v>EPA
United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
E PA/600/9-91/016A
June 1991
External Review Draft
A Research
Strategy for
Electric and
Magnetic Fields:
Research Needs and
Priorities
Review
Draft
(Do Not
Cite or Quote)
This document is a preliminary draft. It has not been formally
released by the U.S. Environmental Protection Agency and
should not at this stage be construed to represent Agency
policy. It Is being circulated for comment on Its technical
accuracy and policy Implications.
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DRAFT EPA/600/9-91 /016A
DO NOT QUOTE OR CITE June 1991
Review Draft
A RESEARCH STRATEGY FOR ELECTRIC AND MAGNETIC FIELDS:
RESEARCH NEEDS AND PRIORmES
NOTICE
This document is a preliminary draft. It has not been formally released by the U.S.
Environmental Protection Agency and should not at this stage be construed to represent
Agency policy. It is being circulated for comment on its technical accuracy and policy
implications.
Office of Research and Development
U.S. Environmental Protection Agency
Washington, D.C.
Printed on Recycled Paper
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A RESEARCH STRATEGY FOR ELECTRIC AND MAGNETIC FIELDS:
RESEARCH NEEDS AND PRIORITIES
CONTENTS
Executive Summary ES-1
Chapter I. Introduction 1-1
Chapter II. Health Effects 11-1
A. Methodologic Issues for Epidemiology 11-1
B. Cancer II-3
C. Reproductive and Developmental Effects II-5
D. Nervous System Effects II-6
E. Immune System Effects II-9
Chapter III. Biophysical Mechanisms 111-1
A. Physical Interactions III-2
B. Biological Interactions III-3
Chapter IV. Exposure Assessment IV-1
A. Source Identification and Characterization IV-1
B. Instrumentation and Calibration IV-2
C. Environmental Measurement and Documentation IV-2
D. Exposure Modeling IV-3
E. EMF Coupling to Biological Objects IV-4
F. Laboratory Exposure Systems IV-5
Chapter V. Control Technology V-1
A. Transmission and Distribution Lines V-2
B. Residences and Workplaces V-3
C. Special Considerations V-5
Chapter VI. Summary and Conclusions VI-1
Bibliography R-1
Glossary G-1
Appendix A. Research Recommendations A-1
Appendix B. EPA Work Group B-1
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EXECUTIVE SUMMARY
Recently, widespread media attention has been focused on whether adverse human
health effects could result from exposure to electric and magnetic fields (EMF). Public and
private concerns are based on research reports of a statistical association between EMF
exposure to human populations and some forms of cancer, as well as measurable biological
effects in laboratory animals, tissues, and cells. Although the existing evidence is insufficient
for discerning a cause-effect relationship for EMF exposure and human disease or injury, it
does suggest the need for further research to allow for a realistic assessment of the
possibility of health risks and their magnitude.
The goal of this document is to describe a strategic framework which identifies the
major research topics and their relative priorities. It is meant to be a "research strategy" and
not a "research plan." That is to say the focus is on general EMF research needs and relative
priorities within the context of the EMF question; not on development of specific research
plans for each area of potential interest. The prioritization is based on a determination of
which research topics are most likely to provide near-term results that will improve and/or
strengthen our assessment of EMF health risks.
The discussion is devoted exclusively to EMF in the range of 0 to 500,000 Hertz (Hz).
Sources emitting EMF in this spectrum include electric power lines (e.g., transmission and
distribution lines, electric circuits in the home), electrically powered devices in the home and
office (e.g., electric blankets, televisions, hair dryers, video display terminals, fluorescent
lights), industrial equipment (e.g., arc welding machines, lathes, induction furnaces), civilian
and military communication systems (e.g., LORAN, OMEGA, GWEN), and medical devices
(e.g., magnetic resonance imagers). Although EMF at frequencies above 500,000 Hz may
also have potential health effects, the lower range is emphasized because of the concern
about EMF from power lines and commonly used electric devices in the home and workplace.
The strategy evaluates research needs in four major areas:
o Animal and human studies to determine if adverse health effects (cancer and
reproductive, nervous, and immune system effects) might result from EMF
exposure.
o Investigation of biophysical mechanisms, including both physical and biological
interactions, that underlie any effects which may occur from exposure to EMF
o Improved assessment of human exposure to EMF, including source
identification and characterization, instrumentation development, exposure
measurement and modeling, EMF coupling to biological objects, and
laboratory exposure systems.
o Determining what type of control technology, if any, may be needed to prevent
and reduce human exposure to EMF.
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High priority research areas are those determining possible carcinogenic health
effects, biophysical mechanisms, and human exposure assessment. The possible effects on
reproductive and nervous systems were assigned a medium research priority. A low priority
rank was given to immune system effects and control technology investigation. Research
recommendations are summarized in the conclusions (Chapter VI) and listed by topic in
Appendix A.
Although the research needs and relative priorities are based primarily on
consideration of health risk assessment issues, the research to be accomplished is not
specific to any particular public or private organization.
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CHAPTER I
INTRODUCTION
The high standard of living in the United States is due in large measure to the use of
electricity. Our technological society developed electric power generation, distribution, and
utilization with little expectation that exposure to the resultant electric and magnetic fields (EMF)
might possibly be harmful beyond the obvious hazards of electric shocks and burns, for which
protective measures were instituted. Today, the widespread use of electric energy is clearly evident
by the number of electric power lines and the myriad of electrically energized devices in the home,
workplace, medical arena, and outside environment.
Because of the extensive use of electric power, everyone in the United States today is
exposed to a wide range of EMF not present in the pre-technological world. Recent research
reports describe an association between exposure to EMF and health effects in human populations,
biological effects in laboratory animals, and biological effects in cells and tissues derived from
human beings and laboratory animals. Although the evidence is insufficient to relate human health
effects to specific exposure levels of EMF or to prove a cause-and-effect relation between EMF
exposure and human disease, the potential for health effects is a concern because of the huge
population exposed to EMF. More than 100,000,000 people -- virtually all those born in the United
States since 1940 - have been exposed throughout their lives to technology-generated electric and
magnetic fields.
This document addresses sources of EMF that emit electric and magnetic fields at
frequencies of 0 to 500,000 Hertz (Hz). Such sources include electric power lines, including
transmission and distribution lines as well as electric circuits within homes, offices, and industrial
facilities, electric grounding systems, and electrically powered devices such as home appliances,
office and industrial equipment, civilian and military communication and navigation systems, and
medical devices. Specific examples of the above include electric blankets, electrically heated water
beds, electric razors, hair dryers, video display terminals (VDTs), photocopiers, printers, facsimile
machines, lathes, drill presses, fluorescent lights, light dimmers, televisions, arc welding machines,
induction furnaces, magnetic resonance imaging equipment, navigational and communication
systems such as LORAN, OMEGA, and GWEN; and electric trains, cars and other mass transit
systems. Although exposure to EMF at frequencies above 500,000 Hz is also a health concern, the
lower range is emphasized because of the heightened concern for possible health effects from
exposure to 60 Hz EMF from power lines and to commonly used devices in the home and
workplace that emit EMF below 500,000 Hz. An EPA report entitled "Biological Effects of
Radiofrequency Radiation" (EPA 600/8-83-026F), published in 1984 is a critical and comprehensive
review of the literature on frequencies above 500,000 Hz.
This report describes a research strategy to address the concern that exposure to EMF,
aside from electric shocks and burns, might have significant human health effects. The goal of this
document is to identify needs and specify priorities for research to determine the possible
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health effects of EMF exposure, define exposure conditions, and determine what type of control
technologies might be needed to mitigate EMF exposure in the home, workplace, and outside
environment. The recommendations in this report describe research needs for (1) human health
effects that specifically address cancer, reproduction and development, the nervous system, and
the immune system; (2) biophysical mechanisms; (3) exposure assessment; and (4) possible
control technologies. Examples are used for each of these categories to illustrate the types of
important research needs.
The report format consists of two parts. First, an overview of the current state of knowledge
for each of the four subject areas is presented; the overview identifies research gaps and explains
the rationale for the recommendations. Second, research recommendations are given for important
unresolved issues and emerging technologies. The discussion of research needs and priorities is
based on literature reviews and other reports listed on page R-1. The literature is not reviewed in
detail and original research articles are not cited.
Important questions considered in this report are:
o What, if any, are the health effects in human populations exposed to EMF?
o What, if any, are the other biological effects of EMF exposure?
o What are the biophysical mechanisms that underlie interactions between EMF and
biological systems?
o What electric and magnetic fields exist in the home, workplace, and the outdoor
environment?
o What are the sources of the fields?
o If necessary, how can exposure be mitigated?
The document is written for scientists and engineers, managers, regulators, and policy
makers who are interested in the research issues associated with EMF. It is meant to identify
important research needs and to prioritize those needs based on their relevance for future
decisions about the likelihood and magnitude of human health effects resulting from EMF exposure.
The research strategy outlined here is envisioned as a framework from which mission-oriented
research programs can be derived. It was developed without consideration for which organizations
might perform the necessary research.
Concerns about potential health effects associated with EMF were the stimulus for recent
interest by Federal agencies in the associated research questions. The EPA critically reviewed the
literature on cancer in "Evaluation of the Potential Carcinogenicity of Electromagnetic Fields"
(External Review Draft, EPA/600-6-90/005B, October 1990). They concluded that the data are
insufficient to determine whether a cause-and-effect relation exists between EMF exposure and
cancer; clearly highlighting the need for further research. The Food and Drug Administration
briefed (11/14/90) an advisory committee on EMF exposure levels and possible human health
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effects associated with use of electric blankets. The National Institute for Occupational Safety and
Health sponsored a workshop on the Health Effects of Electromagnetic Radiation on Workers (1/30-
31/91) to identify research that would close the knowledge gaps and permit reliable
recommendations for protecting workers. The National Institute of Health held a workshop on
Recent Developments in the Health Consequences and Clinical Applications of Low Frequency
Electromagnetic Fields (2/11/91) to brief members of a research grant panel on the current state of
knowledge of EMF.
In addition to Federal agencies, a wide range of national and international groups, industrial
associations, and state agencies have recognized the importance of EMF research. A sampling of
comments is given below.
With advances in technology and the ever greater need for electric energy, human
exposure to 50/60 Hz electric and magnetic fields has increased to the point that valid
questions are raised concerning safe limits of such exposure...From a review of the scientific
literature, it is apparent that gaps exist in our knowledge, and more data need to be collected
to answer unresolved questions concerning biological effects of exposure to these fields.
(International Radiation Protection Association, Health Physics, vol. 58, pp. 113-114, 1990)
Further study is needed on the influence of electric and magnetic fields on cellular and
animal systems, particularly in the areas of the nervous system and the reproductive
system...Emphasis should be given to validating recent findings that suggest an association
between cancer and exposure to ELF [extremely low frequency] fields...Because the lack of
exposure data is the greatest source of uncertainty in investigations of human health effects,
increased effort is needed to improve exposure assessment techniques for future human
studies. (World Health Organization, Nonionizing Radiation Protection, Second Edition, pp.
223-224, 1989)
Research results available raise important scientific questions in the areas of
developmental biology, neural function, dosimetry, and mechanism. To answer these
questions and to assess their implications for potential health hazards will require high quality
research, fastidious reporting, and independent replication of experiments. (Nonthermal
Effects of Nonionizing Radiation, Final Report, National Academy of Sciences, National
Research Council, pp. 5-6, 1986)
Although too little is known about field effects on cells and effects in the whole animal
to conclude that there is a causal connection between ELF [extremely low frequency] fields
and disease, there is also too much evidence for effects of weak fields on important biological
functions to ignore the possibility that harmful health effects may occur. More research is
needed to decide if the biological interactions with ELF fields are only interesting laboratory
phenomena or are the signature of a widespread environmental health problem. (Potential
Health Effects of Electric and Magnetic Fields From Electric Power Lines, Report to the
California State Legislature, September 15, 1989, p. 100)
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The possibility of EMF playing a role in carcinogenesis cannot be ruled out, but much
work remains to be done in identifying a carcinogenic mechanism, if any, and in providing an
accurate assessment of human risk...However, much additional research needs to be done
on the issue. Exposure standards and reliable estimates of human risk cannot be
ascertained without such necessary research. (Extremely Low Frequency Electric and
Magnetic Fields and Cancer: A Literature Review, Electric Power Research Institute, EPRI EN-
6674, December 1989, see Report Summary)
A critical need, at present, is significant increases in federal funding for research on
interaction mechanisms and animal studies, while maintaining efforts in epidemiology but with
greater emphasis on confounding factors and co-carcinogens and agents with known
carcinogenicity. Moreover, a measurement program to identify and characterize sources of
electric and magnetic fields would be essential before procedures for exposure mitigation
could be implemented, if needed. (Statement to the Subcommittee on Natural Resources,
Agriculture Research, and Environment Committee on Science, Space, and Technology, U.S.
House of Representatives, James C. Lin, Chairman, Committee on Man and Radiation,
Institute of Electrical and Electronic Engineers, July 25, 1990)
Recent years have seen dramatic developments in the science which have prompted
many observers to conclude that the issue of possible 60 Hz health risks should be taken
seriously... Already concerns have prompted vigorous public intervention and litigation which
has significantly impeded the ability of private and public utilities to construct new power
transmission facilities. Such protests will probably grow and its seems likely that similar
concerns about fields will soon be raised at other levels. Without adequate science on which
to base answers, the resulting contention could go on for many years and have costs
significantly greater than the costs of the needed research. (Biological Effects of Power
Frequency Electric and Magnetic Fields-Background Paper, U.S. Congress, Office of
Technology Assessment, OTA-BP-E-53, May 1989, pp. 80-81)
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CHAPTER II
HEALTH EFFECTS
Many epidemiological studies report an association between EMF exposure and health
effects. The most frequently reported health effect is cancer. In particular, EMF exposure has
been reported to be associated with elevated risks of leukemia, lymphoma, and nervous system
cancers in children. Occupational studies of adults describe an association between EMF
exposure and leukemia, lymphoma, nervous system cancer, and other cancers. Although there
have been more than 40 epidemiological studies of children and adults conducted, uncertainties
remain in our understanding of the potential health effects of EMF. For example, uncertainties
surrounding exposure assessment are significant. Few epidemiological studies contain
measured exposure levels. In some studies, exposure levels have been estimated by surrogate
measures such as job title, broad occupational groupings, or the configuration of electric power
lines outside the home. In addition to cancer, other health concerns are associated with the
reproductive, nervous, and immune systems. Further research is needed to clarify these
reported associations.
The proposed research described below first addresses methodologic and study design
issues important to epidemiological studies. Following are discussions of research for both
human and laboratory animal studies for four major types of health effects: cancer, alterations in
reproduction and development, changes in nervous system function, and effects on the immune
system.
A. METHODOLOGIC ISSUES FOR EPIDEMIOLOGY
Human exposure to EMF results from: (1) ambient exposure to fields from sources
outside the home and workplace; (2) residential exposure to fields from sources inside the
home, and (3) occupational exposure to fields from equipment or facilities. These exposure
environments can vary greatly with respect to intensity, duration, frequency, direction of the
fields, and modulation, including the number of on/off cycles. To assess the effect of EMF on
human beings, a variety of characteristics of the exposure field have to be considered. Attention
should focus on resolving apparent discrepancies between magnetic field measurements and
surrogates of exposure, e.g., wiring configurations, so that the relevant exposure parameter(s)
can be identified. Accurate exposure data will decrease misclassification in epidemiological
studies, improve the ability to develop exposure-response relationships, and provide more
reliable risk estimates.
RECOMMENDATION: EMF exposure in the home, workplace, and outside environment
should be more fully characterized to identify common and special exposure situations.
Exposure data are needed for statistically valid population estimates and to help identify the field
parameters that may be biologically active. The development and validation of personal
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external dosimetry methods to document and evaluate the exposure of human beings to EMF
should continue. Epidemiological research and exposure assessment research must be
integrated.
A major concern with the epidemiological data is the paucity of information on factors
which may distort the measure of risk associated with EMF exposure. This concern is not
unique to studies of EMF. Such distortions, if undetected, could seriously affect the
interpretation of the results. The concern for these factors in EMF studies is due in part to our
generally poor understanding of what causes cancer and to relatively poor exposure assessment
of all types of EMF environments. For the latter, many studies were not designed to characterize
total exposure. Some studies of childhood cancer tried to address these other factors through
extensive questionnaires used to interview parents. Recent occupational studies have made
some advances in identifying exposure to agents other than EMF, but more rigorous
investigation is needed. Factors deserving examination include, but are not limited to, smoking
history, chemical exposures, health status, occupational information in studies of residential
exposure, and residential information in studies of occupational exposure.
RECOMMENDATION: Epidemiological studies on the effect of EMF should be designed
to identify and evaluate other factors which may distort the measure of association with EMF
exposure. Studies of humans in controlled laboratory settings, animal studies, and in vitro
studies should be evaluated for exposure parameters and other information that would improve
the design of epidemiological studies on EMF.
In general, epidemiological studies have chiefly examined exposure to EMF associated
with electric power use in the home and workplace, and studies of people exposed to
frequencies other than 60 Hz are neglected. The greatest attention has focused on so-called
"electrical workers" even though other kinds of workers have been identified as possibly at risk
from EMF exposure. On the other hand, the term "electrical worker" is very broad and EMF
exposure can be to a mix of frequencies. Examples of specialized exposed populations
available for study include VDT operators, medical personnel, aluminum smelter workers, and
induction heater operators. Most occupational studies are of men, but reports of increased
miscarriages and increased malformations suggest that women and children potentially exposed
to EMF may be at special risk. Emerging information about a possible link between EMF
exposure and breast cancer points to a need for more cancer studies of women; breast cancer
is the most common cancer in women and thus of significant health concern.
RECOMMENDATION: Epidemiological studies should be conducted on populations
exposed to EMF other than electric power frequency fields. Important populations to examine
are women and highly exposed groups. Three major health effects to investigate are cancer,
reproductive effects, and nervous system changes.
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B. CANCER
B.1. HUMAN
Information on time-dependent factors that affect carcinogenesis is insufficient. The
length of time a person lived in a residential setting has not been adequately addressed in
residential studies. The length of residency in a particular EMF environment may be an
important component of exposure characterization and could provide important information
relevant to exposure-response relations. In a few childhood cancer studies, the risk of cancer
was substantially increased for children who had the same "birth" address as the "diagnosis" or
"death" address, compared to those children who had moved sometime between birth and
diagnosis. The influence of latency and induction time have also not been rigorously examined
in most epidemiological studies. Different types of cancer have different latent periods. For
example, lymphoma, leukemia, and brain cancer have different latent periods that also differ
depending on cell type and whether the patients are children or adults. Researchers may have
been unable to determine the true risks of cancer, especially the risk for specific types of cancer,
because they did not consider the duration and timing of EMF exposure.
RECOMMENDATION: Epidemiological studies on EMF and cancer should assess the
influence of time-dependent factors such as length of residency, duration of exposure, and
latency on the risk of specific types of cancer to (1) identify exposure-response relations with
length of residency as a surrogate for exposure and to (2) validate whether or not specific
cancer types have satisfied known latency and temporal requirements for causality.
Another major problem with some epidemiological studies is the grouping of cancers into
broad categories. In some childhood cancer studies, the strongest associations are between
EMF exposure and all cancers combined. The specific cancers associated with EMF exposure
are leukemia, lymphoma, and nervous system cancer. Yet, each of these categories contain
separate and distinct disease subtypes. Many reports do not distinguish between different
subtypes of cancer. For example, the risk of acute lymphatic leukemia, chiefly a childhood
cancer, may not have been considered separately from other acute and chronic nonlymphatic
leukemias that more typically affect adults. Lymphatic and non-lymphatic leukemia are different
diseases that may involve different mechanisms. Nervous system cancer is a generic term that
includes a number of histologically defined structures with different etiologies, and lymphomas
may constitute a class of different cancers with different causes or processes. Often, studies
group diseases because a low incidence of different types of cancer is found in the study
population. However, specific cancers associated with EMF may be missed in studies that
group cancers into broad categories.
RECOMMENDATION: Epidemiological cancer studies should emphasize identification of
distinct cancer types in populations exposed to EMF because the reporting of cancer by general
class may mask elevated risk for specific cancer types.
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The reported association between EMF exposure and cancer suggests the need for
clinical research based on effects in biological models. Magnetic field exposure of cells derived
from human tissue is reported to increase the rate of DNA synthesis and change the proliferative
capacity of cancer cells. Human lymphoma cells exposed to 60 Hz fields showed an increase in
the activity of ornithine decarboxylase, an enzyme considered to be essential for the growth of
normal as well as cancer cells. Carcinogenic chemicals can also increase the activity of
ornithine decarboxylase. Breast cancer is believed to be mediated by oncogenes and
alterations in oncogenes and tumor-suppressor genes are believed to be important in the
development of colon cancer. Since these biological changes are associated with the
carcinogenic process, they are candidate biomarkers for the disease.
RECOMMENDATION: Human clinical studies should try to identify possible biomarkers
of EMF exposure in the carcinogenic process, including alterations in the pattern of DNA
synthesis, ornithine decarboxylase activity, and oncogene activation.
B.2. ANIMAL
Studies in animals and other biological test systems are needed to examine the
associations reported in human studies between cancer and exposure to EMF. Laboratory
studies provide an opportunity to discover cause-and-effect relations between well-characterized
biological systems and defined, controlled exposures to EMF. Such definitive information cannot
be obtained from human studies.
The EPA document on the potential carcinogenicity of EMF concluded that several
biological phenomena related to carcinogenesis are affected by these fields. EMF exposures
are reported to enhance DNA synthesis, alter transcription of information from DNA into
messenger RNA, alter normal patterns of protein synthesis, delay the mitotic cell cycle, induce
chromosome aberrations, induce enzymes normally active during cell proliferation, inhibit
differentiation and stimulate the growth of carcinoma cell lines, and mimic the effect of phorbol
esters, a class of cancer-promoting chemicals.
The biological phenomena mentioned above are related to postulated mechanisms of
carcinogenesis; however, reports of EMF-induced changes in biological systems do not prove
that the fields are carcinogenic by themselves or that exposure to them are risk factors for
human cancer. Furthermore, the relevance of these findings is questionable because many
occur at field strengths and conditions (e.g., pulsing fields) different from the time-averaged
ambient levels experienced by human populations. Although a wide array of biological systems
have been investigated under a broad range of exposure conditions, independent confirmation
of specific experiments remains important.
RECOMMENDATION: The potential role of EMF in carcinogenesis should be studied in
the laboratory (both in vitro and in whole animals) to discover the basic nature of the field-
dependence of effects. Gene expression, growth of transformed cells, and intracellular reactions
associated with chemical signalling are areas of special interest.
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Epidemiological studies have suggested that exposure to ambient power frequency
magnetic fields may correlate with development of cancer. At this time, the carcinogenicity of
EMF has not been tested in animals under well-defined laboratory exposure conditions, although
some studies concerned with the ability of EMF to promote cancer are now in progress.
RECOMMENDATION: Studies with laboratory animals are needed to examine whether
exposure to power frequency magnetic fields induces a carcinogenic response.
C. REPRODUCTIVE AND DEVELOPMENTAL EFFECTS
C.1. HUMAN
Environmental agents that cause reproductive and developmental effects are important
because they may directly influence health, lifespan, propagation, and functional and productive
capacity of our children. EMF exposure encompasses the entire reproductive and
developmental periods of life, including pre-conceptional germ cell development in parents, the
period from conception to birth, the postpartum growth and development stage, and the
reproductive ages.
Epidemiological studies have reported reproductive and developmental effects from
exposure to EMF generated by devices in the workplace and home. Investigations of women
and the outcome of their pregnancies have included operators of VDTs and users of specific
home appliances (electric blankets, heated water beds, and ceiling electric heat). The reports of
increased miscarriages and increased malformations suggest that maternal EMF exposure may
be associated with adverse effects. In addition, other studies have reported an increased
incidence of nervous system cancer in children whose fathers had occupations with potential
EMF exposure. However, many studies have used surrogate measures of exposure, have
determined exposure at a time other than the one that is biologically relevant to the health effect,
and have examined in a limited fashion, if at all, other factors that could distort the findings
reported in EMF studies. Thus, the human data are not adequate to support a definitive
conclusion that EMF exposure has reproductive and developmental effects.
RECOMMENDATION: Epidemiological studies are needed to confirm reported
reproductive and developmental effects of EMF. Studies should be designed to include EMF
exposure assessment, identify factors other than EMF that may affect the study conclusions,
identify relevant exposure periods, and be guided by our understanding of reproductive and
developmental effects in laboratory animals.
C.2. ANIMAL
Studies of reproduction in laboratory animals include measures of sexual behavior,
capacity to fertilize, reproductive efficiency, sex organ morphology and function, and synthesis of
sex steroids. Although EMF exposure of the parent before conception has been reported to
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affect several reproductive measures, including sexual behavior and maturation, as well as male
fertility, these results have not been independently confirmed.
Laboratory mammals have been used also to study the potential consequences of in
utero exposure to EMF. A wide range of effects have been reported for rats and mice exposed
to such fields and their offspring. The effects include increased embryonic death, decreased
body weight, shifts in weights of hormonally-responsive organs (including gonads and organs
sensitive to steroid levels), changes in levels of chemicals in serum and cells, and altered
behavioral patterns. Most of the effects reported in laboratory animals have not been
independently confirmed.
There is evidence to indicate that magnetic fields may influence embryonic development
in laboratory animals. The most frequently used animal model for demonstrating the effects of
EMF is the chicken embryo. In 17 reports on the chicken embryo exposed to various EMF, 36
of 103 individual experiments showed a statistically significant increase in abnormal embryos,
while 67 did not.
RECOMMENDATION: Research should attempt to confirm independently reported
reproductive effects in mammals. Developmental studies with standard laboratory models
should employ exposure conditions reported to be effective in nonmammalian systems. The
relevance of developmental effects in nonmammalian embryo models to permanent changes in
mammals should be explored because of the significance to epidemiologies! findings.
RECOMMENDATION: The reported association of increased cancer rates in human
offspring, or an association of any effect in offspring, to paternal exposure requires a
mechanistic link via paternal germ cell changes. A link to effects from paternal exposure, as
reported in epidemiologies! studies, needs to be studied in laboratory animals.
D. NERVOUS SYSTEM EFFECTS
D.1. HUMAN
Neurotransmitters and neurohormones are substances involved in communication both
within the nervous system and in the transmission of signals from the nervous system to other
body organs. These regulatory chemicals transmit information and regulate or modulate various
bodily functions that range from the learning of new skills to the control of heart rate and blood
pressure. Neuroregulatory chemicals are released in pulses with a distinct daily or circadian
pattern. Serotonin, melatonin, dopamine, and noradrenaline have been the focus of much
attention in the brain sciences. Aberrant levels of these neurochemicals accompany clinical
disorders like depression and many of the drugs used to treat these diseases interact with these
neurochemicals. Their metabolites can be monitored in easily accessible body fluids and
provide information about the role of neuromodulators in disturbed nervous system function.
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Data of this type from exposed human subjects are not available but relevant animal experiments
report that neurotransmitter metabolite levels are lowered in primates and that circadian patterns
of neurotransmitters and their metabolites are desynchronized in rodents exposed to EMF. The
few studies in which human subjects have been exposed to EMF in controlled laboratory
settings describe the following effects: changes in brain evoked-potential indicative of possibly
slowed information processing, slowed reaction time and altered behavioral performance in
which ability to gauge the passage of time was a pivotal component, and altered cardiovascular
function including slowed heart rate and pulse that may indicate direct action on the heart or the
neurochemicals controlling cardiac function. Results also indicated specific combinations of
electric and magnetic fields may be necessary before alterations are observed.
Melatonin, a hormone released by the pineal gland during the dark period of the daily
cycle, may be an important marker for certain health effects of EMF. Alterations in the circadian
pattern of melatonin accompany depression, "jet lag," and "shift lag," which can occur from
rotating shift work schedules. Disruption of physiological functions, such as sleep, that are
synchronized with melatonin secretion are symptoms for all three conditions. Body temperature
is also synchronized with melatonin rhythms. When humans isolated from external time cues are
exposed to electric fields their sleep-wake periods and core temperature patterns reportedly
shift. Manipulation of the light-dark cycle is used to treat depression, and "jet lag" symptoms are
ameliorated after treatment with light or melatonin. Night-time pineal melatonin levels are
reported to be suppressed in rats exposed to electric fields and intermittent magnetic fields.
EMF may also suppress nocturnally high levels of melatonin in human beings. In one study, the
use of electric blankets configured to allow frequent on/off switching of the magnetic field that
was 50% greater than that associated with a conventional electric blanket, was shown to reduce
the nighttime urinary excretion of melatonin's major metabolite. A possible link between EMF-
induced alteration in melatonin synthesis and cancer has been hypothesized. Studies with rats
show that EMF can suppress the melatonin level in the dark phase of the daily cycle. This
action of reducing melatonin may possibly increase the potential for cancer because melatonin
is known to inhibit the growth of some cancers.
RECOMMENDATION: Work should continue with human subjects in controlled
laboratory settings where exposure to real and sham fields occur under double- blind conditions.
Physiological and behavioral endpoints previously reported to be sensitive, as well as those
reported in animal studies, should be monitored before, during, and after exposure to EMF.
Because of the suspected role of altered melatonin rhythms in clinical disorders and in cancer,
other studies should determine if EMF can alter the circadian pattern of melatonin and its
metabolites in body fluids. Particular attention should be directed to whether the rate of
activation and deactivation of the field (intermittent exposure) has a more marked effect than
continuous application.
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D.2. ANIMAL
Studies examining the related areas of behavior, circadian rhythms, and neurochemistry
have been the focus of laboratory animal research concerned with EMF and the nervous system.
Behavior is the integrated output of the nervous system and alterations in circadian patterns or
neurochemical levels are often reflected in behavioral changes. Physiological and biochemical
processes have a synchronized daily cycle or circadian rhythm and aberrant rhythms have been
linked to a variety of disorders. Such disorders range from altered sensitivity to drugs and toxins
to sleep, performance, and psychiatric disorders, including chronic depression.
The performance of both spontaneous and learned behaviors is affected by EMF.
Studies of spontaneous behavior have provided data on the threshold and possible mechanism
of perception of 60 Hz electric fields. Although detection thresholds vary according to species, it
is generally believed that fields are detected by mammals with fur or hair, including humans,
because hair vibration caused by the oscillating electric field activates sensory mechanisms in
the skin. No perception mechanism for magnetic fields is known except for the visual effect in
humans known as magnetophosphenes or phosphenes (light flashes) caused by high
intensity magnetic fields. This phenomenon, which exhibits a threshold and is highly frequency-
dependent (maximum response in the 20 to 30 Hz range), is apparently caused by induced
electric fields in the eye that stimulate the retina. Thus, a pulsed magnetic stimulus is interpreted
as flashes of light by the brain.
The performance of several learned behaviors in animals is reported to be affected by
EMF. The reaction time of non-human primates is compromised by exposure to electric fields.
Rats trained to respond with a certain pattern and rate of behavior to earn rewards are less
efficient when exposed to EMF. Magnetic fields decrease the sensitivity of mice to the pain-
relieving action of drugs such as morphine and other opiates. Sixty-Hertz magnetic fields also
reduce the number of seizures induced in rats by an epileptogenic drug. The latter studies
indicate that research incorporating a drug challenge may help to identify the interaction of EMF
with the nervous system.
Research results also suggest that circadian rhythms can be altered by EMF. In
nonhuman primates, patterns of food and oxygen consumption were affected by field intensity;
for some monkeys, these altered biological rhythms persisted after the cessation of exposure.
Other work shows that 60 Hz electric fields produced phase delays in activity and metabolism
rhythms in mice. In addition, exposure to electric fields has been shown to affect the
circadian rhythm of serotonin, noradrenaline, and dopamine in rats. As mentioned previously,
alterations in the level and rhythm of neurochemicals with respect to the natural daily light-dark
cycle may have implications for sleep and mood disorders, including chronic depression.
One of the most consistent neurochemical findings is that the circadian pattern of
melatonin synthesis in the rat can be altered by EMF. Melatonin levels vary with the daily
light/dark cycle and are higher in the dark phase. The finding that EMF can suppress the higher
melatonin level in the dark phase may possibly be related to purported carcinogenic effects of
EMF because melatonin inhibits the growth of some cancers. A possible link between EMF-
induced alteration in melatonin synthesis and cancer development requires study.
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RECOMMENDATION: Studies of EMF effects on behavior of laboratory animals should
emphasize learned tasks and drug interactions. Other work should determine whether the
effects of EMF on circadian rhythms and neurochemical levels are significant in related areas
such as behavior and cancer. The consistent finding that EMF affects melatonin synthesis
should be the focus of studies to determine the sites and mechanisms of interaction. A primary
goal of research on EMF and the nervous system is to define causative exposure conditions;
particular attention should be given to the possible differential effects of electric versus magnetic
fields.
E. IMMUNE SYSTEM EFFECTS
E.1. HUMAN
The immune system defends against cancer and other diseases. Environmental agents
that compromise the effectiveness of the immune system could potentially increase the
incidence of cancer and other diseases. No research recommendation is given for the human
studies category because of the lack of data on immune system effects in human beings and
the preliminary state of knowledge of such effects in both in vitro and in vivo laboratory studies
(see below).
E.2. ANIMAL
A series of comprehensive investigations in the United States on the effect of 60 Hz
electric fields on the immune system of laboratory animals found no effect of chronic exposure
of rats and mice. Thus, it was concluded that power frequencies have small or no effects on the
immune systems of exposed animals. However, the role of magnetic fields was not investigated.
In vitro tests have also been used to investigate the effect of EMF on the immune system.
The results suggest that the magnetic field alone or in combination with an electric field can
affect immune function. Magnetic fields have been reported to inhibit the proliferation of immune
cells, inhibit killing of abnormal cells by the immune system, and to change the proliferative
capacity of cancer cells. Independent confirmation of the in vitro immune results would open a
promising research approach to investigate the possible link between exposure to EMF and
cancer. In addition, these tests would help to define effective exposure parameters because
some immune effects are reported to be frequency-specific and to have a nonlinear exposure-
response relation. Also, work with modulated high-frequency radiation indicates that the low
frequency of modulation is the biologically effective frequency.
RECOMMENDATION: Research is needed to confirm independently the reported in vitro
immune effects. In addition, immune responses in laboratory animals exposed chronically to
magnetic fields warrants investigation.
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CHAPTER III
BIOPHYSICAL MECHANISMS
Studies of biophysical mechanisms are important because the research examines both
stages of the interaction process: (1) the nature of the initial physical/chemical interaction of
EMF with biological systems and (2) the expression of the physical/chemical change as a
biological response. This information is needed to identify field parameters and biological
responses important for health research.
There is a substantial body of literature upon which the investigation of biophysical
mechanisms can be based. It is apparent from this literature that EMF should not be considered
a single entity, but rather a generic class of physical agents, similar to classes of chemicals.
Because of the infinite number of potential combinations of exposure parameters, such as
frequency, intensity, modulation, etc., it is possible that more than one mechanism may account
for the variety of EMF effects. Examples of reported biological responses to electric and
magnetic fields include: (1) alteration of melatonin synthesis in the pineal gland, (2) response of
brain tissue, e.g., ion flux changes and behavioral changes, (3) intervention in biochemical
signalling across the plasma membrane, including second-messenger systems and protein-
kinase action pathways that are important in hormone-induced responses, (4) alterations in
circadian rhythms, (5) effects on developmental and immune processes, (6) bone fracture
healing, and (7) alterations in gene regulation that are implicated in tumor production.
The biological effects of EMF can be best understood by a three-step paradigm:
transduction, amplification, and expression. In the first step, energy in electric or magnetic fields
must be converted, or transduced, into a biochemical or biophysical change to affect a
biological system. The EMF intensities reported to cause effects and the photon energy of
frequencies in the 0 to 500,000 Hz range are very small. Even if the transduction step were
100% efficient, there is insufficient energy to break chemical bonds. The second step,
amplification, is needed to boost the initial biophysical changes triggered by the field.
Amplification would then lead to the third step, expression of the effect as an observable entity in
the laboratory; expression could occur through a constellation of both intra- and extra-cellular
biological changes.
Advances in understanding the principles of physical interaction of EMF with
biochemicals and living cells will further define both transduction and amplification. Well-known
biochemical amplification systems are probably also important to study in the context of EMF.
Expression appears to be primarily caused by the interplay of various biological and biochemical
systems. The following discussion of biophysical mechanisms is presented in two parts:
physical interactions and biological interactions.
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A. PHYSICAL INTERACTIONS
In the past, characterization of the physical interactions of EMF with biological materials
emphasized electric field interactions. Recently, this focus has changed because data from
epidemiological studies suggest that the magnetic component may be the active agent. Thus,
interest has shifted to the biological consequences of the induced current resulting from a
changing magnetic field. The biological influence of these magnetically induced currents has
not been well characterized. Magnetic fields may also affect biological objects by acting directly
through naturally occurring magnetic dipoles in the body.
RECOMMENDATION: The interaction of magnetic fields with biological systems needs to
be explored to test the hypothesis that induced currents from oscillating magnetic fields are
causative. It is also important to establish whether the effects of currents induced by electric
fields differ categorically from those produced by magnetic fields. These two issues, in addition
to the evidence that magnetic fields also interact with biological systems via magnetic dipoles
(e.g., magnetic resonance imaging), need to be developed and examined for physiological
significance and risk implications.
Other physical parameters establish and define the electric and magnetic conditions that
cause biological changes. The field frequency can influence the reaction sites and processes
that are affected. The biological response as a function of frequency can be used to identify the
number and character of response sites. The intensity of the field is equally important, because
it can provide information about kinetics of the response, which leads to specific biological
processes. Furthermore, signal shape and temporal dynamics, including high peak-intensity
single or multiple pulses, can have a substantial effect. In more limited situations, the presence
of a static magnetic field and its orientation with regard to alternating electric and magnetic
components has been shown to be an important feature of exposure.
RECOMMENDATION: Principles established in ultraviolet radiation biology, which
examines biological responses as functions of field intensity, frequency and time, should form
the basis for the investigation of the biological effects of EMF. Adjunct studies should include
examination of frequency bandwidth, signal shape and modulation, and the involvement of the
earth's magnetic field with frequency-specific effects. Furthermore, the interaction of combined
electric and magnetic fields in biological systems should be examined.
Models of the interaction of EMF with biological objects can identify the critical physical
aspects of the exposure situation that should be tested. Models that successfully predict effects
can provide a basis for extrapolating exposure outcomes to other situations and to focus
research planning. To utilize modeling capabilities, measurements and analyses must be
performed at various levels of biochemical and biological organization. These range from
measurements of the dielectric constant and magnetic susceptibility, and analysis of the
thermodynamic models of chemical reactions, to analyses incorporating complex reactions in
non-equilibrium systems. The emphasis of such models should be on intensities of EMF that
would provide a basis to understand ambient exposure levels in terms of risk identification and
assessment.
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RECOMMENDATION: Models of possible mechanisms of action are needed. Such
models could be molecular, thermodynamic, or non-equilibrium in nature. Some of the models
developed for the study of EMF at frequencies above 500,000 Hz should be examined for
relevance to lower frequencies. New models may also be required.
B. BIOLOGICAL INTERACTIONS
The health effects of EMF are described in general terms in Chapter II. This chapter
emphasizes those biological effects and models important to guide research on mechanisms of
interaction.
Changing magnetic fields, because they are more penetrating than electric fields, can
induce electric fields and currents throughout biological systems. At the cellular level, several
sites of interaction and biochemical processes have been identified as likely targets. Both
models and experimental results indicate that membrane interfaces are a primary site of
transduction of field energy to biochemical change. The principal membrane involved is thought
to be the plasma membrane because of its role in the transfer of biochemical information
between the exterior and interior of the cell. Potential sites of action in the membrane include
membrane lipids and membrane/protein interfaces such as ion channels, gap junctions, and
hormone receptors. Biochemical transmembrane signal-transduction processes are reported to
be involved in EMF effects. In addition to possible membrane interactions, magnetic fields have
been reported to affect gene regulation, presumably at the nucleic acid level. This interaction
may occur through alteration of intermediate complexes of DNA and repressor/inducer or
polymerase molecules. Thus, electric and magnetic fields could differentially influence various
cellular components and processes.
RECOMMENDATION: Research is needed to identify and characterize the influence of
EMF on plasma membrane sites such as ion channels, gap junctions, and transmembrane
signal-transduction processes. Reports of altered gene expression should be independently
confirmed, and where warranted, models should be developed to establish the exposure
conditions necessary to cause changes.
Response dynamics of cellular or biochemical systems can provide critical insight into
mechanisms of action. Linear or monotonic exposure-response kinetics have been observed in
some experiments but nonlinear exposure responses also have been reported in cells and
tissues capable of excitation. In the latter studies, only certain ranges of frequencies and
intensities produce effects, whereas other ranges have no effect. These nonlinear "windowed"
results may reflect the involvement of a resonant or a dynamic system. Such results could
provide the basis for amplification to account for changes at ambient exposure conditions that
more classical analyses can not address.
RECOMMENDATION: Research should continue to examine the "windows' of intensity,
frequency, and pulse repetition rate that cause responses. These conditions need to be
incorporated into a coherent physical and biochemical interaction scheme in order to establish
mechanisms of action.
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Another way to view biological interactions of EMF is at the tissue/ organism level,
particularly in tissues with cells in electrical contact with one another. The fact that electrical
currents normally occur in bone during growth and fracture repair, in soft tissue during healing
and nerve regeneration, and in tissues during development and differentiation suggest that
exogenous or external currents might alter biological systems. For example, magnetic fields
have been used in over 50,000 human cases to enhance reunion of fractured bones.
Understanding critical field parameters and mechanisms involved in the healing process allow
potential benefits to be optimized and potential adverse effects to be assessed.
RECOMMENDATION: Research on mechanisms should include studies of EMF exposure
characteristics reported to have therapeutic action in biological systems.
This discussion of biophysical mechanisms deals primarily with cellular and subcellular
levels of organization. Whole animal studies also provide the opportunity to examine
mechanisms of action, particularly between interacting tissue systems. Research needs
involving whole animals in the areas of cancer, reproduction and development, the nervous
system, and the immune system are described in Chapter II.
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CHAPTER IV
EXPOSURE ASSESSMENT
This chapter describes engineering and physical science research needed to reduce
uncertainties in the exposure assessment of EMF. Although exposure assessment is the most
verifiable, least controversial, and best supported area of EMF research, the following six areas
require study: (1) source identification and characterization, (2) instrumentation and calibration; (3)
environmental measurements and documentation; (4) exposure modeling; (5) EMF coupling to
biological objects; and (6) laboratory exposure systems.
A. SOURCE IDENTIFICATION AND CHARACTERIZATION
Electric and magnetic fields at the power frequency of 60 Hz are generated by the
production, delivery, and use of electric power. Sources of exposure include power transmission
and distribution lines, electric circuits in homes, offices, and industrial facilities; electric grounding
systems, electric appliances (e.g., hair dryers, electric blankets, and electric razors); office
equipment (e.g., facsimile machines, photocopiers, and printers); and industrial power equipment
(e.g., lathes and drill presses). Higher frequency fields as well as 60 Hz fields are generated by
switching transients and by devices such as fluorescent lights, light dimmers, televisions, VDTs, arc
welding machines, and induction furnaces. A number of civilian and military navigational and
communication transmitters generate fields at frequencies below 500,000 Hz. Existing electrically
powered transportation systems such as mass transit systems or electric trains and proposed
systems such as magnetically levitated trains and electric automobiles may generate strong
magnetic fields at frequencies above and below 60 Hz.
Although many EMF sources in our environment have been identified, in general, the electric
and magnetic fields associated with these sources have not been well-characterized. An exception
is high voltage transmission lines. Less effort has been expended on the characterization of fields
associated with distribution lines which, in comparison to transmission lines, are much more
extensive and are a much more common source of exposure in residential areas. Even less effort
has been devoted to field characterization in the home, office, and workplace where people live and
work in close proximity to electric circuits in buildings, appliances, and office and industrial
equipment. Thus, a program on exposure assessment of EMF should include characterization of
sources in the home, office, and workplace as well as distribution and transmission lines in the
outside environment.
RECOMMENDATION: The identification of sources of electric and magnetic field exposure
should be an explicit part of a program of exposure assessment. The identification process
requires some preliminary effort in source characterization involving exploratory measurement
and/or basic physical understanding of field sources. Logging of activities and location during
personal exposure monitoring studies can assist in source identification. Maintenance of a source
inventory or data base should be a continuing effort
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B. INSTRUMENTATION AND CALIBRATION
Instrument development in the private sector as welt as in the government has been
responsive to perceived needs for field measurements. In particular, a number of survey
instruments that measure electric and magnetic fields that vary with time are now available, and
miniaturized pocket-size recording instruments have been developed recently. Also available are
instruments for measuring static electric and magnetic fields. In addition to the purpose for which
they were developed, these instruments can be used as a development base to assemble devices
that measure and record a wide range of field parameters as the need arises. Important
measurement issues include the definition of appropriate meter characteristics and the routine
availability of calibration services. The question of what field parameter(s) to measure requires the
collaborative interaction of specialists in engineering, the physical sciences and the biological
sciences.
RECOMMENDATION: Specifications and calibration procedures for instrumentation should
be developed to provide appropriate measurements of fields for health effects studies. This can be
accomplished by a continuing series of workshops to evaluate and update the methodology.
C. ENVIRONMENTAL MEASUREMENT AND DOCUMENTATION
Electric and magnetic fields have been measured in residences and occupational settings to
help resolve uncertainties in the interpretation of epidemiological results. Although state and local
governments, utilities, private firms, and individuals are currently measuring EMF, these
measurements are often conducted without adequate supervision and expertise. In general,
measurements have not been appropriate for determining population or occupational exposures.
Moreover, no central data base on EMF measurements exists.
RECOMMENDATION: EMF measurement training must be emphasized for individuals
responsible for field measurements and efforts to develop protocols for electric and magnetic field
measurements should continue to be supported. A program to sample exposure of the general
population and high exposure subgroups should be initiated with emphasis on monitoring exposure
during daily activities and in specific environments such as schools and residences. Occupational
measurements should focus initially on those job categories that epidemiological studies have
reported to be associated with a health risk. Additional occupational measurements are needed to
assess environments in which workers are exposed continuously to strong electric and magnetic
fields. Concurrently, an effort should be initiated to develop a central file of measurement data by
collecting and indexing available information. Development of a certification program for field
measurements is not recommended at this time because of the difficulty of defining field parameters
associated with health effects.
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D. EXPOSURE MODELING
Mathematical models to estimate EMF exposure have been developed because
measurement of fields at all locations and under all conditions of interest is not practical. Two
types of models, theoretical and statistical, are described here. The application of theoretical
models usually involves a numerical solution in which field parameters are determined as a function
of current or voltage on electrical conductors. The frequency of interest has a wavelength that is
large compared to the dimensions of the exposed object and thus models, such as "quasi-static"
models, can be applied to a range of frequencies. For example, the same model used to calculate
60 Hz fields near a power line may be used to determine higher frequency transient fields
generated by the power line.
Theoretical models can only be developed for well-documented configurations of electric
conductors and field-perturbing materials. Thus, most theoretical modeling of 60 Hz fields has
been applied to power transmission lines because such models can be constructed easily. Home
environments with a number of sources have not been modeled, although some models have been
made of ground currents in water pipes. Individual appliances in which the primary sources are
transformers, motors, or heating elements have not been modeled except for electric blankets.
However, computer programs are being developed to estimate fields in the home.
Statistical modeling makes use of magnetic field measurements of appliances at non-
standardized distances within homes. These models are used to develop statistical estimates of
average exposure. Statistical modeling does not predict individual exposures, but provides
estimates for groups of the population, e.g., school children, homemakers, and workers. This
approach could benefit from characterization of important microenvironments where exposures
occur, such as schools, homes, offices, and factories. Although microenvironmental modeling is a
relatively new concept, it is readily adaptable to EMF exposure modeling.
A combination of statistical and theoretical approximations of measurement data could be
used to develop specific source, microenvironmental, and general environmental models to
estimate EMF exposure. For example, in the general environment, application of Geographic
Information System (GIS) technology could be used to analyze and display EMF levels measured
outdoors from sources such as power lines as well as comparative EMF levels measured indoors
(microenvironmental measurements), and to calculate the distribution of exposed populations. A
measurement and source data base could be used to create exposure models to estimate human
exposure to EMF sources and to evaluate the effectiveness of control technologies.
RECOMMENDATION: Research on exposure modeling is needed to develop more refined
models to estimate exposures resulting from sources in the home, workplace, and the outside
environment. Modeling data are needed to complement EMF measurement programs and to
support quality control programs.
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E. EMF COUPUNG TO BIOLOGICAL OBJECTS
The previous sections in this chapter have dealt strictly with determining the unperturbed
electric and magnetic field in the absence of a human body. In the presence of a body, the electric
field immediately outside the body is strongly perturbed and the intensity of the field may differ
greatly from that of the unperturbed field. In contrast to the electric field, the magnetic field that
penetrates the body is essentially unchanged. Both external electric and magnetic fields that vary
with time induce electric fields internally and electric current inside the body is proportional to the
induced internal electric field.
It is a common assumption that biological effects are related to the induced currents.
However, it is not known whether low-level effects are caused by the internal electric fields and
associated currents, by the magnetic field acting directly on magnetic dipoles or on moving electric
charges, or by other exposure parameters. If effects are due only to the magnetic field acting
directly, then further study of inductive field coupling would not be a priority. If the effects are at
least in part due to induced electric fields and currents, then field coupling research is critical.
Internal electric fields depend strongly on the size and shape of the exposed body or system.
Thus, EMF coupling analysis is necessary when scaling internal electric fields or currents from
animal and in vitro exposures to human exposures.
Much of the work on EMF coupling analysis has involved a model in which the sample is
assumed to be electrically uniform and linear. The internal field values obtained under these
assumptions may be misleading. At lower frequencies, for example, it is likely that currents flow
principally around and not through cells. Therefore, extracellular current density may be much
greater than the average current density calculated over a mass of tissue. Even if the details of a
model seem complete from a physical perspective, caution needs to be exercised in extrapolating
the results to a living organism because of the complexity of biological systems. The reports that
weak electric and magnetic fields cause biological effects implies that processes such as
amplification and frequency and intensity selectivity can occur. The latter includes "windowed"
responses, that is, discrete bands of frequency and intensity that produce effects separated by
bands that have no effect.
RECOMMENDATION: Exploratory research is needed to develop models to explain how
electric and magnetic fields interact with cells and tissue to produce the reported biological
effects. Efforts in progress to develop better cellular and anatomical models of the electric
characteristics of human beings, laboratory animals, and in vitro samples need additional support.
Work on implantable probes for macroscopic and microscopic measurement of internal currents,
voltages, and other field parameters in living systems should continue. A long-term goal is the
development of a standard formula and unit of "dose* that is dependent on external exposure
fields and is proportional to biological effect and/or human health risk.
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F. LABORATORY EXPOSURE SYSTEMS
If the process by which biological effects occur were simple and relatively straightforward,
then minor variations in EMF exposure conditions or other parameters might not affect the
results significantly. If such were the case, independent confirmation of experimental results should
be a relatively simple matter of repeating the experiment. If, however, effects are a complex
function of several exposure conditions that may not be well controlled, then confirmation becomes
problematic. The history of EMF research implies that careful control of important experimental
variables is needed.
It is important that laboratory exposure systems allow potentially critical exposure variables
to be controlled. For example, the steady magnetic field of the earth has been implicated as an
important exposure variable. This implies that the earth's geomagnetic field in the exposure system
needs to be controlled or at least measured and reported. Also, exposure can easily be correlated
with vibrations, switching noises, and possibly heat from the EMF source. Thus, experimental
procedures must ensure that the treatment of exposed samples is identical to control samples
except for the intended EMF exposure. Incidental EMF in the laboratory must be considered also.
For example, steady magnetic fields are produced by magnetized tools and magnetic door latches,
whereas time-varying magnetic fields are produced by magnetic stirrers and incubator heating coils.
Basic biological research aimed at testing specific theoretical models requires relatively
simple field configurations that can be varied in a controlled manner. However, environmental
exposure to EMF is far more complex than exposure regimens typically used in the laboratory. This
complexity may be an important factor in determining the risk of a given exposure. Once biological
responses are established as markers of risk, they can be used to test the effectiveness of
simulated EMF environments.
RECOMMENDATION: Exposure systems for health research should be designed and
constructed to allow electric and magnetic fields, including time-varying and steady fields, to be
controlled and monitored. Facilities for chronic and lifetime exposure of laboratory animals to
electric and magnetic fields will be needed. A need may develop for exposure systems that
simulate ambient EMF environments.
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CHAPTER V
CONTROL TECHNOLOGY
For purposes of this research strategy document, the issue of EMF control technology
is almost entirely dependent upon the results of health effects and biophysical research
programs discussed earlier. Clearly, if the scientific research finds no relationship between
EMF exposure and adverse health effects, there is no rationale or need, from a human health
standpoint, to develop exposure controls for EMF. Research on control technology for EMF
exposure is, therefore, a low priority research area within the overall EMF research strategy
discussed in this document. Despite the lack of demonstrated need for control technologies
at present, identifying and characterizing EMF sources by measurement or modeling is
important. This procedure defines the framework for possible future research on control
technologies, by surveying the current state-of-the-science for EMF control technology.
The major source of environmental exposure to EMF is the electric power system, which
includes transmission lines, the distribution system (substations, lines, and transformers),
residential and commercial wiring, and appliances and machinery. Although considerable
effort has been focused on the control of EMF from electric utility systems, little work has
been done on controlling fields generated by electrically powered appliances and tools,
industrial equipment, and clinical devices. (Note: this text is not intended to apply to the
purposeful exposure of patients to EMF.)
Concurrent with the increase in concern for the possible health effects of EMF
exposure has been the development and widespread use of devices like the VDT and
magnetic resonance imager. These devices, along with emerging technologies, such as
electric automobiles and magnetically levitated transportation systems, offer the important
advantages of convenience, economy, or clinical and diagnostic power. Nevertheless, the
EMF they emit may be significantly different than that emitted by transmission or distribution
lines. Furthermore, unlike transmission and distribution facilities, these technologies are not
generally controlled by one segment of the electric industry. Control technologies may,
therefore, need to be developed so as to be available to producers of products that emit
EMF, should a need to control EMF be demonstrated.
In most circumstances, the strength of low-frequency EMF decreases with distance
from the source. One simple mitigation approach is therefore to increase separation distance
(e.g., increase the right-of-way for a transmission line). At low frequencies, such as 60 Hz, the
electric and magnetic components of EMF are essentially uncoupled and each field
component must be considered separately by control technologies. Thus, techniques that
reduce electric fields may or may not reduce magnetic fields, and vice versa. Three mitigation
methods are known to be effective regardless of frequency: shielding; proper design,
location, and choice of components; and filtering. These methods are described in more
detail below.
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Shielding: One of the most important components of EMF control technology is
shielding. The shielding effectiveness of a given material is a measure of the reduction in
field intensity. Magnetic fields cannot be effectively shielded with readily available and
inexpensive materials, especially at 60 Hz, because most materials are essentially transparent
to magnetic fields. Effective magnetic shielding requires a special class of metals called
ferromagnetic or MU metals. On the other hand, low frequency electric fields including 60 Hz
fields can be shielded by readily available and inexpensive metals. Thus, electric fields can
be effectively shielded by metal enclosures, but the equivalent magnetic enclosure is not as
practical or effective.
Design. Location, and Component Choice: After shielding, proper grounding of power
distribution systems in buildings is of utmost importance to reduce EMF, especially magnetic
fields. Improper grounding, in addition to increasing exposure per se, can reduce shielding
effectiveness. Ground currents result when a structure, such as a house, has multiple
grounds such as water pipes, ducts, anchors, etc., in addition to the ground at the electrical
service panel. In an electric conductor, the magnetic field is proportional to the current in the
wire. Thus, strong ground currents produce strong magnetic fields. To avoid ground current
loops, only one grounding connection should be made.
Another important consideration for the mitigation of EMF exposure is the location of
electric conductors. For example, consider two wires in close proximity to one another. One
wire supplies the current and the other wire conducts the return current back to the source
(required to complete the circuit). Since the supply and return currents are in opposite
directions, they produce equal but opposite magnetic fields that cancel each other. This
illustrates a very important principle: for every supply current there is an equal and opposite
return current. The location of the return current is the most crucial determinant of the
strength of the magnetic field. Thus, when wires are closely spaced and the currents are
fairly well balanced (no ground loops), the magnetic fields will be small. For this reason
twisted-pair wiring and coaxial cables produce little or no external magnetic fields.
Filtering: Transformers and motors may produce EMF with harmonic content, that is,
frequencies that are multiples of the primary frequency, which is usually 60 Hz. Secondary
distribution lines, grounding circuits, and appliances might have harmonic frequencies up to
the 11 to 17th harmonic (660 to 1020 Hz). Solid-state electronic devices can also produce
high-frequency emissions. Capacitors can be installed at appropriate locations on circuits
and electrical equipment to filter or reduce the harmonic or high-frequency waveforms.
Transmission lines and primary distribution lines have little or no harmonic content.
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A. TRANSMISSION AND DISTRIBUTION UNES
Control technology for transmission and distribution lines has been developed and
could be applied if warranted. These techniques focus on compaction and shielding of
transmission conductors. Compaction is based on the principle that for three-phase,
balanced, conductor systems, the net field, electric or magnetic, of the three phases is zero.
A disadvantage of compaction is that it results in an increase in electrical arcing, which affects
system reliability. For situations in which compaction was an ineffective control technology,
shielding techniques have been developed that reduce the electric field at the edge of the
right-of-way by approximately tenfold. Compaction techniques and super-compaction
techniques (cable technology) that have been developed include gas-insulated transmission
lines, super-conducting cables, and direct-current cable technologies. In cable or gas-
insulated transmission technologies, conductors are inside a metallic sheath in which the
electric field exists only between the conductors and the sheath; electric fields external to
cable sheaths are essentially zero. Super-compaction or cable circuits significantly reduce
magnetic fields because the magnetic fields from the phase conductors are self-canceling.
Distribution circuits, unlike transmission circuits, rarely contain three-phase balanced
conductor systems. There is usually a net current flow and, if this net current does not return
in the cable sheath or in an immediately adjacent neutral circuit, then large current loops exist
between the cable circuit and the actual return path of the net current. Therefore, distribution
cable circuits can produce fields that are similar to that of overhead transmission lines, even
though voltage and current levels are much smaller.
Two states have developed programs related to EMF control technology for
transmission and distribution lines. One program will identify and characterize sources of
magnetic fields and investigate means of reducing magnetic field levels associated with power
delivery and use. The other program requires the utility industry to allocate funds for research
on management of magnetic fields from transmission and distribution lines. One goal is to
develop design options for the reduction of ground level EMF from power lines.
RECOMMENDATION: Control technology research in this area is supported or
conducted by organizations with long-standing interest in the design and development of
transmission and distribution facilities; this effort should continue. A future strategy for the
reduction of public exposure to EMF from transmission lines might include generation of
electricity at the site of use by new technologies (photovoltaic systems and fuel cells) as they
become available and competitive.
B. RESIDENCES AND WORKPLACES
Residences: EMF inside the home can be emitted from appliances, the wiring system,
including the grounding, underground and overhead distribution lines, and transmission lines.
Most mitigation research has focused on the magnetic field because electric fields are fairly
easy to shield. As stated earlier, the characterization (measurement/calculation) and control
of EMF are intimately related, consequently any mitigation program should be accompanied
by a characterization effort.
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The power frequency magnetic fields in the home have been characterized in a limited
fashion. In most of these studies, fields were measured at unstandardized distances from
appliances, and frequencies other than 60 Hz, in addition to field transients and other field
parameters, were largely ignored. Therefore, exposure to EMF in the home has not been well
characterized.
The magnetic fields emitted by some appliances have been measured as a function of
distance from the appliance, although such data may not be particularly useful in developing
magnetic field control strategies. The devices that produce strong magnetic fields have been
identified, but how the field is produced has not been well characterized. A few appliances,
especially electric blankets and heated water beds, have been identified as important sources
of magnetic field exposure because of their close proximity to the body for long periods of
time. Electric blanket and waterbed heater manufacturers have responded by developing low
magnetic field appliances. Procedures for making the measurements and therefore for
determining the effectiveness of the control technology have not been standardized.
It is important to standardize measuring procedures in the home environment. These
measurements should take into account use of electric appliances and living habits. Actual
exposure of different parts of the body should be determined. Research volunteers, wearing
dosimetric devices on various parts of the body, could be used to determine the exposure
characteristics of different home environments. For magnetic field control in the home, a
standardized measurement strategy that can be adjusted to account for appliance usage is
required. This should be accompanied by an effort to create models that can predict
magnetic field exposure on the basis of home design and appliance installation. In such
models, emphasis could be placed on the devices that produce the strongest fields, on
chronic exposure, on strong transient fields, or on other exposure conditions deemed
important. If the field characteristics of an appliance were well documented, then simple
engineering principles such as twisted-pair wiring or control of circular current loops might be
sufficient to control the magnetic fields. Localized shielding techniques may be effective on
small volume devices.
Workplaces: Little is known about occupational exposure. The utility industry has
conducted a series of studies of personnel with nominally high exposure, such as
transmission and distribution line maintenance workers. These studies have shown that the
average exposure for these personnel is not necessarily greater than that of the general
workforce. Occupations that have not been examined in an organized manner include
workers in heavy industrial environments: operators of lathes, drill presses, and induction
furnaces; workers near arc furnaces; and operators of demagnetizing equipment. A
standardized measurement/mitigation procedure is needed, much like that discussed for the
home but applied to different types of work environments.
RECOMMENDATION: Source Characterization/Mitigation. To characterize the EMF
from residential appliances and industrial equipment, three-dimensional field maps should be
generated by measurement or calculation. These fields should be given as magnitudes as a
function of frequency for steady-state operation. Magnitude and frequency changes, as a
function of duty cycle, as well as transient fields, should also be documented. Once the field
sources have been identified and characterized, the development of control techniques can
be addressed.
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Mapping living and working environments requires a methodical way to accommodate
the time and space variability of fields that are produced by randomly positioned current
paths. These current paths exist in electric devices, the leads supplying the devices, the
internal and external electric power supply lines, and stray ground return paths. Thus,
measurement protocols are required that will realistically assess exposure levels for
complicated EMF environments.
RECOMMENDATION: Grounding Practice Review. National and local electric safety
codes have specific requirements for electric service grounding to control the hazard of
shock. Yet, these current paths, intentionally created, contribute significantly to magnetic field
exposure. The advantages in terms of magnetic field management versus disadvantages
from interference, reliability, and safety should be carefully evaluated for delta (ungrounded),
single-point grounded, and multi-grounded circuits. From the point of consumer interface and
in the consumer (residential, commercial, or industrial) environment, single-point grounding,
ground potential shift, and interference with ground-fault interrupt circuits need to be carefully
evaluated. Effects on co-located utility (e.g., communication cables on power poles)
grounding practices will have to be evaluated to maintain service reliability and worker safety.
RECOMMENDATION: Shielding. Research should be devoted to the development of
new materials to shield magnetic fields, e.g., a malleable high permeability material.
Concurrently extending the range of permeability as a function of low magnetic field strength
could be very useful if the purported health effects of magnetic field exposures identified in
epidemiological studies are confirmed. Research into magnetically modified polymers may be
fruitful, since both fabrication and field strength problems may be solved by one material.
Active magnetic shielding approaches should be investigated. In this approach,
magnetic fields are purposely generated to cancel other magnetic fields.
Also, robotic technology could be evaluated for some work environments as an
alternative to human exposure to EMF.
C. SPECIAL CONSIDERATIONS
Existing mass transit systems (subways and electric trains) and emerging technologies
such as magnetically levitated trains, electric automobiles, and superconducting magnetic
energy storage devices require special consideration. These systems can produce magnetic
fields over large areas at different frequencies. Passengers on magnetically levitated trains
will be exposed to static fields and to frequencies up to about 1,000 Hz. Existing engineering
control technologies may not be sufficient to significantly reduce exposure, if mitigation is
needed.
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Another device that merits special concern is the VDT. In addition to being energized
by 60 Hz power, VDTs can produce EMF at frequencies of up to 250,000 Hz. This higher-
frequency EMF is generated by the deflection yoke that controls the horizontal deflection
system and produces images on the VDT screen. VDT manufacturers, however, have begun
to reduce fields by shielding techniques. Metal enclosures are used to shield electric fields,
while active magnetic shielding techniques are used to reduce magnetic fields. In the latter
case, purposely generated magnetic fields act to cancel the magnetic field produced by the
deflection yoke in VDTs.
RECOMMENDATION: Both research on field characterization and shielding
technologies may be required for special devices. Recently developed magnetic field
monitoring equipment may need to be adapted to measure the unique magnitude-frequency-
time course characteristics of these fields.
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CHAPTER VI
SUMMARY AND CONCLUSIONS
International and national organizations, industrial associations, federal and state
agencies, Congress, and the public have expressed concern about the potential health
effects of exposure to EMF. This document describes a research strategy to determine the
possible health effects of EMF; to define exposure conditions in the home, workplace, and
outside environment; and to determine what types of control technologies may be necessary
to mitigate EMF exposure. EMF in the frequency range of 0 to 500,000 Hz is the focus of the
proposed research because this range includes EMF emitted from power lines and from
commonly used devices, such as video display terminals. Research recommendations are
presented for (1) health effects that specifically address cancer, reproduction and
development, the nervous system, and the immune system; (2) biophysical mechanisms; (3)
exposure assessment; and (4) possible control technology.
The literature on EMF is substantial but considerably diverse because of the variety of
biological systems tested and the complex nature of the physical agent. Rather than a single
entity, EMF is more appropriately considered a generic class of physical agents, similar to
classes of chemicals. Because of the complexity of EMF exposure conditions, most studies
of biological effects have been hypothesis-generating studies rather than hypothesis-testing
research and many of the reported effects have not been independently confirmed.
Confirmation of key findings in biological studies is a major research issue.
The relative priorities for EMF research are summarized below. Highest priority was
assigned to those issues where it was felt targeted research over 3-5 years could potentially
provide decision makers with better information upon which to base decisions about the
likelihood and magnitude of potential health effects from EMF exposure.
TABLE 1. RELATIVE PRIORITIES FOR EMF RESEARCH
RESEARCH AREAS RELATIVE PRIORITY
HEALTH EFFECTS
Cancer High
Reproductive and Developmental Effects Medium
Nervous System Effects Medium
Immune System Effects Low
BIOPHYSICAL MECHANISMS High
EXPOSURE ASSESSMENT High
CONTROL TECHNOLOGY Low
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High-priority research areas are cancer, exposure assessment, and biophysical
mechanisms of action. Cancer research is a top priority because there are more than 40
human studies on this subject and it is most important to independently confirm key human
cancer studies with improved protocols and exposure assessments. A major concern with
the epidemiological data is the dearth of information on factors that may confound the
estimate of risk; therefore, human studies should address this issue. Epidemiological studies
should assess the influence of time-dependent factors such as length of residency, duration
of exposure, and latency on the risk of specific types of cancer to (1) identify exposure-
response relations with length of residency as a surrogate for exposure and (2) to validate
whether or not specific cancer types have satisfied known latency and temporal requirements
for causality. In addition, a continuing examination of the potential role of EMF in
carcinogenesis should be conducted in laboratory studies of animals and in cells and tissues
to discover the basic nature of the exposure-response relation and the effective exposure
conditions.
Exposure assessment research is also high priority because it is essential to the
successful interpretation of the biological response and is critically important for risk
assessment. In all types of biological studies, exposure data are needed to define exposure-
response relations and to establish cause-and-effect relations. In particular, cancer research,
both in human populations and in laboratory studies, requires definitive exposure data to
judge the validity of the suggested causal link between EMF exposure and cancer. The
agenda for exposure assessment identifies research needs in the following areas: source
identification and characterization; instrumentation and calibration; EMF coupling to biological
objects; and laboratory exposure systems. In addition, research needs for environmental
measurements and exposure modeling reflect the fact that exposure to EMF in the home and
workplace has not been well characterized. Measurement and modeling efforts are needed
to define exposure to EMF from appliances, wiring systems including transmission and
distribution lines, grounding systems, medical devices, and office and industrial equipment.
These data are also needed to define the direction for control technology research.
Another high priority research area is biophysical mechanisms. An understanding of
how EMF interacts with biological systems is needed to minimize uncertainty in extrapolating
laboratory data to human exposure situations and to identify effective exposure parameters.
In particular, mechanistic research is needed to test hypotheses that (1) the cell membrane is
the primary site of interaction with EMF and (2) the magnetic field, not the electric field, is the
critical exposure parameter in cancer development. A number of biological effects, including
those reported to have therapeutic potential, offer promising avenues for research on
mechanisms of interaction of electric and magnetic fields.
Research on human reproductive effects should emphasize the independent
confirmation of isolated reports of increased miscarriages and increased malformations, and
reports of increased incidence of nervous system cancer in children whose fathers had
occupations with potential EMF exposure. The results of laboratory studies of non-
mammalian models that exhibit developmental effects from exposure to EMF should be used
to design studies with mammals. Research on reproductive and developmental effects is a
medium priority, but confirmation of developmental effects in human beings or in laboratory
mammals would elevate the priority.
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Research on the nervous system should further examine physiological, neurochemical,
and behavioral endpoints in human subjects reported to be sensitive to EMF. Laboratory
studies on the effect of EMF on the behavior of laboratory animals should emphasize learned
tasks and drug interactions. A primary goal is the identification of effective exposure
conditions, such as possible differential effects of electric and magnetic fields. The consistent
finding that EMF affects melatonin synthesis in the pineal gland should be further
investigated. Research on the nervous system is a medium priority because the reported
biological effects in both human studies and laboratory experiments may be generally
regarded as hypothesis-generating.
Research on the immune system is a low priority because reported effects occur
primarily in isolated cellular systems. The research recommendation for immunology
emphasizes independent confirmation of the cellular effects and screening studies of
laboratory animals exposed to magnetic fields. The need for this research is related to the
important role of the immune system in cancer prevention.
The potential need for future controls to reduce risks from exposure to EMF is the
rationale for control technology research. This research is a low priority because no cause-
and-effect relation between human health risk and EMF exposure has been established.
However, products from the control technology research recommended in this report may
ultimately be needed to mitigate EMF exposure in the home, workplace, and outside
environment. The research strategy addresses electric grounding issues important to public
health and recommends that the ongoing effort to develop control technology for
transmission and distribution systems be continued. Similarly, other control technology
research should be done in concert with health and exposure assessment research so that
mitigation procedures and devices will be available if warranted by future health risk
assessments of EMF exposure.
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BIBLIOGRAPHY
Evaluation of the Potential Carcinogenicity of Electromagnetic Fields. U.S. Environmental
Protection Agency, External Review Draft, EPA/600/6-90/005B, October 1990.
Extremely Low Frequency Electromagnetic Fields: The Question of Cancer. Wilson, B.W.,
R.G. Stevens, and LE. Anderson, Editors. Battelle Press, Columbus, Ohio, 1990.
Biological Effects of Power Frequency Electric and Magnetic Fields - Background Paper, U.S.
Congress, Office of Technology Assessment, OTA-BP-E-53, Washington, DC, U.S.
Government Printing Office. May 1989.
Electric and Magnetic Fields at Extremely Low Frequencies. Anderson, L.E., and W.T. Kaune.
In Nonionizing Radiation Protection, M.J. Suess, and D.A. Benwell-Morison, Editors, World
Health Organization, Regional Office for Europe, Copenhagen, 1989. Chapter 5, pp. 175-
243.
Nonionizing Radiation: Extremely Low Frequency Electric and Magnetic Fields. In EPA
Indoor Air Quality Implementation Plan. Appendix A. Preliminary Indoor Air Pollution
Information Assessment. EPA/600/8-87/014. June 1987. Section 2.10, pp. 2-162 to 2-167.
Nonthermal Effects of Nonionizing Radiation. National Research Council, Advisory Committee
on the Nonthermal Effects of Nonionizing Radiation, Final Report, National Academy Press,
Washington, D.C., 1986, 16 pp.
SUPPLEMENTARY BIBLIOGRAPHY
Federal Research on the Potential Health Effects of Power Frequency Electromagnetic
Radiation; Statement to the Subcommittee on Natural Resources, Agriculture Research, and
Environment; Committee on Science, Space, and Technology; U.S. House of
Representatives. J.C. Lin, Chairman, Committee on Man and Radiation, IEEE-United States
Activities, 1828 L Street, N.W., Suite 1202, Washington, DC. July 25, 1990.
Draft Statement on Research Needs and Funding Priorities in the Area of Health Effects of
Power Line Frequency Electric and Magnetic Fields. Ad Hoc Subcommittee on Power Line
Frequency Electric and Magnetic Fields, committee on Man and Radiation, The Institute of
Electrical and Electronics Engineers, Inc. March 4, 1991.
Potential Health Effects of Electric and Magnetic Fields from Electric Power Facilities. A report
to the California State Legislature by the California Public Utilities Commission in
cooperation with the California Department of Health Services. September 15, 1989.
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GLOSSARY
Ambient. Encompassing or surrounding area.
Behavior. Action that can be observed directly and studied in relation to antecedent
conditions. In animals, a distinction can be made between learned and spontaneous
behaviors. Learning is a long-lasting change that results from experience with environmental
events and includes actions such as solving a maze for food. Spontaneous behaviors are
actions that do not result from a response to direct stimulation and include behaviors like
locomotor activity.
Biomarker. An indicator of variation in cellular or physiological components or processes,
structures, or functions that are measurable in a biological system or sample.
Biophysical mechanisms. Physical and/or chemical interactions of electric and magnetic
fields with biological systems.
Capacitor. A device made of two electrically conducting surfaces, separated by an insulator
that stores electric charge.
Carcinogen. A chemical, biological, or physical agent capable of producing tumor growth.
Carcinogenic process. A series of stages at the cellular level culminating in the development
of cancer.
Chromosome. A very long molecule of DMA, complexed with protein, containing genetic
information.
Circadian rhythms. Biological processes that have synchronized daily cycles of approximately
one day (24 hours).
Circuit. A closed conducting path for the flow of electric current.
Conductor. A material that allows the flow of electric charge, e.g., wires on transmission
lines.
Control technology. The application of engineering approaches to manage or mitigate
exposure to environmental agents, e.g., electric and magnetic fields.
Current The flow of electric charge.
Cytotoxicity. Toxic effects in cells.
DNA. Deoxyribonucleic acid. The nucleic acid molecule in chromosomes that contains the
genetic information.
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Developmental effects. Effects in the developing offspring due to exposure before conception
(either parent), prenatally, or postnatally to the time of sexual maturation. Developmental
effects may be expressed at any time in the life span of the organism. Developmental effects
are a subset of reproductive effects.
Electric dipole. Two separated electric charges; a molecule (or other structure) having the
effective centers of positive and negative charges separated.
Electric field. A field describing the electrical force on a unit charge in space. Electrical
charges are a source of electric fields. The electric field from a power line is an alternating,
60 Hz field.
Electric and magnetic fields (EMF). Energy in the form of electric and magnetic fields. In this
report, the frequency range of interest for EMF is 0 to 500,000 Hz.
Embryo. The early stages in the developing organism in which organs and organ systems
are developing. For humans, this stage lasts between the second through eighth weeks after
conception.
EMF. See Electric and magnetic fields.
EndpoinL An observable or measurable biological, chemical, or functional event used as an
index of the effect of a chemical, physical, or biological agent on a cell, tissue, organ,
organism, etc.
Epidemiology. The study of the occurrence and distribution of a disease or physiological
condition in human populations and of the factors that influence this distribution.
Exposure. The joint occurrence in space and time of an organism and the agent of concern,
expressed in terms of the environmental level of the agent.
Exposure assessment. Measurement or estimation of the magnitude, frequency, duration,
and route of exposure of an organism to environmental agents. The exposure assessment
also describes the nature of exposure and the size and nature of the exposed populations,
and is one of four steps in risk assessment.
Exposure-response relation. A relationship between exposure and the effect produced by the
exposure. Response can be expressed either as the severity of injury or proportion of
exposed subjects affected.
Extrapolation. An estimate of response or quantity at a point outside the range of the
experimental data. Also refers to the estimation of a measured response in a different
species or by a different route than that used in the experimental study of interest (i.e.,
species-to-species, route-to-route, acute-to-chronic, high-to-low).
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Field. Any physical quantity that takes on different values at different points in space.
Frequency. The number of complete cycles of a periodic waveform per unit time. Frequency
is expressed in Hertz (Hz), which is equivalent to one cycle per second.
Gene. The simplest complete functional unit in a DMA molecule. A linear sequence of
nucleotides in DNA that is needed to synthesize a protein and/or regulate cell function.
Geomagnetic field. The earth's natural magnetic field.
Germ cell. A cell capable of developing into a gamete (ovum [egg] or sperm).
Grounding. The connection of a conductor to something that will accept excess electrical
charge, for example, the earth.
Hertz (Hz). One cycle per second.
Hormone. A chemical substance, formed in one organ or part of the body and carried in the
blood to another organ or part where it alters the functional activity, and sometimes the
structure, of one or more organs in a specific manner.
Immune system. The body's primary defense against abnormal growth of cells (i.e., tumors)
and infectious agents such as bacteria, viruses, and parasites.
Insulator. A nonconductor of electrical charges.
In utero. In the uterus; unborn.
In vitro. Isolated from the living organism and artificially maintained, as in a test tube or
culture dish.
In vivo. Occurring within the whole living body.
Ion efflux. The movement of ions, charged atoms or molecules, from a sample into a
surrounding solution.
Latency. The time between exposure to an injurious agent and the manifestation of a
response.
Learned behavior. See behavior.
Leukemia. A progressive, malignant disease of the blood-forming tissues, marked by an
excessive number of white blood cells and their precursors.
Lymphoma. Any abnormal growth (neoplasm) of the lymphoid tissues. Lymphoma usually
refers to a malignant growth and thus is a cancer.
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Magnetic dipole. Two separated magnetic poles; an object such as a permanent magnet,
particle, or current loop, that gives rise to a magnetic field. The object acts as if it consists of
two magnetic poles of opposite sign separated by a small distance.
Magnetic field. A field describing the force experienced by magnetic objects or moving
electrical charges in space.
Malformation. A permanent structural change in a developing organism that may adversely
affect survival, development, or function.
Mechanisms. See Biophysical mechanisms.
Messenger RNA. See RNA.
Metabolism. The biochemical reactions by which energy is made available for the use of an
organism from the time a nutrient substance enters, until it has been utilized and the waste
products eliminated.
MicroenvironmenL The immediate local environment of an organism.
Mitosis. Cellular and nuclear division that involves duplication of the chromosomes of a
parent cell and formation of two daughter cells.
Model. (1) Mathematical model. A mathematical representation of a natural system intended
to mimic the behavior of the real system, allowing description of empirical data, and
predictions about untested states of the system. (2) Biological model. A condition or disease
in animals similar to the condition or disease in human beings.
Modulation. The process of varying the amplitude, frequency, or phase of EMF.
Neurotransmitter. A chemical substance that transmits nerve impulses across the space
between nerve endings called the synapse.
Oncogene. A mutation of a naturally occurring gene involved in growth regulation that results
in uncontrolled growth. Oncogenes are associated with the development of some forms of
cancer.
Photon. A particle of electromagnetic energy.
Plasma membrane. The membrane surrounding plant and animal cells.
Power. The time rate at which work is done. Electrical power is proportional to the product
of current and voltage.
Proliferation. Production of new cells through the process of cell division.
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Promotion. The second hypothesized stage in a multistage process of cancer development.
The conversion of initiated cells into tumorigenic cells.
Reproductive effects. Effects on reproduction which may include, but not be limited to,
alterations in sexual behavior, onset of puberty, fertility, gestation, parturition, lactation,
pregnancy outcomes, premature reproductive senescence, or modifications in other functions
that are dependent on the integrity of the reproductive system. Developmental effects are a
subset of reproductive effects.
Risk assessment. The scientific activity of evaluating the toxic properties of an environmental
agent and the conditions of human exposure to it in order to ascertain the likelihood that
exposed humans will be adversely affected, and to characterize the nature of the effects they
may experience. May contain some or all of the following four steps:
Hazard identification - The determination of whether a particular agent is or is not
causally linked to particular health effect(s).
Dose-response assessment - The determination of the relation between the magnitude
of exposure and the probability of occurrence of the health effects in question.
Exposure assessment - The determination of the extent of human exposure.
Risk characterization - The description of the nature and often the magnitude of
human risk, including attendant uncertainty.
RNA. Ribonucleic acid. Messenger RNA, the nucleic acid in cells that is the template for the
sequential ordering of amino acids during protein synthesis, is synthesized in the nucleus of
the cell during the process of transcription.
Spontaneous behavior. See behavior.
Static fields. Electric and magnetic fields that do not vary in intensity or strength with time.
Survey instrument. A portable instrument capable of measuring the strength of electric and
magnetic fields.
Time-varying fields. Electric and magnetic fields that change in intensity or strength with time.
Examples include 60 Hz, modulated, and transient fields.
Transcription. The cellular process in which messenger RNA is synthesized, i.e., the process
in which the genetic information in DNA is transcribed in the form of a single molecule of
messenger RNA.
"Windowed" responses. Effects found within bands or ranges of frequency or intensity
separated by bands or ranges without effect; nonlinear exposure-response relations.
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APPENDIX A:
RESEARCH RECOMMENDATIONS
I. HEALTH EFFECTS
A. METHODOLOGIC ISSUES FOR EPIDEMIOLOGY
RECOMMENDATION: EMF exposure in the home, workplace, and outside
environment should be more fully characterized to identify common and special exposure
situations. Exposure data are needed for statistically valid population estimates and to help
identify the field parameters that may be biologically active. The development and validation
of personal external dosimetry methods to document and evaluate the exposure of human
beings to EMF should continue. Epidemiological research and exposure assessment
research must be integrated.
RECOMMENDATION: Epidemiological studies on the effect of EMF should be
designed to identify and evaluate other factors which may distort the measure of association
with EMF exposure. Studies of humans in controlled laboratory settings, animal studies, and
in vitro studies should be evaluated for exposure parameters and other information that would
improve the design of epidemiological studies on EMF.
RECOMMENDATION: Epidemiological studies should be conducted on populations
exposed to EMF other than electric power frequency fields. Important populations to
examine are women and highly exposed groups. Major health effects to investigate are
cancer, reproductive effects, and nervous system changes.
B. CANCER
1. HUMAN STUDIES
RECOMMENDATION: Epidemiological studies on EMF and cancer should assess the
influence of time-dependent factors such as length of residency, duration of exposure, and
latency on the risk of specific types of cancer to (1) identify exposure-response relations with
length of residency as a surrogate for exposure and to (2) validate whether or not specific
cancer types have satisfied known latency and temporal requirements for causality.
RECOMMENDATION: Epidemiological cancer studies should emphasize identification
of distinct cancer types in populations exposed to EMF because the reporting of cancer by
general class may mask elevated risk for specific cancer types.
RECOMMENDATION: Human clinical studies should try to identify possible
biomarkers of EMF exposure in the carcinogenic process, including alterations in the pattern
of DNA synthesis, ornithine decarboxylase activity, and oncogene activation.
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2. ANIMAL STUDIES
RECOMMENDATION: The potential role of EMF in carcinogenesis should be studied
in the laboratory (both in vitro and in whole animals) to discover the basic nature of the field-
dependence of effects. Gene expression, growth of transformed cells, and intracellular
reactions associated with chemical signalling are areas of special interest.
RECOMMENDATION: Studies with laboratory animals are needed to examine whether
exposure to power frequency magnetic fields induces a carcinogenic response.
C. REPRODUCTIVE AND DEVELOPMENTAL EFFECTS
1. HUMAN STUDIES
RECOMMENDATION: Epidemiological studies are needed to confirm reported
reproductive and developmental effects of EMF. Studies should be designed to include EMF
exposure assessment, identify factors other than EMF that may affect the study conclusions,
identify relevant exposure periods, and be guided by our understanding of reproductive and
developmental effects in laboratory animals.
2. ANIMAL STUDIES
RECOMMENDATION: Research should attempt to confirm independently reported
reproductive effects in mammals. Developmental studies with standard laboratory models
should employ exposure conditions reported to be effective in nonmammalian systems. The
relevance of developmental effects in nonmammalian embryo models to permanent changes
in mammals should be explored because of the significance to epidemiological findings.
RECOMMENDATION: The reported association of increased cancer rates in human
offspring, or an association of any effect in offspring, to paternal exposure requires a
mechanistic link via paternal germ cell changes. A link to effects from paternal exposure, as
reported in epidemiological studies, needs to be studied in laboratory animals.
D. NERVOUS SYSTEM EFFECTS
1. HUMAN STUDIES
RECOMMENDATION: Work should continue with human subjects in controlled
laboratory settings where exposure to real and sham fields occur under double-blind
conditions. Physiological and behavioral endpoints previously reported to be sensitive, as
well as those reported in animal studies, should be monitored before, during, and after
exposure to EMF. Because of the suspected role of altered melatonin rhythms in clinical
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disorders and in cancer, other studies should determine if EMF can alter the circadian
pattern of melatonin and its metabolites in body fluids. Particular attention should be directed
to whether the rate of activation and deactivation of the field (intermittent exposure) has a
more marked effect than continuous application.
2. ANIMAL STUDIES
RECOMMENDATION: Studies of EMF effects on behavior of laboratory animals
should emphasize learned tasks and drug interactions. Other work should determine whether
the effects of EMF on circadian rhythms and neurochemical levels are significant in related
areas such as behavior and cancer. The consistent finding that EMF affects melatonin
synthesis should be the focus of studies to determine the sites and mechanisms of
interaction. A primary goal of research on EMF and the nervous system is to define causative
exposure conditions; particular attention should be given to the possible differential effects of
electric versus magnetic fields.
E. IMMUNE SYSTEM EFFECTS
1. HUMAN STUDIES
RECOMMENDATION: No research recommendation is given for this category
because of the lack of data on immune system effects in human beings and the preliminary
state of knowledge of such effects in both in vitro and in vivo laboratory animal studies.
2. ANIMAL STUDIES
RECOMMENDATION: Research is needed to confirm independently the reported in
vitro immune effects. In addition, immune responses in laboratory animals exposed
chronically to magnetic fields warrants investigation.
II. BIOPHYSICAL MECHANISMS
A. PHYSICAL INTERACTIONS
RECOMMENDATION: The interaction of magnetic fields with biological systems
needs to be explored to test the hypothesis that induced currents from oscillating magnetic
fields are causative. It is also important to establish whether the effects of currents induced
by electric fields differ categorically from those produced by magnetic fields. These two
issues, in addition to the evidence that magnetic fields also interact with biological systems
via magnetic dipoles (e.g., magnetic resonance imaging), need to be developed and
examined for physiological significance and risk implications.
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RECOMMENDATION: Principles established in ultraviolet radiation biology, which
examines biological responses as functions of field intensity, frequency and time, should form
the basis for the investigation of the biological effects of EMF. Adjunct studies should
include examination of frequency bandwidth, signal shape and modulation, and the
involvement of the earth's magnetic field with frequency-specific effects. Furthermore, the
interaction of combined electric and magnetic fields in biological systems should be
examined.
RECOMMENDATION: Models of possible mechanisms of action are needed. Such
models could be molecular, thermodynamic, or non-equilibrium in nature. Some of the
models developed for the study of EMF at frequencies above 500,000 Hz should be examined
for relevance to lower frequencies. New models may also be required.
B. BIOLOGICAL INTERACTIONS
RECOMMENDATION: Research is needed to identify and characterize the influence
of EMF on plasma membrane sites such as ion channels, gap junctions, and transmembrane
signal-transduction processes. Reports of altered gene expression should be independently
confirmed, and where warranted, models should be developed to establish the exposure
conditions necessary to cause changes.
RECOMMENDATION: Research should continue to examine the "windows" of
intensity, frequency, and pulse repetition rate that cause responses. These conditions need
to be incorporated into a coherent physical and biochemical interaction scheme in order to
establish mechanisms of action.
RECOMMENDATION: Research on mechanisms should include studies of EMF
exposure characteristics reported to have therapeutic action in biological systems.
III. EXPOSURE ASSESSMENT
A. SOURCE IDENTIFICATION AND CHARACTERIZATION
RECOMMENDATION: The identification of sources of electric and magnetic field
exposure should be an explicit part of a program of exposure assessment. The identification
process requires some preliminary effort in source characterization involving exploratory
measurement and/or basic physical understanding of field sources. Logging of activities and
location during personal exposure monitoring studies can assist in source identification.
Maintenance of a source inventory or data base should be a continuing effort.
B. INSTRUMENTATION AND CALIBRATION
RECOMMENDATION: Specifications and calibration procedures for instrumentation
should be developed to provide appropriate measurements of fields for health effects
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studies. This can be accomplished by a continuing series of workshops to evaluate and
update the methodology.
C. ENVIRONMENTAL MEASUREMENT AND DOCUMENTATION
RECOMMENDATION: EMF measurement training must be emphasized for individuals
responsible for field measurements and efforts to develop protocols for electric and magnetic
field measurements should continue to be supported. A program to sample exposure of the
general population and high exposure subgroups should be initiated with emphasis on
monitoring exposure during daily activities and in specific environments such as schools and
residences. Occupational measurements should focus initially on those job categories that
epidemiological studies have reported to be associated with a health risk. Additional
occupational measurements are needed to assess environments in which workers are
exposed continuously to strong electric and magnetic fields. Concurrently, an effort should
be initiated to develop a central file of measurement data by collecting and indexing available
information. Development of a certification program for field measurements is not
recommended at this time because of the difficulty of defining field parameters associated
with health effects.
D. EXPOSURE MODELING
RECOMMENDATION: Research on exposure modeling is needed to develop more
refined models to estimate exposures resulting from sources in the home, workplace, and the
outside environment. Modeling data are needed to complement EMF measurement programs
and to support quality control programs.
E. EMF COUPLING TO BIOLOGICAL OBJECTS
RECOMMENDATION: Exploratory research is needed to develop models to explain
how electric and magnetic fields interact with cells and tissue to produce the reported
biological effects. Efforts in progress to develop better cellular and anatomical models of the
electric characteristics of human beings, laboratory animals, and in vitro samples need
additional support. Work on implantable probes for macroscopic and microscopic
measurement of internal currents, voltages, and other field parameters in living systems
should continue. A long-term goal is the development of a standard formula and unit of
"dose" that is dependent on external exposure fields and is proportional to biological effect
and/or human health risk.
F. LABORATORY EXPOSURE SYSTEMS
RECOMMENDATION: Exposure systems for health research should be designed and
constructed to allow electric and magnetic fields, including time-varying and steady fields, to
be controlled and monitored. Facilities for chronic and lifetime exposure of laboratory animals
to electric and magnetic fields will be needed. A need may develop for exposure systems
that simulate ambient EMF environments.
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iv. CONTROL TECHNOLOGY
A. TRANSMISSION AND DISTRIBUTION UNES
RECOMMENDATION: Control technology research in this area is supported or
conducted by organizations with long-standing interest in the design and development of
transmission and distribution facilities; this effort should continue. A future strategy for the
reduction of public exposure to EMF from transmission lines might include generation of
electricity at the site of use by new technologies (photovoltaic systems and fuel cells) as they
become available and competitive.
B. RESIDENCES AND WORKPLACES
RECOMMENDATION: Source Characterization/Mitigation. To characterize the EMF
from residential appliances and industrial equipment, three-dimensional field maps should be
generated by measurement or calculation. These fields should be given as magnitudes as a
function of frequency for steady-state operation. Magnitude and frequency changes, as a
function of duty cycle, as well as transient fields, should also be documented. Once the field
sources have been identified and characterized, the development of control techniques can
be addressed.
Mapping living and working environments requires a methodical way to accommodate
the time and space variability of fields that are produced by randomly positioned current
paths. These current paths exist in electric devices, the leads supplying the devices, the
internal and external electric power supply lines, and stray ground return paths. Thus,
measurement protocols are required that will realistically assess exposure levels for
complicated EMF environments.
RECOMMENDATION: Grounding Practice Review. National and local electric safety
codes have specific requirements for electric service grounding to control the hazard of
shock. Yet, these current paths, intentionally created, contribute significantly to magnetic field
exposure. The advantages in terms of magnetic field management versus disadvantages
from interference, reliability, and safety should be carefully evaluated for delta (ungrounded),
single-point grounded, and multi-grounded circuits. From the point of consumer interface and
in the consumer (residential, commercial, or industrial) environment, single-point grounding,
ground potential shift, and interference with ground-fault interrupt circuits need to be carefully
evaluated. Effects on co-located utility (e.g., communication cables on power poles)
grounding practices will have to be evaluated to maintain service reliability and worker safety.
RECOMMENDATION: Shielding. Research should be devoted to the development of
new materials to shield magnetic fields, e.g., a malleable high permeability material.
Concurrently extending the range of permeability as a function of low magnetic field strength
could be very useful if the purported health effects of magnetic field exposures identified in
epidemiological studies are confirmed. Research into magnetically modified polymers may be
fruitful, since both fabrication and field strength problems may be solved by one material.
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Active magnetic shielding approaches should be investigated. In this approach,
magnetic fields are purposely generated to cancel other magnetic fields.
Also, robotic technology could be evaluated for some work environments as an
alternative to human exposure to EMF.
C. SPECIAL CONSIDERATIONS
RECOMMENDATION: Both research on field characterization and shielding
technologies may be required for special devices. Recently developed magnetic field
monitoring equipment may need to be adapted to measure the unique magnitude-frequency-
time course characteristics of these fields.
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APPENDIX B:
EPA WORK GROUP
Joe Elder, Ph.D., Chairman
Health Effects Research Laboratory
Research Triangle Park, NC
Carl Blackman, Ph.D., Special Assistant
Health Effects Research Laboratory
Research Triangle Park, NC
Diane Miller, Ph.D., Special Assistant
Health Effects Research Laboratory
Research Triangle Park, NC
David Bayliss, M.S.
Office of Health and Environmental Assessment
Washington, DC
Ezra Berman, D.V.M.
Health Effects Research Laboratory
Research Triangle Park, NC
Rebecca Calderon, Ph.D.
Office of Health Research
Washington, DC
Norbert Hankin, M.S.
Office of Radiation Programs
Washington, DC
Doreen Hill, Ph.D.
Office of Radiation Programs
Washington, DC
Edwin Mantiply, B.S.
Office of Radiation Programs
Las Vegas, NV
Robert McGaughy, Ph.D.
Office of Health and Environmental Assessment
Washington, DC
Sherry Selevan, Ph.D.
Office of Health and Environmental Assessment
Washington, DC
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Ronald Spiegel, Ph.D.
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC
James Walker, Ph.D.
Office of Radiation Programs
Washington, DC
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