.05) in the incidence of acute myeloid leukaemia 
(on the basis of a total of 4 cases) in power linemen and telephone 
linemen, two groups for which the Washington data yielded 
insignificant PMRs. 

    Additional data on occupational leukaemia rates in the United 
Kingdom were provided in two letters.  McDowall (1983) found an 
increased evidence of leukaemia in occupationally-exposed 
electrical workers using PMRs and also by a case-control study.  
Coleman et al. (1983) also examined the leukaemia incidence for the 
same electrical occupations with evidence of a 17% excess that was 
especially strong for electrical fitters and telegraph operators, 
for whom the extent of electric or magnetic field exposure was not 

    These occupational groups have a number of environmental 
factors in common, viz, exposure to electromagnetic fields and a 
variety of metals and chemical fluxes.  Electricians working in 
homes usually work on equipment that is not operating or operates 
at low voltages.  Telecommunication and electronic personnel are 
normally exposed to levels of power frequency electric or magnetic 
fields no higher than those encountered in the average modern home.  
These reports are inadequate in many ways for use in determining if 
there is any association between leukaemia and exposure to electric 
or magnetic fields.  However, they merit further detailed study to 
elucidate the signficance of the findings. 

    Finally, Vagero & Olin (1983) examined data from the Swedish 
Cancer Environment Registry for the incidence of all types of 
cancer among electrical or electronic industry workers compared 
with the general working population.  The authors claimed a nearly 
two-fold excess of pharyngeal cancers among the test population.  
However, the accuracy of the job classifications over the relevant 
time periods was questionable.  The authors were careful to point 
out that caution was needed for any conclusions with regard to 

    The association of electrical occupation with leukaemia 
suggested in these studies was not consistent and often involved 
very few disease cases in an occupational category.  Deficiencies
these studies could be summarized as follows (Repacholi, 1984a): 

    (a) lack of consistency in designating occupational

    (b) no account was taken of mobility between occupations;

    (c) occupational groups sharing exposure to electric and
        magnetic fields were undoubtedly exposed to other
        physical and chemical agents.

In studies such as these, associations can be detected with a 
reasonable degree of certainty, if appropriate statistics are 
applied to a large enough data base of good integrity.  The 
suggestion of field-related leukaemia raises important questions 
that should be addressed using studies of adequate statistical 
power in which exposure is more accurately determined. 

    Bauchinger et al. (1981) examined the chromosomes in blood 
lymphocytes of 32 switch-yard workers (380 kV) and did not find any 
differences in comparison with matched, unexposed workers.  However,
the control group demonstrated a rather high incidence of chromatid 
gaps, 17 ± 1.3 per 1000 cells, compared with the "positive" control 
group of nuclear power plant workers (15.0 ± 1.0 per 1000 cells).  
In Sweden (Nordström et al., 1981), preliminary work has been 
described in which increased frequency of chromosome breakage was 
seen in a few workers exposed to 400 kV.  Furthermore, congenital 
deformities were found in 10% of 119 children of substation workers, 
whereas only 2.7% of children of unexposed workers showed such 
deformities (Nordström et al., 1983).  Analyses of these data raise 
major questions in the interpretation of the results, because the 
highest percentage of abnormal progeny appears to be related to 
type of job rather than to level of exposure (Anderson & Phillips, 

    More research is this area is necessary in properly-designed 
human studies of significant magnitude to establish whether any 
asociation exists between exposure to ELF and induction of 
chromosome aberrations. 

    Nordström & Birke (1979) carried out a retrospective study on 
the incidence of congenital malformation in the progeny of 542 male 
employees of the Swedish State Power Board.  The increased frequency
of malformations reported in this study occurred evenly throughout 
the populations studied, irrespective of whether they worked in 400 
kV, 130 - 200 kV, or 70 kV situations. 

    Employees exposed to very low level ELF electric fields 
(generally less than 0.05 V/m and accompanying magnetic flux of 
densities 10-5 T) at the site of a test communications antenna 
(Project Sanquine) did not show any pathological effects related to 
the fields.  In particular, an investigation for neurological 
symptoms did not reveal any effects (Krumpe & Tockman, 1974). 

6.4.  Studies on the General Population

    Wertheimer & Leeper (1979) reported a two- to three-fold 
increase in the incidence of leukaemia among Colorado children 
presumably exposed to magnetic fields of strengths up to 0.7 mT.  
Magnetic fields were estimated by scoring the type of electrical 
wiring configuration close to the homes (power lines of various 
voltages and current-carrying capacity) into categories of high- or 
low-current configurations. 

    The same authors (Wertheimer & Leeper, 1982), extended their 
work to a study of the incidence of adult cancer in people living 
near high-current electric wiring.  The associations suggested were 
not dependent on age, urbanism, neighbourhood, or socio-economic 
level and were more clearly demonstrated when urban/industrial 
factors were not present to obscure the pattern.  The four types of 
cancer that appeared to be particularly elevated in the exposed 
adult populations were cancer of the nervous system, uterus, 
breast, and lymphomas.  The authors suggested that magnetic fields 
might have a promoter effect since the increases were maximal, 7 
years from the time of taking up residence in the area. 

    These preliminary studies have limitations common to many 
epidemiological studies involving cohort selection.  Additional 
problems include possible biases in the techniques for scoring the 
wiring configurations, and in the assumption that the scoring does 
accurately segregate magnetic field strength levels among the cases 

    Further questions are raised since the data were not collected 
blind and cases were ascertained after death, no account being 
taken of cancer cases still alive.  Furthermore, both birth and 
death addresses were used, which introduces a potential for 
observer bias. 

    Considerable interest has been provoked by these findings and 
it is expected that many of the issues will be dealt with in 
follow-up studies. 

    The hypothesis that such weak magnetic fields (of the order of 
0.1 - 0.7 µT) induce biological effects has raised questions such 
as those of Miller (1980), who criticized the Wertheimer & Leeper 
studies on the basis that the magnetic field from electrical 
appliances in the home would far exceed any contributions from 
electrical wiring configurations in the environment. 

    A similar study carried out by Fulton et al. (1980) in Rhode 
Island failed to reveal any evidence to support the Wertheimer and 
Leeper hypothesis.  However, Wertheimer & Leeper (1980) reanalysed 
the Rhode Island data using their own study method and found a 
slight association of childhood cancer with electrical wiring 

    Tomenius et al. (1982) reported a similar finding of increased 
leukaemia incidence in children living in homes where the levels of 
the magnetic field measured outside the front door were 0.3 µT or 
above.  The data involved a small number of cases and, again, the 
field measurement was questionable because the relation of actual 
exposure to the field outside the home was not established.  These 
studies and the preliminary occupational data (see above) relating 
some concern to electric or magnetic field exposure must be 
investigated further to determine if the suggested link with cancer 
induction or promotion can be established. 

6.4.1.  Studies on inhabitants of areas in the vicinity of HV-lines

    A four-year study on 70 men, 65 women, and 132 children living 
within 25 metres of 200 and 400 kV lines has been reported by 
Strumza (1970).  The control group consisted of 74 men, 64 women, 
and 120 children living more than 125 metres from the lines.  The 
author failed to discover any differences between the exposed and 
control groups on the basis of medical records, frequency of visits 
to family doctors, or expenditure on pharmaceutical prescriptions.  
Eckert (1977) tried to establish a relationship between the sudden 
infant death syndrome and ELF fields, but the method and results 
were questionable. 

    In a study by Dumansky et al. (1977), no effects were found in 
farmers exposed to fields of 12 kV/m for 1.5 h/day. Similarly, 
Busby et al. (1974) did not find any effects in 18 farmers working 
on farms in the vicinity of a 765 kV line. 

    Reichmanis et al. (1979) and Perry et al. (1981) have suggested 
a link between electromagnetic field exposure and suicide.  It has 
been pointed out (Bonnell et al., 1983) that the reports lack any 
biological hypothesis.  Suicide is frequently a symptom of a 
pre-existing psychotic illness, and it is these diseases that are 
important in studying suicide.  Furthermore, these authors claimed 
that the conclusions were contradictory and open to serious 
criticism on the basis of incorrect use of epidemiological data.  
The calculation of the magnitude of electric fields was also in 
error by a factor of 10 000 (Bonnell et al., 1983). 

6.5.  Studies on Human Volunteers

    There is only a limited amount of data on human volunteers 
exposed to electric fields, low-level currents, or spark discharges 
under laboratory conditions.  These data are valuable because of 
the greater control over extraneous influences compared with 
occupational exposures and because they involve the human organism.  

Of course, studies on human beings are limited to physiological and 
behavioural observations that do not cause harm and the test 
sessions are usually relatively short. 

    In considering these studies, it is important to remember that 
microshocks can be felt in fields of above 3 kV/m (Takagi & Muto, 
1971) and therefore can cause unease in subjects.  To assess the 
effects of the ELF field itself, it is necessary to take care to 
eliminate the influence of microshocks in the experimental design. 

    In 1974, R. Hauf and co-workers reported studies on more than 
100 human volunteers exposed to 50 Hz electric fields (up to 20 
kV/m) during laboratory test sessions that involved relatively 
brief exposures to the field.  In the first report (R. Hauf, 1974), 
no field-related effects were observed on reaction time, blood 
pressure, pulse rate, electrocardiogram, or electroencephalogram.  
Changes in some blood cell variables were seen, but these were 
within the normal physiological range.  Each of the 3-h test 
sessions included 2 exposures for 45 min to fields at 1, 15, or 20 
kV/m, and the testing lasted 3 successive days.  Detailed 
descriptions of the studies are available in the reports of R. Hauf 
(1974) and Rupilius (1976). 

    Rupilius (1976) conducted a study on man where 3 days exposure 
to a 20 kV/m electric field at 50 Hz was combined with exposure to 
a 0.3 mT magnetic field at 50 Hz.  Observations for up to 24 h 
after exposure showed no changes in blood chemistry, including 
triglyceride levels.  Eisemann (1975) did not show any effects on 
human subjects exposed for a period of 3 h to a conduction current 
of 200 mA at 50 Hz, by means of electrodes placed on the ankles and 
under the arms. 

    No significant behavioural changes were observed in 20 human 
subjects exposed to an electric field of 20 kV/m (50 Hz) (Johansson 
et al., 1973).  The exposed subjects performed as well as controls 
in tests of reaction time and in psychological tests, and responses 
to a questionnaire did not show any significant differences in 
perceived levels of discomfort between the test and control groups. 

    The results of several studies performed by Wever (1968) 
indicated a significant influence of weak ELF electric fields on 
human circadian rhythms.  He found that the complete absence of 
electric or magnetic fields led to desynchronisation of certain 
biorhythms, but that synchronisation was restored by an applied 
2.5-V/m, 10-Hz, square-wave electric field.  These data are 
difficult to interpret with reference to electric fields at 
environmental levels.  Wever postulated the existence of a 
physiological detector of weak electric fields but did not 
associate this finding with the possibility of health effects from 
imposed ELF fields. 

    Human volunteers were also exposed to both electrical fields of 
20 kV/m and magnetic fields of 5 mT by Sander et al. (1982).  
Neither field produced any evident influence on the different 
parameters studied, except some discontinuous variations in certain 
of them. 

    Studies on the nervous system and behaviour in man are summarized
in Table 9, and studies on the haematopoietic system, in Table 10. 

6.6.  Summary

    Few physiological or psychological effects in human beings have 
been credibly related to electric field exposure.  Such effects, 
when reported, have often been questionable for the following 
reasons (Anderson & Phillips, 1984): 

    (a) monitoring of symptomatology was subjective and was
        frequently not well-defined;

    (b) quantitative evaluation of effects was either not
        performed or was not clearly described;

    (c) control populations were poorly matched with exposed
        groups or were absent;

    (d) electric fields had been confounded by secondary
        factors (e.g., microshocks);

    (e) observation periods were often short;

    (f) exposure levels varied widely or were not documented,
        making it difficult to estimate accurately the
        magnitude and duration of exposure;

    (g) numbers of subjects in many of the earlier studies
        were insufficient to establish the statistical
        significance of adverse effects.

Table 9.  Studies on the nervous system and behaviour in man
Exposure            Frequency  Effects examined                    Reference
1, 15, or 20 kV/m   50         altered reaction time within        G. Hauf (1974)
(up to 2 h)                    normal range; no effect on EEG      R. Hauf (1974)
                                                                   R. Hauf (1976)

20 kV/m, 0.3 mT     50         no effect on reaction time or EEG   Rupilius (1976)
(for 3 h)                                                          R. Hauf (1976)

0.3 mT              50         no effect on reaction time or EEG   Mantell (1975)
                                                                   R. Hauf (1976)

200 µA (for 3 h)    50         no effect on reaction time or EEG   Eisemann (1975)

6 kV/m (2 x 3 min)  50         effect on EEG when field "on"       Waibel (1975)

380 - 400 kV        50         no effect on manual dynamometry     Fole et al. (1974)

400 kV switch-yard  50         neuromuscular deficits among        Sazonova (1967)
workers                        exposed workers

400 kV switch-yard  50         various clinical diagnoses related  Asanova & Rakov 
workers                        to CNS                              (1966)

Table 10.  Haematopoietic studies in man
Exposure            Frequency  Effect                     Reference
1, 15, or 20 kV/m   50         altered total leukocytes,  G. Hauf (1974)
(for 3 h)                      absolute neutrophils and   R. Hauf (1974)
                               reticulocytes - all        R. Hauf (1976)
                               within normal range

0.3 mT (for 3 h)    50         no effects                 Mantell (1975)
                                                          R. Hauf (1976)

20 KV/m, 0.3 mT     50         no effects                 Rupilius (1976)
                                                          R. Hauf (1976)

200 µAa             50         no effects                 Eisemann (1975)
                                                          R. Hauf (1976)

5 mT (for 4 h)      50         no effects outside normal  Sander et al.
                               range                      (1982)

20 kV/m (6.22 h/    50         no effects outside normal  Sander et al.
day) (for 1 week)              range                      (1982)
a No field, only conduction current via electrodes (approximately
  equivalent to exposing man in a 12-kV/m field).


    In making an evaluation of the health risks of exposure to 
ELF electric and magnetic fields, a number of factors must be 
considered (Repacholi, 1984a).  Criteria must be developed to 
identify which effects are to be considered a hazard for human 
health.  A distinction needs to be made between the concepts of 
interaction, biological effect, perception, and hazard. 

    Difficulty in defining the term health hazard occurs because 
value judgements are involved that may not be based on scientific 
analysis.  Some may consider any field-induced interaction 
hazardous.  Others suggest that the field is hazardous if it is 
capable of inducing a physiological perturbation in a biological 
system that is either measurable or at least theoretically 
possible.  Still others note that a stimulus-producing sensation 
without pain or discomfort is often assumed to be harmless, but 
modern research has demonstrated that the opposite may be true 
(Grissett, 1980). 

    Interactions that lead to measurable biological effects, which 
remain within the normal range of physiological compensation of the 
body and do not detract from the physical and mental well-being of 
human beings, should not be considered hazardous.  Interactions 
that lead to biological effects outside the normal range of 
compensation of the body may be an actual or potential health 
hazard (Repacholi, 1983). 

    When making a health risk evaluation, strict guidelines must be 
established prior to reviewing the literature on the biological 
effects of exposure to static and ELF fields.  Certain studies 
(generally  in vitro) are conducted to identify underlying 
mechanisms of interaction.  Health risk evaluations cannot be made 
on the basis of  in vitro experiments alone, because effects found 
 in vitro many not necessarily occur  in vivo.  With  in vitro  
experimentation, the toxicity of an agent can be determined in 
increasingly complex steps.  For example, effects on solutions of 
biological molecules might be used as a model system to study a 
predominant mechanism of action.  Uncomplicated systems can assist 
in the exploration and evaluation of mechanisms and may serve as a 
useful basis for designing experiments at the cellular level - the 
next level of biological complexity.  By restricting the complexity 
of the experimental system, there will be less chance of possible 
subtle effects being masked by gross or dominant effects. 

    Thus, health agencies can place only limited value on  in vitro  
studies and must await the results of similar or related studies 
conducted  in vivo.  The  in vitro results may indicate that a 
cautious or prudent approach should be adopted when setting 
standards (Repacholi, 1983).  This may be reflected in the 
development of a safety factor which is applied to the lowest level 
of exposure at which adverse effects are observed.  Once the 
mechanisms of interaction are understood and found to occur in 
animals, the next step is to determine if it is possible to 
extrapolate the results to man. 

    Unfortunately, the state of knowledge of the interacting 
mechanisms operating when biological systems are exposed to 
ELF fields is very limited.  At present, it is impossible to 
furnish any theory to predict the effects of exposure to these 
fields.  Because of this lack of information, care must be taken 
in attempting to predict or extrapolate effects in man from effects 
found in animals.  Physical differences (size, shape, fur-bearing, 
etc.) result in marked differences in the internal field distribution
(Kaune & Phillips, 1980), and in different behavioural and 
homeostatic responses. 

    With such limited data available on biological effects and 
interaction mechanisms, the only practical approach left for making 
a health risk evaluation is to evaluate the available data on 
exposure levels and effects to determine if thresholds for effects 
occur (Repacholi, 1984a).  In undertaking such an evaluation, it is 
necessary to be selective as far as the data are concerned.  Only 
reports that provide adequate information on experimental technique 
and dosimetry should form part of the evaluation.  Ideally, from a 
regulatory viewpoint, only data that have been established and have 
a direct bearing on health risk should be considered.  Publication 
in a peer reviewed journal helps, but in the final analysis, unless 
the data have been confidently reproduced, the results should be 
considered tentative pending confirmation. 

    It would be ideal to make health risk evaluations on the basis 
of well-conceived, well-conducted, and well-analysed epidemiological 
studies.  Unfortunately, all such studies on human beings exposed 
to ELF fields have suffered from one or more deficiencies, as 
indicated in section 6. 

    With such a limited scientific data base, the determination of 
the existence of a true threshold exposure level below which no 
adverse health effect occurs, cannot be made with confidence.  
Thus, any health risk analysis for the development of standards 
must inevitably adopt a phenomenological approach (Kossel, 1982; 
Repacholi, 1983).  In this case, a review of the literature is made 
to determine the lowest exposure levels at which adverse biological 
effects have been established.  A biological effect that occurs in 
living organisms or animals may be detected as some general or 
specific alteration.  If the change appears irreversible or 
pathological, it might be presumed that it could be hazardous to 
man under comparable exposure conditions.  This assumption is made 
only because insufficient information is available on the effect or 
the underlying interaction mechanism to make an extrapolation to 
exposure conditions producing similar effects in human beings and 
to make a well-substantiated health risk evaluation. 

    The epidemiological studies (Wertheimer & Leeper, 1979, 1982; 
Tomenius et al., 1982) suggesting a relationship between childhood 
or adult cancer and residence in houses at various distances from 
high current flow due to external electrical wiring configurations, 
can only be considered as preliminary because of the many criticisms
that have been levelled at the studies (section 6). 

    The studies (Milham, 1982; Wright et al., 1982; Coleman et al., 
1983; McDowell, 1983; Vagero & Olin, 1983) suggesting an association
between electrical occupations (exposure to electric and magnetic 
fields) and cancer were analyses of occupational mortality data and 
subject to many sources of errors (section 6). 

    Thus, although these reports suggest potential adverse health 
effects, they cannot be evaluated in terms of health risk until the 
potentially confounding factors and sources of errors are eliminated.
It is of concern, however, that no studies have yet been published 
following up these reports. 

    Laboratory studies on human volunteers exposed for short 
periods to electric fields (up to 20 kV/m) have, in general, shown 
no effects (Hauf & Wiesinger, 1973; Johansson et al., 1973; Hauf, 
1974; Rupilius, 1976; Sander et al., 1982).  The results of these 
studies suggest that no apparent acute effects are likely from 
exposure to strong electric fields.  However, they cannot be used as 
indicators that no health effects will occur from long-term 
exposure (months or years). 

    Studies on the health status of linemen and switch-yard workers 
have not revealed any differences between exposed and control 
groups (Knave et al., 1979; Stopps & Janischensky, 1979).  As 
indicated in section 6, these epidemiological studies, although 
among the more complete, have still suffered from a lack of numbers 
of persons exposed to high electric field strengths for extended 
periods.  However, these workers are exposed to potentially the 
highest electric field strengths albeit for short periods of time 
(section 6, Table 7).  These studies do not provide a good data 
base on which to evaluate the possible health effects from long-
term exposure of the general public to electric fields near 
transmission lines.  More definitive information is needed, which 
in general, can only be provided through both large-scale 
epidemiological studies and developments in dosimetry that will 
make it possible to extrapolate the experimental animal results to 
human beings. 

    While attempting to arrive at general conclusions concerning 
the health hazards of ELF electric fields for protection purposes, 
the fundamental question that requires an answer is whether or not 
exposure to these electric fields induces any physiological or 
pathological effects in man. 

    From a careful review of laboratory studies  in vivo and  in 
 vitro, and from human studies, the following conclusions can be 

    (a) Adverse human health effects from exposure to ELF
        electric field levels normally encountered in the
        environment or the workplace have not be established.

    (b) Some human beings feel spark discharges in electric
        fields of about 3 kV/m and perceive the fields
        between 2 - 10 kV/m.  At present, there are no
        scientific data that suggest that perceiving a field
        produces an adverse pathological effect.

    (c) Exposure to ELF electric fields can alter cellular,
        physiological, and behavioural events.  Although it
        is not possible to extrapolate these findings to
        human beings, at present, these studies serve as a
        warning that unnecessary exposure to electric fields
        should be avoided.

    (d) The preliminary nature of the epidemiological
        findings on the increased incidence of cancer among
        children and adults exposed to ELF fields from
        electric wiring and the relatively small increment in
        reported incidence, suggest that, although the
        epidemiological data cannot be dismissed, there must
        be considerable study before they can serve as useful
        imputs for risk assessment.


    A standard is a general term incorporating both regulations and 
guidelines and can be defined as a set of specifications or rules 
to promote the safety of an individual or group of people.  A 
regulation is promulgated under a legal statute and is referred to 
as a mandatory standard.  A guideline generally has no legal force 
and is issued for guidance only - a voluntary standard.  Standards 
can specify exposure limits and other safety rules for personal 
exposure, or provide details on the performance, construction, 
design, or functioning of a device. 

    To protect the general population and persons occupationally 
exposed to ELF fields, exposure standards are promulgated.  These 
are basic standards of personnel protection that do not apply to 
particular devices or equipment, but generally refer to maximum 
levels to which whole or partial body exposure is permitted from 
any number of radiation emitting devices.  This type of standard 
normally incorporates safety factors and provides the basic guide 
for limiting personnel exposure. 

    To date, few regulatory exposure standards have been 
promulgated limiting human exposure to ELF fields.  Guidelines 
have been developed in a number of countries, mostly as an interim 
measure until sufficient information on adverse biological effects 
becomes available to make some reasonable assessment of health 
risks, and the exposure levels at which hazards occur. 

    This section includes a review of all known ELF electric field 
standards known to the Task Group at the time of publication. 


    From a recent review of ELF standards, Repacholi (1984a) found 
that the greatest interest in regulations or guidelines was in ELF 
electric fields at power frequencies.  With the growth in number 
and length of high voltage transmission lines, increasing concern 
has occurred among the public, regulatory agencies, and scientists 
about possible human health effects from exposure to the electric 
fields associated with these lines.  While there is no definitive 
evidence of such effects, mounting public fear and activism over 
hypothesized health risks has caused delays in the licensing and 
construction of major power transmission facilities, and encouraged 
the formation of regulatory policy in some countries. 

    The primary basis for public concern was a series of studies 
conducted in the USSR in the 1960s (Asanova & Rakov, 1966; 
Knickerbocker, 1975).  These studies resulted in the occupational 
safety standard in the USSR (1975), which is summerized in Table 
11.  In addition, a guideline on the design of HV transmission 
lines near residential areas recommends a limit of 1 kV/m (Lyskov 
et al., 1975).  However, this guideline may be under question 
(Bourgsdorf, 1980). 

Table 11.  Electric field exposure limits for workers in 
installations of 400 kV and higher in the USSR (1975)
Electric-field                         Permitted exposure duration
strength (kV/m)                        per day (min)
5                                      Unrestricted
10                                     180
15                                     90
20                                     10
25                                     5
      1.  If workers are exposed to electric fields of 10kV/m or more
          for the full time permitted by the standard, they must remain
          in fields of 5 kV/m or less for the rest of the day.

      2.  Workers exposed to 10 kV/m or above can remain for the
          permitted time, provided they are not subject to spark

    The Soviet standard applies to workers in substations or on 
transmission lines operating at 400 kV and above.  The duration of 
the standard was from 1 January 1977 to 1 January 1982, after which 
it was to be reviewed and either changed or reaffirmed.  At the 
time of publication of this document, a new standard for electric 
50 Hz power frequencies is being discussed by the Council of Mutual 
Economic Assistance (incorporating Bulgaria, Cuba, Czechoslovakia, 
the German Democratic Republic, Poland, Romania, and the USSR). 

    The basis for the Soviet standard is that studies conducted 
since 1962 on the effects on workers on high-voltage power systems 
revealed electric field influences on human beings.  It is believed 
that the reaction of the human body to the direct influence of an 
electrical field is non-specific; it can develop after a
comparatively long time (2 - 5 months); it has a long-term 
consequence, pronounced cumulative effects, and strong dependency 
on individual physiological peculiarities of the body (Lyskov et 
al., 1975). 

    In a design criteria for 1100 kV lines in the USSR, Lyskov et 
al. (1975) and Bourgsdorf et al. (1976) reported that clearances to 
ground were determined in order to limit the electric field to 10 - 
12 kV/m, at points where the HV transmission lines cross roads, and 
to 15 - 20 kV/m elsewhere along unpopulated sections of the line 
routes; a limit of up to 20 kV/m was determined for difficult 
terrain and hardly accessible areas.  These field strengths must 
not be exceeded at the centre of the span at a height of 1.8 m 
above the ground and at the lowest sag (at the maximum 15-year 

    In the United Kingdom, the National Radiological Protection 
Board (NRPB, 1982) has issued a proposal for ELF fields.  In this 
consultative document it states:  "The Board accepts that exposures 
to power frequency fields of less than 10 kV/m are safe, although 

the field may be perceptible at lower values, and that exposures to 
fields up to 30 kV/m are unlikely to be harmful".  The NRPB admits 
that there is very little information that can be used as a 
rational basis for limiting exposure and that at 50 Hz, perceptible 
but harmless effects depend to a large extent on environmental 
factors and individual sensitivities.  However, steps should be 
taken to prevent such effects from occurring with any degree of 
regularity.  This will generally be achieved if the root mean 
square field strengths are kept below 10 kV/m.  Prolonged exposure 
to fields greater than 20 kV/m, which induce currents in excess of 
0.5 mA in the body, is also undesirable, according to the NRPB. 

    In Japan, all electric power equipment is subject to the 
regulation "Technical Practices of Electrical Equipment", an 
ordinance of the Ministry of International Trade and Industry.  The 
ordinance (Repacholi, 1984a) includes such technical specifications 

    (a) minimum height of electrical conductors;

    (b) necessary clearance between a transmission line and
        building; and

    (c) the electrical field strength on the ground surface
        under the line.

    In summary, the ordinance states that the unperturbed electrical
field strength 1 m above the ground surface must not exceed 3 kV/m 
rms.  In addition, the line must be built so that it does not pose 
any risk for human beings.  However, in lightly-populated areas 
such as rice fields, farms, and forests, this limitation is not 
applied when the line is constructed so that there are no risks for 

    A description of the technical basis for this 3 kV/m standard 
is provided by the Japan IERE Council (1976).  The standard is 
based on the electrostatic induction sensed by a person who has his 
cheek or finger in contact with the metallic part of the grip of an 

    In Poland (1980), the electromagnetic radiation standard for 
frequencies from 0.1 - 300 000 MHz, includes a limit on electric 
field strength at the single frequency of 50 Hz.  The standard, 
effective from 31 January 1980, establishes two "safety" zones.  
For exposure to 50-Hz electric fields, the zones are: 

    1st zone (electric fields above 10 kV/m) - prohibited to
    everyone except workers in electrical substations and
    personnel working on power lines;

    2nd zone (above 1 kV/m to 10 kV/m) - agriculture and
    recreational activities are allowed, but not the
    construction of housing, hospitals, schools or
    kindergartens, except where buildings and farms existed
    before the regulations were established.

The standard provides details of administrative controls, approval 
procedures and electromagnetic field measuring authorities.  
However, no rationale for the values in the standard appear to have 
been published. 

    In the USA, there are a number of different standards with 
regard to the control of electric fields at the edge of RoW (see 
Glossary for definition) for high-voltage transmission lines.  
General population and media pressure have prompted public hearings 
and extensive debate over health effects from these lines.  The US 
Department of Energy, Bonneville Power Administration (BPA) has a 
criterion on electric field exposure levels that results in a low 
probability of human perception or annoyance from field effects 
(Lee et al., 1982).  BPA allows a maximum of 9 kV/m on the RoW, 
when measured 1 m above the ground (Lee et al., 1982).  It would 
seem that the rationale for setting the 9-kV/m level is so that 
induced body currents in human beings under the lines will not 
exceed the current permitted by the National Electric Safety Code 
(5 mA rms). 

    All 50 states in the USA have some legislation for regulating 
the safety of the general population in the proximity of 
transmission lines.  Of these, 25 states have enacted legislation 
requiring the preparation of environmental impact statements for 
proposed overhead transmission lines with respect to electrical 
effects.  A comprehensive study was completed by the state of New 
York (1979), in which testimony indicated potential impacts from 
audible noise and from electrostatic shocks that people can receive 
when they touch a large vehicle parked under the lines.  The 
testimony failed to demonstrate biological hazards from the field, 
though further research is necessary to understand better the 
effects of the fields on biological systems. 

    Many of the state regulatory agencies have carried out similar 
studies (Shah, 1979; Montana, 1983) reaching the same basic 
conclusions as New York (1979).  Guidelines from each state on the 
maximum electric field permitted at the edge of the RoW differ, but 
are within the range of 1 - 3 kV/m (Table 12).  Guidelines for 
maximum field strength within the RoW varied from 7 to 11 kV/m.  
Most states comply with the National Electric Safety Code (NESC), 
which restricts currents in the human body to no more than 5 mA 

Table 12.  Recommended electric field levels for high-voltage
transmission lines in the USAa
              Max E field (kV/m)
State         In RoW    Edge RoW  Comments       Reference
Minnesota     8         -         Resolution     Shah (1979)

Montana       -         1         Resolution     Montana (1983)

New Jersey    -         3         Resolution     New Jersey (1981)

New York      -         1b        Temporary      New York (1978)
                                  resolution -           
                                  new EHV lines

              7         -         Public roads   Shah (1979)

              11        -         Private roads  Shah (1979)

North Dakota  9         -         Resolution     Shah (1979)

Oregon        9         -         State law      Shah (1979)
a  From:  Repacholi (1984a).
b  1 kV/m for flat terrain - use 1.6 kV/m as criterion (Sheppard 
   (1983), personal communication).

Note:  Most states have adopted NESC (5mA rms).

    Only two states in Australia, Victoria and New South Wales, 
have guidelines for the construction of 500 kV HV transmission 
lines (Table 13). 

    In Victoria, the State Electricity Commission designs the 500 
kV lines so that the electric field does not exceed 10 kV/m in the 
RoW or 2 kV/m at the edge of the RoW, when measured 1 m above the 
ground.  Workers in switch-yards are normally restricted to 
exposures below 10 kV/m, wherepractical. 

    The rationale for their guideline, contained in Johnson et al. 
(1976), was also based on the fact that these values were generally 
acceptable in many other standards, including the Soviet standard 
(USSR, 1975). 

Table 13.  Guidelines for constructing 500 kV high voltage
transmission lines in Australiaa
State                                 Max. E field (kV/m)          
                              In RoW                       Edge RoW
New South Walesb              -                            2

Victoria                      10                           2
a  From: Repacholi (1984a).
b  Personal communication, Sydney, Australia, Electricity 
   Commission of New South Wales.

    The Electricity Commission of New South Wales has an internal 
design standard for 500-kV HVAC lines that states that the electric 
field strength at the edge of the RoW should not exceed 2 kV/m.  
However, in practice, the RoW is made sufficiently wide that values 
of 0.5 kV/m are not exceeded at its edge. 


9.1.  Goals

    This criteria document does not recommend specific values for 
electric-field standards, but where a health agency finds that 
standards are necessary, it provides guidance on the development of 

    It is understood that standards may be required when it is 
necessary to ensure that physical agents are not introduced into 
the environment at levels that may reduce the quality of life.  The 
overall assessment of the impact of electric power on the quality 
of life involves the balance of positive and negative factors 
implicit in a cost-benefit analysis.  At this time, a cost-benefit 
analysis cannot be conducted with quantitative precision. 

9.2.  Groups to be Protected

    Protective measures may be considered for electrical utility 
workers exposed near substations, transformers, capacitors, and 
circuit breakers or workers exposed near live power transmission or 
distribution conductors.  Depending on the equipment, individual 
policies and worker/job classifications, the extent of exposures 
may vary widely, requiring careful review by each affected 
organization.  Workers primarily involved with communications 
facilities may also be affected.  In cases where joint facilities 
are used (e.g., high-voltage lines near or having common RoWs with 
low-voltage communications lines), the communications workers may 
be considered together with electric power utility workers.  Workers
in industry may also be affected, principally through magnetic 
field exposures from low-frequency induction heaters and furnaces, 
large motors, transformers, and similar devices to which personnel 
are exposed, often at close proximity. 

    Exposure of the general population occurs during occasional 
visits to electrical utility facilities, often for recreation in 
RoWs or, in the case of farmers, for work.  Exposures also result 
from living in the vicinity of a high-voltage transmission line, in 
the course of using electrical appliances, and generally as an 
essential aspect of the widespread use of electric power for 
illumination and power.  It should be noted that high-voltage 
direct current transmission also involves alternating currents as a 
result of the AC/DC conversion process.  These currents occur at 
several harmonic frequencies in the range below 1 kHz at amplitudes 
that are much below the level of direct currents.  The specific 
conversion technology and its operational mode must also be 

    At present, protective measures for the general population are 
at issue with respect to dwellings located near power-transmission-
line corridors.  Exposures that originate in the home or home 
environment are generally weak and exposures to appliance-generated 
fields are very intermittent.  Although they are not thought to be 
of concern, they have not been closely studied. 

9.3.  Protection Rationale

    Occupational exposures among utility workers have been 
characterized in data reviewed by Knave et al. (1979) and Male et 
al. (1982).  Relatively few hours are spent in fields at levels 
above 5 kV/m, in any job.  In fields above 10 kV/m, workers are 
subject to recognised influences of perceptible shock discharges, 
that reduce worker comfort and increase the possibility of 
accidents with tools or accidents arising from faulty judgement. 

    The following protective measures can be taken with regard to 
workers in fields of about 10 kV/m or more: 

    (a) the designing of equipment to reduce the likelihood
        of large potential differences or large current flow
        between a person and conducting objects;

    (b) reduction of daily duration of exposure in proportion
        to the degree of discomfort experienced; since job
        assignments, weather, and clothing appear to be major
        factors, rules can be developed on the basis of
        practical experience;

    (c) use of devices or clothing that reduce the strength
        of electric fields acting on the body; particular
        attention should be paid to the protection of linemen
        working on HV lines with the bare-hand method, when
        the total residual body current should not exceed
        values that arise from exposure to external field
        strengths of less than 10 kV/m.

    Electric field exposure up to 20 kV/m, apart from effects due 
to shocks, is not believed to be an occupational hazard on the 
basis of information now available.  For this reason, protective 
measures, apart from an altered work schedule, are not suggested in 
fields below 20 kV/m.  Although an occupational hazard is not 
established in fields above 20 kV/m, as a prudent measure it is 
suggested that attempts should be made to reduce exposures to 
levels where no unacceptable discomfort occurs. 

    In view of the fact that there is no health effect that could 
be attributed specifically to ELF exposure, it is not practicable 
to recommend any specific medical examinations, apart from those 
that may be appropriate for electrical fitters and linemen in 


ALTERNATING CURRENT:  an electric current varying sinusoidally
in time.

ALTERNATING ELECTRIC FIELD:  the electric field produced by a
sinusoidally-oscillating electric charge.

ALTERNATING VOLTAGE:  a voltage varying sinusoidally in time.

BIOPHYSICAL:  relating to the physical properties of biological
systems, e.g., the conductivity of tissue or its permittivity
are biophysical quantities.

CIRCADIAN RHYTHM:  daily cycle of certain physiological
processes such as activity, temperature, and as indicated by
the levels of electrolytes, hormones, etc., in body fluids or
tissues.  More generally, the term refers to a periodic
physiological or biochemical change.

CONTROLS:  animals, tissues, etc., not subjected to the field
or other experimental treatment (see also SHAM-EXPOSED).

CURRENT DENSITY:  the flow of electric current across a unit
area, a measure of the distribution of current within the
object or body tissues measured in amperes per square metre
(A/m2), or microamperes per square centimetre (µA/cm2).

EARTH:  electrical ground.

EFFECTIVE FIELD:  the time-averaged electric field to which a
biological system is exposed; this field is less than the
unperturbed field because of mutual shielding, e.g., by
animals housed as a group.

ELECTRIC FIELD:  concept used to represent the force exerted on
the unit charge due to the location of electric charges at
various sites in a region; the high-voltage-transmission lines
electric field is an alternating (50- or 60-Hz) field due to
the sinusoidally-oscillating charges located on the conducting
wires of the transmission line.  Electric fields are capable
of performing work on other electric charges moving between
points at different potential.

ELECTRIC-FIELD STRENGTH:  magnitude of the electric field,
measured in volts per metre; (see VOLT PER METRE).  The electric-
field strength beneath a HV transmission line is generally 
measured at a fixed height above ground (usually 1 m).

ELF:  abbreviation for extremely low frequency.

EXTREMELY LOW FREQUENCY:  a frequency between 3 and 300 Hz; but
defined in this document as any frequency below 300 Hz.


FARADAY SHIELD CAGE:  grounded cage made of conducting material
used to enclose an object subjected to an electric field; the
shield, usually composed of metal (eg., copper wire); reduces
the electric field strength inside the cage to nearly zero.

FIELD:  a region of space in which certain phenomena occur,
described by a scalar or vector quantity, the knowledge of
which allows the effects of the field to be evaluated.

FREE SPACE:  an ideal, perfectly homogeneous medium that
possesses relative dielectric and magnetic constants of unity,
and in which there is nothing to reflect, refract, or absorb
energy.  A perfect vacuum possesses these qualities.

GROUND:  zero potential, electric earth.

HERTZ (Hz):  the unit of frequency for a periodic oscillation
corresponding to a complete oscillation per second (ops) or
cycle per second (cps).

HIGH TENSION LINE:  a high-voltage transmission line.

HORIZONTAL ELECTRIC FIELD:  an electric field directed parallel
to the Earth's surface; in the laboratory, such fields are
created by vertical plates.

HVTL:  high-voltage transmission line; typically one operating
at or above 345 kV.

IMPEDANCE:  the physical property of a material that determines
the relation between current flow and potential difference in
the material; for direct currents, impedance is identical to
resistance; for alternating currents impedance includes the
properties of resistance, capacitance, and inductance.

IMPEDANCE TO GROUND:  an impedance measured between an object
and earth (ground); in caged laboratory animals, this property
depends on the caging materials, construction, and electrical
design, and the biophysical properties of the animal's
footpad; for human beings, skin, clothing, or shoe properties
are significant.

INTERNAL ELECTRIC FIELD:  electric-field strength measured or
calculated for points within the body of an animal or human
being exposed to an external electric field.

MAGNETIC FIELD:  a concept to describe the force exerted on a
unit current produced by moving electrical charges, such as
those in an electrical current; the transmission line magnetic
field is due to the flow of current in the wires.  A magnetic
field exerts a force on moving electric charges, such as those
in another wire-carrying current or in a moving wire (dynamo
principle) always perpendicular to the direction of motion.

MICRO:  prefix for 10-6; e.g., microvolt, microampere,
micrometre; symbol - µ (Greek letter mu).

MILLI:  prefix for 10-3; e.g., millivolt, milliampere; symbol - m.

NANO:  prefix for 10-9; symbol - n.

NEUROPHYSIOLOGICAL:  relating to the function of the nervous
system, e.g., peripheral nerves, the brain, spinal cord, the
sub-divisions of those organs and their cellular components,
including the nerve fibres.

PHASOR (vector):  a phasor is a complex number.  It is used in
connection with quantities related to the steady alternating
state in a linear network or system.

PICO:  prefix for 10-12; symbol - p.

PULSE POWER:  the power averaged over the duration of a single pulse.

PULSE REPETITION RATE:  the rate, usually given in cycles (or
pulses) per second, at which pulses are emitted by a pulse

PULSE WIDTH:  the duration of a pulse in the time interval
between the points on the leading and trailing edges.

RIGHT-OF-WAY (RoW):  the provision of access to power lines for
inspection and maintenance purposes; the concept varies from
one country to another.  It may take the form of the ownership
of land over which the power line passes, or the statutory
control of access to this land, or the negotiation of
agreements with the landowners.  In some countries, the
right-of-way applies to a corridor (strip of land), of a
certain width, along the transmission line, in which the
public access or property rights may be restricted.

rms:  root mean square, the square root of the temporal average
over a period of the square of the field strength magnitude.

SCALAR:  a quantity that is completely specified by a single number.

SCALING:  relating an exposure of one animal species to another
so that the effect of the electric field can be interpreted on
an equal basis; because of shape- and orientation-dependence
for both internal and external fields, human beings and
animals exposed to the same unperturbed field have very
different surface and internal fields.

SHAM-EXPOSED:  a control experimental condition in which the
animals, tissues, etc., are treated identically to the exposed
objects, except that the field or other treatment is not
present; distinguished from "controls" by the use of apparatus
that is in all ways identical to the exposure apparatus which
is not operating.

SPECTRAL CHARACTERISTICS:  the frequencies and amplitudes
inherent in a particular electric or magnetic field as
revealed by a mathematical or experimental technique that
"decomposes" the signal into its component frequencies and
field strengths (Fourier analysis).

SURFACE ELECTRIC FIELD:  the electric field at the outer margin
of the object or body; this field is influenced by the shape
and configuration of a conducting body and, depending on the
degree of curvature, is locally greater than the unperturbed
electric field.

TERATOLOGICAL:  relating to abnormal anatomy, resulting in
deformities, fetal death, still birth, etc., especially in a
developing or newborn organism.

UNPERTURBED ELECTRIC FIELD:  the field that would exist at the
body's location if there were no body located in the electric
field.  In the case of a uniform field, the field that exists
far from the location of a conducting object (such as the
human or animal body).

VECTOR:  a mathematical-physical quantity that represents a
vector quantity - it has magnitude and direction.

VECTOR QUANTITY:  any physical quantity in which specifications
involve both magnitude and direction and which obeys the
parallelogram law of addition.

VERTICAL ELECTRIC FIELD:  an electric field directed
perpendicular to the Earth's surface; in the laboratory, such
fields are created by horizontal electrodes.

VOLT PER METRE:  unit of electric field strength; a field of
one volt per metre is created in the centre of the midplane of
two parallel plates separated by 1 metre and having a
potential difference of 1 volt.


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The electromagnetic environment in the homea
A.    60-Hz electric-field strengths at the centre of various rooms in a
      typical home in the USA in 1974

      Room                                           V/m

      Laundry room                                   0.8
      Dining room                                    0.9
      Bathroom                                       1.2 - 1.5
      Kitchen                                        2.6
      Bedrooms                                       2.4 - 7.8
      Living room                                    3.3
      Hallway                                        13.0

B.    Typical values of electric-field strength (V/m) from 115-V, 60-Hz
      home appliances (USA) at 30 cm from source

      Electric blanket                               250b
      Broiler                                        130
      Stereo                                         90
      Refrigerator                                   60
      Electric iron                                  60
      Hand mixer                                     50
      Toaster                                        40
      Hair Dryer                                     40
      Colour TV                                      30
      Coffee pot                                     30
      Vacuum cleaner                                 16
      Incadescent light bulb                         2

C.    Localized 60-Hz magnetic flux densities in the vicinity (a few cm)
      of some electric appliances (mT)

      1 - 2.5      325 watt soldering gun
                   Hair dryer

      0.5 - 1.0    Can opener
                   Kitchen range
                   Electric shaver
                   Fluorescent desk lamp

      0.1 - 0.5    Colour TV
                   Food mixer
                   Electric drill

      0.01 - 0.1   Garbage disposal
                   Clothes dryer
                   Vacuum cleaner
                   Electric toaster

APPENDIX I (contd.)
D.    Leakage currents passing through the body to earth from household
      appliances (mA); the values should be compared to ANSI standards for
      fixed appliances (750 mA) and for cord-connected appliances (500 mA)

      Coffee mill                                     380
      Refrigerator                                    40
      Sewing machine                                  34
      Coffee pot                                      6

E.    Induced currents flowing in the earthed arm of an 80-kg, 1.75-m
      human being with a heating pad or electric blanket in a
      representative location

      Heating pad                                     18 µA
      Electric blanket                                7 - 27 µA

F.    Typical  values  of   measured   dispersed  ambient   magnetic  flux

      Location                                         Magnetic Flux Density

      University of Pennsylvania Hospital              0.2 - 0.4; 60 Hz
      Princeton Hospital                               0.03 - 0.1; 60 Hz
      Park Falls (Wisconsin) Hospital                  0.05 - 0.8; 60 Hz
      Industrial Plant, Park Falls (Wisconsin)         0.3 - 6; 60 Hz
      Scientific Laboratory, Pensacola, Florida        0.5 - 1; 60 Hz
      IIT Research Institute office areas              5; 60 Hz
      Stamford (Conneticut) railroad station           2 - 20; 25 Hz
      Private dwelling                                 0.1 - 10.l; 60 Hz
a  From: Miller (1974), Bridges (1975), Sheppard & Eiisenbud (1977),
   Atoian (1978), Bridges & Preache (1981).
b  Actual human exposure would be higher since the blanket would be at a
   distance of less than 30 cm.
c  From: Miller (1974).


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    See Also:
       Toxicological Abbreviations