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173
Biological effects of non-ionizing
electromagnetic energy: A critical
review of the reports by the
US National Research Council
and the US National Institute of
Environmental Health Sciences as
they relate to the broad realm of
EMF bioeffects
Magda Havas
Abstract: Our dependence on electricity and our growing dependence on wireless telecom-
munication technology is causing this planet to be inundated with electromagnetic energy
ranging in frequency from less than 60 Hz to greater than 2 GHz. Concerns expressed by
the public, who live near power lines, cell phone antennas, or television and radio broadcast
towers, have prompted two major reviews: one by the US National Research Council (NRC)
and the other by the US National Institute of Environmental Health Science (NIEHS). Both
of these documents deal with the biological and health effects primarily in a residential
setting of extremely low frequency (ELF) or power frequency (50 and 60 Hz) fields. This
paper critically evaluates the NRC and NIEHS documents. This evaluation includes both the
content and the process leading to the final reports. It summarizes the information available
on human exposure to electric and magnetic fields and identifies key biological markers
and potential mechanisms that have been linked to electromagnetic exposure. It examines
the conclusions of both documents in terms of the slightly broader realm associated with
occupational exposure, non-power frequency fields, EMF hypersensitivity, and response
of species other than humans. It presents some of the scientific controversy surrounding
the question “Are low frequency electric and magnetic fields harmful?” and examines the
concepts of bias and consistency in data interpretation. This paper also attempts to place
the discussions about technologically generated fields (technofields) into a much broader
perspective, a perspective that includes naturally occurring geofields and biofields.
Key words: leukemia, breast cancer, melatonin, calcium flux, extremely low frequency
electromagnetic fields, radio frequency radiation.
Résumé: Notre dépendance de l’électricité et notre dépendance croissante des technologies
de communication sans fils conduisent à une inondation de la planète par l’énergie électro-
magnétique, de fréquences de moins de 60 Hz à plus de 2 GHz. Les préoccupations des
Received June 28, 1999.Accepted March 13, 2000. Published on the NRC Research Press web site on
October 11, 2000.
M. Havas. Environmental & Resource Studies,Trent University, Peterborough, ON, Canada K9J 7B8
(e-mail: mhavas@trentu.ca).
Environ. Rev. 8: 173–253 (2000) © 2000 NRC Canada
174 Environ. Rev. Vol. 8, 2000
gens qui vivent à proximité des lignes de transport d’électricité, des antennes de téléphones
cellulaires, ou des tours d’émission de radio et de télévision, ont provoqué la mise sur
pied de deux programme d’évaluation de leurs effets, aux Etats-Unis : le premier par le
Conseil national de recherches (NRC), et le second par l’Institut national des sciences
de l’environnement et de la santé (NIEHS). Les deux rapports traitent des effets sur la
biologie et la santé, surtout dans des environnements résidentiels exposés à des fréquences
extrêment basses (ELF) ou à des champs de fréquences énergétiques (50 et 60 Hz). L’auteur
présente une revue critique des rapports des NRC et NIEHS américains. Cette évalution
fait état des contenus ainsi que des processus qui ont conduit à ces rapports finaux. On
résume l’information disponible sur l’exposition des humains aux champs électriques et
magnétiques, et on identifie des marqueurs biologiques clés et des mécanismes possibles
qui ont été reliés à l’exposition aux ondes électromagnétiques. On examine les conclusions
des deux rapports en termes d’une réalité un peu plus large associée aux expositions
occupationnelles, aux champs de fréquences non-énergétiques, à l’hypersensibilité aux EMF,
et à la réaction de d’autres espèces que les humains. On fait état de quelques controverses
scientifiques entourant la question « Les basses fréquences électriques et les champs
magnétiques sont-ils nuisibles? » et on examine les concepts de biais et de congruence
dans l’interprétation des données. Cette revue tente également de situer la discussion sur les
champs technologiquement générés (technofields) dans une perspective beaucoup plus large
incluant les champs géologiques (geofields) et les champs biologiques (biofields) d’origine
naturelle.
Mots clés: leucémie, cancer du sein, mélatonine, flux calcique, champs électromagnétiques à
fréquences extrêment basses, radiation des radio fréquences.
[Traduit par la Rédaction]
1. Introduction
The biological effects of low frequency electric and magnetic fields (EMF) have become a topic
of considerable scientific scrutiny during the past two decades. The flurry of research in this area has
contributed greatly to our understanding of the complex electromagnetic environment to which we are
exposed but it has not resolved the controversy over whether the effects are harmful. If anything it has
polarized into two camps the small group of scientists concerned with health effects: those who think
exposure to low frequency electromagnetic fields causes adverse health effects and those who do not.
Those who believe there is a causal association are trying to find the mechanisms responsible and those
who question the concept of causality think this research is a waste of time and money. In contrast,
the majority of scientists in this field are concerned with the science and not health effects, and they
recognize that the data show there are effects that are of interested from the standpoint of basic research.
Controversy is the norm when complex environmental issues with substantial economic and health
consequences are scientifically scrutinized. Asbestos, lead, acid rain, tobacco smoke, DDT, PCBs (and
more recently estrogen mimics) were all contentious issues and were debated for decades in scientific
publications and in the popular press before their health effects and the mechanisms responsible were
understood. In some cases the debate was scientifically legitimate while in others interested parties
deliberately confused the issue to delay legislation (Havas et al. 1984).
The public, uncomfortable with scientific controversy and unable to determine the legitimacy of a
scientific debate, wants a clear answer to the question, “Are low frequency electric and magnetic fields
harmful?”
As a direct response to public concern two major reports have been published recently on the
health effects of low frequency electric and magnetic fields. The first, published in 1997 and entitled
Possible Health Effects of Exposure to Residential Electric and Magnetic Fields, was conducted by an
Expert Committee of the US National Research Council. The second, Assessment of Health Effects from
Exposure to Power-Line Frequency Electric and Magnetic Fields, published 1 year later, was a Working
Group Report of the US National Institute of Environment Health Sciences.
These reports attempt to make sense of the many (and what sometimes appears to be contradictory)
©2000 NRC Canada
Havas 175
results from different fields of study, related to the health effects of power-line frequency fields. They
can be considered state of the art reports on health effects of low frequency (50 and 60 Hz) electric and
magnetic fields and are likely to be highly influential documents. For this reason, it makes sense to start
a review on the biological effects of electromagnetic fields with these two reports.
Henceforth, the two documents, cited below, will be referred to as the NRC and NIEHS Reports.
National Research Council (US) Committee on the Possible Effects of Electromagnetic
Fields on Biologic Systems. 1997. Possible Health Effects of Exposure to Residential Elec-
tric and Magnetic Fields, NationalAcademy Press, Washington, D.C., 356 pp.
Portier,C.J.,andWolfe, M.S. (Editors). 1998c.Assessment of HealthEffectsfromExposure
toPower-LineFrequencyElectricandMagneticFields.NationalInstituteofEnvironmental
Health Sciences Working Group Report of the National Institutes of Health. NIH Publica-
tion No. 98-3981, Research Triangle Park, N.C., 508 pp.1
However, these documents, instead of illuminating the biological effects of electromagnetic fields,
cast a spotlight only on a small part of the electromagnetic spectrum and only on a portion of the EMF
debate, and for that reason they need to be placed in perspective. So, while this review will begin with
the NRC and NIEHS documents it will not end with them.
The purpose of the present paper is 4-fold:
(1) to evaluate the NRC and NIEHS documents including the content and the process leading to the
final report
(2) to characterize human exposure to electric and magnetic fields
(3) to identify key biological markers and mechanisms that have been linked to EMF exposure and
to assess the degree of confidence associated with each
(4) to examine the conclusions of both reports in terms of the slightly broader area of biological
effects associated with
(i) occupational exposure rather than just residential exposure
(ii) frequencies other than those associated with power distribution (from static fields to those
generated by wireless communication technology in the microwave region of the electro-
magnetic spectrum)
(iii) hypersensitivity to electromagnetic energy
(iv) response of species other than humans
The question “Are low frequency electric and magnetic fields harmful?” is valid and timely. The answer
is likely to have far reaching consequences, considering our growing dependency on electric power,
computertechnology,andwirelesstelecommunication,andislikelytobeofinteresttoalargepopulation
using, manufacturing, selling, and regulating this technology.
2. Background information
In the broadest sense, research involving electromagnetic energy can be classified into three cate-
gories based on the source of that energy. Public concern is focused on electromagnetic fields generated
by our technology, which I call technofields. These include radiation and fields produced by power
1On December 3, 1998, the Department of Health and Human Services sent out an Erratum for the EMF Working Group Report.
Those corrections are included in this review.
©2000 NRC Canada
176 Environ. Rev. Vol. 8, 2000
distribution networks, by computers and microwave ovens, by cell phones and wireless communication
towers, and by satellite communication systems worldwide.
In addition to these technofields, all living organisms are also exposed to naturally produced elec-
tromagnetic fields/radiation generated by the earth, the sun, and the rest of the cosmos, which I call
geofields. Geofields are naturally occurring abiotic fields that have components that are unpredictable
in their fluctuations (solar eruptions), cyclic (diurnal, seasonal), and relatively stable (earth’s magnetic
field).
The third field is generated by all living organisms during any form of metabolic activity, which I
call biofields. Most of the research has focused on either electric or magnetic fields generated by the
heart, brain, and nerve cells. Biofields tend to be much weaker than either geofields or technofields but
can be measured and have been used to monitor metabolic activity and to diagnose ill health. Some even
claim that these biological energies can be used to restore energy imbalance and to heal (therapeutic
touch, reiki, acupressure). Biofields have been recognized since ancient times and have been called,
among other things, subtle energy, acupuncture points and meridians, prana, aura, chi, and chakras.
These three sources of electromagnetic energy, depicted as three overlapping Venn diagrams in
Fig. 1, interact and it is these interactions that most interest us. Solar flares may be sufficiently powerful
to knock out satellites or to disrupt power distribution, as happened on March 13, 1989, during a
particularly powerful solar storm when the province of Quebec was plunged into darkness (Kappenman
1996). The ionosphere reflects certain electromagnetic frequencies, much like a mirror reflects light,
and enables short-wave radio communication across the globe. Both of these are examples of geofield
and technofield interactions. The interactions in Fig. 1 are not intended to be all inclusive but rather to
provide a broad range of potential field interactions, a number of which have yet to be scientifically
investigated.
The areas of current debate are the interactions between living organisms and technologically gener-
ated fields at power line frequencies (60 Hz in NorthAmerica and 50 Hz elsewhere) and at frequencies
generated by computers, cell phones, etc., in the kilo (103), mega (106), and giga (109) hertz range
(Fig. 2).
Until recently, frequencies below the microwave band were assumed to be “biologically safe.”This
began to change in the 1960s and early 1970s when the Soviet Union reported health effects experienced
by their high voltage switchyard workers (Korobkova et al. 1972).
Within several months of the first 500 kV substation becoming operable in the Soviet Union, mainte-
nance workers complained of headaches, reduce sexual potency, and general ill health. The electric field
was assumed to be responsible for the health complaints. Personnel working with 500 and 750 kV lines
were compared with workers at 110 and 220 kV substations. Maximum intensities within the 500 and
750 kV switchyard were generally between 15 and 25 kV/m and biological effects were reported above
5kV/m.The report states that acurrent of “80–120 µAflowingthrough a man for a longtime affects him
unfavorably.” No specific details are presented. The document recommends methods of screening and
provides a time limit for daily exposure as follows: unlimited exposure at 5 kV/m, 180 min at 10 kV/m,
90 min at 15 kV/m, 10 min at 20 kV/m, and 5 min at 25 kV/m. This document, one of a series on the
effects of 500 and 750 kV substations on workers, received little attention in the West. It took another
decade for the West to document the harmful effects of high voltage power lines on substation workers
and their families (Nordstrom et al. 1983; Nordenson et al. 1984). These documents are presented later
in this report.
It was not until Nancy Wertheimer and her colleague, Ed Leeper, reported an increased incidence
of childhood leukemia, lymphoma, and nervous system tumors associated with residential exposure to
power line frequency fields in Denver, Colorado, that the West began to take notice (Wertheimer and
Leeper 1979). Paul Brodeur did much to publicized this type of information in The NewYork Times and
elsewhere (see Brodeur 1993), alerting the public and enraging members of the scientific community
who were unwilling to accept the Wertheimer and Leeper results.
©2000 NRC Canada
Havas 177
Fig. 1. Examples of interactions of electromagnetic fields generated by geofields (G), biofields (B), and technofields (T).
©2000 NRC Canada
178 Environ. Rev. Vol. 8, 2000
Fig. 2. Electromagnetic spectrum showing frequencies from ionizing radiation to direct current. Selected tech-
nologies and the frequencies at which they operate are shown. (Reprinted with permission from EMF Rapid 1996,
Questions and answers: EMF in the workplace.)
The Wertheimer and Leeper study was repeated in various locations, and by the early 1990s more
than a dozen studies were published on childhood cancer.While some studies found no effects (Fulton
et al. 1980; Verkasalo et al. 1993, 1994; Tynes and Haldersen 1997), others confirmed the Wertheimer
and Leeper results (NRPB 1992; Ahlbom et al. 1993; Washburn et al. 1994; Feychting et al. 1995;
Meinert and Michaelis 1996; Linet et al. 1997; Michaelis et al. 1998).
©2000 NRC Canada
Havas 179
Studies of childhood cancers were followed by studies of adult cancers in occupational as well
as residential settings and by effects of electromagnetic fields on reproduction. Residential exposure
was associated with miscarriages (Wertheimer and Leeper 1986, 1989) while occupational exposure
was linked to various reproductive problems as well as adult cancers, including primary brain tumors,
leukemias, and breast cancer among both men and women (Lin et al. 1985; Goldhaber et al. 1988;
Demers et al. 1991; Matanoski et al. 1991; Floderus et al. 1993; Floderus et al. 1994; London et al.
1994; Loomis et al. 1994; Cantor et al. 1995; Savitz and Loomis 1995; Coogan et al. 1996; Miller
et al. 1996; Feychting et al. 1997; Kheifet et al. 1997). Members of the scientific community, seeing
similarities between childhood and adult cancers, became greatly concerned.
One major problem with the epidemiological studies was that information on exposure was scarce.
Wire codes were used to provide a surrogate metric for the magnetic field. Once portable gauss meters
sensitive to power line frequencies became available, the spot measurement and 24-h monitoring sup-
plemented the wire codes. Of these three methods, the wire codes are highly associated (as measured
by odds ratios or relative risk) and the spot measurements are poorly associated with magnetic field
exposure and health effects in epidemiological studies (London et al. 1991; Feychting andAhbol 1993;
Savitz et al. 1988). The odds ratio (OR) and relative risk (RR) are two metrics epidemiologists use
to compare a test population (observed) with a control population (expected) for a specific endpoint
(cancer, for example). The higher the OR (ratio of observed to expected), the greater the association
between an agent and an end point.
In the past decade appliances, rooms, and houses have been monitored and we have a much better
understanding of the magnetic flux density to which we are exposed (EPA 1992; EPRI 1993 as cited
in NRC 1997). Whether magnetic flux density is the only biologically important metric or, indeed, the
one we should be measuring remains to be determined.
The epidemiological studies were complemented by in vivo and in vitro studies that explored the
mechanisms responsible for the biological effects of electromagnetic fields. Because of the novelty of
this type of research there were (and still are) no standardized protocols for testing. In the literature
experimental intensities for magnetic flux density range from less than 0.1 µT to greater than 300 mT;2
dailyexposurevariesfrom30 min to 24 h; andduration of exposure extends from days to years(Ekstrom
et al. 1998; Beniashvili et al. 1991; Loscher et al. 1994; Mevissen et al. 1996, 1998a,b; NTP 1998).
Some of the tests involve continuous, homogeneous fields, others involve gradients, and still others use
intermittent fields (pulsed or digital) with on:off cycles ranging from seconds to hours. Interpreting such
a wide array of exposure conditions is not an easy task. With an understanding of all of these difficulties,
the NRC and the NIEHS committees examined the literature. What follows is a review of these two
documents: the mandate, the process, and the conclusions.
3. Process used by the National Research Council and the National
Institute of Environmental Health Science
3.1. Mandate
The NRC and NIEHS were charged by Congress to review the scientific literature and to assess
the biological effects of exposure to low frequency electromagnetic fields. Although these reports were
independent of each other, several members served on both committees and both committees liaised
with the US Department of Energy.
2The strength of the magnetic field, technically referred to as “magnetic flux density” and represented by the symbol “B”is
measured in units of tesla (T) in the preferred SI system and in units of gauss (G) in the cgs system. One T is equal to 10 000 G.
To place these units into perspective, the earth’s “average” magnetic field is about 50 µT (500 mG); fields under power lines
are in the order of 1 µT (10 mG), fields associated with childhood cancers are above 0.2 µT (2 mG), and the fields generated
by living cells are considerably less than 0.001 µT (0.01 mG).
©2000 NRC Canada
180 Environ. Rev. Vol. 8, 2000
National Research Council mandate
The specific mandate placed before the NRC Expert Committee is the following (NRC 1997, p. 1):
(1) To reviewandevaluatetheexistingscientificinformationonthe possible effects of ex-
posure to electric and magnetic fields on the incidence of cancer, on reproduction and
developmental abnormalities, and on neurobiologic response as reflected in learning
and behavior;
(2) To focus on exposure modalities found in residential settings; and
(3) To identify future research needs and to carry out a risk assessment insofar as the
research data justified this procedure.
National Institute of Environmental Health Science mandate
The National Institute of Environmental Health Sciences (NIEHS) was charged by Congress to
prepare and submit an evaluation of the potential human health effects from exposure to extremely low
frequency electric and magnetic fields (ELF EMF) (NIEHS Report 1998, p. iii). In addition to their
“evaluation” (which is the NIEHS Report, 1998), NIEHS funded research to address key questions
(some of those are presented in their final report) and sponsored three science symposia.
Comparison of the National Research Council and National Institute of Environmental Health
Science mandates
Both Committees focus on low frequency electric and magnetic fields (those associated with power
distribution at 50 and 60 Hz). Consequences of exposure to ionizing radiation, ultraviolet, visible,
infrared, microwave, and radio frequencies are not included in either report, except in a cursory fashion.
The mandate of the NRC Committee is much more restricted in its scope than that of the NIEHS
Committee. Occupational exposure is not part of the NRC Committee mandate, hence its brief, but
significant, discussion in the document does not appear anywhere in the Executive Summary. Other
sources of exposure within the home (appliances, for example) and outside the home (transportation)
are discussed in a much more cursory fashion in the NRC document than in the NIEHS document.
A narrow focus on power line frequencies in both reports (with insufficient assessment of higher
frequencies associated with cell phones, for example) and an absence of occupational exposure and
electromagnetic sensitivities in the NRC mandate are the key weaknesses.
Although not part of their mandate, both documents provide excellent summaries of the physics of
electric and magnetic fields; of exposure assessment; and of the advantages and limitations of in vitro,
in vivo, and epidemiological studies. They also summarize the bioeffects of electromagnetic fields as
studied in genotoxicology, neuroendocrinology, cellular communication/replication, and biophysics.
3.2. Participants and the selection process
Contributors to the National Research Council document
The Expert Committee, convened by the National Research Council (NRC), consisted of 16 mem-
bers, 9 with previous experience on the biological effects of EMFs and 7 new to this area but with
related expertise. No details are given about the selection criteria used. Four of the members served on
both the NRC and the NIEHS Committees, as indicated in Table 1.
©2000 NRC Canada
Havas 181
Number citeda
Name Affiliation Position and expertise NRC NIEHS
Charles F. Stevens
(Chair) Howard Hughes Medical Institute,
Salt Institute, La Jolla, Calif. Professor, neurobiology 0 0
David A. Savitz
(Vice-Chair) Department of Epidemiology,
University of North Carolina,
Chapel Hill, N.C.
Professor, epidemiology,
cancer and
reproduction
99
Larry E. AndersonbPacific Northwest National Labora-
tory, Richland, Wash. Staff Scientist,
neurochemistry 01
Daniel A. Driscoll Department of Public Service, State
of New York, Albany, N.Y. Professional Engineer,
electrical and
biomedical
00
Fred H. Gage Laboratory of Genetics, Salt
Institute, San Diego, Calif. Professor, central
nervous system
disorders
00
Richard L. Garwin IBM Research Division,
T.J. Watson Research Division,
Yorktown Heights, N.Y.
Fellow Emeritus, nuclear
physics 00
Lynn W. Jelinski Center for Advanced Technology-
Biotechnology, Cornell
University, Ithaca, N.Y.
Professor, nuclear
magnetic resonance 00
Bruce J. Kelman Health and Environmental
Sciences, Golder Associates, Inc.,
Redmond, Wash.
National Directory,
reproductive and
developmental
toxicology
00
Richard A. LubenbDepartment of Biomedical
Sciences, University of California
at Riverside, Riverside, Calif.
Associate Professor,
cellular and molecular
biology
42
Russel J. Reiter Department of Cellular and
Structural Biology, University of
Texas Health Sciences Center,
San Antonio, Tex.
Professor,
neuroendocrinology,
brain chemistry, repro-
ductive and behavioral
biology
93
Paul Slovic Decision Research, Eugene, Oregon,
and Department of Psychology,
University of Oregon
President and Professor,
risk analysis 10
Jan A.J. Stolwijk Department of Epidemiology and
Public Health, Yale University,
School of Medicine, New Haven,
N.C.
Professor, epidemiology 0 0
Maria A. Stuchly Department of Electrical and
Computer Engineering, University
of Victoria, Victoria, B.C.
Professor, numerical and
experimental modeling 54
Table 1. Members of the NRC Committee on the Possible Health Effects of Exposure to Residential
Electric and Magnetic Fields; primary affiliation and areas of expertise (NRC 1997).
©2000 NRC Canada
182 Environ. Rev. Vol. 8, 2000
Number citeda
Name Affiliation Position and expertise NRC NIEHS
Daniel WartenbergbDepartment of Environmental and
Community Medicine,
UMDNJ-Robert Wood Johnson,
Medical School, Piscataway, N.J.
Associate Professor,
epidemiology 21
John S. Waugh Department of Chemistry,
Massachusetts Institute of Tech-
nology, Cambridge, Mass.
Professor, nuclear
magnetic resonance 00
Jerry R. WilliamsbThe John Hopkins Oncology Center,
Baltimore, Md. Professor, oncology 0 0
aNumber of first-authored papers cited in the NRC and NIEHS Reports.
bServed as member on both NRC and NIEHS Committees.
Table 1. (concluded).
The following individuals presented papers at a workshop to aid the Expert Committee: Anders
Ahlbom (Karolinska Institute), Edward P. Washburn (DOE), Keith Florig (Resources for the Future),
JosephV. Brady (John Hopkins University),Robert L. Brent(DupontInstitute and the Jefferson Medical
College), Gary S. Stein (University of Massachusetts), James Weaver (MIT), Ken McLeod, who also
served as a member of the NIEHS Committee (State University of New York at Stonybrook), and Robert
Tardiff (E.A. Engineering Sciences and Technology, Inc.). Jay Lubin (National Cancer Institute), John
Tukey (Princeton University), and William Feero (Electric Research and Management Inc.) provided
statistical evaluation and exposure assessment.
Contributors to the National Institute of Environmental Health Science document
Members of the NIEHS Working Group were “selected carefully after screening by the NIEHS and
discussions with its two standing external advisory boards,” the National EMF Advisory Committee
and the EMF Interagency Committee (NIEHS, p. 8). No information on the specific selection criteria
is provided.
NationalInstitute of EnvironmentalHealth Science organizeda30-memberWorkingGroup(Table2)
who, in turn, did a comprehensive review of the data that included a review of more than 830 references.
They attended three science symposia and participated at a working group meeting held at Brooklyn
Park, Minnesota, 16–24 June 1998, during which time they wrote their report. The report was later
reviewed and edited for clarity by a science writer, E. Heseltine, an Associate Professor at Université
Lumiere. This 9-day report took 7 person-years of effort of which 4 person-years were attributed to the
summaries of the three science symposia.
Additional contributions were made by G.M. Blumenthal (NIEHS) and J.E. Morris (Battelle, Pa-
cific Northwest National Laboratories), who helped write the first draft, nine staff from the NIEHS,
two Technical Training specialists from OAO Corporation, Diana Phillips (personal Communication
Services Inc.), S.D. Linde (National EMF Advisory Committee), and Imre Gyuk (US DOE).
There were also 18 “Observers,” 2 listed as “private citizens” and the rest affiliated with either
privateenterprise, government, or research and publication groups. These affiliations include the Federal
Energy Regulatory Commission, US EPA, Office of Naval Research, IEEE-EMF Society, EMF Health
and Safety Digest, National Electrical Manufacturers Association, Minnesota Power, Northern States
Power Co., Inc., Research Institute of Electric Power, Edison Electric Institute, Caring Technologies,
Inc., Central United Illuminating, Watson & Renner, and Robert S. Banks Associates.
©2000 NRC Canada
Havas 183
Number citeda
Name Affiliation Position NIEHS NRC
M.A. Gallo (Chair) Department of Environmental and
Community Medicine, UMDNJ-Robert
Wood Johnson Medical School,
Piscataway, N.J.
Director and
Professor 00
A.L. Brown
(Vice-Chair) Department of Pathology and Laboratory
Medicine, University of Wisconsin at
Madison, Madison, Wisc.
Professor 0 0
C.J. Portier (Meeting
Coordinator) Laboratory of Computational Biology &
Risk Analysis and EMF Hazard Evalu-
ation, NIEHS, Research Triangle Park,
N.C.
Chief and
Coordinator 30
L.E. AndersonbBattelle, Pacific Northwest National
Laboratories, Richland, Wash. Research Scientist 1 0
J.D. Bowman National Institute for Occupation Safety
and Health, Taft Laboratories,
Cincinnati, Ohio
Research Industrial
Hygienist 50
E. CardiscUnit of Radiation and Cancer, Interna-
tional Agency for Research on Cancer,
Lyon Cedex, France
Chief 0 0
F.M. Dietrich Electric Research and Management, Inc.,
Pittsburgh, Pa. Principal Engineer 0 0
M.L. Dubocovich Department of Molecular Pharmacology
and Biological Chemistry, Northwest-
ern University Medical School,
Chicago, Ill.
Professor 1 0
J.S. FeltoncMolecular and Structural Biology Divi-
sion, University of California,
Livermore, Calif.
Division Leader 0 0
M. Feychting Institute of Environmental Medicine,
Karolinska Institute, Stockholm,
Sweden
Epidemiologist 8 2
P.C. Gailey Electric and Magnetic Fields Bioeffects
Research Program, Oak Ridge
National Laboratory, Oak Ridge, Tenn.
Director 1 0
C. Graham Department of Life Sciences, Midwest
Research Institute, Kansas City, Mo. Senior Advisor 0 0
G.J. Harry Laboratory of Toxicology, National Insti-
tute of Environmental Health Sciences,
Research Triangle Park, N.C.
Group Leader
(neurotoxicology) 00
L.I. Kheifets EPRI, Stanford, Los Altos Hills, Calif. Senior Scientist 4 0
R.A. LubenbDepartment of Biomedical Sciences,
University of California at Riverside,
Riverside, Calif.
Associate Dean of
Research 24
Table 2. Members of the NIEHS Working Group on the Assessment of Health Effects from Exposure to
Power-Line Frequency Electric and Magnetic Fields (NIEHS 1998).
©2000 NRC Canada
184 Environ. Rev. Vol. 8, 2000
Number citeda
Name Affiliation Position NIEHS NRC
M-O. Mattsson Department of Cellular and Developmen-
tal Biology, Umea University, Umea,
Sweden
Associate Professor 0 0
K.J. McLeod (pre-
sentationtoNRC
Committee)
Department of Orthopedics, State Univer-
sity of New York at Stony Brook,
Stony Brook, N.Y.
Associate Professor 9 0
S.C. MillerbSignal Transduction Program, Pharma-
ceutical Discovery Division, SRI
International, Menlo Park, Calif.
Director 2 0
M. MisakianbNational Institute of Standards and
Technology, Gaithersburg, Md. Physicist 3 3
C. PolkbDepartment of Electrical and Computer
Engineering, University of Rhode
Island, Kingston, R.I.
Professor Emeritus 9 6
W.R. RogerscEnvironmental Sciences, Department of
Family Practice, School of Public
Health, University of Texas, San
Antonio, Tex.
Associate Professor 5 1
A. Sastre Health Assessment and Research Center,
Midwest Research Institute, Kansas
City, Mo.
Principal Scientist 0 0
C.D. Sherman Department of Mathematics, San Fran-
cisco State University, San Francisco,
Calif.
Assistant Professor 0 0
L.E. Slesin Microwave News, New York, N.Y. Editor 0 0
R.G. Stevens Department of Molecular Biosciences,
Battele, Pacific Northwest National
Laboratory, Richland, Wash.
Staff Scientist 3 1
L. Tomatis Instituto Per L’Infanzia, Trieste, Italy Scientific Director 0 0
D. WartenbergbDepartment of Environment and Commu-
nity Medicine, UMDNJ-Robert Wood
Johnson Medical School, Piscataway,
N.J.
Associate Professor 1 2
J.R. Williamsa,cDepartment of Radiation Oncology, John
Hopkins University, Baltimore, Md. Professor of
Oncology 00
H. Yamasaki Unit of Multistage Carcinogenesis,
International Agency for Research on
Cancer, Lyon Cedex, France
Chief 0 0
M.G. Yost Department of Environmental Health,
University of Washington, Seattle,
Wash.
Associate Professor 3 2
P.L. ZweiackercEnvironmental Permitting, Texas Utilities
Services, Dallas, Tex. Manager 0 0
aNumber of first-authored papers cited in the NRC and NIEHS Reports.
bMember on both NRC and NIEHS Committees.
cCo-author of Minority Report.
Table 2. (concluded).
©2000 NRC Canada
Havas 185
Comparison of the National Research Council and National Institute of Environmental Health
Science committee membership
Two keyconcerns need to be addressedin any group deliberation: expertiseand bias.Are individuals
able to contribute their expertise about a certain issue; can they weigh the evidence fairly and then come
to a conclusion that is devoid of bias or prejudgment?
The first concern, that of expertise, is not an issue. Membership on the committees is diverse and
distinguished (Tables 1 and 2). Members cover a broad range of expertise, including epidemiology,
cancer research, neuroendocrinology, reproductive and developmental biology, physiology, physics,
engineering, and risk assessment. Some key individuals are missing but numbers need to be limited in
any selection process.
The second concern, that of bias, was a concern of the founding organizations as well. In the Preface
to the NRC Report the following statement is made:
Data are seldom sufficient to provide a definitive answer to the possible health effects of a
physical or chemical agent in the environment. In such cases, professional judgment plays
a large role in forming conclusions. It is especially important that the scientists selected for
the evaluations be open to the evidence about the issues to be studied, wherever it might
lead.
In my opinion there is evidence of bias in several chapters of the NRC Report. However, I am
unable to judge, based solely on the written text, the degree to which this is cultural bias, associated
with standards used by scientific subdisciplines, or prejudicial bias.
Whatis clear is astrong disagreement between the epidemiologistsand the cell/animal physiologists
evident in several chapters but particularly in the one on Risk Assessment. The signal-to-noise ratio for
much of the published literature is low and while the epidemiologists hear the signal, the physiologists
hear the noise and are thus unable to come to an agreement. If conclusions were based on majority vote
(as they were in the NIEHS Report) then the number of committee members in each subdiscipline may
be important. The democratic process of voting does not necessarily ensure truth in science since the
majority can be wrong.
3.3. Source of information
National Research Council references
The NRC document reviewed 520 references published from 1953 to 1996 with the majority of the
references published in the 1980s (38 %) and 1990s (51%) (Table 3). A paper had to be published in a
peer-reviewed journal for inclusion in this document.Technical reports delivered at scientific meetings
provided background information, but were not used to form judgments, with the exception of the US
Environmental ProtectionAgency (EPA) and Electric Power Research Institute (EPRI) publications on
exposure data (NRC p. 19).
In forming judgments, the members had more exacting criteria:
Thebody of evidence is weighed together toreachan overallassessment of possible hazard.
Iftheresults from severalareasofresearch(e.g., epidemiologic studies, tests in cell systems,
or whole-animal studies) are consistent and have been replicated, and if a biologically
plausible mechanism of action for the effect is evident, the evidence for the effect is given
great weight. In contrast, a body of evidence that includes inconsistent and conflicting
results, no replication of results, and effects that are often at the threshold of detection
might be given little weight in reaching a conclusion (NRC, p. 16).
©2000 NRC Canada
186 Environ. Rev. Vol. 8, 2000
Decade of publication
NRC 1997 NIEHS 1998aReferences in common
Number % Number % Number %
1997 and 1998b001581900
1990s 263 51 625 75 113 60
1980s 200 38 162 20 66 35
1970s 46 9 33 4 9 5
1960s 8 1.5 7 0.8 0 0
1950s 2 0.4 1 0.1 1 0.5
1940s 0 0 1 0.1 0 0
TOTAL 519±1 100 829±2 100 189±3 100
aOne reference without a date.
bThese references were not available to the NRC Committee. They are included in 1990s counts for the NIEHS Report.
Table 3. References cited in the reports by the National Research Council (1997) and the National Insti-
tute of Environmental Health Science (1998) according to date of publication.
National Institute of Environmental Health Science references
The NIEHS document reviews 830 references published from 1941 to 1998 with the majority of the
references (75%) published in the 1990s (Table 3). Only 186 references are common to both the NRC
and NIEHS Documents. An additional 158 references published in 1997 and 1998, which the NRC
Committee did not have access to, are also included in the NIEHS Document. Two key questions that
need to be addressed are (1) Do these new references answer key questions raised in the NRC Report?
and (2) Do the data confirm or refute the NRC conclusions?
Although not explicitly stated, the criterion for reference selection appears to be similar to that
used by the NRC Committee, namely papers in peer-reviewed journals.Also, three symposia provided
background information for the expert committee to consider (Portier and Wolfe 1997, 1998a, 1998b).
The Committees relied almost exclusively on post 1980 data and ignored some excellent research
conducted in the 1960s and 1970s. Several key studies by pioneers (Adey, Becker, Frey, and Marino,
to name a few) were not considered, and neither was the work done in the former Soviet Union and
in Eastern European countries despite English translations (Presman 1970; Dubrov 1978; Kulczycki
1989). Literature that might provide a broader perspective, biological responses to geomagnetic and
geoelectric fields, was also not considered (Tromp 1974; Sulman 1980; Kirschvink et al. 1985).
Ifthe fundamental question is,“Do low frequency electromagnetic fields affect living systems,”then
these two reports are incomplete. They focus on a narrow band of the electromagnetic spectrum (power
frequencies). They consider EMFs generated by our technology (technofields) but not those naturally
generated by natural processes (geofields and biofields). They focus entirely on response of humans
and ignore other species. Even the in vivo studies with rats and mice and the in vitro studies with cell
suspensions are designed to help us better understand the mechanisms as they pertain to humans. They
examine the potentially harmful effects and ignore beneficial therapeutic uses (except for healing of
bone fractures). To properly answer the question raised above, a much broader perspective is needed,
but this was outside their mandate.
3.4. Decision making process
National Research Council decision making
The NRC document provides little information on the decision making process. The Chair states
that the report took nearly 3 years of committee study and numerous hours of committee deliberations,
©2000 NRC Canada
Havas 187
which “we spent assessing and evaluating the data and synthesizing our conclusions based on the data.”
National Institute of Environmental Health Science decision making
The NIEHS conducted research on the carcinogenicity in experimental animals and improved meth-
ods of measuring exposure. NIEHS also enacted a two-tiered process for collecting and evaluating
information for the final report.
Asthe first partofthisprocess, three ScienceReviewSymposiawereheld. Thesymposiawereopen to
the public and were designed to encourage debate. The first was in Durham, North Carolina, in March
1997. Participants were asked to address specific questions concerning the mechanisms governing
the interactions of ELF EMF with biological systems in vitro and using biophysical theories. The
second symposium was on the epidemiology of exposure to ELF EMF held in San Antonio, Texas, in
January 1998, and the third on in vivo clinical investigations held in Phoenix, Arizona,April 1998. The
discussions of these symposia have been edited by Portier and Wolfe (1997, 1998a, 1998b).
As the second part of this process a Working Group was selected (as previously discussed) to
conduct “... a rigorous, multi-disciplinary, scientific assessment of available data on the health effects of
EMF ... The Process was publicly open, scholarly, objective, and sufficiently flexible to accommodate
the changing face of EMF research and public health concerns.” (NIEHS 1998, p. 8). At a 9-day
working session in Brooklyn Park, Minnesota, members prepared the final NIEHS document. Working
in subgroups on a draft prepared in advance of the meeting, members read, modified, and rewrote the
drafts to reflect Group consensus.
The evaluations of carcinogenicity (and other health end-points) were reached following the guide-
lines used in the International Agency for Research on Cancer (IARC) Monographs on the Evaluation of
theCarcinogenicRisk of Chemicals to Humans with minor modificationsas presentedintheirAppendix.
Foreach criticalstatement dealingwiththebiologicaleffectof electric andmagneticfields,members
voted and the votes were recorded. One member of the Working Group was unable to continue serving,
hence 29 individuals were eligible to vote. The votes are summarized in Tables 4, 5, and 6.
The procedures used by the two Committees to evaluate reports were probably similar but more
explicitly stated in the NIEHS Document.
3.5. Document organization
National Research Council document
This NRC Document consists of a detailed and comprehensive Executive Summary, followed by
seven chapters: (1) Introduction, (2) Exposure and Physical Interactions, (3) Cellular and Molecular
Effects, (4)Animal and Tissue Effects, (5) Epidemiology, (6) Risk Assessment, and (7) Research Needs
and Research Agenda.
This document contains 14 figures and 53 tables with a massive amount of data summarized,
especially in the appendix. The appendix also explains wire codes and residential exposure assessment.
The NRC document has a glossary of terms and an index.
National Institute of Environmental Health Science document
The NIEHS Document consists of five chapters: (1) Introduction, (2) Occurrence and Measure-
ment of Extremely Low Frequency Electromagnetic Fields, (3) Internal Dosimetry, (4) Biological Data
Relating to the Toxicity of ELF Electromagnetic Fields, and (5) Final Summary and Evaluation.
Chapter 4 makes up the bulk of the book, approximately 300 pages, and provides a detailed account
of biological data pertaining to EMF exposure. The data are considered under three main categories:
(i)Cancer in animals, adult humans, and children. The human cancer is based entirely on epidemi-
ological data.
©2000 NRC Canada
188 Environ. Rev. Vol. 8, 2000
(ii)Non-Cancer Health Effects in experimental animals, including effects on immunology, hema-
tology, nervous system, reproduction and development, melatonin, and tissue repair; in human
epidemiology, including occupational and residential exposure; in human laboratory studies,
including perception, and effects on the central nervous system, cardiovascular system, neuroen-
docrine system, mood, and hypersensitivity.
(iii)Mechanistic Effects based on in vitro experiments and biophysics of EMF interactions.
At the end of each section the information is summarized. An additional summary, provided in
Chapter 5 Final Summary and Evaluation, can be considered equivalent to an Executive Summary.
This document contains 9 figures and 63 tables, including information from many recent sources
(post 1996). It also has abbreviations, a glossary, and two appendices (one is the IARC Monographs
Programme, discussed below, and the other is the Minority Statement on Animal Carcinogenicity).
There is neither an index nor a biographical sketch of the Working Group Members.
4. Executive summary
4.1. National Research Council executive summary
The overall conclusions of the NRC Expert Committee, as stated in the Executive Summary, are as
follows (NRC 1997, p. 2):
“... the currentbodyofevidence doesnotshowthatexposureto these fields presentsahuman
health hazard. Specifically, no conclusive and consistent evidence shows that exposures to
residential electric and magnetic fields produce cancer, adverse neurobehavioral effects or
reproductive and developmental effects.”
“ ... At exposure levels well above those normally encountered in residences, electric and
magnetic fields can produce biologic effects (promotion of bone healing is an example),
but these effects do not provide a consistent picture of a relationship between the biological
effects of these fields and health hazards.”
“Anassociationbetweenresidentialwiringconfiguration(calledwirecodes,definedbelow)
and childhood leukemia persists in multiple studies, although the causative factor responsi-
ble for that statistical association has not been identified. No evidence links contemporary
measurements of magnetic-field levels to childhood leukemia.”
Hence, two major biological effects linked to EMFs have been agreed upon. One is that very high
fields, higher than those normally found in the home, can have biological effects, and the other is that
only the wire codes associated with a residence have been statistically linked with childhood leukemia.
The rest of the research in this area was deemed to be too inconsistent to warrant a link between
EMF exposure and biological effects.Although the Committee noted that power frequency fields “have
not been proven scientifically to be harmful, the panel recommends adoption of a policy of prudent
avoidance” (NRC 1997, p. 19).
4.2. National Institute of Environmental Health Science executive summary
Membersof the committee voted on the finalsummary and evaluationspresentedin chapter five, and
the vote count is given with explanations for those who did not vote in favor of a particular statement.
Themajority report is accompaniedby a Minority Statement onAnimal Carcinogenicity in the appendix
and is signed by five of the committee members (Table 2).
©2000 NRC Canada
Havas 189
Residential exposure: evaluation statement
Voting summary (number and percent)
Response Strong/
sufficient Moderate/
limited Weak/
inadequate None/
lack of Abstention Absent
Cancer in children
Cancer (all types) There is limited evidence that residential exposure to
ELF magnetic fields is carcinogenic to children. 0
0% 20
69% 6
21% 0
0% 2
7% 1
3%
Central nervous
system There is inadequate evidence with respect to childhood
nervous system tumors. 0
0% 0
0% 25
86% 0
0% 2
7% 2
7%
Lymphoma There is inadequate evidence with respect to childhood
lymphoma. 0
0% 0
0% 25
86% 0
0% 2
7% 2
7%
Cancer in adults
Cancer There is inadequate evidence that residential exposure to
extremely low frequency electromagnetic fields is car-
cinogenic to adults.
0
0% 0
0% 24
83% 1
3% 1
3% 3
10%
Non-cancer in adults
Depression There is inadequate evidence that environmental expo-
sure to ELF EMF has adverse effects on pregnancy
outcomeorisassociatedwithdepression.
0
0% 0
0% 23
79% 1
3% 1
3% 4
14%
Hormones/
neurotransmitters There is weak evidence that short term human exposure
to ELF EMF causes changes in suppression of
melatonin.
0
0% 1
3% 16
55% 2
7% 5
17% 5
17%
Sleep disturbance There is weak evidence that short term human exposure
to ELF EMF causes changes in sleep disturbance. 0
0% 0
0% 15
52% 0
0% 9
31% 5
17%
Cardiovascular
system There is weak evidence that short term human exposure
to ELF EMF causes changes in heart-rate variability. 0
0% 1
3% 13
45% 2
7% 8
28% 5
17%
a29 members were eligible to vote.
Table 4. NIEHS evaluations and votes: summary of residential epidemiological studies (Chapter 4, NIEHS 1998 Report).
©2000 NRC Canada
190 Environ. Rev. Vol. 8, 2000
Response Occupational exposure: evaluation statement
Voting summary (number and percent)
Strong/
sufficient Moderate/
limited Weak/
inadequate None/
lack of Abstention Absent
Cancer in adults
Chronic lymphocytic
leukemia There is limited evidence that occupational exposure to
ELF magnetic fields is carcinogenic to adults. This
evalutation is based on the results of studies of
chronic lymphotic leukemia.
0
0% 14
48% 11
38% 0
0% 2
7% 2
7%
Other cancers There is inadequate evidence for all other cancers. 0
0% 2
7% 22
76% 1
3% 2
7% 2
7%
Non-cancer in adults
Amyotrophic lateral
sclerosis There is inadequate evidence that occupational expo-
sure to ELF EMF causes amyotrophic lateral
sclerosis.
0
0% 0
0% 24
83% 0
0% 1
3% 4
14%
Cardiovascular
disease There is inadequate evidence that occupational expo-
sure to ELF EMF causes cardiovascular disease. 0
0% 0
0% 24
83% 0
0% 1
3% 4
14%
Alzheimer disease There is inadequate evidence that occupational expo-
sure to ELF EMF causes Alzheimer disease. 0
0% 0
0% 23
79% 1
3% 1
3% 4
14%
Reproduction and
development There is inadequate evidence that maternal occupa-
tional exposure to ELF EMF causes adverse birth
outcomes.
0
0% 0
0% 22
76% 2
7% 1
3% 4
14%
Reproduction There is inadequate evidence that paternal occupa-
tional exposure to ELF EMF causes reproductive
effects.
0
0% 0
0% 20
69% 3
10% 2
7% 4
14%
Depression There is inadequate evidence that occupational
exposure to ELF EMF causes suicide or depression. 0
0% 0
0% 17
59% 6
21% 2
7% 4
14%
a29 members were eligible to vote.
Table 5. NIEHS evaluations and votes: summary of occupational epidemiological studies (Chapter 4, NIEHS 1998 Report).
©2000 NRC Canada
Havas 191
Voting summary (number and percent)
Response Organism In vivo and in vitro studies: valuation statement Strong/
sufficient Moderate/
limited Weak/
inadequate None/
lack of Abstention Absent
in vivo
Perception Animals There is strong evidence that electric fields can
be perceived. 18
62% 0
0% 0
0% 0
0% 2
7% 9
31%
Bone repair Animals and
humans There is strong evidence that exposure to elec-
tric and magnetic fields affects bone repair
and adaptation.
14
48% 5
17% 0
0% 0
0% 8
28% 2
7%
Melatonin Rodents There is weak evidence that exposure to electric
and magnetic fields alters the levels of
melatonin in rodents.
0
0% 9
31% 14
48% 0
0% 4
14% 2
7%
Neurology Animals There is weak evidence for the neurobehavioral,
neuropharmacologiocal, neurophysiobiological,
and neurochemical effects in electromagnetic
fields.
0
0% 8
28% 9
31% 0
0% 3
10% 9
31%
Cancer Animals There is inadequate evidence in experimental
animals for carcinogenicity from exposure to
extremely low frequency electromagnetic
fields.
0
0% 0
0% 19
66% 8
28% 1
3% 1
3%
Immune system Animals There is no evidence in experimental animals
for effects of ELF EMF on the immune
system.
0
0% 0
0% 6
21% 13
45% 1
3% 9
31%
Reproduction
and
development
Animals There is no evidence in experimental animals
for the reproductive and develpmental effects
of exposure to sinusoidal magnetic fields.
0
0% 0
0% 3
10% 17
59% 8
28% 1
3%
Hematology Rodents There is no evidence that exposure to
power-line frequency EMF affects the
hematologicla parameters of rodents.
0
0% 0
0% 0
0% 17
59% 1
3% 11
38%
Table 6. NIEHS evaluations and votes: summary of in vivo and in vitro studies (Chapter 4, NIEHS 1998 Report).
©2000 NRC Canada
192 Environ. Rev. Vol. 8, 2000
Voting summary (number and percent)
Response Organism In vivo and in vitro studies: valuation statement Strong/
sufficient Moderate/
limited Weak/
inadequate None/
lack of Abstention Absent
Melatonin Sheep and
baboons There is no evidence that exposure to electric
and magnetic fields affects the levels of
melatonin in sheep or baboons.
0
0% 0
0% 0
0% 14
48% 13
45% 2
7%
Soft tissue
repair Vertebrates The Working Group could not reach a conclu-
sion about whether exposure to electric and
magnetic fields affects nervous and non-bone
connective tissue repair and adaptation in
vertebrates.
12
41% 10
34% 6
21% 0
0% 0
0% 1
3%
in vitro
Mechanism Animal cells A limited number of well-performed studies
provide moderate evidence for mechanically
plausible effects of EMF greater than 0.1 mT
(100 µT, 1000 MG) in vitro at endpoints gen-
erally regarded as reflecting the action of
toxic agents.
0
0% 27
93% 0
0% 0
0% 2
7% 0
0%
Mechanism Animal cells There is weak evidence for an effect of fields
lower than approximately 0.1 mT (100 µT,
1000 mG).
0
0% 0
0% 26
90% 0
0% 3
10% 0
0%
a29 members were eligible to vote.
Table 6. (concluded).
©2000 NRC Canada
Havas 193
Wordingofthe evaluationrelated to riskofhuman carcinogenicity followsthe protocol establishedby
the International Agency for Research on Cancer (IARC).Agents (mixtures or exposure circumstances)
are classified into four groups with decreasing probability of carcinogenicity as follows (NIEHS Report,
modified from pages 498–499, emphasis is mine):
Group 1: The agent (mixture or exposure circumstances) is carcinogenic to humans.
This category is used when there is sufficient evidence of direct carcinogenicity in humans or when
this evidence is considered insufficient but strong in exposed humans and sufficient in experimental
animals.
Group 2A: The agent is probably carcinogenic to humans.
This category is used when there is limited evidence of carcinogenicity in humans but sufficient evi-
dence in experimental animals and strong evidence that the carcinogenesis is mediated by a mechanism
that also operates in humans.
Group 2B: The agent is possibly carcinogenic to humans.
This category is used when there is limited evidence of carcinogenicity in humans but less than
sufficient evidence in experimental animals. It can also be used when the evidence is inadequate in
humans but sufficient in experimental animals.
Group 3: The agent is not classifiable as to its carcinogenicity to humans.
This category is used when the evidence of carcinogenicity is inadequate in humans and inadequate
or limited in experimental animals. An exception includes agents (mixtures) for which there is strong
evidence that the mechanism, carcinogenicity in experimental animals, does not operate in humans.
Group 4: The agent is probably not carcinogenic to humans.
This category is used when there is evidence suggesting lack of carcinogenicity in humans and in
experimental animals or inadequate evidence in humans but consistent and strong evidence suggesting
lack of carcinogenicity in experimental animals.
The overall evaluation of the majority of the Working Group is that extremely low frequency EMF
can be classified as “possibly carcinogenic” (Group 2B) and that this “is a conservative, public-health
decisionbased on limitedevidenceof an increasedriskforchildhood leukemias withresidentialexposure
and an increased occurrence of CLL (chronic lymphocytic leukemia) associated with occupational
exposure. For these particular cancers, the results of in vivo, in vitro, and mechanistic studies do not
confirm or refute the findings of the epidemiological studies.” (NIEHS 1998, p. 402).
They go on to state that “Because of the complexity of the electromagnetic environment, the review
of the epidemiological and other biological studies did not allow precise determination of the specific,
critical conditions of exposure to ELF EMF associated with the disease endpoints studied.” (NIEHS
Report, p. 400).
The NIEHS Report also provides the results of their specific deliberations as shown in Tables 4, 5,
and 6). Committee members (29 eligible) voted that the evidence to support a particular statement was
either A, strong/sufficient; B, moderate/limited; C, weak/inadequate; or D, non-existent. According to
these tables the areas of greatest agreement are as follows:
A. There is strong /sufficient evidence that:
A-1 electric fields can be perceived (62% voted in favor of statement, 31% were absent).
A-2 exposure to electric and magnetic fields affects bone repair and adaptation (48% vote with
28% abstentions).
©2000 NRC Canada
194 Environ. Rev. Vol. 8, 2000
B. There is moderate/limited evidence that:
B-1 mechanistically plausible toxic effects of EMF greater than 0.1 mT (100 µT, 1000 mG)
have been demonstrated in vitro (93% vote).
B-2 B-2 residential exposure to ELF magnetic fields is carcinogenic to children (69% vote).
B-3 occupational exposure to ELF magnetic fields causes chronic lymphocytic leukemia (CLL)
in adults (48% vote).
C. There is weak /inadequate evidence that:
C-1 electric fields lower than approximately 0.1 mT (100 µT, 1000 mG) have effects in vitro
(90%).
C-2 residential exposure is associated with childhood nervous system tumors (86%) and child-
hood lymphoma (86%).
C-3 residential exposure to extremely low frequency EMF is carcinogenic to adults (83%).
C-4 occupational exposure to ELF magnetic fields causes cancers (other than CLL) (76%);
amyotrophic lateral sclerosis (83%); Alzheimer disease (79%).
C-5 environmental exposure to ELF EMF has adverse effects on pregnancy outcome or is asso-
ciated with depression (79%).
C-6 maternal(76%) and paternal (60%)occupational exposure to ELF EMFcauses reproductive
effects.
C-7 exposure to ELF EMF is carcinogenic to experimental animals (66%).
C-8 occupational exposure to ELF EMF causes suicide or depression (59%).
C-9 short-term human exposure to ELF EMF suppresses melatonin (55%), causes sleep distur-
bance (52%); changes heart-rate variability (45%).
C-10 exposure to electric and magnetic fields alters the levels of melatonin in rodents (48%).
C-11 electromagnetic fields cause neurobehavioral, neuropharmacologic, neurophysiological,
and neurochemical effects in vivo (31%).
D. There is a lack of evidence that:
D-1 exposure to sinusoidal magnetic fields affects reproduction and development in vivo (59%).
D-2 exposure to power-line frequency EMF affects hematological parameters of rodents (59%).
D-3 exposureto electric and magnetic fields alters levels of melatonin in sheep or baboons (48%).
D-4 exposure to EMF affects the immune system in vivo (45%).
The Committee was unable to reach a conclusion on the effectiveness of EMF for soft tissue repair
in vertebrates.
My interpretation of the voting is that it was conservative, erring on the side of “no effect.” The
evidenceis considerably stronger than appears in this evaluationif a much broader literature is examined.
In section A above, neither statement is controversial. Electric fields can be perceived (Chatterjee et
al. 1986) and electric and magnetic fields dopromote bone repair and have been clinically used for years
(Bassett 1995). There is evidence that magnetic fields can also be perceived by several species (bees,
birds, turtles, for example), although studies with humans are inconclusive (Blakemore 1975; Larkin
and Sutherland 1977; Gould et al. 1978; Walcott et al. 1979, see also excellent review by Kholodov et
al. 1990).
©2000 NRC Canada
Havas 195
I do not agree with either statement B-2 or B-3 that epidemiological evidence indicates a causal
relationship between EMF exposure and childhood and adult cancer.What has been documented is an
association between extremely low frequency EMF and some forms of childhood and adult cancer.
The association seems to be one of promotion rather than initiation. An uncritical reader may interpret
this statement to mean that ELF EMFs initiate cancer and that conclusion would be false based on the
evidence available.
Regarding statement B-1, I would go further and suggest that plausible mechanisms for toxic effects
of EMFs have been demonstrated. Studies have shown suppression of night-time melatonin between
0.2 and 1.2 µT (Liburdy et al. 1993), altered calcium flux at various intensities (Bawin and Adey
1976; Blackman et al. 1979; Dutta et al. 1989); chromosomal aberrations at 30 µT of intermittent or
pulsed exposure (Nordenson et al. 1994); altered ornithine decarboxylase activity (ODC in its signal
transduction role) at 1, 10, and 100 µT (Litovitz et al. 1991); increased cell proliferation above 100 µT
(Liburdy et al. 1993; Katsir et al. 1998), and tumor initiation in two human cell lines following short (2
h) exposure to 400 mT (Miyakoshi et al. 1996; Miyakoshi et al. 1998).
Of the statements for which the evidence is classified as “weak or inadequate,” I would suggest that
the evidence for some (C-2, 5, 9, and 11) is “moderate or limited.” Breast cancer is not specifically
mentioned in C-4, which is unusual since this is one area where epidemiological, in vivo and in vitro
studies seem to suggest that EMF effects on night-time melatonin may stimulate estrogen-responsive
breast cancer cells (Liburdy et al. 1993).
4.3. Conclusions regarding electric and magnetic field exposure and biological effects
My own conclusions, based on NRC and NIEHS Documents as well as on references covering a
much broader scope are as follows:
(1) low frequency electric and magnetic fields, separately and in combination, can affect living
organisms.
(2) effects can be neutral,harmful,orbeneficial,
(3) effects can occur at low intensities, commonly found in residential settings, and some effects are
intensity specific (intensity windows).
(4) effects can occur at low frequencies, at, above, and below the power distribution frequencies and
some effects are frequency specific (frequency windows).
(5) timing of exposure (day vs. night, for example) is critical for some effects (time windows).
(6) location of exposure (as it relates to the geomagnetic field) is important for some effects.
(7) sensitivitiestoEMFs varyenormously,express themselves in different ways, and may be initiated
by EMF exposure or chemical exposure.
(8) numerous species (bacteria, insects, birds, reptiles, fish, mammals) are able to detect and respond
to changes in electromagnetic fields and this detection has adaptive significance.
(9) we understand some of the mechanisms responsible and are at the threshold of understanding
others that are involved.
(10) theclassicaltoxicologicalmodelofdose/response may be inappropriate for electric and magnetic
field exposure.
©2000 NRC Canada
196 Environ. Rev. Vol. 8, 2000
5. Exposure
Ed Leeper, who co-authored the seminal paper on childhood cancers and power lines (Wertheimer
and Leeper 1979), reasoned that in a residential setting the magnetic component of the electromagnetic
fields was likely to be the most important biologically since the electric component is blocked by
buildings and trees. He also reasoned that the strength of the magnetic field was likely to be a function of
the number of residents serviced (current) and the distance between lines and transformers to individual
homes. He devised a wire code that included both of these factors (Fig. 3). TheWertheimer and Leeper
(1979) study, and many since, have relied on wire codes as a surrogate for magnetic field measurements.
As instrumentation for measuring weak, low frequency magnetic fields became more readily avail-
able, wire codes were supplemented by the spot measurement. The spot measurement is useful in a
setting with a constant magnetic field, at a specific distance from an appliance for instance. However,
in a residential setting the magnetic field fluctuates normally with a bimodal peak in the morning and
evening corresponding to maximum power use.
A more precise measurement for a fluctuating magnetic field is a time-integrated measurement,
often done in a residential setting for a 24-h period and in an occupational setting for the duration of the
work day.These integrated monitors can be placed in a specific location or worn as personal monitoring
devices. With each improvement in our ability to precisely measure the magnetic flux density, we have
become aware of the dynamic nature of our electromagnetic environment.
5.1. Residential exposure
Ina residential setting there are three majorsourcesof technologically generated magnetic fields: the
outdoordistribution systemconsistingofeither belowgroundorabove groundwiresandtransformers (as
representedby the wire code);the indoor distribution system consistingof indoor wiring and grounding;
and appliances. The early studies assumed that power lines provided the major source of magnetic fields
inside the home and both indoor wiring and appliance use were ignored. More recent studies enable
us to calculate TWA (time-weighted average) magnetic flux densities for a given environment (see
Components of Residential Exposure).
Outdoor distribution system
Wire codes may provide a good relative surrogate for the magnetic flux density within a commu-
nity. However, they become less reliable when different communities are compared. Table 7 shows the
magnetic flux densities associated with wire codes for different studies. If we assume, for the moment,
that the magnetic flux density in Table 7 is due entirely to the outdoor power distribution system we
can see that the magnetic flux density can range from 0.02 to 8.7 µT. Within each wire code category,
the magnetic flux density (as measured by spot measurements and 24-h measurements) can differ con-
siderably between studies leading to considerable overlap. This is one of the inherent weaknesses with
respect to wire codes. So, while a comparison of wire codes within a community is useful, comparison
of wire codes for different communities has limitations.
The electric field was not considered to be important in the residential epidemiological studies.
Unlike the 15 to 25 kV/m electrical potentials in 500 kV switchyards, electric fields immediately
beneath overhead neighborhood distribution lines are likely to be less than 30V/m (unpublished data).
However, there is a trend among electric utilities to increase the voltage of power distribution lines to
minimize energy loss due to resistance. Power transmission lines lose approximately 1% per 100 miles
and loss of power due to resistance has been calculated to be between 5 and 10% per year. The cost
of this is considerable. By increasing the voltage, resistance drops as does power loss. So this move to
higher voltage makes economic sense. However, as voltage increases so does the intensity of the electric
field, and studies have now shown that the harmful effects associated with magnetic field exposure may
be worse in the presence of a strong electric field (Miller et al. 1996).
©2000 NRC Canada
Havas 197
Fig. 3. A simplified schematic of the basic features of the differences in the wire codes as defined to support
epidemiological studies. VHCC, OHCC, OLCC, VLCC stand for very high, ordinary high, ordinary low, and
very low current configurations. (Reprinted with permission from Possible health effects of exposure to residential
electric and magnetic fields. Copyright 1997 by the National Academy of Sciences. Courtesy of the National
Academy Press. Washington, D.C.)
Indoor distribution system
Indoor wiring is another important source of magnetic fields in the home. Within a properly wired
building far from a power line normal fields should not exceed 0.03 µT and even this low field would
be due to fluorescent lights (Riley 1995). In a building with faulty wiring or with older knob and tube
wiring, fields may be 0.2 to 3 µT and even higher near walls, ceilings, and floors (Bennett 1994; Riley
1995).
The EPRI (1993 as cited in NIEHS 1998) conducted a survey of 1000 homes and took both 24-h and
spot measurements in different rooms.A summary of the results (Table 8) shows that median magnetic
flux densities for 24-h measurements vary more than 10-fold with 50% of the homes exceeding 0.05 µT
(and 1% of the homes exceeding 0.55 µT). The highest wire code category (VH) in the Wertheimer
and Leeper (1982) study was 0.25 µT and according to the EPRI study, 5% of the homes exceeded this
value. Note also that the 24-h measurement includes the combined field from power lines and grounding
system.
©2000 NRC Canada
198 Environ. Rev. Vol. 8, 2000
Power source and
measurement
Distance Magnetic flux density
(µT)
Source (ft) (m)
Very high (VH)
High Voltage Transmission
Lines 500 kV 0 0 8.7
High Voltage Transmission
Lines 230 kV 0 0 5.8
High Voltage Transmission
Lines 115 kV 0 0 3
High Voltage Transmission
Lines 500 kV 50 15 2.9 Max. 8.7
High Voltage Transmission
Lines 230 kV 50 15 2 Median 0.48
High Voltage Transmission
Lines 115 kV 50 15 0.7 Min. 0.11
Wertheimer and Leeper 1982 Median 50 15 0.25
Savitz et al. 1988 Low pwr spot: mdn 50 15 0.22
Severson et al. 1988 Small subsample 50 15 0.17
Tarone et al. 1988 24-h means: mdn 50 15 0.13
Preston-Martin et al. 1996b24-h bedrm mean: mdn 50 15 0.11
London et al. 1991 24-h median: GM 50 15 0.11
Ordinary high (OH)
High Voltage Transmission
Lines 500 kV 100 30 1.3
High Voltage Transmission
Lines 230 kV 100 30 0.7
High Voltage Transmission
Lines 115 kV 100 30 0.2
Wertheimer and Leeper 1982 Median 130 40 0.12 Max. 1.3
Severson et al. 1988 Small subsample 130 40 0.11 Median 0.11
Tarone et al. 1988 24-h means: mdn 130 40 0.1 Min. 0.06
Savitz et al. 1988 Low pwr spot: mdn 130 40 0.09
London et al. 1991 24-h median: GM 130 40 0.07
Preston-Martin et al. 1996b24-h bedrm mean: mdn 130 40 0.06
Ordinary low (OL)
High Voltage Transmission
Lines 500 kV 200 60 0.32
High Voltage Transmission
Lines 230 kV 200 60 0.18
Tarone et al. 1988 24-h means: mdn 150 50 0.08
Table 7. Magnetic flux density associated with wire codes (based on Table 2.1, p. 28, NRC 1997;
Tables 2.7 and 2.9, pp. 76 and 36, NIEHS 1998).
©2000 NRC Canada
Havas 199
Power source and
measurement
Distance Magnetic flux density
(µT)
Source (ft) (m)
London et al. 1991 24-h median: GM 150 50 0.06 Max. 0.32
Savitz et al. 1988 Low pwr spot: mdn 150 50 0.05 Median 0.05
Wertheimer and Leeper 1982 Median 150 50 0.05 Min. 0.04
Severson et al. 1988 Small subsample 150 50 0.05
Preston-Martin et al. 1996b24-h bedrm mean: mdn 150 50 0.04
High Voltage Transmission
Lines 115 kV 200 60 0.04
Very low (VL)
High Voltage Transmission
Lines 500 kV 300 90 0.14
High Voltage Transmission
Lines 230 kV 300 90 0.08
Preston-Martin et al. 1996b24-h bedrm mean: mdn 150 50 0.06
Wertheimer and Leeper 1982 Median 150 50 0.05 Max. 0.14
Tarone et al. 1988 24-h means: mdn 150 50 0.05 Median 0.05
London et al. 1991 24-h median: GM 150 50 0.04 Min. 0.02
Severson et al. 1988 Small subsample 150 50 0.03
Savitz et al. 1988 Low pwr spot: mdn 150 50 0.03
High Voltage Transmission
Lines 115 kV 300 90 0.02
Underground (UG)
Preston-Martin et al. 1996b24-h bedrm mean: mdn 150 50 0.05
Tarone et al. 1988 24-h means: mdn 150 50 0.05 Max. 0.047
London et al. 1991 24-h median: GM 150 50 0.05 Median 0.046
Savitz et al. 1988 Low pwr spot: mdn 150 50 0.03 Min. 0.03
Note: Low pwr spot = low power spot measurement, field measured with appliances turned off; mdn = median;
GM = geometric mean; bedrm = bedroom.
Table 7. (concluded).
The spot measurements for magnetic flux density differed in rooms and some were sufficiently high
to suggest faulty wiring. Rooms with the highest average spot measurements ranged from 0.11 µT
(50th percentile, 50% of the homes exceeded this value) to 1.22 µT (99th percentile, 1% of the homes
exceeded this value).A personal 24-h monitoring device offers the most reliable estimate of exposure.
However, to identify sources of the magnetic field, multiple indoor and outdoor measurements are
necessary.
Improperly installed indoor wiring can account for very high fields. In a survey of 150 buildings,
Riley(1995) reported that 66% ofthe high fields above 3 mG(0.3 µT) were due to wiringand grounding
problems, 18% were due to the proximity to power lines, and 3% were due to appliances. Of the wiring
problems, 12% were due to knob-and-tube wiring used in older buildings, 22% were due to improper
grounding to the plumbing system, and 65% were due to wiring violations. Knob-and-tube is a system
of wiring used until the 1940s. The hot and neutral conductors are separated by several inches to several
©2000 NRC Canada
200 Environ. Rev. Vol. 8, 2000
60-Hz magnetic flux density (µT)
Spot measurementsa24-h
measurementb
%ofhomesinwhich
values were exceeded
All rooms All rooms
Kitchen Bedrooms HighestcMean Median Median
50 0.07 0.05 0.11 0.06 0.05 0.05
25 0.12 0.1 0.21 0.11 0.1 0.1
15 0.24 0.2 0.38 0.21 0.17 0.18
5 0.35 0.29 0.56 0.3 0.26 0.26
1 0.64 0.77 1.22 0.66 0.58 0.55
aData from 992 residences.
bData from 986 residences; combined field from power-line and grounding system.
cRoom with highest spot reading.
Table 8. Estimated magnetic flux density based on spot measurements and 24-h measurements in the
1000 homes survey (NIEHS 1998, Table 2.9, p. 36).
feet. The greater the separation the higher the magnetic field that is produced and the less it decreases
with distance (1 ×r−1for a single line conductor rather than 1×r−2for close parallel line conductors).
Common wiring faults that lead to large magnetic fields include neutral to ground connections,
separation of conductors (as with knob-and-tube wiring), grounding to water pipes, and parallel neutrals
(i.e.,neutralsfrom differentcircuitsconnectedtogether on the load side of the breaker box) (Riley1995).
One common source of higher magnetic fields is the use of extra ground connections through water
pipes. According to Bennett (1994) rerouting or adding ground return wires can produce background
magnetic fields in the order of 1 µT in the home.
While we might assume that our indoor exposure to magnetic fields has increased with our increas-
ing reliance on electrical appliances, older homes (pre-1940) with knob-and-tube wiring can generate
substantial magnetic fields. Knob-and-tube wiring with wires spaced 6 in. (15 cm), carrying a current
of 20 A (rms), can produce a magnetic field of 0.61 µT at a distance of 1 m (Bennett 1994). If the wires
are closer together (2.5 in. or 6.3 cm) the field is reduced to 0.25 µT. Modern wiring (such as Romex or
a twisted pair of BX cables), carrying the same current, produces even lower fields of 0.03 to <0.01 µT,
respectively, (Bennett 1994).
Based on the preliminary results from the 1000 home survey presented at a conference, Riley noted
that the magnetic flux density increased with age of dwelling. The older homes (>50 years) had an
average magnetic flux density of 0.082 µT while the newer homes (<10 years) had 0.038 µT. In
attempting to verify this I requested a copy of the industry-funded EPRI study. I was informed that the
report is available free to industrial partners who funded the research and can be purchased by others
for $20 000 in US funds for each of two volumes. The preliminary report is available for $2000 US
per volume. This extraordinarily high price has made the report inaccessible to non-utility scientists
and others interested in the results, a most unfortunate consequence. This pricing policy obviously has
nothing to do with protecting patent rights nor is it an attempt to raise money, since libraries cannot
afford such prices for individual volumes.The only conclusion one can draw is that the power industry
does not want to make this information publicly available.
Appliances
The EPA (1992) measured the magnetic fields produced by a variety of household and office appli-
ances (Table 9). According to this study, the magnetic fields generated by appliances differ enormously
and drop off rapidly (generally 1 ×r−3) with distance. Magnetic flux densities, in Table 9 range from
©2000 NRC Canada
Havas 201
Magnetic flux density (µT)
Room/source Distance
from source ~cm
ft 15
0.5 30
160
2120
4
Bathroom
Electric shavers Low 0.4 — — —
Median 10 2 — —
High 60 10 1 0.1
Hair dryers Low 0.1 — — —
Median 30 0.1 — —
High 70 7 1 0.1
Bedroom
Analog clocks (conventional face) Low — 0.1 — —
Median — 1.5 0.2 —
High — 3 0.5 0.3
Digital clocks Low — — — —
Median — 0.1 — —
High — 0.8 0.2 0.1
Baby monitor Low 0.4 — — —
Median 0.6 0.1 — —
High 1.5 0.2 — —
Electric blanket (conventional)aAverage 2.2 5 cm distance
High 3.9 5 cm distance
Electric blanket (PTC)a, b Average 0.09 5 cm distance
High 0.27 5 cm distance
Kitchen
Blenders Low 3 0.5 — —
Median 7 1 0.2 —
High 10 2 0.3 —
Can openers Low 50 4 0.3 —
Median 60 15 2 0.2
High 150 30 3 0.4
Coffee makers Low 0.4 — — —
Median 0.7 — — —
High 1 0.1 — —
Crock-pots Low 0.3 — — —
Median 0.6 0.1 — —
High 0.9 0.1 — —
Table 9. Magnetic flux density of common household and office appliances. (from EPA 1992, in Levitt
1995, pp. 254–258 and from US Food & Drug Adminisration, in Q&A about EMF 1995, p. 42).
©2000 NRC Canada
202 Environ. Rev. Vol. 8, 2000
Magnetic flux density (µT)
Room/source Distance
from source ~cm
ft 15
0.5 30
160
2120
4
Dishwashers Low 1 0.6 0.2 —
Median 2 1 0.4 —
High 10 3 0.7 0.1
Electric ovens Low 0.4 0.1 — —
Median 0.9 0.4 — —
High 2 0.5 0.1 —
Electric ranges Low 2 — — —
Median 3 0.8 0.2 —
High 20 3 0.9 0.6
Food processors Low 2 0.5 — —
Median 3 0.6 0.2 —
High 13 2 0.3 —
Garbage disposals Low 6 0.8 0.1 —
Median 8 1 0.2 —
High 10 2 0.3 —
Microwave ovens Low 10 0.1 0.1 —
Median 20 4 1 0.2
High 30 20 3 2
Mixers Low 3 0.5 — —
Median 10 1 0.1 —
High 60 10 1 —
Refrigerators Low — — — —
Median 0.2 0.2 0.1 —
High 4 2 1 1
Toasters Low 0.5 — — —
Median 1 0.3 — —
High 2 0.7 — —
Living/family room
Air conditioners (window) Low — — — —
—0.30.1—
High — 2 0.6 0.4
Ceiling fan Low — —
Median 0.3 — —
High 5 0.6 0.1
Black and white TVs Low 0.1 — —
Median 0.3 — —
High 1 0.2 0.1
Table 9. (continued).
©2000 NRC Canada
Havas 203
Magnetic flux density (µT)
Room/source Distance
from source ~cm
ft 15
0.5 30
160
2120
4
Colour TVs Low — — —
Median 0.7 0.2 —
High 2 0.8 0.4
Tuners/tape players (including VCRs) Low — — — —
Median 0.1 — — —
High 0.3 0.1 — —
Laundry room
Electric clothes dryers Low 0.2 — — —
Median 0.3 0.2 — —
High 1 0.3 — —
Washing machines Low 0.4 0.1 — —
Median 2 0.7 0.1 —
High 10 3 0.6 —
Irons Low 0.6 0.1 — —
Median 0.8 0.1 — —
High 2 0.3 — —
Vacuum cleaners Low 10 2 0.4 —
Median 30 6 1 0.1
High 70 20 5 1
Office
Air cleaners Low 11 2 0.3 —
Median 18 3.5 0.5 0.1
High 25 5 0.8 0.2
Copy machines Low 0.4 0.2 0.1 —
Median 9 2 0.7 0.1
High 20 4 1.3 0.4
Fax machines Low 0.4 — — —
Median 0.6 — — —
High 0.9 0.2 — —
Fluorescent lights Low 2 — — —
Median 4 0.6 0.2 —
High 10 3 0.8 0.4
Electric pencil sharpeners Low 2 0.8 0.5 —
Median 20 7 2 0.2
High 30 9 3 0.3
Table 9. (continued).
©2000 NRC Canada
204 Environ. Rev. Vol. 8, 2000
Magnetic flux density (µT)
Room/source Distance
from source ~cm
ft 15
0.5 30
160
2120
4
Video-display terminals (PCs with colour
monitors) Low 0.7 0.2 0.1 —
Median 1.4 0.5 0.2 —
High 2 0.6 0.3 —
Battery chargers Low 0.3 0.2 — —
Median 3 0.3 — —
High 5 0.4 — —
Portable heaters Low 0.5 0.1 — —
Median 10 2 0.4 —
High 15 4 0.8 0.1
Power drills Low 10 2 0.3 —
Median 15 3 0.4 —
High 20 4 0.6 —
Power saws Low 5 0.9 0.1 —
Median 20 4 0.5 —
High 100 30 4 0.4
aData from the Centre for Devices and Radiological Health, USFDA.
bPTC = positive temperature coefficient (low-magnetic field electric blankets).
Table 9. (concluded).
150 µT for can openers to less than 0.1 µT for tape players. There are considerable model differences
as well. For example, hair dryers can range from a high of 70 µT to a low of 0.1 µT depending on make
and model.
The appliances of greatest concern are those with high magnetic flux densities and long exposure
times. Electric blankets, for example, generate a field of 2 to 4 µT and are in contact with the body for
several hours each night. New models, known as the positive temperature coefficient electric blankets,
now generate magnetic fields that are one tenth or lower than those generated by the older models.
Hair dryers and electric shavers generate a high magnetic field near the head. Power saws generate high
magnetic fields and they may be of concern for the professional carpenter.
One metric that might have biological significance is cumulative exposure. This depends on three
variables: the magnetic flux density of the appliance, distance at which it is used, and the duration
of exposure. Based on Table 9 we can estimate daily exposure if we make certain assumptions about
appliance use.
One series of assumptions is provided in Table 10. This table includes nine appliances commonly
used in North America. For each appliance a high and low magnetic flux density (based on the EPA
1992 study) is calculated for two models, two distances, and two exposures to provide a maximum and
minimum value. The sum of these gives eight daily cumulative exposures for appliance use. These range
from a low of 0.37 to a high of 165 µT·h (an almost 500-fold difference). Hence individuals living in
the same house may be exposed to very different magnetic flux densities attributable entirely to use of
appliances.
©2000 NRC Canada
Havas 205
Components of residential exposure
Based on an estimate of the magnetic flux density associated with appliance use, indoor wiring, and
the outdoor distribution lines, we can calculate the relative contribution of each of these sources (see
Table 11).
In Example A, for properly wired newer homes (low field) far from outdoor power lines (low field),
appliances are likely to be the major residential source and may account for more than 60% of magnetic
field exposure (Table 11).
In Example B, in new homes (low field) near power lines (high field), external sources are likely
to be considerable (>80%) with low appliance use and measurable (10–30%) with moderate to high
appliance use (refer to Table 10 for characterization of appliance use and Table 11 for examples A to D).
InExample C, inolderhomes(or homes withfaultywiring) (high field) farfromexternal sources(low
field), indoor wiring is likely to be the major source of magnetic field exposure (>50%) if appliance use
is moderate to low. Indoor wiring can also contribute measurably to exposure (>10%) when appliance
use is high.
In Example D, in older homes (high field) near external power lines (high field), both indoor and
outdoor wiring become significant sources (>30 %) of magnetic field exposure and except for the
highest appliance use, they can account from 20% to 97% of exposure in a residential setting.
Accordingto these calculations maximum daily cumulative exposure can be attributed to appliances,
indoor wiring, or outdoor power lines depending on the circumstances. Also, individuals living in the
same residence may be exposed to different magnetic fields based on the amount of time and type
of appliances they use and the time they spent in various rooms. These differences, not considered
in the early epidemiological studies, may account for some of the discrepancy in the results. Future
epidemiological studies should take them into consideration.
Data from personal monitoring devices indicate the variability of the electromagnetic environment.
Measurements of the 24-h magnetic flux for a 9-year-old girl in California showed values varied from
less than 0.05 to 0.4 µT at home after school. They increased to a high of 0.7 µT during the early part
of the night when she slept under an electric blanket. At school, the following day, background values
were low (approximately 0.05 µT) although several peaks, many of them with unidentifiable sources,
exceeded 2 µT (Hitchcock and Patterson 1995). These data are disturbing if you consider that values
of 0.2 µT and higher have been linked with excess cases of childhood leukemia (Michaelis et al. 1998;
Savitz et al. 1988; Olsen et al. 1993).
5.2. Occupational exposure
Just as the early residential epidemiological studies used wire codes as surrogates for magnetic
fields, the early occupational epidemiological studies initially based their result on job titles. As interest
in occupational exposure increased, more measurements of magnetic fields in various occupational
settings and associated with individual exposure began to be documented. Because of the variability
within and among occupations as well as between types of measurements (spot measurement vs. time
weight averages), comparisons of occupations is difficult and can only be considered tentative at this
time.
Personal monitoring of workers provides the most information and, in the long term, may prove
to be the most useful measurement. Examples of four occupations, in Fig. 4, demonstrate the variabil-
ity of EMF exposure. These examples should not be interpreted as typical EMF exposures for these
occupations.
The National Institute of Environmental Health Science (NIEHS1998) accumulated a vast amount
of data for time weighted average magnetic field exposures, which has been summarized according to
industry type in Table 12. The original data were ranked in decreasing order of exposure and classified
into percentile groupings. The 95th percentile was at 0.66 µT and can be considered very high exposure
©2000 NRC Canada
206 Environ. Rev. Vol. 8, 2000
Appliance exposure time
(short and long)
Appliance
magnetic
field
Distance Time-weighted magnetic flux density (µT·h)
Near Far Near Far
(cm) (µT) (cm) (µT) Long Short Long Short
Hair dryers Low 15 0.1 30 0.01 0.0083 0.0033 0.0008 0.0003
(2and5min) High 70 75.81 2.31 0.581 0.231
Analog clocks Low 30 0.1 60 0.01 0.8 0.6 0.08 0.06
(6and8h) High 30.5 24 18 43
Electric blanket Low 50.01 50.01 0.08 0.06 0.08 0.06
(6and8h) High 3.9 3.9 31.2 23.4 31.2 23.4
Microwave ovens Low 30 0.1 120 0.01 0.0083 0.0017 0.0008 0.0002
(1and5min) High 20 21.66 0.34 0.166 0.034
Colour TVs Low 60 0.01 120 0.01 0.04 0.01 0.04 0.01
(1and4h) High 0.8 0.4 3.2 0.8 1.6 0.4
Air cleaners Low 30 260 0.01 16 40.08 0.02
(2and8h) High 50.2 40 10 1.6 0.4
Fluorescent lights Low 30 0.01 60 0.01 0.08 0.02 0.08 0.02
(2and8h) High 30.4 24 63.2 0.8
Video-display terminals Low 30 0.2 60 0.1 0.8 0.1 0.4 0.05
(0.5and4h) High 0.6 0.3 2.4 0.3 1.2 0.15
Power saws Low 15 530 0.9 1.65 0.85 0.297 0.153
(10 and 20 min) High 100 30 33 17 9.9 5.1
All appliances Low Daily sum (µT·h) 19.5 5.6 1.1 0.37
High 165.3 78.2 53.4 33.5
All appliances Low Function of lowest exposure 53 15 31
High 447 211 144 91
Table 10. Time-weighted daily magnetic flux density calculated for short and long exposure at two distances for each of nine appliances found in the home
(based on data in Table 9).
©2000 NRC Canada
Havas 207
Daily magnetic field exposure (percent of total residential exposure)
Example A Example B Example C Example D
Indoor wiringa:→LOW LOW HIGH HIGH
Outdoor wiringb:→LOW HIGH LOW HIGH
AppliancescTime AppldIndoor
wiringaOutdoor
wiringbAppldIndoor
wiringaOutdoor
wiringbAppldIndoor
wiringaOutdoor
wiringbAppldIndoor
wiringaOutdoor
wiringb
LOW Short 34 22 44 6491 589 6353 44
Long 60 13 26 15 382 13 82 5850 42
MODERATE Short 89 4847 251 42 54 430 38 32
Long 96 1276 123 72 26 260 22 18
HIGH Short 98 1184 115 81 17 172 15 13
Long 99 0190 010 87 12 180 11 9
VERY HIGH Short 99 0193 0791 8186 87
Long 100 0096 0396 4093 43
aIndoor wiring: LOW, properly wired newer home = 0.01 µT (0.24 µT·h for 24 h exposure); HIGH, older home with knob and tube wiring and/or with faulty
wiring = 0.3 µT(7.2µT·h for 24 h exposure) (Bennett 1994; Riley 1994).
bOutdoor wiring: LOW, very low current configuration, 0.02 µT(0.48µT·h for 24 h exposure); HIGH, very high current configuration, 0.25 µT(6µT·h for 24 h exposure)
(Wertheimer and Leeper 1982).
cAppliance code: LOW, appliance with low magnetic flux density, far exposure; MODERATE, appliance with low magnetic flux density, near exposure; HIGH, appliance
with high magnetic flux density, far exposure; VERY HIGH, appliance with high magnetic flux density, near exposure.
dBased on data in Tables 9 and 10.
Table 11. Relative contribution of appliances, indoor wiring, and outdoor wiring to the daily magnetic field exposure in a residential setting.
©2000 NRC Canada
208 Environ. Rev. Vol. 8, 2000
with only 5% of the work force exposed to higher TWA magnetic fields. The 75th percentile was at
0.27 µT and is close to the values associated with very high current configuration (VH) for power lines
(Wertheimer and Leeper 1982). The median (50th %) TWA magnetic flux density was at 0.17 µT and
the 25th percentile was at 0.12 µT. These percentile rankings are also presented in Table 12 and are
associated with considerable variability. Similar results can be seen for various occupations in Table 13.
Despite the variability of occupational exposure, some general conclusions can be drawn. For in-
stance, some of the highest exposures occur in the textile, utility, transportation, and metallurgical
industries. Among textile works, dressmakers and tailors who use industrial sewing machines are ex-
posed to some of the highest fields. In the utility industry, linemen, electricians, cable splicers, as well
as power plant and substation operators are among those with the highest magnetic field exposure. In
transportation, railway workers have high exposures. Among metal workers, welders, and those who
do electrogalvanizing or aluminum refining (Table 14) tend to have high magnetic field exposure .
Another industry with notable exposure is telecommunications, especially telephone linemen, tech-
nicians, and engineers. Individuals repairing electrical and electronic equipment can also be exposed to
aboveaverage magnetic fields, as can dental hygienists and motion picture projectionists (Tables12–14).
In an office environment, magnetic fields are generally at or below average (≤0.17 µT), except
near computers, photocopiers, or other electronic equipment (Table 14). People in sales, in computer
services and in the construction industry are generally exposed to lower magnetic fields.
According to Table 12, teachers were below average with aTWA magnetic flux density of 0.15 µT.
This is twice as high as the average magnetic flux densities of 0.082 µT reported for Canadian schools
(Sun et al. 1995). Schools, particularly elementary schools, are of concern because of the time young
children spend in these environments. Where and when a measurement is taken is important if you
consider the highly fluctuating environment, as previously presented, for the 9-year-old girl at school.
Normally we think of high EMF exposure only or primarily in electrical occupations and perhaps in
an office setting with computers and copy machines. However, a number of occupations not normally
classified “electrical” can be exposed to high EMFs. These include some of the professions already
mentioned (tailors and seamstresses, metal workers, and medical technicians), but they can also include
airplane pilots, streetcar and train conductors, hair dressers, and professional carpenters.
Hairdressers use hand-held hair dryers for several hours each day. A 2-h exposure to a high-intensity
hand-held hair dryer at 15 cm would give a daily exposure of 140 µT·h. Similarly, carpenters who use
power tools for extended periods on a daily basis can be exposed to exceedingly high fields. Once again
based on the highest fields associated with power saws (Table 9) at 15 cm for a 2-h daily exposure would
give a 200 µT·h exposure.
Magneticresonanceimaging(MRI)alsoknownas nuclear magnetic resonance (NMR) isan imaging
technique that exposes the body to a strong static magnetic field, approximately 60 000 times that of
the earth’s magnetic field, and to bursts of radio frequencies.The static field aligns hydrogen atoms in
the body and the radio frequency absorbed by the atoms is re-emitted to give a signal that generates the
image.The magnetic flux densityto which techniciansare exposed ranges from 0.05 to 28 µT (Table14).
Patientsareexposedtomuchhigher values.Littleinformation is availableaboutthelong-term health
effects associated with MRI. This technology should be carefully monitored because of the very high
fields generated and the increasing use of this technology in diagnosis and research.
5.3. Transportation
The few studies that document magnetic field exposure associated with transportation suggest that
exposure can be quite high depending on the mode of travel.
Typical magnetic fields for commuter trains (Table 15) are much higher than for most occupational
exposure (Table 12). According to Bennett (1994), magnetic flux densities of 24 µT have been recorded
1 m above the floor and 4 m from the line of an electric commuter train. In the Amtrak train from
Washington to NewYork, the average magnetic field at 25 Hz was 12.6 µT and the maximum field was
64 µT.
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Fig. 4. Personal exposures to magnetic fields measured with exposure meters worn by four workers in different occupations. The plots do not necessarily represent
typical EMF exposures for workers in these occupations. (Reprinted with permission from EMF Rapid 1996, Questions and answers: EMF in the workplace.)
©2000 NRC Canada
210 Environ. Rev. Vol. 8, 2000
Magnetic flux density
(µT)
Occupation Mean SD Code
Textile industry
Dressmakers and tailors 3.00 0.28
Worker 1.40 1.47
Clothing cutter 0.21 0.25
Utility industry
Lineman 3.61 10.92
Electrician 3.01 nd
Machinest 2.69 nd
Electrician 1.56 1.63
Cable splicer 1.50 3.12
Power plant operator 1.43 2.24
Relay technician 1.34 2.34
Technician 1.32 nd
Electrician 1.11 2.18
Power plant operator 1.08 nd
Lineman 1.03 nd
Substation operator 0.80 1.13
Welder 0.80 1.08
Electric generation plant operator 0.79 2.34
Mechanic 0.77 nd
Machinist 0.72 1.95
Lineman 0.65 1.59
Employee 0.57 1.51
Painter 0.45 0.45
Serviceman 0.41 0.69
Instrument and control technician 0.40 1.12
Rigger 0.38 0.37
Technical worker 0.36 0.62
Engineer 0.33 0.67
Mechanic 0.30 0.23
Pipe coverer 0.28 0.44
Foreman 0.24 0.47
Mechanic 0.23 0.3
Transportation industry
Engineer, railroad 4.03 nd
Conductor 0.61 nd
Lineman, railroad 0.59 nd
Railroad track walker 0.59 nd
Conductor and motorman 0.57 0.61
Driver, tram 0.57 0.61
Table 12. Electrical occupations derived from job titles with time-weighted average
(TWA) magnetic field exposures (NIEHS, based on Table 2.4, pp. 61–72).
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Magnetic flux density
(µT)
Occupation Mean SD Code
Station master and train dispatcher 0.30 nd
Air traffic controller 0.14 0.23
Dispatcher 0.14 0.23
Metal work
Welder and flame cutters 2.00 4.01
Electrician 1.56 1.63
Sheet metal worker 1.34 4.19
Welder 1.02 nd
Boilermaker 0.41 1.05
Factory hand and other unskilled worker 0.36 0.43
Machine molder 0.18 0.09
Coil winder 0.15 0.02
Small equipment
Repair, household appliance and power tool 0.46 0.52
Repair, office machines 0.44 0.74
Repair, radio, TV, and electronic appliances 0.36 0.23
Repair, AC, heating and refrigeration 0.31 0.27
Assembler, household appliances 0.15 0.02
Repair, data processing machine 0.15 0.64
Electrician, non-utility
Electrician 1.56 1.63
Assembler, electrical and electronics 0.57 0.25
Repair, electrical and electronic equipment 0.51 0.61
Electrician 0.37 0.32
Repair, electronic equipment 0.36 0.23
Technician, electrical engineering 0.35 0.27
Electrical and electronic engineer 0.33 0.67
Technician, electronics wireman 0.29 0.39
Sales, electrical equipment 0.26 0.14
Electrician 0.25 0.18
Supervisor, electrician 0.24 0.47
Technician, engineering 0.2 0.6
Assembler, electrical machinery 0.15 0.02
Repair, data processing equipment 0.15 0.64
Repair, electrical, and electronic equipment 0.14 0.19
Construction industry
Carpenter 0.22 0.14
Heavy equipment operator 0.21 0.16
Brickmason 0.11 0.05
Engineering
Engineer 0.32 0.67
Table 12. (continued).
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212 Environ. Rev. Vol. 8, 2000
Magnetic flux density
(µT)
Occupation Mean SD Code
Engineer (nonspecified) 0.25 0.41
Other engineers 0.25 0.41
Industrial engineer 0.23 0.23
Operating engineer 0.21 0.16
Computer services
Computer programer 0.30 0.55
Computer programer 0.25 0.28
Computer system engineer/analyst 0.21 0.41
Computer operator 0.18 0.24
Repair, computers and business machines 0.15 0.64
Computer programer 0.1 0.1
Machinist
Tool and die maker 0.28 0.40
Printing machine operator 0.18 0.09
Lathe worker 0.17 0.06
Telecommunication industry
Lineman 0.43 0.05
Technician, telephone 0.43 0.10
Technician 0.35 0.55
Engineer 0.33 0.67
Repair 0.25 0.03
Telephone fitter 0.2 0.13
Repair and installation, telephone 0.2 0.13
Repair 0.17 0.02
Repair and installation, telephone 0.16 0.09
Assembler 0.15 0.02
Broadcast equipment operator 0.14 0.23
Communications equipment operator 0.14 0.23
Other communications operator 0.14 0.23
Performer, radio and TV 0.14 0.23
Announcer, radio 0.14 0.23
Operator, radio/telegraph 0.14 0.23
Operator, telegraph operator 0.14 0.23
Chief communications operator 0.13 0.15
Foreman 0.13 0.15
Operator, telephone 0.1 0.01
Office work
Mail and message distributing occupations 0.43 0.41
Receptionist 0.21 0.47
Billing, posting, and calculating machine operator 0.14 0.13
Table 12. (continued).
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Magnetic flux density
(µT)
Occupation Mean SD Code
Accountant 0.15 0.1
Author and technical writer 0.15 0.17
General office occupations 0.15 0.18
Statistician and scientist 0.1 0.05
Sales
Sales occupations, retail 0.26 0.14
Supervisor, sales insurance, real estate 0.2 0.08
Stock handlers and baggers 0.14 0.08
Shop assistant 0.11 0.02
Miscellaneous
Forestry and logging 2.48 7.70
Projectionist, motion pictures 0.80 0.68
Dental hygienist 0.64 1.65
Groundskeeper and gardener 0.41 0.90
Traffic, shipping, and receiving clerks 0.36 0.30
Maintenance man 0.31 0.31
Precision inspectors 0.29 0.39
Farmer 0.27 0.54
Food and beverage preparation 0.22 0.13
Janitor and cleaner 0.17 0.09
Teacher 0.15 0.09
Highway patrolman 0.15 0.09
Chemist 0.15 0.06
Medical technologist 0.13 0.19
Social worker 0.09 0.02
Note: Very high: 0.66 µT, 95th%; above average: 0.27 µT, 75th%; average:
0.17 µT, 50th%; below average: 0.12 µT, 25th%; TWA = time weight average; sd = standard
deviation.
Table 12. (concluded).
Passengers may not be on these commuter trains for long but workers are exposed to them all
day.The MAGLEV (magnetic levitation) electric train produces varying frequencies and magnetic flux
densities. Alternating currents in a set of magnets in the guide way change polarity to push/pull the
train. The train is accelerated by increasing the ac frequency. Magnetic flux densities of 50 000 µThave
been reported in the passenger compartment where people work (Bennett 1994).
Airplanes generate a 400 Hz electromagnetic field. The highest fields are in the cockpit with values
above 10 µT near the conduits behind the pilot and co-pilot and near the windshield (heating element).
In the passenger part of the airplane, values between 3 to 0.3 µT are more common (unpublished data).
Since flights generally last several hours, cumulative exposure can be considerable, especially for the
pilot, co-pilot, and stewards. Employees and passengers are also exposed to higher than average cosmic
radiation at these altitudes.
Extensive monitoring of automobiles has not been done, to my knowledge. Preliminary monitoring
of a few vehicles suggests much lower magnetic fields than those associated with either commuter trains
or airplanes (unpublished data). Drivers are exposed to higher magnetic fields in smaller vehicles than
©2000 NRC Canada
214 Environ. Rev. Vol. 8, 2000
Occupation
Magnetic flux density (µT) Code
Median 5th% 95th% Median 95th%
Garment industry (Finland)
Sewing machine operator 2.20 1.00 4.00
Other factory workers 0.30 0.10 0.60
Electrical workers (various industries)
Welders 0.82 0.17 9.60
TV repairers 0.43 0.06 0.86
Construction electricians 0.31 0.16 1.20
Electrical engineers 0.17 0.05 1.20
Electric Utilities
Distribution substation operators 0.72 0.11 3.40
Electricians 0.54 0.08 3.40
Line workers 0.25 0.05 3.50
Clerical workers with computers 0.12 0.03 0.63
Workers off the job (home, travel, etc.) 0.09 0.03 0.37
Clerical workers without computers 0.05 0.05 0.16
Telecommunications
Cable splicers 0.32 0.07 1.50
Central office technicians 0.21 0.05 0.82
Install, maintenance, and repair technicians 0.16 0.09 0.31
Employed men (Sweden)
Retail sales 0.27 0.08 0.44
Machine repair and assembly 0.17 0.03 0.37
Teachers in theoretical subjects 0.12 0.04 0.31
Motor vehicle drivers 0.08 0.03 0.19
Construction machine operators 0.04 0.02 0.06
Auto transmission manufacturing
Machinists 0.19 0.06 2.80
Assemblers 0.07 0.02 0.49
Hospitals
X-ray technicians 0.15 0.10 0.22
Nurses 0.11 0.05 0.21
Note: Code based on NIEHS occupational exposure: very high: TWA 0.66 (µT), 95th%; above average:
TWA 0.27 (µT), 75th%; average: TWA 0.17 (µT), 50th%; below average: TWA 0.12 (µT), 25th%.
Table 13. Magnetic flux density averaged over a workday for various occupations (EMF Rapid 1996,
p. 35).
in larger ones, presumably since they sit closer to the alternator. Air conditioning, heating, and radios
all contribute to the ambient magnetic field. Motorbike riders are exposed to high magnetic fields in
excess of 3 µT on the seat of the motorbike (unpublished data).
©2000 NRC Canada
Havas 215
Industry and sources ELF magnetic flux
density (µT) Other frequencies Comments
Equipment manufacturing
Electric resistance heater 600–1400 VLF
Hand-held grinder 300 Tool exposures measured at operator’s chest
Induction heater 1–46 High VLF
Grinder 11
Lathe, drill press, etc. 0.1–0.4
Electrogalvanizing
Rectification room 100–460 High static field
Outdoor electric line and substation 10–170
Aluminum refining
Rectification room 30–330 High static field
Aluminum pot rooms 0.34–3 Very high static field
Steel foundry
Ladle refinery: electrodes active 17–130 High ULF
Electrogalvinizing unit 0.2–110 High VLF
Television broadcasting
Video tape degausser 16–330 1 foot away
Light control center 1–30 Walk-through survey
Video cameras (studio and microcams) 0.72–2.4 VLF
Studios and newsrooms 0.2–0.5
Table 14. Extremely low frequency magnetic fields at various occupational sites (EMF Rapid 1996, p. 37).
©2000 NRC Canada
216 Environ. Rev. Vol. 8, 2000
Industry and sources ELF magnetic flux
density (µT) Other frequencies Comments
Telecommunication
Switching rooms 0.01–130 Static, ULF–ELF transients Walk-through survey
Relay switching racks 0.15–3.2 Static, ULF–ELF transients 2-3 inches from relays
Underground phone vault 0.3–0.5 Walk-through survey
Hospitals
Magnetic resonance imaging (MRI) 0.05–28 Static, VLF, RF Technician’s work location
Intensive care unit 0.01–22 VLF Nurse’s chest
Post-anesthesia care unit 0.01–2.4
Government offices
Building power supply 2.5–18
Desktop cooling fan 100 6 inches away
Other office appliances 1–20
Power cables in floor 1.5–17
Desks near power center 1.8–5
Desk work locations 0.01–0.7 Peaks due to laser printer
Note: Static: direct current, 0 Hz; ULF: ultra-low frequency, <30 Hz; ELF: extremely low frequency, 30–300 Hz; VLF: very low frequency, 300–30 kHz; RF: radio
frequency, 30 kHz – 300 MHz.
Table 14. (concluded).
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Magnetic flux density (µT)
Train Minimum Average Maximum Commentsa
Amtrack (nonelectric) 0.09 0.64 1.3
nd 3.5a26aNY to New Haven
(60 Hz)
nd 12.6a64aWashington to NY
(at 25 Hz)
MAGLEV (electric) 0.99 3.06 7.7 50 mT and 700 V/m
maximum where
people work
Electric Railroad (worst case) nd nd 24a1 m above ground
and 4 m from line
Boston Subway (electric) 0.02 0.34 1.8
Washington, D.C. Subway
(electric) 0.60 6.02 14.6
Note: nd: no data.
aSource: Bennett 1994.
Table 15. Typical magnetic fields from commuter trains. Measurements made at 3.5 ft (110 cm) above
the floor and include the frequency range of 5 to 2560 Hz (source EPA 1993, in NRC 1997, Table 2.8,
p. 35).
5.4. Complications with exposure
Although we are beginning to get a clearer picture of the magnetic environment we have created and
can now estimate cumulative exposures, there is much we still do not know. It is not clear what attributes
of the field are important biologically.Are values above a certain threshold critical; if so, what is that
threshold? Are the rapid changes between high and low intensities biologically significant or should
we focus on time-weighted cumulative exposure? We have yet to determine the metric of biological
significance.
To complicate matters, the electromagnetic environment consists of an electric field as well as a
magnetic fields. Although the previous section and much of the literature have focused on magnetic
fields, conditions exist where both fields are present (a person standing directly under a power line or
someone in contact with an electrical appliance, for example). A changing electric field generates a
magnetic field and a changing magnetic field generates an electric current. Therefore, relative motion
betweenexternalmagnetic fields and an individual cangenerateinternalelectriccurrents,soadistinction
between the electric and magnetic components is not simple. The biological response is likely to be a
function of the fields or currents induced within our bodies rather than the external fields to which we
are exposed. This induced internal field/current is difficult to measure and equally difficult to calculate.
More than one frequency can be generated by the power distribution system. While the dominant
frequency might be 60 Hz, harmonics (multiples of the original frequency) and subharmonics (fractions
of the original frequency) as well as transients (spikes generated by random on and off switching) are
produced. The monitoring devices used to measure EMFs over a 24-h period do not necessarily record
transients. Some of the studies suggest both frequency and intensity windows, namely biological effects
thatarefrequencyandintensityspecific(Blackmanet al. 1979; Liboff1985;Dutta et al. 1989).A slightly
higher or lower frequency (or intensity) may not necessarily illicit the same biological response. Frey
(1994) comments that a good model for biological response may be one based on the radio tuned to a
specific modulation.
Not only do the electric and magnetic fields fluctuate at several superimposed frequencies and vary
©2000 NRC Canada
218 Environ. Rev. Vol. 8, 2000
in time and space but they also vary in direction. The field to which a person is exposed near a power
line depends on whether he is standing (vertical) or lying down (horizontal). Electric field exposure also
depends on the degree of grounding, which is influenced by the type of footware.
Biologicalresponse may also be influenced by thelocalmagneticfield produced by the earth and this
field may be spatially and temporally heterogeneous (Liboff 1985). What is becoming obvious is that
the area of research concerned with EMF exposure is immensely complex. It is also of vital importance
if we plan to untangle the threads of a vast storehouse of data and if we plan ultimately to understand
biological interactions with electromagnetic fields.
6. Biological response to electromagnetic fields
6.1. Cancer
Epidemiological studies of cancer have focused on two primary populations: children in residen-
tial settings and adults in occupational settings. The main cancers associated with EMF exposure are
leukemias, lymphomas, and central nervous system tumors in children and leukemias, breast cancer,
and central nervous system tumors in adults.
Cancer in children
A summary of meta-analyses for childhood cancers is provided in Table 16. The odds ratio (OR)
represents the ratio of observed cases to expected cases for a particular form of cancer. The higher the
OR the greater is the incidence rate for that cancer in the population under study.An OR of 1 suggests
no difference between cases and the reference population. Size of population and proper matching of
controls are critical for a valid statistical outcome.
The results in Table 16 indicate that most of the OR are above 1 with only a few studies at or below
1 (hatched) and half of these are for low (<0.2 µT) EMF exposure. Not all OR above 1 are necessarily
significant. If the odds ratios above 1 are due entirely to chance, however, the number of studies with
OR above and below 1 would be comparable and this is not the case.
Two studies suggest a dose/response relationship (Feychting et al. 1995; Meinert and Michaelis
1996). Odds ratios at and above 0.2 µT (Wertheimer and Leeper 1982; Ahlbom et al. 1993) appear to be
critical for childhood cancers. At 0.3 µT and higher, odds ratios above 5 have been reported, which sug-
gests more than a 5-fold increased incidence of these cancers in children (Meinert and Michaelis 1996;
Feychting et al. 1995). These values are low compared with other known carcinogens like cigarettes and
asbestos but are certainly well above background. One point that must be kept in mind is that exposure
to EMF is so “universal and unavoidable that even a very small proven adverse effect of exposure to
electric and magnetic fields would need to be considered from a public health perspective: a very small
adverse effect on virtually the entire population would mean that many people are affected.” (NRC
1997, p. 196).
The other point that needs to be remembered is that we do not have true controls in the sense of zero
exposure to technofields. Zero exposure to technologically generated EMF is no longer possible. Even
in remote regions people are increasingly exposed to broadcast frequencies from radio, television, and
satellitecommunication devices. Hence, all of these studiescompare higher exposure to lower exposure.
Irrespective of which metric is used (wire codes, distance, measurements, or calculations of ex-
posure), when viewed as a whole (Table 17), the majority of the studies suggest an OR well above 1.
Criticaldistances appear to beapproximately 50 m from apowerline and critical magnetic fluxdensities
are above 0.15 µT. Daytime spot measurements give the lowest ORs while median night measurements
gave the highest. Night-time exposure may be particularly important and may represent a “time-window
effect.”
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Havas 219
Recent studies of childhood cancers
Threeepidemiological studies were published during thereviewof this paper thatrelateto childhood
cancers and power lines. Two were Canadian studies (McBride et al. 1999; Green et al. 1999) and one
was British (Day et al. 1999). I summarize them here to keep this review as current as possible. Green et
al. (1999) conducted a case (n=88) control (n=133) study in Ontario and used different methods to
assessEMFexposure,including 48-h personal monitoring, point-in-time measurements, and wire codes.
Green et al. found an increased risk of leukemia associated with both point-in-time measurements of
the magnetic flux density in the child’s home and average magnetic flux density measured by personal
monitors . A significant (adjusted) OR of 4.5 was calculated for all leukemias among children up
to age 14 exposed to an average magnetic flux density (personal monitoring) at or above 0.14 µT.
The OR was lower (3.5) and non-significant for acute lymphoblastic leukemia. For children less than
6 years old the statistically significant OR (unadjusted) was 3.7 for all leukemias and 5.7 for acute
lymphoblastic leukemia for the same average magnetic flux density of 0.14 µT. Neither the very high
current configuration wire code used by Wertheimer and Leeper nor the high wire code used by Kaune
and Savitz showed a significant OR.
In contrast to this study, McBride et al. (1999) reported no significant odds ratios for leukemia
among children from five provinces (British Columbia,Alberta, Saskatchewan, Manitoba, and Quebec).
McBride’s group assessed EMF exposure also using different methods (48-h personal monitoring, 24-
h bedroom measurements, and wire codes) in a case-control study consisting of 399 cases and the
same number of controls. Although this study was not specifically designed to test risk associated with
distance, the authors found that “confounder-adjusted OR” for children living with 100 m or 50 m of a
line were elevated but not statistically significant (OR 1.81 for all types of leukemia and OR 1.99 for
acute lymphatic leukemia).
One possible source of error in this study is that data from the five provinces were combined for wire
codes. We saw in Table 7 that magnetic flux densities can vary enormously for wire codes in different
jurisdictions and for that reason should not be combined unless statistical tests show that they are the
same within a particular wire code category. This does not explain the lack of relationship with 48-h
personal monitoring of magnetic flux density and incidence of leukemia. Clearly this study does not
provide support for an increased risk of childhood leukemias with EMF exposure.
Unlike previous childhood epidemiological studies, both Green et al. (1999) and McBride et al.
(1999) monitored electric field exposure as well as magnetic flux density. Neither found a significantly
higher risk (OR) of leukemia with increasing electric field exposure. The highest electric potential
categories were above 11.6V/m in the Green study and between 25 and 65 V/m in the McBride study.
One key question needs to be answered and that is what metric should be measured? Does a 48-h
personal monitoring adequately assess our exposure to electromagnetic fields? Could it be that exposure
in these environments to pollutant aerosols is a contributing factor to cancer as suggested by Fews et al.
(1999)who found elevateddepositionof radon decay products near400,275,and132 kV ac transmission
lines?
One of the largest childhood cancer studies associated with exposure to power-frequency magnetic
fields was recently published by Day (1999). This was a case-control study covering England,Wales,
and Scotland and consisted of 3838 cases and 7629 controls. Despite the large sample size, only 17
individuals (8 cases and 9 controls) or less than 0.4% of the study group were exposed to magnetic flux
densities above 0.4 µT. The adjusted odds ratios for acute lymphoblastic leukemia and total leukemias
wereanon-significant1.51and1.68,respectively.The only statistically significant result wasfor cancers
of the central nervous system for the category between 0.1 and 0.2 µT. Higher magnetic field exposures
were non-significant for CNS cancers. According to the author this study provided no support for the
hypothesis that power-frequency magnetic fields increase the risk of childhood cancer. However, Day
does state that “a scientific question may still remain about the effect of exposures higher than 0.4 µT.”
©2000 NRC Canada
220 Environ. Rev. Vol. 8, 2000
Meta-analyses Descriptiona
NRPB 1992bWire codes (HCC vs. LCC)
Distance from EMF source
Measured EMF
Ahlbom et al. 1993 Calculated EMF
Washburn et al. 1994cDistance: 50 m boundary
NAS Report 1994c,dWire codes (HCC vs. LCC): fixed
Wire codes (HCC vs. LCC): random
Wire codes and distance <100 m: fixed
Wire codes and distance <100 m: random
Spot measurements (≥2 mG): fixed
Spot measurements (≥2 mG): random
Feychting et al. 1995eEstimated 0.1–0.19 µT
Estimated >0.2 µT
Estimated >0.5 µT
Meinert and Michaelis 1996c,fWire code (HCC vs. LCC)
Distance: <100 m
Distance: <50 m
Distance: <25 m
EMF measured: >0.1 µT
EMF measured: >0.2 µT
EMF measured: >0.3 µT
Note: OR > 1, 95th% Cl ≥1; OR > 1, 95th% Cl < 1; OR ≤1, 95th% Cl ≤1.
aHCC = high current configuration; LCC = low current configuration.
bWertheirmer and Leeper (1979) study not included.
cWertheirmer and Leeper (1979) study included.
dEstimates based on fixed and random effects statistical models.
eReference <0.1 µT (adjusted for age, gender, and country).
fDichotomous cut-points.
Table 16. Summary of meta-analyses for childhood cancers (based on Table 4.25,
©2000 NRC Canada
Havas 221
Odds ratios (95% confidence intervals)
All cancers Leukemias CNS tumors Lymphomas All Leu CNS Lym
1.53 (1.04–2.25) 1.39 (1.08–1.78) 2.04 (1.11–3.76)
1.11 (0.71–1.73) 1.31 (0.72–2.21) 1.09 (0.50–2.37)
1.82 (1.09–3.04) 1.16 (0.65–2.08) 1.85 (0.91–3.77)
1.3 (0.9–2.1) 2.1 (1.1–1.41) 1.5 (0.7–3.2) 1.0 (0.3–3.7)
1.49 (1.11–2.00) 1.89 (1.34–2.67) 1.58 (0.91–2.76)
1.48 (1.18–1.85)
1.52 (1.08–2.14)
1.36 (1.13–1.63)
1.38 (1.08–1.76)
0.92 (0.57–1.49)
0.89 (0.51–1.57)
1.4 (0.6–2.9) 2.0 (0.7–5.3) 1.1 (0.3–3.6) 0.7 (0.1–5.6)
1.5 (0.9–2.7) 2.0 (1.0–4.1) 0.8 (0.3–2.4) 2.1 (0.8–5.5)
3.5 (1.7–7.3) 5.1 (2.1–12.6) 2.3 (0.6–8.0) 3.3 (0.7–15)
1.37 (0.94–2.00) 1.66 (1.11–2.49) 1.50 (0.69–3.26) 1.32 (0.52–3.37)
1.09 (0.89–1.35) 1.13 (0.79–1.62)
1.10 (0.86–1.40) 1.31 (0.92–1.87) 1.53 (0.19–12.0)
1.42 (0.88–2.29) 1.85 (0.98–3.49)
0.97 (0.82–1.15) 1.55 (0.88–2.73) 0.89 (0.39–2.05) 2.18 (0.51–9.34)
1.23 (0.96–1.57) 1.89 (1.10–3.26) 1.30 (0.78–2.19) 2.21 (0.72–6.80)
1.62 (1.10–2.39) 1.27 (0.28–5.76) 1.89 (0.80–4.43) 1.69 (0.43–6.59)
pp. 205–206 in NIEHS 1998).
©2000 NRC Canada
222 Environ. Rev. Vol. 8, 2000
Cancer in adults
For adults, the link between EMF exposure and leukemia (Table 18), brain tumors (Table 19), and
breast cancer (Table 20) is also convincing when viewed as a whole. Two forms of leukemia seem
to predominate: acute myeloid leukemia (AML) and chronic lymphocytic leukemia (CLL). As with
childhood cancers there is some evidence for a dose/response relationship (Table 18) although it is very
difficult to measure dose in an occupational setting and estimates can provide only ball-park figures.
For this reason it is difficult to provide a threshold value, if indeed one exists, based on the information
available.
Among the cancers, the one with the highest OR is breast cancer in men. Several studies in Table 20
indicate a relative risk (RR) above 4 for men while the highest value for women is 2. This form of cancer
is rare among men and the presence of one or two cases is likely to result in a high risk estimate. The
lower OR of 2 for women should not be taken lightly since as many as 5 000 women die from breast
cancer each year in Canada and as many as 44 000 die in the United States (WHO 1998).
Another concern related to cancer is parental exposure and pre-natal exposure to electromagnetic
fields with subsequent tumor development in offspring. Once again, there is some evidence that relative
risk (RR) or the standardized incidence ratio (SIR)3is elevated (Tables 21 and 22) but, for these studies,
sample size is low and the 95% confidence interval is broad. Only two of the seven studies in Table 21
reported a significant elevated relative risk for central nervous system tumors in offspring of EMF-
exposed parents. This topic is discussed in greater detail in the section on Reproduction.
Mechanisms
The fact that different cancers are associated with EMF exposure and that not all studies show a
higher incidence (or odds ratio) for a particular form of cancer is not an inconsistency if EMFs promote
rather than initiate cancer.
Animal studies confirm this perspective. Exposing laboratory animals to EMFs does not result in
cancer unless they already have cancerous cells in their body. Often strains prone to develop a specific
type of cancer are selected as the test organism or well-known cancer initiators such as MNU (N-
methyl-N-nitrosourea) or DMBA (7,12-dimethylbenz[ a] anthracene) are used prior to EMF exposure
in laboratory studies.
Some of the most convincing studies deal with mammary cancer in rats (Table 23). Several inter-
esting observations can be made when the data are viewed together. The data in Table 23 have been
ranked according to the magnetic flux density used in the experiment.At higher magnetic flux densities
(≥250 µT) there is some evidence of a beneficial effect of EMF exposure. In experiments that tested a
magnetic flux density of 100 µT or less, the tumor promoting effects of EMFs (based on incidence rates,
number of tumors per animal, tumor size, and latency period) become more evident. This supports the
concept that higher intensities may not necessarily be more harmful and that the classical toxicological
model based on dose-response may not be an appropriate model for EMF exposure.
Of the metrics used to quantify tumor promotion, increases in the incidence rate and decreases in
the latency period seem to be most strongly associated with EMF exposure below 100 µT (Table 24).
Both of these suggest that EMFs compromise the immune system or promote cell division, resulting in
a more aggressive form of cancer.
Studies show that cell proliferation is enhanced in the presence of an alternating EMF (Katsir et
al. 1998). This is also supported by early studies on the effects of varying geomagnetic fields on cell
mitosis (for human skin carcinoma) (Dubrov 1978). The rate of mitosis seems to be enhanced in a
varying electromagnetic field. Thus, the apparent inconsistency that links EMFs to healing and cancer
3Standardized incidence ratio (SIR), standardized mortality ratio (SMR), relative risk (RR), and odds ratio (OR) are three ways
of measuring the “risk” of association in different types of epidemiological studies.
©2000 NRC Canada
Cited in Reference
(location) Associated magnetic
flux density (µT)a,bCrude OR
or RRc
NRC NIEHS Categorya95% CI
Wire code
Yes Yes Wertheimer and Leeper 1979 HCC vs. LCC: at death HCC = 0.25 (median) 3.0 1.8–5.0
(Denver, Colo., U.S.A.) HCC vs. LCC: at birth LCC < 0.05 (median) 2.3 1.3–3.9
Yes No Fulton et al. 1980 VH VH = 0.18 (mean) 1.0 0.6–1.8
(Rhode Island, N.Y., U.S.A.) OH OH = 0.096 (mean) 1.2 0.7–2.1
OL OL = 0.065 (mean) 1.1 0.6–1.9
Reference = VL VL = 0.044 (mean)
Yes Yes Savitz et al. 1988 VH vs. VL VH = 0.216; VL = 0.03 2.8 0.9–8.0
(Denver, Colo., U.S.A.) OH vs. L OH = 0.09; OL = 0.05 1.5 0.9–2.6
Yes Yes London et al. 1991 VH VH = 0.107 (median) 2.2 1.1–4.3
(Los Angeles, Calif., U.S.A.) OH OH = 0.066 (median) 1.4 0.8–2.6
OL OL = 0.058 (median) 1.0 0.5–1.7
Reference = VL VL = 0.043 (median)
No Yes Linet et al. 1997 VH 0.9 0.5–1.6
New (location not given) OH 1.0 0.7–1.5
Acute Lymphoblastic Leukemia OL 1.1 0.7–1.5
(ALL) UG + VL = reference Reference for wire code ALL
Distance
Yes No Feychting and Ahlbom 1993 To power line <51 m = 0.138 (mean) 2.9 1.0–7.3
(Sweden) To power line 51–100m=0.065(mean) 1.1 0.4–2.7
Reference ≥101m=0.044(mean)
Yes No Coleman et al. 1989 To substation 0–24m=0.18(mean) 1.6 0.3–8.4
(SE London, U.K.) To substation 25–49m=0.096(mean) 1.5 0.6–3.6
To substation 50–99m=0.065(mean) 0.7 0.4–1.4
Reference >100 m = 0.044 (mean)
Measured
Yes Yes Savitz et al. 1988 At low power 0.2 1.9 0.7–5.6
(Denver, Colo., U.S.A.) At high power 0.2 1.4 0.6–3.5
Yes No Tomenius 1986 Total residence ≥0.3 0.3 0.1–1.1
(Stockholm, Sweden) Reference <0.3
Yes No London et al. 1991 24-h ≥0.268 1.5 0.7–3.3
(Los Angeles, Calif., U.S.A.) 24-h 0.119–0.267 0.9 0.5–1.7
24-h 0.068–0.124 0.7 0.4–1.2
Odds ratio or relative risk
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Cases Controls
145 154
136 136
47.5 56.3
55.4 56.3
49.5 56.3
45.5 56.3
35 96
97 259
42 24
80 68
58 75
20 27
408 (matched cases)
634
689
26 431
33
11 12
22 48
48 78
36 207
37 204
410
239 202
20 11
24 22
35 42
Table 17. Residential electromagnetic field exposure and childhood leukemia. Based on Table A5-4 in NRC 1997 and Table 4.21 in NIEHS 1998.
Cited in Reference
(location) Associated magnetic
flux density (µT)a,bCrude OR
or RRc
NRC NIEHS Categorya95% CI
Reference for 24-h ≤0.067
No Yes Linet et al. 1997 24-h 0.4–0.499 6.4 1.3–32
New (location not given) 24-h 0.3–0.399 1.5 0.6–3.5
Acute Lymphoblastic Leukemia 24-h 0.2–0.299 1.3 0.7–2.5
(ALL) 24-h 0.1–0.199 1.2 0.8–1.7
Matched analysis 24-h 0.065–0.099 1.0 0.7–1.4
Reference <0.065
No Yes Michaelis et al. 1998 Median at night ≥0.2 3.9 0.9–17
New (Germany) Median measurement ≥0.2 3.2 0.7–15
Mean measurement ≥0.2 1.5 0.4–5.5
Control <0.2
No Yes Michaelis et al. 1997 Median at night ≥0.2 3.8 1.2–12
New (Lower Saxony, Germany) Median measurement ≥0.2 2.3 0.8–6.7
Reference <0.2
Yes No London et al. 1991 Spot >0.125 1.2 0.5–2.8
(Los Angeles, California, USA) Spot 0.068–0.124 1.4 0.7–2.9
Spot 0.032–0.067 1.0 0.6–1.9
Reference ≤0.031
Estimated
Yes No Feychting and Ahlbom 1993 Spot >0.2 0.6 0.2–1.8
(Sweden) Spot 0.1–0.19 0.2 0.0–0.9
Reference <0.1
Yes No Feychting and Ahlbom 1993 Estimated ≥0.3 3.8 1.4–9.3
(Sweden) Estimated ≥0.2 2.7 1.0–6.3
Estimated 0.1–0.29 1.5 0.4–4.2
Estimated 0.1–0.19 2.1 0.6–6.1
Reference <0.09
Yes Yes Olsen et al. 1993 Estimated ≥0.4 6.0 0.8–44
(Denmark) Estimated ≥0.25 2.5 0.3–6.7
Adjusted OR used Estimated ≥0.1 1.0 0.3–3.3
Estimated 0.1–0.39 0.3 0.0–2.0
Estimated 0.1–0.24 0.5 0.1–4.3
Reference <0.1
Table 17. (continued).
Odds ratio or relative risk
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Cases Controls
85 69
463 matched pairs
129 2 controls
per case
16 11
23 14
34 28
67 56
470
167
19 207
732
746
447
433
27 475
31
54
48
17
14
829 1658
Cited in Reference
(location) Associated magnetic
flux density (µT)a,bCrude OR
or RRc
NRC NIEHS Categorya95% CI
Yes Yes Verkasalo et al. 1993, 1994 10-yr cumm. exposure ≥1.0 3.5 0.7–10
(Finland) 10-yr cumm. exposure ≥0.40 1.2 0.3–3.6
10-yr cumm. exposure 0.01–0.39 0.9 0.6–1.3
Yes Yes Verkasalo et al. 1993, 1994 Average exposure ≥0.2 1.6 0.3–4.5
(Finland) Average exposure >0.01–0.19 0.9 0.6–1.3
No Yes Tynes and Haldorson 1997 Closest to diagnosis ≥0.2 0.5 0.1–2.2
New (Norway) Closest to diagnosis ≥0.14 0.8 0.3–2.4
Closest to diagnosis 0.05–0.13 1.5 0.7–3.3
Reference <0.05
Note: wire code; distance; measured; estimated.
aWire codes: VH = very high; OH = ordinary high; OL = ordinary low; VL = very low; HCC = high current configuration; LCC = low current
configuration; UG = underground
bMagnetic fields for wire codes and distance categories are based on data in Appendix B, NRC 1997.
cOR = odds ratio; RR = relative risk; cumm. = cummulative; expected = based on population at large.
Table 17. (concluded).
Odds ratio or relative risk
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Cases Controls
144 cohort size
cases 68 300 boys
identified 66 500 girls
3 1.93 expected
32 36.1 expected
500 max 2004 max
5 controls/case selected
Reference, country, study type, and
sample size Description
a
Exposure (µTunless
otherwise noted)
Leukemia Acute myeloid leukemia Chronic lymphocytic
leukemia
Cases OR
b
95% CI
c
Cases OR
b
95% CI Cases OR
b
95% CI Leu AML CLL
Matanoski et al. 1993 CE: TWA > median 35 2.5 0.7–8.6 ns
USA, AT&T employees Peak > median (w/all switches) 35 1.6 0.5–4.9 ns
3 controls/case Peak > median (w/old switches) 35 2.6 0.8–8.6
c
Sahl et al. 1993 Total CE: TWA 25 µT-year 13 1.1 0.8–1.5
Cal. Edison Co. utility workers Total CE: median 3.5 µT-year 10 1.0 0.75–1.4
10 controls/case Total CE: 2–12 years before death: median 3.5 µT-year nd 0.6 0.32–1.2
Miller et al. 1996 CE TWA: E-field: nd 3.2–7 µT-year 16 1.7 0.58–4.8
Canada, Ontario Hydro Cohort utility workers ≥7.1 µT-year 24 1.6 0.47–5.2
1484 cancer cases, 50 leukemia cases
CE TWA: E-field: 172–344 V/m-year 3.2–7 µT-year 2 1.2 0.10–15
≥7.1 µT-year 6 7.8 1.1–58
CE TWA: E-field: E-field > 345 V/m-year 3.2–7 µT-year 8 11 1.5–84
≥7.1 µT-year 17 11 1.3–97
Johansen and Olsen 1998 TWA: low exposure (men only) 0.1–0.29 16 1.0 ns
Denmark, utility worker cohort, TWA: medium exposure (men only) 0.3–0.99 16 0.9 ns
total 32 006 TWA: high exposure (men only) >1.0 12 1.1 ns
Kheifet et al. 1997 Measured: 50th–75th% Low 1.2 0.94–1.6
Meta-analysis of 38 studies Measured: 75th–90th% Medium 1.4 1.1–1.8
EMF exposed workers Measured: >90th% High 1.3 1.0–1.7
Broad definition: high EMF exposure or electrical occupations 18 1.4 1.2–1.7 12 1.6 1.1–2.2
London et al. 1994 TWA: highest category ≥0.81 30 1.4 1.0–2.0 10 2.3 1.4–3.8 4 0.8 0.4–1.5 CML
LA County, electrical workers For chronic myeloid leukemia
Case-control
Floederus et al. 1993 TWA: 2nd quartile 0.16–0.19 24 1.0 0.5–1.8 17 1.1 0.5–2.3
Sweden TWA: 3rd quartile 0.2–0.28 18 0.8 0.4–1.6 33 2.2 1.1–4.3
Table 18. Epidemiological studies of leukemia with full-shift measurements of magnetic fields (Table 4.11, pp. 147–150, NIEHS 1998).
Reference, country, study type, and
sample size Description
a
Exposure (µTunless
otherwise noted)
Leukemia Acute myeloid leukemia Chronic lymphocytic
leukemia
Cases OR
b
95% CI
c
Cases OR
b
95% CI Cases OR
b
95% CI Leu AML CLL
Case = 250, control = 1121 TWA: 4th quartile ≥0.29 23 1.0 0.6–1.9 41 3.0 1.6–5.8
TWA: >90th percentile ≥0.41 8 0.9 0.4–2.1 22 3.7 1.8–7.7
Theriault et al. 1994 CE TWA: >median ≥3.1 µT-year 25 3.2 1.2–8.3 24 1.5 0.5–4.4
Canada and France, utility workers CE TWA: >90th percentile ≥16 µT-year 4 2.7 0.5–15 6 1.7 0.44–6.7
4151 cases, 6106 controls
Savitz and Loomis 1995 CE TWA: highest category ≥4.3 µT-year for AML 5 1.6 0.51–5.1 5 0.55 0.17–1.8
USA, electric utility workers case-control CE TWA: highest category ≥2.0 µT-year for CLL
Feychting et al. 1997 TWA: occupational exp only <0.20 26 1.7 0.9–3.2 37 1.2 0.7–1.9
Sweden TWA: occupational exp only ≥0.20 14 1.8 0.9–3.8 28 1.7 1.0–2.9
Case-control
TWA: occup exp > 2.0 µT: resid exp low <0.2 11 1.5 0.6–3.6 26 1.5 0.8–2.7
TWA: occup exp > 2.0 µT: resid exp high ≥0.20 3 6.3 1.5–26 2 2.1 0.4–10
Note: OR > 1, 95% Cl ≥1; OR > 1, 95% Cl < 1; OR ≤1, 95% Cl ≤1.
a
TWA: time-weighted-average; CE: cummulative exposure
b
OR: odds ratio
c
p< 0.05, ns = not significant
d
NST = nervous system tumors (includes brain cancer)
Table 18. (concluded).
Havas 223
is resolved, if the underlying mechanism accelerates cell division, since the growth of cancerous cells
as well as healthy cells involved in the healing process can be stimulated.
But changes in the rate of mitosis provides only part of the picture; melatonin provides another.
Melatonin plays many roles in the body. One is the regulation of estrogen levels. When melatonin levels
are low, estrogen levels are high, and high levels of estrogen stimulate estrogen-sensitive breast cancer
(Stevens 1987a,b). This appears to be true for endogenous estrogen (estrogen produced by the body)
and for exogenous estrogen (estrogen supplements) taken by post-menopausal women for example.
Melatonin has several cycles in the body. It has a diurnal cycle with night-time maxima. It has a
seasonalcyclewith winter maxima. Both ofthese may be linked tolightexposure.Night-time melatonin
levelsalso decrease aspeopleage.Theproduction of melatonin is partly controlledbyvisible light. Even
short periods of light exposure in the evening can decrease night-time melatonin levels while similar
exposure earlier in the day has no effect. Electromagnetic frequencies, other than those of visible light,
can also influence melatonin synthesis (Wilson et al. 1990).
In animal studies, there is a clear connection among melatonin, mammary cancer, and exposure
to EMFs (at visible light and at extremely low frequencies) (Wilson et al. 1990). In humans, the link
between light and melatonin has been firmly established and the disruptions of the normal daily cycles
of melatonin synthesis are a risk factor for human breast cancer (Stevens 1987a,b).
Although we know that light affects melatonin, the question remains, “Can electromagnetic fields at
power line frequencies and at intensities commonly found in residential or occupational settings affect
melatonin production in humans?” This critical question has now been answered. Liburdy et al. (1993)
reported a threshold for night-time melatonin production between 0.1 and 1.2 µT. These magnetic flux
densities can be found in both residential and occupational settings (see section on Exposure). As with
light, timing of exposure may be critical. So exposure to power line frequency EMF at intensities found
in the home can reduce night-time melatonin production in humans.
With lower melatonin, estrogen levels increase, which in turn stimulates estrogen-responsive breast
cancer. Breast cancer in men and women have been linked to EMF exposure, as shown in Table 21. The
EMF – melatonin – estrogen – breast cancer connection is supported by many different types of studies
and is one of the more probable mechanisms implicated in EMF exposure. Liburdy et al. (1993) report
that normal physiological concentrations of melatonin can decrease the growth rate of MCF-7 cells
(human estrogen-responsive breast cancer cells). Melatonin may play a role in other forms of cancer
as well since it is a powerful antioxidant that inhibits the proliferation of cancerous cells (Reiter et al.
1995).
Similar results have been obtained for tamoxifen, a strong anti-cancer drug. The action of tamoxifen
is blocked at very low magnetic flux densities of 1.2 µT for breast cancer (Harland and Liburdy 1997;
Harland et al. 1998). Results have been replicated and extended to other cell lines including human
glioma cells (Afzal and Liburdy 1998). The significance of this is that exposure to high electromagnetic
fields may block the potential of the drug and thus reduce the effectiveness of chemotherapy for cancer
treatment.
The evidence at ambient intensities is mounting to support at least two plausible mechanisms in-
volved in cancer promotion — increased rate of cell division and the role of melatonin in estrogen
regulation and as an antioxidant.