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Prepared in Response to the 1992 Energy Policy Act
(PL 102486, Section 2118)
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2008-1991
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NIEHS REPORT on
Health Effects from Exposure to Power-Line
Frequency Electric and Magnetic Fields
Prepared in Response to the 1992 Energy Policy Act
(PL 102-486, Section 2118)
4tfNIE
National Institute of Environmental Health Sciences
National Institutes of Health
Dr. Kenneth Olden, Director
Prepared by the
NIEHS EMF-RAPID Program Staff
NIH Publication No. 99-4493
Supported by the NIEHS/DOE
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DEPARTMENT OF HEALTH & HUMAN SERVICES Public Health Service
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National Institutes of Health
National Institute of
Environmental Health Sciences
P. O. Box 12233
Research Triangle Park, NC 27709
May 4, 1999
Dear Reader:
In 1992, the U.S. Congress authorized the Electric and Magnetic Fields Research and Public
Information Dissemination Program (EMF-RAPID Program) in the Energy Policy Act.
The Congress instructed the National Institute of Environmental Health Sciences (NIEHS),
National Institutes of Health and the U.S. Department of Energy (DOE) to direct and
manage a program of research and analysis aimed at providing scientific evidence to clarify
the potential for health risks from exposure to extremely low frequency electric and
magnetic fields (ELF-EMF). The EMF-RAPID Program had three basic components: 1) a
research program focusing on health effects research, 2) information compilation and
public outreach and 3) a health assessment for evaluation of any potential hazards arising
• from exposure to ELF-EMF. The NIEHS was directed to oversee the health effects
research and evaluation, and the DOE was given the responsibility for overall
administration of funding and engineering research aimed at characterizing and mitigating
these fields. The Director of the NIEHS was mandated upon completion of the Program to
provide this report outlining the possible human health risks associated with exposure to
ELF-EMF. The scientific evidence used in preparation of this report has undergone
extensive scientific and public review. The entire process was open and transparent.
Anyone who wanted "to have a say" was provided the opportunity.
The scientific evidence suggesting that ELF-EMF exposures pose any health risk is weak.
The strongest evidence for health effects comes from associations observed in human
populations with two forms of cancer: childhood leukemia and chronic lymphocytic
leukemia in occupationally exposed adults. While the support from individual studies is
weak, the epidemiological studies demonstrate, for some methods of measuring exposure, a
fairly consistent pattern of a small, increased risk with increasing exposure that is
somewhat weaker for chronic lymphocytic leukemia than for childhood leukemia. In
contrast, the mechanistic studies and the animal toxicology literature fail to demonstrate
any consistent pattern across studies although sporadic findings of biological effects have
been reported. No indication of increased leukemias in experimental animals has been
observed.
The lack of connection between the human data and the experimental data (animal and
mechanistic) severely complicates the interpretation of these results. The human data are
in the "right" species, are tied to "real life" exposures and show some consistency that is
difficult to ignore. This assessment is tempered by the observation that given the weak
magnitude of these increased risks, some other factor or common source of error could
explain these findings. However, no consistent explanation other than exposure to ELF-
EMF has been identified.
•
Page 2
Epidemiological studies have serious limitations in their ability to demonstrate a cause and
effect relationship whereas laboratory studies, by design, can clearly show that cause and
effect are possible. Virtually all of the laboratory evidence in animals and humans and
most of the mechanistic work done in cells fail to support a causal relationship between
exposure to ELF-EMF at environmental levels and changes in biological function or disease
status. The lack of consistent, positive findings in animal or mechanistic studies weakens
the belief that this association is actually due to ELF-EMF, but it cannot completely
discount the epidemiological findings.
The NIEHS concludes that ELF-EMF exposure cannot be recognized at this time as
entirely safe because of weak scientific evidence that exposure may pose a leukemia hazard.
In my opinion, the conclusion of this report is insufficient to warrant aggressive regulatory
concern. However, because virtually everyone in the United States uses electricity and
therefore is routinely exposed to ELF-EMF, passive regulatory action is warranted such as
a continued emphasis on educating both the public and the regulated community on means
aimed at reducing exposures. The NIEHS does not believe that other cancers or non-
cancer health outcomes provide sufficient evidence of a risk to currently warrant concern.
The interaction of humans with ELF-EMF is complicated and will undoubtedly continue to
be an area of public concern. The EMF-RAPID Program successfully contributed to the
scientific knowledge on ELF'-EMF through its support of high quality, hypothesis-based
research. While some questions were answered, others remain. Building upon the
• knowledge base developed under the EMF-RAPID Program, meritorious research on ELF-
EMF through carefully designed, hypothesis-driven studies should continue for areas
warranting fundamental study including leukemia. Recent research in two areas,
neurodegenerative diseases and cardiac diseases associated with heart rate variability, have
identified some interesting and novel findings for which further study is ongoing.
Advocacy groups have opposing views concerning the health effects of ELF-EMF. Some
advocacy groups want complete exoneration and others want a more serious indictment.
Our conclusions are prudent and consistent with the scientific data. I am satisfied with the
report and believe it provides a pragmatic, scientifically-driven basis for any further
regulatory review.
I am pleased to transmit this report to the U.S. Congress.
Sincerely,
Kenneth Olden, Ph.D.
Director
S
S
NIEHS EMF-RAPID PROGRAM STAFF
Gary A. Boorman, D.V.M., Ph.D., Associate Director for Special Programs,
Environmental Toxicology Program and Director, EMF-RAPID Program
Naomi J. Bernheim, M.S., Biologist, Office of Special Programs, Environmental
Toxicology Program and Program Assistant, EMF-RAPID Program
Michael J. Galvin, Ph.D., Health Scientist Administrator, Division of Extramural
Research and Training and Extramural Program Administrator, EMF-RAPID
Program
Sheila A. Newton, Ph.D., Director, Office of Policy, Planning and Evaluation
Fred M. Parham, Ph.D., Staff Scientist, Laboratory of Computational Biology and Risk
Analysis
Christopher J. Portier, Ph.D., Associate Director for Risk Assessment, Environmental
Toxicology Program; Chief, Laboratory of Computational Biology and Risk
Analysis; and Coordinator, EMF Hazard Evaluation
Mary S. Wolfe, Ph.D., Associate Coordinator, EMF Hazard Evaluation, Environmental
Toxicology Program
•
ACKNOWLEDGEMENTS
This report would not have been possible without the concerted and generous help of
literally hundreds of research scientists. Many of the scientists who wrote the articles,
which are cited in this report, attended our science review symposia where their research
was carefully evaluated and critiqued. Their patience with our questions and their
professional attitude in evaluating their own work was extraordinary and is greatly
appreciated. We are also indebted to the many scientists from outside of the electric and
magnetic fields (EMF) research community who participated in our symposia and spent
time and effort evaluating these data on our behalf; this provides a clear example of the
dedication of scientists concerned about health issues.
Special thanks are extended to the 30 scientists who attended the Working Group
Meeting in June 1998. Their hard work and conscientious effort led to one of the most
concise and clear reviews of the extremely low frequency (ELF) EMF literature ever
developed. The thousands of man-hours extended by this group in such a short period of
time provided us with a background document on ELF-EMF health risks that made this
report a much simpler task. We wish especially to thank Dr. Arnold Brown for attending
our public meetings on the Working Group Report; his extensive experience and
insightful comments helped to make these meetings a great success. We would also like
to thank Dr. Brown and Dr. Paul Gailey for reviewing this report prior to its release and
Mr. Fred Dietrich for advising us on exposure issues during the preparation of this
document. Finally we would like to acknowledge the U.S. Department of Energy as our
partner in the EMF-RAPID Program and its EMF program officer, Dr. Imre Gyuk.
•
TABLE OF CONTENTS
EXECUTIVE SUMMARY i
INTRODUCTION
NIEHS CONCLUSION ii
BACKGROUND iii
Program Oversight and Management iii
ELF-EMF Health Effects Research iv
Information Dissemination and Public Outreach iv
Health Risk Assessment of ELF-EMF Exposure v
INTRODUCTION 1
Funding 2
Oversight and Program Management 3
ELF-EMF Health Effects Research 3
• Information Dissemination and Public Outreach 4
Literature Review and Health Risk Assessment 6
DO ELECTRIC AND MAGNETIC FIELDS POSE A HEALTH RISK? 9
SCIENTIFIC EVIDENCE SUPPORTING THIS CONCLUSION 10
Background on the Limitations of Epidemiology Studies 10
Childhood Cancers 12
Adult Cancers 15
Non-Cancer Findings in Humans 16
Animal Cancer Data 19
Non-Cancer Health Effects in Experimental Animals 23
Studies of Cellular Effects of ELF-EMF 25
Biophysical Theory 29
HOW HIGH ARE EXPOSURES IN THE U.S. POPULATION? 31
CONCLUSIONS AND RECOMMENDATIONS 35
Previous Panel Reviews 35
NIEHS Conclusion 35
Recommended Actions 37
Future Research 38
REFERENCES 41
•
•
EXECUTIVE SUMMARY
Introduction
Electrical energy has been used to great advantage for over 100 years. Associated
with the generation, transmission, and use of electrical energy is the production of
weak electric and magnetic fields (EMF). In the United States, electricity is
usually delivered as alternating current that oscillates at 60 cycles per second
(Hertz, Hz) putting fields generated by this electrical energy in the extremely low
frequency (ELF) range.
Prior to 1979 there was limited awareness of any potential adverse effects from
the use of electricity aside from possible electrocution associated with direct
40 contact or fire from faulty wiring. Interest in this area was catalyzed with the
report of a possible association between childhood cancer mortality and proximity
of homes to power distribution lines. Over the next dozen years, the U.S.
Department of Energy (DOE) and others conducted numerous studies on the
effects of ELF-EMF on biological systems that helped to clarify the risks and
provide increased understanding. Despite much study in this area, considerable
debate remained over what, if any, health effects could be attributed to ELF-EMF
exposure.
In 1992, the U.S. Congress authorized the Electric and Magnetic Fields Research
and Public Information Dissemination Program (EMF-RAPID Program) in the
Energy Policy Act (PL 102-486, Section 2118). The Congress instructed the
National Institute of Environmental Health Sciences (NIEHS), National Institutes
of Health and the DOE to direct and manage a program of research and analysis
aimed at providing scientific evidence to clarify the potential for health risks from
exposure to ELF-EMF. The EMF-RAPID Program had three basic components:
1) a research program focusing on health effects research, 2) information
compilation and public outreach and 3) a health assessment for evaluation of any
potential hazards arising from exposure to ELF-EMF. The NIEHS was directed
to oversee the health effects research and evaluation and the DOE was given the
responsibility for overall administration of funding and engineering research
aimed at characterizing and mitigating these fields. The Director of the NIEHS
was mandated upon completion of the Program to provide a report outlining the
S
i
• possible human health risks associated with exposure to ELF-EMF. This
document responds to this requirement of the law.
This five-year effort was signed into law in October 1992 and provisions of this
Act were extended for one year in 1997. The Program ended December 31 , 1998.
The EMF-RAPID Program was funded jointly by Federal and matching private
funds and has been an extremely successful Federal/private partnership with
substantial financial support from the utility industry. The NIEHS received
$30. 1 million from this program for research, public outreach, administration and
the health assessment evaluation of ELF-EMF. In addition to EMF-RAPID
Program funds from the DOE, the NIEHS contributed $ 14.5 million for support of
extramural and intramural research including long-term toxicity studies conducted
by the National Toxicology Program.
NIEHS Conclusion
The scientific evidence suggesting that ELF-EMF exposures pose any health risk
is weak. The strongest evidence for health effects comes from associations
observed in human populations with two forms of cancer: childhood leukemia and
chronic lymphocytic leukemia in occupationally exposed adults. While the
support from individual studies is weak, the epidemiological studies demonstrate,
for some methods of measuring exposure, a fairly consistent pattern of a small,
• increased risk with increasing exposure that is somewhat weaker for chronic
lymphocytic leukemia than for childhood leukemia. In contrast, the mechanistic
studies and the animal toxicology literature fail to demonstrate any consistent
pattern across studies although sporadic findings of biological effects (including
increased cancers in animals) have been reported. No indication of increased
leukemias in experimental animals has been observed.
The lack of connection between the human data and the experimental data (animal
and mechanistic) severely complicates the interpretation of these results. The
human data are in the "right" species, are tied to "real-life" exposures and show
some consistency that is difficult to ignore. This assessment is tempered by the
observation that given the weak magnitude of these increased risks, some other
factor or common source of error could explain these findings. However, no
consistent explanation other than exposure to ELF-EMF has been identified.
Epidemiological studies have serious limitations in their ability to demonstrate a
cause and effect relationship whereas laboratory studies, by design, can clearly
show that cause and effect are possible. Virtually all of the laboratory evidence in
animals and humans and most of the mechanistic work done in cells fail to
support a causal relationship between exposure to ELF-EMF at environmental
levels and changes in biological function or disease status. The lack of consistent,
positive findings in animal or mechanistic studies weakens the belief that this
•
ii
association is actually due to ELF-EMF, but it cannot completely discount the
epidemiological findings.
The NIEHS concludes that ELF-EMF exposure cannot be recognized as entirely
safe because of weak scientific evidence that exposure may pose a leukemia
hazard. In our opinion, this finding is insufficient to warrant aggressive
regulatory concern. However, because virtually everyone in the United States
uses electricity and therefore is routinely exposed to ELF-EMF, passive
regulatory action is warranted such as a continued emphasis on educating both the
public and the regulated community on means aimed at reducing exposures. The
NIEHS does not believe that other cancers or non-cancer health outcomes provide
sufficient evidence of a risk to currently warrant concern.
The interaction of humans with ELF-EMF is complicated and will undoubtedly
continue to be an area of public concern. The EMF-RAPID Program successfully
contributed to the scientific knowledge on ELF-EMF through its support of high
quality, hypothesis-based research. While some questions were answered, others
remain. Building upon the knowledge base developed under the EMF-RAPID
Program, meritorious research on ELF-EMF through carefully designed,
hypothesis-driven studies should continue for areas warranting fundamental study
including leukemia. Recent research in two areas, neurodegenerative diseases and
cardiac diseases associated with heart rate variability, have identified some
• interesting and novel findings for which further study is ongoing.
Background
Program Oversight and Management
The 1992 Energy Policy Act created two committees to provide guidance and
direction to this program. The first, the Interagency Committee (IAC), was
established by the President of the United States and composed of representatives
from the NIEHS, the DOE and seven other Federal agencies with responsibilities
related to ELF-EMF. This group receives the report from the NIEHS Director
and must prepare its own report for Congress. The IAC had responsibility for
developing a strategic research agenda for the EMF-RAPID Program, facilitating
interagency coordination of Federal research activities and communication to the
public and monitoring and evaluating the Program.
The second committee, the National EMF Advisory Committee (NEMFAC),
consisted of representatives from public interest groups, organized labor, state
governments and industry. This group was involved in all aspects of the
EMF-RAPID Program providing advice and critical review to the DOE and the
NIEHS on the design and implementation of the EMF-RAPID Program's
activities.
•
111
• ELF-EMF Health Effects Research
The EMF-RAPID Program's health effects research initiative relied upon
accepted principles of hazard identification and risk assessment to establish
priorities. All studies supported by the NIEHS and the DOE under this program
were selected for their potential to provide solid, scientific data on whether
ELF-EMF exposure represents a human health hazard, and if so, whether risks are
increased under exposure conditions in the general population. Research efforts
did not focus on epidemiological studies (i.e. those in the human population)
because of time constraints and the number of ongoing, well-conducted studies.
The NIEHS health effects research program focused on mechanistic, cellular and
laboratory studies in the areas of neurophysiology, behavior, reproduction,
development, cellular research, genetic research, cancer and melatonin.
Mechanistic, cellular and laboratory studies are part of the overall criteria used to
determine causality in interpreting epidemiological studies. In this situation, the
most cost-effective and efficient use of the EMF-RAPID Program's research
funds was clearly for trying to clarify existing associations identified from
population studies. The DOE research initiatives focused on assessment of
exposure and techniques of mitigation.
The EMF-RAPID Program through the combined efforts of the NIEHS and the
DOE radically changed and markedly improved the quality of ELF-EMF
• research. This was accomplished by providing biological and engineering
expertise to investigators and emphasizing hypothesis-driven, peer-reviewed
research. Four regional facilities were also set-up where state-of-the-art magnetic
field exposure systems were available for in-house and outside investigators to
conduct mechanistic research. The EMF-RAPID Program through rigorous
review and use of multi-disciplinary research teams greatly enhanced the
understanding of the interaction of biological systems with ELF-EMF.
Information Dissemination and Public Outreach
The EMF-RAPID Program provided the public, regulated industry and scientists
with useful, targeted information that addressed the issue of uncertainty regarding
ELF-EMF health effects. Two booklets, a question and answer booklet on
ELF-EMF and a layman's booklet addressing ELF-EMF in the workplace, were
published. A telephone information line for ELF-EMF was available where
callers could request copies of ELF-EMF documents and receive answers to
standard questions from operators. The NIEHS also developed a web-site for the
EMF-RAPID Program where all of the Program's documents are on-line and
links are available to other useful sites on ELF-EMF. Efforts were made to
include the public in EMF-RAPID Program activities through sponsorship of
scholarships to meetings; holding open, scientific workshops; and setting aside a
two-month period for public comment and review on ELF-EMF and the
workshop reports. In addition, the NIEHS sponsored attendance of NEMFAC
iv
•
members at relevant scientific meetings and at each of the public comment
meetings.
Health Risk Assessment of ELF-EMF Exposure
In preparation of the NIEHS Director's Report, the NIEHS developed a process to
evaluate the potential health hazards of ELF-EMF exposure that was designed to
be open, transparent, objective, scholarly and timely under the mandate of the
1992 Energy Policy Act. The NIEHS used a three-tiered strategy for collection
and evaluation of the scientific information on ELF-EMF that included: 1) three
science review symposia for targeted ELF-EMF research areas, 2) a working
group meeting and 3) a period of public review and comment. Each of the three
symposia focused on a different, broad area of ELF-EMF research: mechanistic
and cellular research (24-27 March 1997, Durham, NC), human population
studies (12- 14 January 1998, San Antonio, TX) and laboratory human and clinical
work (6-9 April 1998, Phoenix, AZ). These meetings were aimed at including a
broad spectrum of the research community and the public in the evaluation of
ELF-EMF health hazards, identifying key research findings and providing opinion
on the quality of this research. Discussion reports from small discussion groups
held for specific topics were prepared for each meeting.
Following the symposia, a working group meeting (16-24 June 1998, Brooklyn
• Park, MN) was held where a scientific panel reviewed historical and novel
evidence on ELF-EMF and determined the strength of the evidence for human
health and biological effects. Stakeholders and the public attended this meeting
and were given the opportunity to comment during the process. The Working
Group conducted a formal, comprehensive review of the literature for research
areas identified from the symposia as being important to the assessment of
ELF-EMF-related biological or health effects. Separate draft documents covering
areas of animal carcinogenicity, animal non-cancer findings, physiological
effects, cellular effects, theories and human population studies (epidemiology
studies) in children and adults for both occupational and residential ELF-EMF
exposures were rewritten into a single book. The Working Group characterized
the strength of the evidence for a causative link between ELF-EMF exposure and
disease in each category of research using the criteria developed by the
International Agency for Research on Cancer (IARC).
The IARC criteria fall into four basic categories: sufficient, limited, inadequate
and evidence suggesting the lack of an effect. After critical review and
discussion, members of the Working Group were asked to determine the
categorization for each research area; the range of responses reflected the
scientific uncertainty in each area. A majority of the Working Group members
concluded that childhood leukemia and adult chronic lymphocytic leukemia from
occupational exposure were areas of concern. For other cancers and for non-
• cancer health endpoints, the Working Group categorized the experimental data as
V
• providing much weaker evidence or no support for effects from exposure to
ELF-EMF.
Following the Working Group Meeting, the NIEHS established a formal review
period for solicitation of comments on the symposia and Working Group reports.
The NIEHS hosted four public meetings (14-15 September 1998, Tucson, AZ;
28 September, Washington, DC; 1 October 1998, San Francisco, CA; and
5 October 1998, Chicago, IL) where individuals and groups could voice their
opinions; the meetings were recorded and transcripts prepared. In addition, the
NIEHS received 178 written comments that were also reviewed in preparation of
this report. The remarks that NIEHS received covered many areas related to
ELF-EMF and provided insight about areas of concern on behalf of the public,
researchers, regulatory agencies and industry.
•
S
vi
•
INTRODUCTION
Electricity is used to the benefit of people all over the world. Wherever electricity
is generated, transmitted or used, electric fields and magnetic fields are created.
These fields are a direct consequence of the presence and/or motion of electric
charges. It is impossible to generate and use electrical energy without creating
these fields; hence they are an inevitable consequence of our reliance on this form
of energy. Electrical energy is generally supplied as alternating current where the
electricity flows in one direction and then in the other to complete a cycle. The
number of cycles completed in a fixed period of time (such as a second) is known
as the frequency and is generally measured in units of Hertz (Hz), which are
cycles per second. In the United States, electricity is usually delivered as 60 Hz
alternating current; 50 to 60 Hz cycles are generally referred to as the power-line
frequency of alternating current electricity. Just as alternating current electricity
• has a frequency, so do the associated electric and magnetic fields (EMF). Thus,
60 Hz alternating current electricity will generate a 60 Hz electric field and a
60 Hz magnetic field. EMF with cycle frequencies of greater than 3 Hz and less
that 3000 Hz is generally referred to as extremely low frequency (ELF) EMF. In
addition to magnetic fields associated with electricity, the earth also has a static
magnetic field (frequency of 0 Hz) that varies by location from approximately 30
to 501.a,
Electricity has been used, to great advantage, for 100 years and with this
widespread use, there has been limited awareness of any potential adverse health
effects other than effects caused by direct contact such as electrocution or by
faulty wiring such as fire. Research into potential health effects caused by the
ELF-EMF resulting from indirect exposure to electrical energy has been
underway for several decades. The catalyst that sparked increased study in this
area of research was the 1979 report by Wertheimer and Leeper (1) that children
living near power lines had an increased risk for developing cancer. Since that
initial finding, there have been numerous studies of human populations, animals
and isolated cells aimed at clarification of the observations of Wertheimer and
Leeper and others. Despite this multitude of research, considerable debate
remains over what, if any, health effects can be attributed to ELF-EMF exposure.
In 1992, under the Energy Policy Act (FL 102-486, Section 2118), the U.S.
• Congress instructed the National Institute of Environmental Health Sciences
1
(NIEHS), National Institutes of Health and the U.S. Department of Energy (DOE)
to direct and manage a program of research and analysis aimed at providing
scientific evidence to clarify the potential for health risks from exposure to
ELF-EMF. This resulted in formation of the EMF Research and Public
Information Dissemination Program (EMF-RAPID Program). The EMF-RAPID
Program had three basic components: I) a research program focusing on health
effects research primarily through mechanistic studies of ELF-EMF and
engineering research targeting measurement, characterization and management of
ELF-EMF; 2) information compilation and dissemination through brochures,
public outreach and an ELF-EMF information line for communicating with the
public; and 3) a health assessment including an analysis of the research data
aimed at summarizing the strength of the evidence for evaluation of any hazard
possibly arising from exposure to ELF-EMF. The NIEHS was directed to oversee
the health effects research and evaluation and the DOE was given responsibility
for engineering research aimed at characterizing and mitigating these fields.
Under the Energy Policy Act, the Director of the NIEHS is mandated upon
completion of the EMF-RAPID Program to provide a report outlining the possible
human health risks associated with exposure to ELF-EMF. This document
responds to this requirement of the law.
Funding
• The EMF-RAPID Program was funded jointly by Federal and matching private
funds; through fiscal year 1998, authorized funding for this program was
approximately $46 million. Administration of funding for the EMF-RAPID
Program was the responsibility of the DOE with funds for NIEHS-sponsored
program activities transferred from the DOE to the NIEHS. The EMF-RAPID
Program has been an extremely successful FederaUprivate partnership with
substantial financial support from the utility industry. The NIEHS received $30. 1
million from this program for research, public outreach, administration and the
health assessment evaluation of ELF-EMF. Of the funds received, the NIEHS
spent the majority (89%) for research through grants and contracts. The
remainder was used for public outreach/administration (2%) and the health risk
evaluation (9%). In addition to EMF-RAPID Program funds from the DOE, the
NIEHS contributed $ 14.5 million for support of extramural grants and contracts
and intramural research as well as long-term toxicity studies conducted by the
National Toxicology Program.
S
2
• Oversight and Program Management
The 1992 Energy Policy Act created two committees that have provided guidance
and direction to the EMF-RAPID Program. One committee is the Interagency
Committee (IAC) and is composed of representatives from NIEHS, DOE and the
seven Federal agencies (listed below) with responsibilities related to ELF-EMF:
• Department of Defense
• Department of Transportation
• Environmental Protection Agency
• Federal Energy Regulatory Commission
• National Institute of Standards and Technology
• Occupational Safety and Health Administration
• Rural Electrification Administration
The IAC, which was established by the President of the United States, will
receive the report from the NIEHS Director, and must prepare its own report for
Congress. The IAC had responsibility for developing a strategic research agenda
for the Program, making recommendations for coordination of Federal research
activities and communication to the public and monitoring and evaluating the
EMF-RAPID Program.
•
The second committee is the National Electric and Magnetic Fields Advisory
Committee (NEMFAC) that consists of representatives from public interest
groups, organized labor, state governments and industry. This group advised
DOE and NIEHS on design and implementation of the EMF -RAPID Program and
provided input and recommendations to the IAC. The NEMFAC was involved in
all aspects of the EMF-RAPID Program, providing critical public review
throughout the process of evaluating evidence for potential health effects.
ELF-EMF Health Effects Research
The research initiative sponsored under the EMF-RAPID Program's health effects
research program relied on the accepted principles of hazard identification and
risk assessment to establish priorities. All studies supported by the NIEHS and
the DOE under this program were selected for then potential to provide solid,
scientific data on whether ELF-EMF exposure represents a human health hazard,
and if so, whether risks are increased under exposure conditions in the general
population.
Research efforts did not focus on epidemiological studies (i.e. those in the human
population) because of time constraints and the number of ongoing, well-
conducted studies. The NIEHS health effects research program focused on• 3
• mechanistic, cellular and laboratory studies in the areas of neurophysiology,
behavior, reproduction, development, cellular research, genetic research, cancer
and melatonin. Information about the health effects research projects that were
supported by the NIEHS is compiled into a booklet (2). Mechanistic, cellular and
laboratory studies are part of the overall criteria used to determine causality in
interpreting epidemiological studies. In this situation, the most cost-effective and
efficient use of the EMF-RAPID Program's research funds was clearly for trying
to clarify existing associations identified from population studies. The DOE
research initiatives focused on assessment of exposure and techniques of
mitigation. Presentation of the DOE-sponsored research was presented at an
engineering review symposium in April 1998 (3).
The EMF-RAPID Program through the combined efforts of the NIEHS and the
DOE radically changed and markedly improved the quality of ELF-EMF
research. This was accomplished by providing biological and engineering
expertise to investigators and emphasizing hypothesis-driven, peer-reviewed
research. These efforts resulted in better exposure systems, better documentation
of the exposure systems and more complete reporting of the exposures in the
literature. The EMF-RAPID Program through rigorous review and use of multi-
disciplinary research teams greatly enhanced the understanding of the interaction
of biological systems with ELF-EMF.
• The EMF-RAPID Program, in a collaborative effort between the DOE and
NIEHS, established four regional ELF-EMF exposure facilities where state-of-
the-art magnetic field exposures could be conducted. Two facilities were located
in DOE laboratories (Pacific Northwest Laboratories, Richland, WA and Oak
Ridge National Laboratories, Oak Ridge, TN) while NIEHS oversaw ELF-EMF
exposure facilities at the Food and Drug Administration (FDA, Rockville, MD)
and at the National Institute for Occupational Safety and Health (NIOSH,
Cincinnati, OH). During the course of the EMF-RAPID Program, these facilities
focused on in-house mechanistic studies, and advances were made in conducting
studies that have minimal bias. These centers also served as sites for investigators
who wanted to conduct preliminary investigations without the expense of having
to build their own exposure facilities.
Information Dissemination and Public Outreach
One of the three major components of the EMF-RAPID Program is dissemination
of information on ELF-EMF. Both NIEHS and DOE share responsibility for the
communication aspects of the program and jointly developed an outreach plan
and oversaw its implementation. Both the IAC and NEMFAC reviewed
information materials developed under this program.
The EMF-RAPID Program provided information to any interested parties about
• possible human health effects of ELF-EMF, the types and extent of human
4
• exposure, technologies for measuring and characterizing fields, methods for
assessing and managing exposure and other topics specified in the legislation.
The Program strove to provide the public, regulated industry and scientists with
useful, targeted information based upon established risk communication
principles (4, 5). The communication program candidly addressed the issue of
scientific uncertainty regarding ELF-EMF health effects and the overall
complexity of the ELF-EMF issue, while providing information in a format
appropriate for a variety of audiences.
The EMF-RAPID Program developed a question and answer booklet on
ELF-EMF that was published in January 1995. This booklet is easy to read and
has become very popular with more than 100,000 copies distributed nationwide.
Because of the diversity of the U.S. population and the needs of the Spanish
speaking community, a Spanish version of this booklet was also developed and
more than 10,000 copies have been distributed. The EMF-RAPID Program, in
conjunction with NIOSH, also developed and published a booklet entitled "EMF
in the Workplace" in September 1996. This publication provides basic
information in lay terms about ELF-EMF exposures in the workplace.
The EMF-RAPID Program made available an ELF-EMF public information line
where interested parties could call with questions about ELF-EMF and request
information. The U.S. Environmental Protection Agency (EPA) initiated this
• telephone line with funds from the EMF-RAPID Program in 1995 and transferred
its oversight to the NIEHS in August 1997. The information line was open
10 hours a day for five days a week and received approximately 380 calls per
month. Callers were provided copies of the ELF-EMF public information
documents, and the operators were trained to give accurate responses to standard
questions.
The NIEHS took the lead in developing the EMF-RAPID Program web-site
(www.niehs.nih.gov/emfrapid/home.htm) that began operation on
October 1 , 1996. All of the EMF-RAPID Program's documents are available
online in their entirety including the public information booklets described earlier,
research information, the NIEHS Science Review Symposia reports (described
below), the NIEHS Working Group Report (described below) and the public
meeting comments received on these reports. There are links to other useful sites
relating to ELF-EMF including the four regional exposure facilities. This site
receives an average of 500 visits per day from approximately 21 countries. The
requests come from individuals as well as commercial, educational, government,
military and non-profit organizations.
The NIEHS actively recruited the inclusion of concerned citizens into the
EMF-RAPID Program in several ways. Two scholarships were created to allow
representatives from two citizen groups to attend an annual research review
• meeting conducted by the DOE. All EMF-RAPID Program sponsored meetings
5
were open to any interested parties and public comments at them were welcome.
The NIEHS also set aside a two-month period for public comment and review on
ELF-EMF and the meeting reports. In addition, costs for NEMFAC members to
attend the Science Review Symposia, the chair of NEMFAC to attend the
Working Group Meeting and one member of the NEMFAC to attend each of the
public meetings were also provided. Finally, in cooperation with the EPA, a
workshop was held in May 1995 to give policymakers current information on
ELF-EMF and provide them with access to experts knowledgeable in
communicating information on this topic.
After the EMF-RAPID Program ends, the documents from this program will
continue to be publicly available through the National Technical Information
Service. Also, copies of these materials are located in the Library of Congress
and libraries of the EPA regional offices, the NIEHS and the National Academy
of Sciences.
Literature Review and Health Risk Assessment
Recent scientific panels on methods for health risk assessment (4-6) have
advocated open, participatory processes for the evaluation of health risks from
environmental exposures. The strategy developed by the NIEHS for collecting
and evaluating research information in preparation of the Director's report
• followed many of the recommendations of these recent panels. The resulting
program, reviewed and accepted by both the IAC and NEMFAC, provides a
blueprint for future risk assessments and is novel in the risk assessment
community (7, 8). The program focused on a broad-based, scientific debate
covering all of the diverse fields represented in ELF-EMF research and included
scientists from both within and outside the EMF community. In addition, an
aggressive outreach program was used to invite and include all interested parties
in the debate. This program consisted of three basic tiers:
• A series of three science review symposia focused on 1) mechanistic research,
2) epidemiological research and 3) laboratory research (animals and humans).
At each meeting participants considered the quality and reproducibility of the
scientific evidence, suggested what literature provides the strongest scientific
evidence for making a decision, suggested additional avenues for research and
provided opinions on whether or not there is support for a causal linkage
between exposure to ELF-EMF and an associated biological or health effect.
• A working group meeting where a select panel of scientists critically
evaluated the entirety of research evidence on ELF-EMF health effects and
determined the strength of the evidence for human health effects.
• A period of public review and comment on the reports from the symposia and
working group prior to their use by NIEHS in preparing this report.
•
6
• The Science Review Symposia were designed as open, public workshops aimed at
including a broad spectrum of the research community in evaluating ELF-EMF
health hazards. To minimize bias, outstanding research scientists from outside of
the ELF-EMF research community were included in all reviews; these scientists
provided an objective evaluation of the experimental methods used and the
hypotheses underlying many of the studies. These EMF and non-EMF scientists
were given the task of identifying key research findings and providing opinion on
the quality of the research. The workshops were held 24-27 March 1997 in
Durham, NC; 12-14 January 1998 in San Antonio, TX; and 6-9 April 1998 in
Phoenix, AZ. Over 100 individuals attended each meeting and included
representatives from the public, stakeholders, regulatory agencies, NEMFAC and
IAC as well as scientists from varied disciplines including, but not limited to,
medicine, epidemiology, molecular and cellular biology, physics, engineering,
statistics, toxicology, pathology and neurobiology. The format for these meetings
included plenary sessions with overview lectures to familiarize attendees about
research findings and issues for specific ELF-EMF topics and small breakout
discussion groups. The breakout group sessions (composed of 25-30 attendees
per group) provided time for in-depth discussions on the quality and
reproducibility of ELF-EMF research findings and possible linkages with health
effects. The rapporteurs and facilitator for each session prepared a short report
that was reviewed by attendees of that breakout group. The breakout group
reports from each science review symposium are available as printed documents
• (9-11) or on the EMF-RAPID Program web-site.
The Working Group Meeting was held 16-24 June 1998 in Brooklyn Park, MN.
Prior to this meeting, a group of select scientists was given the task of conducting
a formal, comprehensive review of the literature for research areas identified from
the symposia as being important to the assessment of ELF-EMF-related biological
or health effects. At the Working Group Meeting, the panel of 30 international
scientists, both from within and outside the field of ELF-EMF research, critically
evaluated and rewrote the draft chapters into a single book (12). In addition to
reviewing the literature, the Working Group also characterized the strength of the
evidence in each category of research using the criteria developed by the
International Agency for Research on Cancer (IARC). These criteria are given in
Appendix A of the Working Group Report. The literature included in the report
was limited to published, cited findings or novel work being prepared for
publication that could be peer-reviewed by the Working Group members.
Following the Working Group Meeting, the NIEHS established a formal review
period of 10 August — 9 October 1998 to receive comments on the Working
Group Report and symposia reports. During this period, the NIEHS hosted four
public meetings (14-15 September 1998, Tucson, AZ; 28 September 1998,
Washington, DC; 1 October 1998, San Francisco, CA; and 5 October 1998,
Chicago, IL) where individuals and groups could voice their comments orally
and/or in writing to NIEHS officials and other scientists involved with preparation
• of this report. The meetings were recorded and a transcript was prepared.
7
SAttendance at the public meetings varied from 32 to 101 attendees per meeting.
Formal comments (8 to 21 per meeting) were provided by various groups
including the general public, researchers, utility industry, advocacy groups and
state governmental agencies. Written comments, independent of oral
presentations, were also solicited during the comment period; 178 entries from
individuals and groups were received. These transcripts and written comments
were used by the NIEHS in preparing this report.
I
i
8
•
Do ELECTRIC AND MAGNETIC
FIELDS POSE A HEALTH RISK.
The scientific evidence suggesting that ELF-EMF exposures pose any health risk
is weak. The strongest evidence for health effects comes from associations
observed in human populations with two forms of cancer: childhood leukemia and
chronic lymphocytic leukemia in occupationally exposed adults. While the
support from individual studies is weak, the epidemiological studies demonstrate,
for some methods of measuring exposure, a fairly consistent pattern of a small,
increased risk with increasing exposure that is somewhat weaker for chronic
lymphocytic leukemia than for childhood leukemia. In contrast, the mechanistic
studies and the animal toxicology literature fail to demonstrate any consistent
• pattern across studies although sporadic findings of biological effects (including
increased cancers in animals) have been reported. No indication of increased
leukemias in experimental animals has been observed.
The lack of connection between the human data and the experimental data (animal
and mechanistic) severely complicates the interpretation of these results. The
human data are in the "right" species, are tied to "real-life" exposures and show
some consistency that is difficult to ignore. This assessment is tempered by the
observation that given the weak magnitude of these increased risks, some other
factor or common source of error could explain these findings. However, no
consistent explanation other than exposure to ELF-EMF has been identified.
Epidemiological studies have serious limitations in their ability to demonstrate a
cause and effect relationship whereas laboratory studies, by design, can clearly
show that cause and effect are possible. Virtually all of the laboratory evidence in
animals and humans and most of the mechanistic work done in cells fail to
support a causal relationship between exposure to ELF-EMF at environmental
levels and changes in biological function or disease status. The lack of consistent,
positive findings in animal or mechanistic studies weakens the belief that this
association is actually due to ELF-EMF, but it cannot completely discount the
epidemiological findings.
•
9
• The NIEHS concludes that ELF-EMF exposure cannot be recognized as entirely
safe because of weak scientific evidence that exposure may pose a leukemia
hazard. In our opinion, this finding is insufficient to warrant aggressive
regulatory concern. However, because virtually everyone in the United States
uses electricity and therefore is routinely exposed to ELF-EMF, passive
regulatory action is warranted such as a continued emphasis on educating both the
public and the regulated community on means aimed at reducing exposures. This
is described in greater detail in the section, Recommended Actions. The NIEHS
does not believe that other cancers or non-cancer health outcomes provide
sufficient evidence of a risk to currently warrant concern.
Scientific Evidence Supporting This Conclusion
The reports from the Science Review Symposia (9-11) and the Working Group
(12) provide detailed reviews of the literature in this area of science. What
follows is a brief synopsis of this evidence. The reader should refer to the
individual reports for greater detail.
Background on the Limitations of Epidemiology Studies
Epidemiological studies are used to investigate the associations between health
IP effects and exposure to a presumed disease agent. A well-designed and
conducted epidemiological study involves several steps including identification of
a study population, definition of the exposure to be studied, choice of the type of
study to conduct (e.g. cohort study versus case-control study) and description of
the period over which the exposure is relevant. All of these factors influence the
quality of a study and the limits that must be placed on interpretation of a study's
findings.
In carefully controlled laboratory and clinical investigations, study subjects are
typically assigned to a treatment or exposure regimen. In epidemiological
investigations, the inability to randomly assign exposures means that investigators
must design their study so that the individuals who develop the disease of interest
(cases) resemble the individuals who are disease-free (controls) in all aspects
except for exposure; this is intended to limit possible bias. Bias due to improper
selection of cases and controls is introduced if exposure is related to
characteristics that would make cases more or less likely to be sampled than
controls, or once sampled, to participate.
In the Nordic countries, comprehensive national population registries are
generally used for selecting controls. If all persons are listed in these population
registries and participation rates are high, bias due to selection of improper
controls is unlikely even if exposure is related to participation. In countries such
as the United States where population registries do not exist, other methods must
• be used to study rare diseases like leukemia for which existing cohort studies are
10
• inadequate. These methods lead to difficulties in identifying, contacting and
recruiting controls that match the cases in all aspects other than exposure. For
example, controls are sometimes identified through stratified random sampling of
individual telephone numbers (random-digit dialing). Random-digit dialing may
not properly identify controls of low socioeconomic status that do not have
telephones; this could bias the results found in studies of childhood leukemias
(13).
It is also possible to introduce bias through the selection of cases. For example,
case selection bias may occur in studies that are based on mortality records (death
certificates) if the survival rates of the exposed and unexposed subjects differ.
This may occur if, for example, the exposure is related to socioeconomic status,
and different socioeconomic groups have different survival rates for the studied
disease (this might be due to a difference in the ability of cases to receive medical
care). In addition, for diseases that are easily cured or allow patients to survive
with the disease for a long period of time, persons who contract the disease and
are treated properly may die of other causes and not appear as cases.
The inability to randomly assign exposures also introduces the possibility of
confounding. Confounding occurs when the exposure of interest is associated
with another factor that can increase (or decrease) the risk of getting the disease of
interest (14). For example, smoking increases the risk of oral cancer; smoking is
• also associated with alcohol consumption, and there is a greater proportion of
smokers among alcohol drinkers than among non-drinkers. Because smoking
increases the risk of oral cancer and alcohol drinkers are more likely to smoke
than non-drinkers are, alcohol drinkers will have a greater risk of oral cancer
simply as a consequence of the greater percentage of smokers among alcohol
drinkers. Thus, any study showing an increased risk of oral cancer associated
with alcohol drinking will overstate that risk (resulting in a positive bias) if the
effect of smoking is not carefully evaluated. Confounding can produce bias in
either direction, artificially increasing or decreasing risks, depending on the
direction of the association between the exposure, the disease and the confounder.
When known, confounding can be controlled through statistical methods.
Because there are very few known causes of childhood leukemias and chronic
lymphocytic leukemia, it is difficult to identify and control potential confounders
in these studies.
Another limitation of epidemiological studies is that exposure occurs through the
natural course of events rather than being assigned and controlled by the
investigator. Thus, a determination of the degree of exposure can be incorrect
leading to what is known as "exposure misclassification." Exposure
misclassification may distort measures of association observed in a study. For
example, in epidemiological studies aimed at exposures received on the job
(occupational studies), it is common to define exposures by the type of job a
person performs. Errors may occur in assigning job titles or the jobs themselves
• may have markedly different exposures for different individuals. It is also
11
• possible that the exposure assignment may differ for diseased and non-diseased
subjects. Information on exposure can be obtained either prospectively (before
the disease has occurred) or retrospectively (after the disease has occurred). In
the case where exposure is determined prior to disease onset, there is a reduced
potential for misclassification of the exposure. In the case where exposure is
determined after the onset of the disease, especially where it is obtained from
questioning individuals with the disease, the recall of exposure may be influenced
by the fact that the patient has a disease and is influenced by previous descriptions
of potential causes of that disease.
Epidemiological studies have used various methods for estimating past ELF-EMF
exposure to provide scientific evidence concerning the possibility of health effects
from exposure to ELF-EMF. Residential exposures to ELF-EMF have been
conducted in five basic ways: wire codes that are essentially based upon distance
to major structures used for delivering electrical energy (e.g. high tension power
lines and transformers); calculated magnetic fields that are based upon a
theoretical calculation of the magnetic field emitted by certain types of power
lines using historical electrical loads on those lines; spot measurements that
generally give a single, instantaneous measurement of the magnitude of the
magnetic field in one or more spots in a residence; average measured fields that
are essentially spot measurements taken repeatedly every few seconds for
24 hours and averaged over time; and personal average measured fields where the
• subject wears a monitor and measurements are taken repeatedly every few
seconds for 48 hours and averaged over time.
The validity of individual exposure assessment methods has been examined and
each has its limitations (12, 15-20). Wire codes and calculated fields have the
advantage of remaining fairly consistent over time making them more likely to be
correctly determined during the time of cancer onset. However, their main
disadvantage over measured fields is a lack of consideration of all possible
sources of exposure, in particular fields from in-home appliances and ground
currents. The relationship of wire codes to direct magnetic field measurements
has been examined; the reliability of wire codes as a quantitative measure of
magnetic field exposure is variable (15, 17, 19, 20).
Childhood Cancers
The hypothesis generated by the seminal study of Wertheimer and Leeper (1)
used wire codes to evaluate residential exposures in children. Four additional
epidemiological studies in which wire codes were used to assess exposure to
ELF-EMF are of sufficient quality to be used in the evaluation of a causal
association between the risk of childhood leukemia and exposure to magnetic
fields. Two of the studies reported an association (21, 22), and two studies
reported no association with the risk for childhood leukemia (23, 24). A trend of
• increasing risk with wire codes classification implying increased fields was
12
• observed in the two positive studies (21, 22). All of these studies, including the
seminal study, could have been affected by the types of biases described earlier
including exposure bias (1), control selection (all five studies), and confounding
from other risk factors (all five studies). In addition, the seminal study and the
four subsequent studies differed in their groupings of leukemias ranging from
evaluating all types of leukemias (1, 21, 22, 24) to evaluating only acute
lymphoblastic leukemia (23, 24), the most common form of the disease in
children. The most recent U.S. study (23) is the largest of the four subsequent
studies for evaluating ELF-EMF exposure. Even though this study (23) shows a
negative association when comparing Wertheimer-Leeper wire codes with
leukemia risks, when combined with the remaining studies (21, 22, 24) in a meta-
analysis (a form of statistical analysis in which like studies are combined to get a
single answer), the results indicate a marginal association for the highest exposure
group versus the lowest exposure groups. Removal of any of the three remaining
studies (21, 22, 24) diminishes this association substantially. After removal of the
one follow-up study with the most severe design limitations (21), the association
is no longer present. Another study (25) was not included in the meta-analysis
due to study limitations; this study showed no effect of wire codes.
Four epidemiological studies (26-29) assessed exposure using calculated fields;
all four studies were conducted in Nordic countries. Three of the studies observed
an increased leukemia risk in one or more exposure group (26-28) although only
• one (26) achieved statistical significance. All four studies were population-based,
with minimal potential for selection bias both in terms of control selection and
participation rates. The main limitations of all four studies are the small number
of cases overall and the small number of cases and controls in the high exposure
group. The general trend of these studies provides marginal support for a small,
increased risk (30).
Four studies in which spot measurements were used to assess exposure to
magnetic fields are clearly of greater quality than the remaining studies
(21, 22, 26, 31). Two of these studies (21, 22) observed increased risks of
marginal significance in one or more exposure groups and the other two (26, 31)
showed no risk. Overall, spot measurements do not show an appreciable excess
risk for leukemia when the four studies are combined (30).
Four studies used 24-hour measured magnetic fields to assess exposure
(22-24, 31)1. The studies examined three different classifications of childhood
leukemias: acute lymphocytic leukemia (23, 24), acute leukemia (31) and
leukemia including nonlymphocytic leukemia (22, 24). The results of three of the
studies showed an increased risk for children in higher exposure class(es); in two
studies there were no statistically significant differences (22, 24), in the largest
study only one experimental category out of many was statistically significant
• This publication (24) only provides a single odds ratio from their analysis of the 24-hour measurements.
Additional information was obtained from the principal author.
13
• (23), and depending on the grouping, the fourth study achieved statistical
significance (31). The data reported for the largest study (23) suggest an
exposure—response relationship that the original authors did not consider
important. The pattern of dose versus response in this study was considerably
different from the pattern in the other two studies with multiple dose groups
(22, 24). The results of these studies, when combined, provide weak evidence for
an association between exposure based on 24-hour measured magnetic fields and
a small, increased incidence of childhood leukemia (30).
One study (24) assessed exposure using 48-hour personal monitors that measured
both magnetic fields and electric fields. Analyses were done for all childhood
leukemias and separately for acute lymphocytic leukemia. The general trend in
the data indicated a negative association for both magnetic fields (current or
predicted two years prior to diagnosis) and electric fields. No statistically
significant positive associations were observed. This study, using personal
exposure meters, does not support an association between ELF-EMF exposure
and childhood leukemia.
Several of the same studies described earlier also looked at electrical appliance
use and the risk of childhood leukemia (22, 32, 33). The results do not fit a
coherent pattern.
• None of the individual epidemiological studies provides convincing evidence
linking magnetic field exposure with childhood leukemia. Hence, in making an
assessment, one must rely upon the evaluation of the data as a whole using expert
judgment and the meta-analyses as a guide. The pattern of response, for some
methods of measuring exposure, suggests a weak association between increasing
exposure and increasing risk. The small number of cases in these studies makes it
impossible to firmly demonstrate this association. This level of evidence, while
weak, is still sufficient to warrant limited concern.
Two other childhood cancers have been sufficiently studied to warrant comment.
Two early studies observed an increased risk of brain cancers using wire codes as
the exposure measure (1, 21). Later studies using wire codes (34, 35), calculated
fields (26-28, 36) and measured fields (35) failed to support this finding. The
association between exposure to ELF-EMF and childhood lymphomas was
considered in several epidemiological investigations (1, 21, 26-28, 36). In all
studies, the number of cases of lymphoma in the high exposure groups was too
small for any reliable inference to be drawn. In general, these data do not support
the concern that exposure to magnetic fields may increase the risk of brain
cancers or lymphomas in children.
S
14
•
Adult Cancers
Epidemiological reports of diseases associated with occupational exposure to
ELF -EMF preceded concerns about residential exposure. Reports of various
health problems in high-voltage substations in the former USSR initially focused
attention on ELF electric fields (37). Initial studies in the United States (38, 39)
led to over 100 epidemiological investigations of workplace exposure to
ELF-EMF and various diseases. The early studies were based on workers in jobs
assumed to entail exposure, and more recent studies used measured fields.
Recent studies evaluating the association between exposure to magnetic fields and
chronic lymphocytic leukemia (40-44) show mixed results. The two studies in the
United States (43, 44) reported no association, but one (44) used death certificates
to identify the cases (chronic lymphocytic leukemia has a rather long survival
time that can confound the diagnosis of the cases). One of the remaining studies
(42) indicated increased risk, which did not achieve statistical significance, and
the two Scandinavian studies (40, 41) showed significantly elevated risks in one
or more exposure groups. Both of the Scandinavian studies had consistently
increasing risks with increasing exposure. Each of these studies has its limitations
and the limitations are different across studies, as are the designs and exposure
assessment methods. Taken together, the studies provide weak evidence for an
association between occupational exposure to magnetic fields and chronic
• lymphocytic leukemia.
Acute myelogenous leukemia was considered in these same epidemiological
studies. The results, which were observed from these studies, are not sufficiently
compelling to support an association.
The association between exposure to magnetic fields and a variety of other
cancers has also been considered in occupational settings. Included are brain
cancers, breast cancers (in both males and females), testicular cancers, cancers in
offspring of workers, lymphoma, multiple myeloma, melanoma, non-Hodgkin's
lymphoma, thyroid cancers and many others. Some evidence exists for an
association between brain cancers and exposure to ELF-EMF and between female
breast cancers and ELF-EMF exposure; however, the studies evaluating these
associations are inconsistent and have limits to their interpretation making them
inadequate for supporting or refuting an effect. In the remaining cases, the
evidence supporting an association is negative or too weak to warrant concern.
The risks of adult cancer based on residential exposure to ELF-EMF have been
evaluated in a number of studies. Risks of leukemia (of all types and of specific
sub-types) from residential exposures were evaluated in several recent studies
(40, 45-50). The calculated field studies (40, 47-50) showed mixed results for the
different sub-types of leukemia studied and for changes in the definition of the
• exposure category. Specifically, when chronic lymphocytic leukemias was
15
• examined separately (this was done in only two of the studies), the results were
inconsistent with one study (40, 48) showing no increased risk and with the other
(49) showing fairly consistent dose-response with increasing cumulative
exposure. The remaining studies, using wire codes (46) and measured fields
(46, 48), demonstrated no increased risk. These data are inadequate for
evaluating the association between exposure to ELF-EMF and leukemias.
Specifically, for chronic lymphocytic leukemia, which demonstrated a weak
association in the occupational studies, there are mixed results for adults in the
residential studies.
The risk for leukemia associated with use of electrical appliances was also
considered in two studies (45, 51). These studies resulted in inconsistent findings
and generally do not support an association between appliance use and increased
leukemia risk.
Limited data are available on risks of male and female breast cancer associated
with residential exposure to ELF-EMF. A small, non-significant association
between use of electric blankets and the risk for breast cancer was observed in
one, large U.S. study (52) but not in another (53). Both found no evidence for an
association with duration of exposure. Three studies, using exposure measured by
calculated fields (50, 54, 55), identified no association between exposure to
magnetic fields and the risk of breast cancer. These same scientists
(40, 47, 48, 50, 55) also looked at exposures to ELF-EMF and cancers of the
central nervous system (such as brain cancers); no associations were found.
None of the associations between cancer and residential exposure to magnetic
fields in adults were indicative of a positive association. However, the specific
adult cancer showing weak evidence of a positive association with occupational
exposure to ELF-EMF, chronic lymphocytic leukemia, was inadequately studied
in residential settings. It cannot, therefore, be concluded that there is no
association.
Non-Cancer Findings in Humans
The relationship between spontaneous abortion and exposure to ELF-EMF has
been considered in several studies. Recent occupational and residential studies
were the focus of this assessment. In the first occupational study (56), no
association was observed. In a second occupational study (57), a significant
association was found with exposure to high ELF -EMF; however, the response
rate was very poor, particularly among controls, which could have biased this
result upward. Pregnancy loss was investigated in two residential cohort studies
(58, 59). In one study (58), an increased risk was observed in the highest
exposure category but not in the intermediate category. In the other (59), no
association was observed for any measure of exposure. In a carefully designed
• prospective study in the United States (60), no association was reported between
16
measured fields (including personal exposure monitoring) and intrauterine
growth, birth weight or gestational age.
Low birth weight (60, 61), intrauterine growth retardation (60), preterm birth (61)
and congenital anomalies arising from the father's exposure (62) were not
associated with occupational exposures to ELF-EMF. The risk for congenital
anomalies in relation to the mother's use of heated waterbeds and electric blankets
around the time of conception was evaluated in three studies (63-65); no
association was observed for heated waterbeds in any study, and inconsistent
results were reported for electric blanket use.
The association between occupational exposure to ELF-EMF and Alzheimer's
disease was considered in five studies (66-70). All five studies showed increases
in one or more exposure groups with four studies (66-69) showing statistically
significant increases and one (70) showing non-statistically significant increases.
All of these studies suffer from design limitations that make it inappropriate to
use them for addressing a causal association between ELF-EMF exposure and
Alzheimer's disease. Two of these (66, 67) are based on diagnoses from death
certificates (Alzheimer's disease is not consistently noted on death certificates).
Two studies (68, 69) used different groups of cases and controls; some of the
control groups included persons with other types of dementia, and proxy
information was used to define the exposure of cases. The one remaining study
(70) was evaluated using data for twins and also suffered many limitations. These
data are inadequate for interpreting the possibility of an association.
The association between exposure to magnetic fields and amyotrophic lateral
sclerosis was assessed in three studies (66, 71, 72). One study (71) showed an
increased risk in the highest exposure group and the other two studies were
negative. Adequate adjustment could not be made for known risk factors
(electric shocks or a family history of amyotrophic lateral sclerosis) making these
studies difficult to interpret.
Suicide and depression were studied in three occupational epidemiological
studies (72-74). These studies do not support an association with ELF-EMF
exposure.
Two occupational studies (75, 76) assessed possible adverse cardiovascular
outcomes that may result from exposure to magnetic fields. In the first study (75),
a significant decrease in risk using a broadly defined cardiovascular grouping was
observed. In the second (76), data from five utilities were examined. This study
was motivated a priori by a biological hypothesis based on the results of human
clinical studies on heart rate variability (77) for increased numbers of deaths due
to arrhythmia and acute myocardial infarct. Significant, exposure-dependent
associations were reported. Lacking additional epidemiological studies to
•
17
• collaborate these results, these data are inconclusive regarding an association
between cardiovascular disease and exposure to ELF-EMF.
Human clinical studies of ELF-EMF exposures were carried out mainly through
three major research initiatives. These include a long series of studies of utility
workers begun in the 1960s in the former USSR (37), human laboratory research
conducted in the 1970s in Germany (78, 79) and the human laboratory research
program started in 1982 at the Midwest Research Institute in the United States
(80). Dedicated facilities for human exposure testing were designed and
constructed in Australia (81), Canada (82), England (83), France (84), Germany
(78), New Zealand (85), the Russian Federation (86) and the United States
(87, 88). Research with human volunteers is currently under way in many of
these facilities.
A large number of clinical end-points were evaluated in these laboratories.
Several effects reported at high exposures warrant little concern as health dangers
such as hair standing on end in very strong electric fields and flickering visual
sensations in very strong magnetic fields. However, a number of measurements
potentially linked to health effects have been studied. The central nervous system
was one of the first areas investigated as a potential site of interaction with
ELF-EMF. Studies of changes in brain wave patterns (electroencephalography)
during waking hours were generally negative showing little or no effect of ELF-
• EMF, especially in the range of power-line frequencies (79, 80, 86, 89-94).
Several studies (95-97) showed decreased sleep and reduced sleep efficiency
during ELF-EMF exposure. These studies all had deficiencies (e.g. disturbance of
subjects by drawing blood and incomplete adaptation of study subjects to the
laboratory environment) making them inconclusive.
Changes in human pulse as a function of exposure to ELF-EMF fall into two
categories: changes in the number of beats per minute (pulse rate) and changes in
the variability of the electro-chemical signals going to the heart (heart-rate
variability). Two research groups examined changes in pulse rate following
exposure to ELF-EMF (80, 91-93, 98, 99). All five clinical studies
(80, 91-93, 99) from the same laboratory showed a decrease in pulse rate in at
least one exposure group; however, all exposures represented rather large,
combined electric and magnetic fields (6 to 12 kV/m and 10 to 30 µ,T,
respectively). The remaining study (98) was a field trial under a high-tension
power line and no effect was observed. The biological mechanism is unknown,
and the general effect is very small making it unlikely that this is a health risk at
lower doses.
Changes in heart-rate variability were evaluated in a retrospective analysis of
three previous studies (77). Some changes in heart-rate variability were observed,
which according to the authors, could indicate a potential for increased risk of
• sudden cardiovascular death. However, even though decreased heart-rate
18
• variability is associated with increased risk of cardiovascular death, it is not clear
that transiently induced changes in healthy individuals will carry any risk. While
these findings are inconclusive, the recent epidemiological result (76) discussed
earlier suggests this area may warrant additional study.
Two possible mechanistic explanations for cancer findings from exposure to
ELF-EMF, changes in melatonin (a hormone associated with sleep) and changes
in the immune system, have been studied. The potential for ELF-EMF exposure
to alter nighttime melatonin levels was addressed in 11 studies
(81, 84, 96, 100-106). The clinical studies (81, 84, 96, 102, 103) demonstrated no
consistent pattern of melatonin reduction (one study saw a marginal effect in men
with already reduced melatonin levels and one saw a reduction in onset of the
nightly increase in melatonin). In the occupational studies (100, 101, 105, 106),
some changes were reported in urinary excretion of melatonin metabolites (the
result of degradation of melatonin in the body) following workplace exposure
(when melatonin levels are generally low), but not in evening melatonin levels.
In the one residential study (104), significant dose-related reductions were
associated with measured fields in bedrooms, but not with other measures (e.g.
wire codes and total 72-hour exposure). All combined, these studies provide little
support that exposure to ELF-EMF is altering melatonin levels in humans. A
number of other hormones were also studied such as testosterone, thyroid
hormones and several stress hormones; no effects of ELF-EMF exposure on these
• levels were observed.
Few laboratories studied the effects of ELF-EMF on the immune system. Three
studies investigated effects of ELF-EMF exposure on the immune system
(80, 107, 108) and all were negative.
Finally, there have been a number of case reports of mood changes and
hypersensitivity thought attributable to ELF-EMF exposure (manifested as
physiological reactions, disturbed sleep, fatigue, headaches, loss of concentration,
dizziness, eye strain and skin problems). These symptoms generally seem to be
intermittent and difficult to study clinically. Several carefully designed
studies (109-113) were performed to evaluate the response of persons with these
symptoms to ELF-EMF. In general, these studies were negative with the
exception of one (112) that reported an increased incidence of skin rashes in
persons exposed to high ambient electric fields (>31 Vim) relative to control
fields (<10 V/m). These data are insufficient to support an association between
ELF-EMF and hypersensitivity.
Animal Cancer Data
Animal carcinogenicity studies are routinely used to identify environmental
agents that may increase cancer risk in humans. Many areas of biological
investigation are more efficiently studied in animal models than in human beings,
19
Sbecause the agent can be studied invasively and under carefully controlled
environmental conditions. The use of animal models in studying effects of
ELF-EMF exposure is limited by two problems: extrapolation of experimental
findings across species and extrapolation of laboratory exposure patterns to
environmental exposure patterns. Animal carcinogenic studies of ELF- EMF were
done at levels of exposure generally much higher and having greater uniformity in
frequency and intensity than would appear in environmental settings. These
experimental conditions were chosen to maximize the ability of a researcher to
detect an effect, if one exists, for a clearly defined exposure.
The laboratory data in animal models are inadequate to conclude that exposure to
ELF-EMF alters the rate or pattern of cancer. There are some sporadic findings
(including increased cancers) with no clear interpretation; however, it is
noteworthy that these data provide no support for the reported epidemiological
findings (discussed earlier) of increased risk for leukemia from ELF-EMF
exposure.
Only a few lifetime bioassay studies (114-116) have been performed for
ELF-EMF exposure. These studies exposed large groups of animals generally for
periods of up to two years at magnetic field intensities considerably higher than
elevated residential exposures. No consistent effects of ELF-EMF exposure on
cancer rates in bioassay animals were found. The most comprehensive study
• conducted through the National Toxicology Program (115) used four exposure
groups (control, 2, 200 and 1000 µT continuous exposure for 18.5 hours per day
and 1000 µT intermittent exposure) and four gender/species groups. There were
no exposure-related clinical findings for rats or mice. The two-year study found
no evidence of carcinogenicity in female rats and male or female mice at any
exposure level and equivocal evidence for carcinogenicity in male rats based upon
an increased incidence of thyroid gland C-cell tumors.
A similar study (114) was conducted in female rats where exposure to 60 Hz
linearly polarized magnetic fields (control, 2, 20, 200 and 2000 µT continuous
exposure) began in utero two days before birth and continued for 20 hours per day
for two years. No consistent, exposure-related clinical findings or evidence of
carcinogenic activity from 60 Hz magnetic fields were reported. In another study
(116) male and female rats were exposed to control, 500 or 5000 µT 50 Hz
magnetic fields for 22.6 hours per day for two years. No differences in cancer
rates between field-exposed and sham-exposed animals were found.
Epidemiological findings have suggested a possible association between magnetic
field exposure and breast cancer in men (117, 118) or women (119). In addition,
a hypothesis was proposed that magnetic field exposure might lower nocturnal
melatonin levels that could increase risk for breast cancer (120). Animal studies
using chemically induced mammary cancer followed by magnetic field promotion
20
• of carcinogenesis were undertaken to test whether mammary cancer was affected
by ELF-EMF exposure.
Following an initial report that magnetic fields promoted mammary tumor
development in rodents (121), a comprehensive series of studies on ELF-EMF
exposure and mammary tumor initiation and promotion in the rodent model was
conducted (122-124). In these studies, female Sprague-Dawley rats were used
and cancer was initiated by intragastric administration of four weekly doses of
7,12-dimethylbenz[a]anthracene (DMBA) followed by promotion with 50 Hz
ELF magnetic fields, 24 hours per day for 13 weeks. One of the early studies in
this series (122), where the data were subsequently examined histologically (125),
provided evidence that magnetic fields of low flux density (100 µT) promoted
increased growth and size of mammary tumors but did not affect tumor incidence.
The same laboratory repeated this work, and in additional studies testing different
magnetic flux densities, examined the question of whether a dose-response
relationship exists with field intensity (126-128). Over the range of 10 to100 µT
magnetic fields (50 Hz), a higher (not statistically significant) number of total
tumors was found in the field-exposed groups. Magnetic field exposure was not
associated with more tumors per tumor-bearing animal. Effects on tumor latency
and size were not consistent across the studies.
The National Toxicology Program (129) conducted similar studies. Animals were
• exposed to magnetic fields at both European frequency (50 Hz, 100 or 500 µT)
and American frequency (60 Hz, 100 µT) 18.5 hours per day, seven days per
week for 13 weeks following intragastric administration of four weekly doses of
DMBA as the initiator. There was no difference in size or incidence of mammary
gland tumors between control and exposed groups. However, the tumor incidence
was high in all groups, and sensitivity was reduced for detecting a promoting
effect of magnetic fields. The study was repeated at a lower dose of DMBA.
Tumor incidence, latency and size, total number of tumors and number of tumors
per tumor-bearing animal were not affected by magnetic field exposure; in the
exposure groups there were slightly fewer total mammary neoplasms (not
statistically significant) than in controls. A 26-week study, where animals
received a single initiating dose of DMBA, gave similar results (129); there were
significantly fewer tumors for the two exposed groups. However, the tumor
incidence was high in all groups, and sensitivity was reduced for detecting
promoting effects of magnetic fields. This collection of studies (129) provides
strong evidence of no effect of magnetic fields on the promotional development of
mammary cancer.
Another laboratory (130) also examined the effects of magnetic field exposure,
which included transients, on mammary tumor development in female Sprague-
Dawley rats. This study differed slightly in experimental design from the ones
described earlier, but used DMBA as initiator and examined similar magnetic
fields, 250 and 500 µT, at 50 Hz. No effects of magnetic fields were observed.
•
21
• The explanation for the observed difference among these studies is not readily
apparent. However, within the limits of the experimental rodent model of
multistage mammary carcinogenesis, the findings do not provide consistent
evidence for a promoting effect of ELF-EMF on chemically induced mammary
cancer.
Animal models of skin carcinogenesis are well established for the study of the
initiation, promotion and progression of cancer (131). Several laboratories
examined whether 50 and 60 Hz magnetic fields promoted or co-promoted
development of cancer using this model (132-137). Skin tumors were initiated by
topical treatment of the animals with a known chemical carcinogen (e.g. DMBA)
followed by exposure to various intensities of magnetic fields or combinations of
magnetic fields plus a known chemical promoter (e.g. 12-O-tetradecanoyl phorbol
13-acetate, TPA). The findings from these studies demonstrated no significant
promotional effect of magnetic fields on skin tumor development.
Rat liver is a most commonly used experimental model for investigating
multistage carcinogenesis in tissues other than the skin (138). Several
experiments from a single laboratory used this model to investigate ELF-EMF
exposure effects and reported no evidence of a promotional or co-promotional
role of magnetic fields in cancer development (139, 140).
Several epidemiological studies have suggested a possible association between
ELF-EMF exposure and an increased risk for leukemia. Two types of animal
models were used for determining whether magnetic fields can alter the time of
onset or incidence of leukemia: 1) initiation with X-rays or chemical carcinogen
followed by ELF-EMF exposure and 2) progression of leukemia by injection of
leukemia cells into the animal followed by ELF-EMF exposure.
The largest ELF-EMF study using an agent to initiate disease involved over 2000
mice with different doses of ionizing radiation to initiate lymphoma followed by
either exposure to 1400 µT magnetic fields or no exposure for up to 30 months.
Exposure to magnetic fields did not affect the incidence or time of onset of
leukemia/lymphoma, the rate of death among animals with leukemia/lymphoma
or the leukemia sub-types (141). In another study (142), no promotional effects
of a 1000 µT 50 Hz magnetic field in mice were found following initiation of
lymphoma/leukemia with DMBA.
A study of leukemia progression was conducted in Fischer rats inoculated with
large granular lymphocytic leukemia cells (143, 144). In the first study (144),
treatment with a 1000 µT continuous 60 Hz magnetic field did not significantly
alter the clinical progression of the disease in exposed versus ambient-field
controls. In the second study (143), an additional, lower inoculum of leukemia
cells was included to increase sensitivity as well as intermittent magnetic field
• presentation (3 min on, 3 min off). No significant effects were observed for the
22
• continuous field exposure at either inoculum; however, with intermittent fields at
the higher inoculum, latency to disease was slightly decreased.
The findings from the lifetime bioassay study ((115), discussed earlier) with
ELF-EMF exposure are also consistent with the absence of an effect on
leukemia/lymphoma. When animals exposed to a range of magnetic fields for up
to two years were examined, no increases in leukemias or lymphomas were found
in the 16 gender/species groups.
Two studies were conducted in genetically altered mice that are prone to leukemia
(145, 146). These studies showed no evidence of magnetic field effects on
lymphoma incidence.
Based upon some evidence from occupational and residential studies suggesting
an increased risk for brain cancer with ELF-EMF exposure, several animal studies
examined this question. Rodent models are relatively insensitive to the induction
of brain cancer by chemicals, and as such, caution should be used in interpreting
the findings from studies with ELF-EMF exposure. The lifetime studies in
rodents (114-116) demonstrated no effect of magnetic field exposure on brain
cancer. In the large initiation/promotion leukemia study in female mice ((141),
discussed earlier), sections of the brain were prepared and reviewed for primary
proliferative lesions (147). No evidence of an effect of magnetic field exposure
• on primary brain tumors was found.
Non-Cancer Health Effects in Experimental Animals
A number of non-cancer end-points were investigated for possible adverse effects
of ELF-EMF exposure. In general, the experimental models used to study
interactions with ELF-EMF have been guided by methods and end-points that
were developed to assay the effects of other physical and chemical agents such as
drugs, chemicals and ionizing radiation.
The effects of ELF-EMF exposure on the immune system were investigated in
multiple animal models including baboons and rodents, and there is no consistent
evidence in experimental animals for effects from ELF-EMF exposure. Reports
of effects in baboons (148) were not confirmed when the study was repeated.
Some studies had methodological difficulties making interpretation of the
findings difficult (127, 149). Other studies found no or inconsistent effects of
ELF-EMF exposure on immune system indices and function (150, 151).
Seven studies examined standard measurements of hematological and clinical
chemistry indices following ELF-EMF exposure (152-158); several included a
limited number of animals and were of short duration. These studies provide no
•
23
• evidence that exposure to ELF-EMF affects hematological or clinical chemistry
parameters in rodents.
A variety of animal models including non-human primates, pigeons and rodents
were exposed to high intensity electric or magnetic fields to study the behavior
and physiology of the nervous system. Detection of electric fields by animals is a
well-established phenomenon, and the sensitivity thresholds for animals appear to
be similar.
Various neuro-behavioral responses including avoidance and aversion and
learning and performance were tested for effects from exposure to ELF-EMF.
The data from studies including baboons and rodents suggest that exposure to
strong electric fields can be perceived (159-162), but there is no evidence that
these fields are harmful at environmental intensities. The addition of a magnetic
field to the electric field appears to modulate the acute behavioral response of
animals to perceptible electric fields (163, 164).
Relatively little evidence is available for evaluating whether exposure to ELF
electric fields can affect performance of learned behavior. The studies in
baboons (160, 161) suggest that any effects are minimal. In contrast, exposure to
ELF magnetic fields was associated with several effects: adverse (165, 166),
beneficial (167) or absent (168, 169) depending upon the task being performed
• and the timing of the magnetic field exposure. Studies in non-human primates
with combined exposure to electric fields and magnetic fields detected no impact
on operant performance (164, 170).
Epidemiological studies have addressed the question of whether ELF-EMF
exposure affects reproduction and development. Studies using avian species were
conducted, but their relevance to mammalian systems is not clear. Studies
examining teratogenic and reproductive end-points were also done in mammalian
systems. An extensive evaluation of magnetic field exposure (control, 2, 200 and
1000 µT continuous exposure and 1000 µT intermittent exposure) on fetal
development and reproductive toxicity in the rodent was conducted (171). There
was no evidence of any maternal or fetal toxicity or malformation. A further
study examined multi-generational reproductive toxicity using a continuous
breeding experiment. The results suggested no evidence of altered reproductive
performance or developmental toxicity in the rat (172).
At the onset of the EMF-RAPID Program, one hypothesis was that magnetic
fields acting through the retina as a sensitive receptor reduce melatonin levels. It
was thought that this depression might act as a risk factor for cancer (120, 173).
Studies examining effects of ELF-EMF exposure on circulating melatonin levels
were conducted in a variety of mammalian species. Overall, the experimental
evidence is lacking in consistency and quality across the studies. The data in
rodents is weak, but suggests that when effects do occur, the result is a decrease in
24
• melatonin concentration. There is no evidence for ELF-EMF effects on melatonin
in sheep and baboons. These findings parallel those reported from clinical
investigations in humans and population studies (discussed earlier).
Long-term exposure to electric fields decreases melatonin concentrations slightly
in rats (174-177); the biological significance of this effect is not understood. In a
series of studies of acute magnetic field exposure in hamsters (178-180), a
suppression of pineal and plasma melatonin levels reported in the earliest study
was not replicated in later studies. Studies in rats with different magnetic field
exposures, field intensities and times of exposure relative to the dark cycle have
not shown consistent effects of magnetic fields on melatonin levels. Some
laboratories reported that long-term exposure to magnetic fields in rats can reduce
nocturnal pineal or blood concentrations of melatonin (123, 181-184), but other
laboratories did not find similar results (127, 129, 185, 186). Interpretation of the
findings from this large data set is complicated by variability across studies in
confounding factors such as species, strain, gender, co-exposure to chemicals,
field characteristics and measured outcomes. Long-term studies of ELF-EMF
exposure in lambs (187, 188) and baboons (189) showed no effects on melatonin
levels.
Studies of Cellular Effects of ELF-EMF
• The number of cellular components, processes and systems that can possibly be
affected by ELF-EMF is large. Historically, testing of potentially toxic
substances has relied on the use of carefully controlled in vitro experimental
systems. In an attempt to identify potentially carcinogenic or toxic effects of an
agent, these studies have typically exposed cells to the agent over a range of doses
including levels above those encountered in the environment. Measurements are
then made of cellular end-points as a means to detect alterations in processes such
as differentiation, proliferation, gene expression and signal transduction
pathways. This toxicological approach was applied to ELF-EMF in general
through exposure of cultured cells over a range of doses. Because nothing is
known about the potential mechanistic action of ELF-EMF on biological end-
points, careful consideration must be given to the range over which the
experimental doses of ELF-EMF is varied. The extrapolation of observed effects
to lower field intensities may be inappropriate as ELF-EMF may have different
mechanistic actions over different patterns of field intensity. Likewise, the actual
agents responsible for the ELF-EMF "dose" to which individuals are exposed are
not clear. Environmental ELF-EMF exposure is complex being composed of not
only pure 60 Hz electric fields and magnetic fields, but also possibly transients
(intermittent spikes and changes in the frequency of the field) and harmonics
(multiples of the pure 60 Hz exposure: 120, 180, 240, etc.). To understand this
complexity, careful control of laboratory exposure conditions also becomes
important to ensure that the exposure being tested is known.
•
25
• The breadth of in vitro data on ELF-EMF produced over the last two decades is
enormous. Many of these investigations were done using unique experimental
protocols in single laboratories. Under the EMF-RAPID Program, a major focus
was research that targeted examination of in vitro effects that might clarify
potential mechanistic actions of ELF-EMF in order to explain reported
epidemiological associations with magnetic fields. Because of the noted
complexity of ELF-EMF exposures, efforts were also made to standardize the
exposure systems used in these studies to allow for comparability of findings
across laboratories. Through oversight by the DOE, on-site quality assurance
evaluations were made of laboratories funded by this program. In addition, four
regional ELF-EMF exposure facilities were established and made available for
use by investigators (discussed earlier).
Through the EMF-RAPID Program, considerable progress was made in the area
of in vitro research on ELF-EMF. Many of these studies of ELF-EMF exposure
focused on end-points commonly associated with cancer (e.g. cell proliferation,
disruption of signal transduction pathways and inhibition of differentiation).
Convincing evidence for causing effects is only available for magnetic flux
densities greater than 100 µT or internal electric field strengths greater than
approximately 1 mV/m. To date, there is no generally accepted biophysical
mechanism by which actions of lower intensity ELF-EMF exposures, including
those reported to be of concern in epidemiological studies, might be explained.
• Given the concern about whether ELF-EMF exposure is carcinogenic,
considerable effort was undertaken to investigate whether ELF-EMF exposures
can damage DNA or induce mutations. It has been generally believed that the
energy associated with ELF-EMF is not sufficient to cause direct damage to
DNA; however, it has been postulated that indirect effects might be possible by
ELF-EMF altering processes within cells that could subsequently lead to changes
in DNA structure. Overall, there was considerable variability in experimental
design and methodology used in these studies resulting in no conclusive evidence
that genotoxic effects result from ELF-EMF exposures.
Studies also examined the potential cytogenetic effects of power-frequency sine
wave or pulsed magnetic fields using model systems of human cells isolated
directly from peripheral blood and amniotic fluid or cultured human lymphocytes
and leukemia cells. Overall, the studies varied considerably, and in general, there
is no evidence of chromosomal damage even when cells were exposed to
relatively strong magnetic fields (190, 191). Chromosomal aberrations were
reported in one study (192) using pulsed magnetic fields; however, the exposures
tested were within the range of exposures reported in other studies to have no
effect.
Relatively few studies have addressed the question of whether ELF-EMF
• exposures cause genetic mutations (193). Studies using bacteria or yeast cells
26
• (194, 195) to investigate possible mutational changes in DNA reported no damage
from ELF-EMF exposure at levels less than 1000 µT. However, at higher field
strength (400,000 µT, 50 Hz), well above environmental field intensities,
enhanced mutagenicity was reported in two cell lines (196, 197). Exposure to
ELF-EMF (magnetic field strengths ≥500 µT) following exposure to ionizing
radiation was reported to produce significant enhancement of mutagenicity
(197, 198); ELF-EMF exposure alone had no effect. Several investigators
examined the ability of ELF-EMF to alter the repair of DNA strand breaks caused
by hydrogen peroxide or radiation; no effects with exposure to either magnetic or
electric fields were observed (199-201).
The concept that ELF-EMF might be carcinogenic through effects on gene
transcription was stimulated by an extensive series of studies in human leukemia
cells (202, 203). It was initially reported that high-intensity ELF-EMF exposure
increased expression of several genes important in carcinogenesis. The presence
of this effect was later reported to occur at field intensities more characteristic of
environmental levels (204) and in three types of human cell lines (203, 205, 206).
Because some of these genes may have a central role in controlling cancer, these
findings were of great significance. Intense efforts by several laboratories failed
to confirm the reported findings (207-210). Follow-up studies by the original
investigators demonstrated strain-specific responsiveness to ELF-EMF of the cell
line (211), although this does not appear to explain the inability of other
• laboratories to confirm the reported findings (209).
Several investigations were undertaken to determine whether cells might respond
to ELF-EMF with transcriptional or translational changes of heat-shock proteins,
which are important in control of stress within a cell. Exposure of cells to
ELF-EMF was reported from a single laboratory to result in increases in some of
these proteins (212-214).
Signal transduction processes aid cells in receiving signals from their environment
and from other cells. These signals help to regulate cellular processes such as
gene expression, metabolic activity, differentiation and proliferation. Signals
received by the cell membrane, which control processes within the cell, have been
proposed as a means by which ELF-EMF might affect cellular function. In the
case of electrical signals, these are not expected to penetrate the cell's outer
membrane but may signal release of proteins on the cell membrane that could
alter cellular function.
Numerous laboratories performed studies to evaluate potential ELF-EMF effects
on cellular end-points related to signal transduction pathways, which if altered,
might be carcinogenic. Overall the body of evidence suggests that ELF-EMF
exposures at magnetic field intensities greater than 100 µT and electric fields
greater than 1 mV/m have shown effects on signal transduction pathways.
• Studies at lower exposures are inconclusive.
27
• Recent studies investigated whether ELF-EMF exposure might play a role in
B-cell leukemogenesis (the major form of childhood leukemia) through signaling
pathways. A series of studies, which focused on one particular signal (the protein
kinase C-linked signaling cascade), provided preliminary evidence that in vitro
exposure to ELF-EMF (100 µT) can affect this pathway (215-217). This finding
was not reproduced by a second independent laboratory (218).
Because of concern about ELF-EMF possibly being carcinogenic, studies were
initiated to investigate whether there were effects on ornithine decarboxylase
(ODC), an enzyme activated during carcinogenesis. An early study (219)
reported increased ODC activity in three cell lines in response to a sinusoidal
60 Hz electric field (10 mV/cm). Subsequent work by others demonstrated
effects of ELF magnetic fields (field strengths ≤ 100 µT) on ODC although the
experimental conditions (e.g. cell line/tissue, field intensity, time of exposure)
varied among laboratories (220-222). One study reported increased ODC activity
in mouse lymphoma cells exposed to 10µT 60 Hz magnetic fields (220).
Attempts to reproduce this finding were not successful (223, 224).
Abnormal cellular proliferation is a hallmark of carcinogenesis. This complex
process is under control of numerous signal transduction pathways. Several
laboratories studied in vitro cellular proliferation as an end-point for ELF-EMF
effects. Alterations in proliferation were observed in a number of laboratories
• using a variety of exposure conditions (magnetic fields strengths of 1000 to
5000 µT) and cell lines (225-227). Two studies (228, 229) did not confirm an
earlier report (227) of increased colony growth for cells exposed to 60 Hz
magnetic fields, although one study (229) used a similar experimental protocol.
Another study, which used several methods for independently assessing
proliferation, reported increased growth over an exposure range of 50 to100 Hz
and 100 to 700 µT (230).
Disruption of the normal circadian rhythm of melatonin, a hormone produced by
the pineal gland, has been postulated as a possible mechanism whereby ELF-EMF
exposure might increase risk for breast cancer (120). Studies in a human breast
cancer cell line (231) showed that cellular proliferation in vitro was decreased by
treatment with physiological levels of melatonin; exposure to a sinusoidal ELF
magnetic field (1 .2 µT) could overcome this effect. These studies were extended
and the anti-proliferative effects of tamoxifen (an anti-cancer therapy) were also
reported to be reversed by a 1 .2 µT field (232). Another laboratory presented
similar findings (233). The original laboratory also reported finding comparable
effects using a second human breast cancer cell line (234) and a human glioma
cell line (23.5). There is some concern about the experimental design of these
studies and further work is underway. In addition, because the observed effect is
small, the importance of these findings for human health is not clear (236).
•
28
•
Numerous investigations have examined ELF-EMF exposure effects on markers
characteristics of cellular differentiation (e.g. matrix protein synthesis; cell
surface characteristics; cell morphology, size and orientation). Several of these
studies demonstrated a role of electric fields in affecting cellular behavior. Two
investigations of alterations in matrix protein production studied effects of electric
fields (237, 238) and found a positive correlation between dose and the
differentiated state of the cells. Studies examining ELF-EMF effects on
alterations of cell surface markers used a variety of cell types. In two of these
investigations, the observed cellular effects were attributed to the induced electric
fields (239, 240). Exposure to 60 Hz electric fields was also found to suppress
formation of osteoclast-like cells in marrow culture (241).
Biophysical Theory
The physics governing the interactions of ELF-EMF with matter were elucidated
over a century ago and succinctly stated in the Maxwell equations. Years of
successful application of these principles for practical advances have left little
doubt about our ability to understand and predict electromagnetic biophysical
phenomena when details of the system and fields are completely described.
Given the complexity, dynamics and organization in living organisms, it is
difficult to apply this knowledge. Living organisms function through the use of
biochemical and electrical signals carefully controlled by the organism's
• structure. Early attempts to explain the biological effects of ELF-EMF focused
on simple application of electromagnetic theory to calculate the forces on
biological molecules and the energies transferred to them by weak ELF-EMF.
The extremely small magnitude of these interactions led many investigators to
conclude that they would not occur at normally encountered field strengths. This
has not fundamentally changed; calculations still strongly suggest that the small
electric fields and magnetic fields associated with ELF-EMF in environmental
settings cannot be expected to supply, by themselves, the energies necessary for
chemical changes.
The complexity and structure of biological systems make uniform application of
these findings difficult. For example, even very small fields might act as control
signals to modify processes that depend on metabolically supplied energy. This
would be analogous to extremely weak radio signals, such as those transmitted
over thousands of miles, that control locally supplied energy or power a loud-
speaker or a large-screen television set. The exact nature of biological signal
processing systems and their susceptibility to control by time-varying ELF-EMF
is of continuing interest. Biological systems contain complex feedback loops and
amplification sequences in which very small changes at one point may ultimately
lead to very large changes further along the communication chain. In considering
ELF-EMF changes on the nature of biological signals, it is essential to recognize
that all aspects of a field (frequency, amplitude and pattern) may be involved.
These considerations make definitive statements based upon biophysical theory
• difficult to apply to living organisms.
29
• Several mechanisms for explaining ELF-EMF effects on biological systems have
been proposed. One set of theories (242-248) predicts effects of ELF-EMF on
chemical reactions due to resonances that depend on complex interactions
between constant and oscillating magnetic fields. There is limited experimental
support for these theories (12); the validity of the assumptions used in the theories
has been questioned (249).
Modification of the transfer of electrons from one molecule to another has also
been suggested as a theoretical mechanism for the effects of ELF -EMF (250-255).
However, the energies involved in electron binding are many orders of magnitude
larger than those contained in weak, externally applied electric fields or magnetic
fields (256-260) making these theories difficult to accept.
It is also possible that ELF-EMF could interact with magnetic particles in human
cells (261-264). However, work with this theory (263-265) would suggest that
such effects can occur only with large magnetic fields and are not applicable to
the normal human environment; these conclusions may be premature (12, 266).
Magnetic fields are capable of altering specific types (e.g. radical pair formation)
of chemical reactions (267-273). Potential effects of ELF-EMF have been
predicted by analytical work (274-278). Such reaction effects have been shown
for strong fields (279), but there are few studies of the effects in biological
systems with moderate to low field intensities.
Biochemical and biomechanical processes are generally dynamic. It has been
suggested that rather than causing changes in the usual state of the system,
ELF-EMF may induce slight changes in the frequency of events that trigger other
processes, especially for effects on chemicals that oscillate within cells and
between cells and their environments (250, 277, 280-286). Both theoretical
(287-291) and biological (292-294) studies exist that support this suggestion.
However, there is open debate about whether this phenomenon is applicable for
ELF-EMF exposures that are generally found in the human environment.
All of the theories for biological effects of ELF-EMF suffer from a lack of
detailed, quantitative knowledge about the processes to be modeled.
Nevertheless, theoretical models are useful, even in the absence of critical data,
because they can indicate what data are needed, suggest previously
uncontemplated experiments, suggest bounds on risks under defined situations
and provide nonlinear methods of analysis of critical data based upon presumed
mechanisms. The current biophysical theories for ELF-EMF would suggest little
possibility for biological effects below exposures of 100 µT. However,
considering the complexity of biological systems and the limitations required by
the assumptions used to mathematically model these theories, this finding has to
be viewed with caution.
I
30
•
How HIGH ARE ExPosuREs IN THE
U. S . POPULATION?
An evaluation of the importance of any environmental agent requires knowledge
of both the potential health impacts associated with exposure and the exposure
levels encountered by the population. For any environmental exposure, a clear
estimate of risk is made more difficult by the lack of a well-defined measure of
dose. For ELF-EMF, it is unknown whether time-averaged fields, time above a
threshold, the electric current induced by the field, the magnetic field itself, or
specific temporal characteristics of the field (e.g. frequency, waveform, or
intermittency) are relevant to human health.
• Recognizing this uncertainty and faced with practical limitations, investigators
have employed several different methods to estimate human exposure to
ELF-EMF. Most of these approaches provide an estimate of the 24-hour time-
average of the 60 Hz magnetic field. The first ELF-EMF epidemiological study,
as well as several subsequent studies, estimated exposure by developing a code to
describe power-line wiring near homes. More recent studies performed actual
measurements of magnetic fields using either survey instruments in homes or
miniature monitors worn by an individual for periods of up to 24 hours or more
(personal exposure measurements). Another approach was to calculate time-
average magnetic field exposures based on electric current in nearby power lines
and distance of homes to the lines. This report focuses entirely on recent studies
that measured magnetic fields, and highlights single spot measurements and
24-hour, time-weighted averages.
Several studies measured magnetic fields in either homes (22, 26, 295-298) or
personal exposures (297, 299). These studies and others (16, 18, 20, 300-309)
compared different types of measurements in an attempt to relate the results
across various epidemiological studies. Two of the studies (297, 299) attempted
to evaluate nationwide exposures in the U.S. population. One study (297)
measured magnetic fields in various locations within homes using fixed meters.
This survey, although not designed to describe individual exposures, provides a
snapshot of residential fields, and the results are probably reasonably
representative of residential conditions. An extensive measurement protocol
• (297) was used including spot measurements inside rooms, field recordings in the
31
•
horn; measurements of field profiles from wiring outside the home,
measurements of household appliances and measurement of fields from currents
in the electrical grounding system. The other study (299) relied entirely upon
personal monitors mailed to participants along with a questionnaire that addressed
characteristics of the individual wearing the monitor. These two studies form the
basis for most of the discussion that follows.
Measured magnetic field exposures to individuals and measurements in homes
tend to have an asymmetric distribution with the bulk of their values in the low
range with fewer values in the range of higher exposures. Therefore, the central
tendency of the values is better represented as a geometric mean (log-weighted
average) and the variation around that mean given as a geometric standard
deviation. Another measure commonly used is the median, which denotes the
estimate of exposure for which 50% of the population have smaller exposures and
50% have larger exposures. In addition, estimates are also presented for the
portion of the population in the upper range of exposure. This report presents
averages as geometric means with geometric standard deviations given in
parenthesis beside the average estimate.
Average 24-hour personal magnetic field exposure for individuals in the U.S.
population (299) is about 0.09 µT (geometric standard deviation of approximately
2.2). About 44% of the population have 24-hour exposures above 0. 1 µT, about
14% above 0.2 µT, about 2.5% above 0.5 µT and less than 1% above 0.75 µT.
The median measured fields using monitors located for 24 hours in several places
in the homes (297) was 0.06 µT with about 28% of the homes exceeding 0. 1 µT,
about 11% of the homes exceeding 0.2 µT and about 2% exceeding 0.5 µT. The
main difference between the home and personal exposure measurements pertains
to exposures incurred outside of the home and the movement of individuals within
the home near ELF-EMF sources.
Personal exposures measured within the home (299) averaged 0.08 µT (2.5) for
time not in bed and 0.05 µT (3.52) for time spent in bed. In comparison, personal
exposures at work averaged 0. 1 µT (2.57), exposure at school averaged
0.06 µT (2. 1) and exposure during travel measured 0. 1 µT (2.0). Approximately
38% of the personal measurements in the home (not in bed) were above 0. 1 µT,
about 14% were above 0.2 µT and about 3.5% were above 0.5µT. Personal
measurements at home and in bed were slightly different in the low exposure
range with approximately 30% of the measurements above 0. 1 µT, but similar in
the high exposure region with about 14% above 0.2 µT and about 4% above
0.5 µT. It is clear from these numbers that personal exposures tend to be
somewhat larger than those observed by fixed measurement of fields in homes.
Personal exposures do not appear to differ by gender, but do differ by age (299)
with young children (less than five years of age) having an average exposure of
• 0.08 µT (2. 1), school-aged children (five to 17 years of age) having an average
32
• exposure of 0.08 µT (2.2), working-aged adults (18 to 64 years of age) having an
average exposure of 0. 1 µT (2.2) and retirement-aged adults (greater than 64
years of age) having an average exposure of 0.09 µT (2.2). There are some
regional differences in exposure across the United States, but these are differences
that are likely to change based upon the seasons and are not likely to have a major
impact upon exposure considerations. Residents of apartments and duplexes
seem to have higher average exposures (approximately 0. 1 µT) compared to
residents of other dwelling types (0.05 to 0.07 µT) (297).
The presence of overhead power lines near homes contributes to both personal
exposures and fixed home measurements. In a large study using fixed monitors in
homes (297), estimates of fields due to power-line fields were determined
independent of exposures measured in the homes. Both the power-line and
grounding system fields were combined and compared to the short-term field
levels measured in the centers of rooms. Combined, the two sources add up to
much of the spot residential fields in homes having higher than usual magnetic
field levels.
A comparison was made between different types of power lines to determine
which ones produced the greatest fields. Transmission lines and certain types of
distribution lines produced the greatest fields (medians ranging from 0.09 to
0.38 µT, although the number of residences exposed to these fields was small),
and several types of primary distribution lines produced the lowest median fields
(medians ranging from 0.01 to 0.02 µT). The majority of homes were associated
with underground distribution lines that still generated fields with a median of
0.03 µT and with 5% exceeding 0. 13 µT (roughly 75% of the median for all
homes).
The effect of power lines on personal exposures was also assessed (299), but in
contrast to the previous discussion, self-reporting was used to classify the types of
power lines. Persons reporting three-phase primary distribution lines (average
exposure at home 0.083 µT), multiple three-phase primary distribution lines
(average exposure at home 0. 1 µT) and transmission lines (average exposure at
home 0. 1 µT) had the highest average exposures, while those reporting single
phase (average exposure of 0.07 µT) and two-phase primary distribution lines
(average exposure of 0.05 µT) had the lowest exposure. For all types of lines,
25% of the population had exposures greater than 0. 1 to 0.2 µT and 5% had
exposures greater than 0.3 to 0.5 µT. At distances of greater than 50 feet, the type
of power lines appeared to have little impact on the average exposure and only a
minor impact on the number of individuals with the highest exposures.
Several other factors contributed to increased personal exposure and/or increased
residential exposure. These included type of home (single family homes had
smaller average exposures than multi-family homes), size of the home (smaller
homes had higher fields), age of the home (older homes had higher fields), water-
33
• line type inside the home (homes with metal pipes tended to have higher fields)
and location of the home (urban and suburban homes had higher fields than rural
homes).
Magnetic fields generated by appliances were also studied (297). Exposures tend
to vary greatly by distance to the appliance and type of appliance. In general,
microwave ovens, toaster ovens, ceiling heat and refrigerators generated the
highest fields. However, the contributions of these fields to personal exposure
will depend upon placement of the appliance, distance from the appliance,
frequency of use, manufacturer, etc. Any observations on exposures from
appliances are not easily generalized.
Occupational exposures have been evaluated in a large number of studies (see
Table 2.4 (12)). The list of occupations with ELF-EMF exposure is quite large
and will not be repeated here. In general, electrical workers, persons working
near machines with electric motors and welders tend to have the highest
exposures with time-weighted average magnetic field exposure levels in the range
of 0. 1 to 4.0 µ,T.
•
•
34
•
CONCLUSIONS AND
RECOMMENDATIONS
Previous Panel Reviews
Since 1990, more than 60 reports and literature reviews written by various expert
panels, individual researchers or governmental officials have examined the
ELF-EMF scientific evidence worldwide. While most of these documents are
one-time assessments, some U.S. states (including Connecticut, Maryland,
Virginia) have recognized public concern for this topic and monitored this issue
on a yearly or periodic basis (310). A number of national reviews of ELF-EMF
research have also been prepared.• The most recent panel reviews (19, 311-316) used a variety of evaluation criteria
and differing types of information to evaluate potential health effects from
ELF-EMF exposures. Several groups concluded that the epidemiological
evidence for childhood and adult cancers was inconsistent and inconclusive and
was insufficient to address risks (19, 311, 312, 315, 316). Several noted that there
existed some associations between exposures and cancers, but without
mechanistic and animal evidence to support the effect, concluded it was still
basically a hypothesis to be studied further (19, 313-315). For all of these
reviews, the conduct of additional research was suggested.
NI'EHS Conclusion
As part of the EMF-RAPID Program's assessment of ELF-EMF-related health
effects, an international panel of 30 scientists met in June 1998 to review and
evaluate the weight of the ELF-EMF scientific evidence (12). Using criteria
developed by the International Agency for Research on Cancer, none of the
Working Group considered the evidence strong enough to label ELF-EMF
exposure as a "known human carcinogen" or "probable human carcinogen."
However, a majority of the members of this Working Group (19/28 voting
members) concluded that exposure to power-line frequency ELF-EMF is a
"possible" human carcinogen. This decision was based largely on "limited
• evidence of an increased risk for childhood leukemias with residential exposure
35
and an increased occurrence of CLL (chronic lymphocytic leukemia) associated
with occupational exposure." For other cancers and for non-cancer health
endpoints, the Working Group categorized the experimental data as providing
much weaker evidence or no support for effects from exposure to ELF'-EMF.
The NIEHS agrees that the associations reported for childhood leukemia and adult
chronic lymphocytic leukemia cannot be dismissed easily as random or negative
findings. The lack of positive findings in animals or in mechanistic studies
weakens the belief that this association is actually due to ELF-EMF, but cannot
completely discount the finding. The NIEHS also agrees with the conclusion that
no other cancers or non-cancer health outcomes provide sufficient evidence of a
risk to warrant concern.
The ultimate goal of any risk assessment is to estimate the probability of disease
in an exposed population. In general, this involves the combination of three basic
pieces of information: the probability that the agent causes the disease, the
response as a function of exposure given that the exposure does cause disease and
the distribution of exposures in the population being studied. The NIEHS
believes that the probability that ELF-EMF exposure is truly a health hazard is
currently small. The weak epidemiological associations and lack of any
laboratory support for these associations provide only marginal, scientific support
that exposure to this agent is causing any degree of harm.
•
The NIEHS concludes that ELF-EMF exposure cannot be recognized as entirely
safe because of weak scientific evidence that exposure may pose a leukemia
hazard. In our opinion, this finding is insufficient to warrant aggressive
regulatory concern. However, because virtually everyone in the United States
uses electricity and therefore is routinely exposed to ELF-EMF, passive
regulatory action is warranted such as a continued emphasis on educating both the
public and the regulated community on means aimed at reducing exposures. The
NIEHS does not believe that other cancers or non-cancer health outcomes provide
sufficient evidence of a risk to currently warrant concern.
Several groups have attempted to determine the risk of childhood leukemia in the
general population under the unproven assumption that ELF-EMF is truly causing
this disease (317-319). If this assumption were correct, these calculations
generally suggest, on average, that between 5% and 15% of childhood leukemias
could be caused by exposures to ELF-EMF with confidence intervals including
0%. Based upon this assumption, our own evaluations using the most current data
and several different methods of analysis do not disagree with these percentages.
The risk of getting leukemia prior to age 15 in the United States is about 0.05%
(5/10,000 people) (320). This would make the lifetime risk of childhood
leukemia attributable to ELF-EMF (again, conditional on the risk being real)
between 2.5 to 7.5 per 100,000 people. On a yearly basis, this conditional risk is
•
36
• approximately 15 times less than the lifetime risk or 2 to 6 additional cases per
million children per year.
The National Toxicology Program routinely examines environmental exposures to
determine the degree to which they constitute a human cancer risk and produces
the "Report on Carcinogens" listing agents that are "known human carcinogens"
or "reasonably anticipated to be human carcinogens." It is our opinion that based
on evidence to date, ELF-EMF exposure would not be listed in the "Report on
Carcinogens" as an agent "reasonably anticipated to be a human carcinogen."
This is based on the limited epidemiological evidence and the findings from the
EMF-RAPID Program that did not indicate an effect of ELF-EMF exposure in
experimental animals or a mechanistic basis for carcinogenicity.
Recommended Actions
Regulatory action on any environmental exposure can be multifaceted and
proceed by any of a number of options. In general, if regulatory action is to be
taken, the types of controls can be broken down into restrictions placed on the
production of the hazard and those placed on individuals who might come in
contact with the hazard. In the case of ELF-EMF, there are several issues that
complicate any regulatory action. First, there is only marginal, scientific support
that exposure to ELF-EMF is a health hazard. Second, it is unclear what aspect of
• the exposure, if any, may be the active component of the field resulting in the
increased cancer risk. While the association observed is with average magnetic
field measures, controls resulting in reductions in these field levels may not
alleviate the risk. Third, it is impossible to remove all ELF-EMF exposure and
remain a modern, technologically advanced society. Finally, considering the
weak degree of evidence involved, it is critical that the potential risks from any
alternatives to our current methods of using electricity be carefully evaluated.
Regulatory actions prompted by this review of ELF-EMF are not the purview of
the NIEHS. The Interagency Committee (IAC, described earlier) has been
involved in all aspects of both our research program and the process of reviewing
these data. The agencies that compose the IAC employ experts who have greater
experience and knowledge concerning mitigation of ELF-EMF exposure than the
NIEHS. However, it is important that the strength of the evidence reported here
be placed in a context that is clear to the regulatory authorities. Therefore, the
NIEHS is providing the following suggestions that are intended to give scope for
future regulatory actions.
The NIEHS suggests that the level and strength of evidence supporting ELF-EMF
exposure as a human health hazard are insufficient to warrant aggressive
regulatory actions; thus, we do not recommend actions such as stringent standards
on electric appliances and a national program to bury all transmission and
distribution lines. Instead, the evidence suggests passive measures such as a
37
• continued emphasis on educating both the public and the regulated community on
means aimed at reducing exposures. NIEHS suggests that the power industry
continue its current practice of siting power lines to reduce exposures and
continue to explore ways to reduce the creation of magnetic fields around
transmission and distribution lines without creating new hazards. We also
encourage technologies that lower exposures from neighborhood distribution lines
provided that they do not increase other risks, such as those from accidental
electrocution or fire.
Exposures in individual residences are linked to certain characteristics. Their
chief causes are improper grounding and improper wiring, which if addressed by
properly following current electrical codes, can be mitigated and exposures
reduced. Older homes may also have higher ambient exposures, but these must
be assessed on a case-by-case basis. Many of the U.S. electric utility companies
will measure fields in their customers' homes and help them to identify sources of
high fields; we encourage continuation of this practice. Finally, the NIEHS would
encourage the manufacturers of household and office appliances to consider
alternatives that reduce magnetic fields at a minimal cost. We feel that the risks
do not warrant major and expensive redesign of modern electrical appliances, but
inexpensive modifications should be sought to reduce exposures.
Certain occupations result in high field exposures. The NIEHS encourages the
• National Institute for Occupational Safety and Health and the Occupational Safety
and Health Administration to review these findings and carefully evaluate if
current occupational exposure standards are adequate.
In summary, the NIEHS believes that there is weak evidence for possible health
effects from ELF-EMF exposures, and until stronger evidence changes this
opinion, inexpensive and safe reductions in exposure should be encouraged.
Future Research
The NIEHS is committed to the support of hypothesis-driven research on any
environmental exposure that is of concern for human beings. Exposure to
ELF-EMF is no different. These exposures warrant continued monitoring
because ELF-EMF exposure is ubiquitous and the use of electromagnetic
technology is growing in our society.
The characteristics of ELF-EMF and their possible interactions with biological
systems have been investigated for several decades. The EMF-RAPID Program
successfully contributed to the scientific knowledge on ELF-EMF through its
support of high quality, hypothesis-based research. While some questions were
answered, others remain. Building upon the knowledge base developed under the
EMF-RAPID Program, meritorious research on ELF-EMF through carefully
• designed, hypothesis-driven studies should continue for areas warranting
38
fundamental study including leukemia. The NIEHS will continue to support
research in this area. Certain areas of research, however, warrant noting.
There are several epidemiological studies of ELF-EMF exposures and childhood
leukemia underway that may help clarify this issue. Any new epidemiological
studies of ELF-EMF exposure are not warranted unless, in some unique manner,
the studies differ from existing ones and can test new hypotheses. Very little is
known about the mechanisms and causes of childhood leukemias and chronic
lymphocytic leukemia in adults. Many agencies, including the National Institutes
of Health, have ongoing programs in these areas aimed at improving our
understanding of these diseases. As risk factors are identified, we strongly
recommend re-analysis of the existing ELF-EMF epidemiology data to determine
if these risk factors reduce or strengthen the reported findings of concern
expressed in this document. Where currently available studies cannot adequately
address newly discovered risk factors, the NIEHS encourages new studies.
Several non-cancer health areas including neurodegenerative and cardiovascular
diseases have been identified as being of national concern, but for which there are
few, high quality studies to evaluate adequately whether ELF-EMF exposure
might have effects. Preliminary work suggests that ELF-EMF exposure may be
linked to cardiovascular deaths resulting from arrhythmia and acute myocardial
infarction. The mechanism for such an effect, if true, is not known, but possibly
occurs through exposure-related effects on autonomic nervous system control of
cardiac function. Also, several exploratory studies have suggested possible
associations between occupational ELF-EMF exposure and neurodegenerative
diseases specifically amyotrophic lateral sclerosis and Alzheimer's disease. The
data on these end-points are inadequate for interpreting the possibility of an
association. Research in these areas should cover all aspects of scientific
investigation including epidemiology, laboratory and mechanistic studies.
Preliminary studies in transformed breast cancer cells suggest that ELF-EMF
exposures can overcome effects of melatonin and tamoxifen in regulating cell
growth. This effect of ELF-EMF appears to occur at magnetic field exposures
that may be encountered in the environment. Several other laboratories have
presented similar, unpublished findings at national meetings. The importance of
this finding for human health is unclear, but considering the magnitude of the
incidence of breast cancer, this area warrants further investigation.
There is a continued need for more biologically realistic mathematical models to
evaluate the biophysics of ELF-EMF and for biological systems specifically
developed to evaluate the validity and utility of these mathematical models.
While it is clearly established that certain animals can sense weak magnetic fields
for navigation and homing, the physical basis for these processes is unknown.
More remains to be learned about the physics of magnetic field interactions with
biological systems.
39
SThe interaction of humans with ELF-EMF is complicated and will undoubtedly
continue to be an area of public concern. The World Health Organization through
its own international program on ELF-EMF will review this field in the year
2003. The NIEHS is a partner in this process.
•
•
40
•
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Cancer: Report of an Advisory Group on Non-Ionising Radiation. Oxon, 1992.
313. NRPB National Radiation Protection Board. Electromagnetic Fields and the Risk of
Cancer: Supplementary Report by the Advisory Group on Non-Ionizing Radiation.
Chilton: National Radiological Protection Board, 1994.
314. Hardell L, Holmberg B, Malker H, Paulsson L-E. Exposure to extremely low
frequency electromagnetic fields and the risk of malignant diseases - An evaluation
of epidemiological and experimental findings. European Journal of Cancer
Prevention 4:3-107(1995).
315. European Commission Directorate V. Public Health and Safety at Work - Non
ionizing radiation: Sources, Exposure and Health Effects ISBN 92-827-5492-8.
Luxembourg, 1996.
• 316. ICNIRP International Commission on Non-Ionizing Radiation Protection.
Guidelines for limiting exposure to time-varying electric, magnetic, and
electromagnetic fields (up to 300 GHz). Health Physics 74:494-522(1998).
317. SNBOSH Swedish National Board of Occupational Safety and Health. Low-
Frequency Electrical and Magnetic Fields: The Precautionary Principle for National
Authorities. Guidance for Decision-Makers. Solna, 1996.
318. Banks RS, Carpenter DO. AC electric and magnetic fields: A new health issue
(article and commentary). Health Environmental Digest 2: 1-4(1988).
319. Grandolfo M. Extremely low frequency magnetic fields and cancer. European
Journal of Cancer Prevention 5:379-381(1996).
320. Gurney JG, Severson RK, Davis 5, Robison LL. Incidence of cancer in children in
the United States. Cancer 75:2186-2195(1995).
•
67
•
June 2002
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Answers
„t„ prepared by the
National Institute of Environmental Health Sciences
4Oi National Institutes of Health
EMEIAPID sponsored by the
NIEHS/DOE EMF RAPID Program
•
imens
•
fat
..contents
Introduction 2
f EMF Basics 4
Reviews basic terms about electric and magnetic
fields.
Evaluating Potential Health Effects 10
Explains how scientific studies are conducted and
evaluated to assess possible health effects.
Results of EMF Research 16
Summarizes results of EMF-related research including
epidemiological, clinical, and laboratory studies.
4 Your EMF Environment 28
Discusses typical magnetic exposures in homes and
workplaces and identifies common EMF sources.
r
EMF Exposure Standards 46
Describes standards and guidelines established by
state, national, and international safety
organizations for some EMF sources and exposures.
6 National and International EMF Reviews 50
Presents the findings and recommendations of
major EMF research reviews including the EMF
RAPID Program.
7 References 58
Selected references on EMF topics.
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Introduction
farod uction
Since the mid-twentieth century, electricity has been an essential part of our lives.
Electricity powers our appliances, office equipment, and countless other devices that
we use to make life safer, easier, and more interesting. Use of electric power is
something we take for granted. However, some have wondered whether the electric
and magnetic fields (EMF) produced through the generation, transmission, and use
of electric power [power-frequency EMF, 50 or 60 hertz (Hz)] might adversely affect
• our health. Numerous research studies and scientific reviews have been conducted
to address this question.
Unfortunately, initial studies of the health effects of EMF did not provide
straightforward answers. The study of the possible health effects of EMF has been
particularly complex and results have been reviewed by expert scientific panels in
the United States and other countries. This booklet summarizes the results of these
reviews. Although questions remain about the possibility of health effects related to
EMF, recent reviews have substantially reduced the level of concern.
The largest evaluation to date was led by two U.S. government institutions, the
National Institute of Environmental Health Sciences (NIEHS) of the National Institutes
of Health and the Department of Energy (DOE), with input from a wide range of
public and private agencies. This evaluation, known as the Electric and Magnetic
Fields Research and Public Information Dissemination (EMF RAPID) Program, was a
six-year project with the goal of providing scientific evidence to determine whether
exposure to power-frequency EMF involves a potential risk to human health.
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Introduction
In 1999, at the conclusion of the EMF RAPID Program, the NIEHS reported to
the U.S. Congress that the overall scientific evidence for human health risk from
EMF exposure is weak. No consistent pattern of biological effects from exposure
to EMF had emerged from laboratory studies with animals or with cells. However,
epidemiological studies (studies of disease incidence in human populations) had
shown a fairly consistent pattern that associated potential EMF exposure with a
• small increased risk for leukemia in children and chronic lymphocytic leukemia in
adults. Since 1999, several other assessments have been PP completed that support an
P
association between childhood leukemia and exposure to power-frequency EMF.
These more recent reviews, however, do not support a link between EMF
exposures and adult leukemias. For both childhood and adult leukemias,
interpretation of the epidemiological findings has been difficult due to the absence
of supporting laboratory evidence or a scientific explanation linking EMF exposures
with leukemia.
EMF exposures are complex and exist in the home and workplace as a result of all
types of electrical equipment and building wiring as well as a result of nearby
power lines. This booklet explains the basic principles of electric and magnetic
fields, provides an overview of the results of major research studies, and
summarizes conclusions of the expert review panels to help you reach your own
conclusions about EMF-related health concerns.
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EMF Basics
�... EMF Basics
This chapter reviews terms you need to know to have a basic understanding of
electric and magnetic fields (EMF), compares EMF with other forms of
electromagnetic energy, and briefly discusses how such fields may affect us.
Q What are electric and magnetic fields?
Electric and magnetic fields (EMF) are invisible lines of force that surround any
electrical device. Power lines, electrical wiring, and electrical equipment all produce
EMF. There are many other sources of EMF as well (see pages 33-35). The focus of
this booklet is on power-frequency EMF—that is, EMF associated with the
generation, transmission, and use of electric power.
Electric fields are produced
411 Electrical Terms Familiar Comparisons by voltage and increase in
strength as the voltage
Voltage. Electrical pressure, the potential Hose connected to an open faucet increases. The electric field
to do work. Measured in volts (V) but with the nozzle turned off. strength is measured in
or in kilovolts (kV) (1kV = 1000 volts). units of volts per meter
(V/m) . Magnetic fields
Lamp plugged in result from the flow of
• but turned off: h wires or current through Water pressure in hose. g
120V Switch electrical devices and
off increase in strength as the
Nozzle closed current increases. Magnetic
fields are measured in units
Current. The movement of electric Hose connected to an open faucet of gauss (G) or tesla (T) .
charge (e.g., electrons). Measured In and with the nozzle turned on.
amperes (A). Most electrical equipment
has to be turned on, i.e.,
Lamp plugged in
and turned on: current must be flowing,
•
120V jjwajrin hose. for a magnetic field to be
switchproduced. Electric fields are
111 °" often present even when
Nozzle open the equipment is switched
off, as long as it remains
Voltage produces an electric field and current produces a magnetic field. connected to the source of
electric power. Brief bursts
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EMF Basics
of EMF (sometimes called A Comparison of Electric and Magnetic Fields
"transients") can also occur Mc FleIds Magnetic Fields
when electrical devices are • Produced by voltage. • Produced by current
turned on or off.
Electric fields are shielded
fraillimimmassalror weakened by materials + + •
that conduct electricity—
even materials that + + 4'
conduct poorly, including
Lamp plugged in but turned off. Lamp plugged in and turned on. Current
trees, buildings, and voltage produces an electric field. now produces a magnetic field also.
human skin. Magnetic • Measured in volts per meter(V/m) • Measured in gauss (G) or tesla (T).
fields, however, pass or in kilovolts per meter(kV/m).
through most materials • Easily shielded (weakened) by • Not easily shielded (weakened) by
and are therefore more conducting objects such as trees and most material.
buildings.
difficult to shield. Both • Strength decreases rapidly with • Strength decreases rapidly with
electric fields and magnetic increasing distance from the source. increasing distance from the source.
fields decrease rapidly as
the distance from the An appliance that is plugged in and therefore connected to a source of electricity has an
source increases. electric field even when the appliance is turned off. To produce a magnetic field, the
appliance must be plugged in and turned on so that the current is flowing.
• Even though electrical
equipment, appliances, and
power lines produce both Magnetic Field Strength Decreases with Distance
electric and magnetic fields, Ma• •tic field measured in milligauss(mG)
most recent research has -
focused on potential health `,�'L�'
effects of magnetic field N# cm)
exposure. This is because ° 1s`
some epidemiological 1
studies have reported an 5 G�'
increased cancer risk +� F 6
associated with estimates of ^ .c o
. .. ,
INS CO et _
magnetic field exposure � �..,.. �.
(see pages 19 and 20 for a .., :;
y
summary of these studies) .
No similar associations
have been reported for ,=
electric fields; many of the
o
studies examining
biological effects of electric e: EMF in kur Environment, EPA, 1992.
fields were essentially
negative. You cannot see a magnetic field, but this illustration represents how the strength of the
magnetic field can diminish just 1-2 feet (30-61 centimeters) from the source. This
magnetic field is a 60-Hz power-frequency field.
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EMF Basics
Characteristics of electric and magnetic fields
Electric fields and magnetic fields can be characterized by their wavelength,
frequency, and amplitude (strength) . The graphic below shows the waveform of an
alternating electric or magnetic field. The direction of the field alternates from one
polarity to the opposite and back to the first polarity in a period of time called one
cycle. Wavelength describes the distance between a peak on the wave and the next
peak of the same polarity. The frequency of the field, measured in hertz (Hz) ,
describes the number of cycles that occur in one second. Electricity in North America
alternates through 60 cycles per second, or 60 Hz. In many other parts of the world,
the frequency of electric power is 50 Hz.
Frequency and Wavelength
Frequency is measured In hertz (Hz).
1 cycle
1 Hz = 1 cycle per second.
Electromagnetic
waveform
Examples:
Source Frequency Wavelength
Power line (North America) 60 Hz 3100 miles (5000 km)
Power line (Europe and most other locations) 50 Hz 3750 miles (6000 km)
Q How is the term EMF used in this booklet?
4 The term "EMF" usually refers to electric and magnetic fields at extremely low
frequencies such as those associated with the use of electric power. The term EMF
can be used in a much broader sense as well, encompassing electromagnetic fields
with low or high frequencies (see page 8) .
Measuring EMF: Common Terms
Electric fields
Electric field strength is measured in volts per meter (Wm) or in kilovolts per meter (kV/m). 1 kV = 1000 V
Magnetic fields
Magnetic fields are measured in units of gauss (6) or tesla (T). Gauss is the unit most commonly used in
the United States. Tesla is the internationally accepted scientific term. 1 T = 10,000 G
Since most environmental EMF exposures involve magnetic fields that are only a fraction of a testa or a
gauss, these are commonly measured in units of microtesla (p1) or milligauss (mG). A milligauss is 1/1,000
of a gauss. A microtesla is 1/1 ,000,000 of a testa. 1 G = 1 ,000 mG; 1 T = 1 ,000,000 pT
To convert a measurement from microtesla (p1) to milligauss (mG), multiply by 10.
1pT = 10 mG; 0.1pT = 1mG
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EMF Basics
When we use EMF in this booklet, we mean extremely low frequency (ELF) electric
and magnetic fields, ranging from 3 to 3,000 Hz (see page 8). This range includes
power-frequency (50 or 60 Hz) fields. In the ELF range, electric and magnetic fields
are not coupled or interrelated in the same way that they are at higher frequencies.
So, it is more useful to refer to them as "electric and magnetic fields" rather than
"electromagnetic fields." In the popular press, however, you will see both terms used,
abbreviated as EMF.
This booklet focuses on extremely low frequency EMF, primarily power-frequency
fields of 50 or 60 Hz, produced by the generation, transmission, and use of electricity.
Q How are power-frequency EMF different from other
types of electromagnetic energy?
A X-rays, visible light, microwaves, radio waves, and EMF are all forms of
J . electromagnetic energy. One property that distinguishes different forms of
electromagnetic energy is the frequency, expressed in hertz (Hz) . Power-frequency
EMF, 50 or 60 Hz, carries very little energy, has no ionizing effects, and usually has
no thermal effects (see page 8). Just as various chemicals affect our bodies in
different ways, various forms of electromagnetic energy can have very different
biological effects (see "Results of EMF Research" on page 16).
• Some types of equipment or operations simultaneously produce electromagnetic
energy of different frequencies. Welding operations, for example, can produce
electromagnetic energy in the ultraviolet, visible, infrared, and radio-frequency
ranges, in addition to power-frequency EMF. Microwave ovens produce 60-Hz
fields of several hundred milligauss, but they also create microwave energy inside
the oven that is at a much higher frequency (about 2.45 billion Hz). We are
shielded from the higher frequency fields inside the oven by its casing, but we are
not shielded from the 60-Hz fields.
Cellular telephones communicate by emitting high-frequency electric and magnetic
fields similar to those used for radio and television broadcasts. These radio-
frequency and microwave fields are quite different from the extremely low
frequency EMF produced by power lines and most appliances.
Q How are alternating current sources of EMF different
from direct current sources?
Some equipment can run on either alternating current (AC) or direct current
' (DC) . In most parts of the United States, if the equipment is plugged into a
household wall socket, it is using AC electric current that reverses direction in the
electrical wiring—or alternates-60 times per second, or at 60 hertz (Hz) . If the
equipment uses batteries, then electric current flows in one direction only. This
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EMF B sacs
Electromagnetic Spectrum
Source Frequency in hertz (Hz)
11 It...4 it.
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IV Ili CO
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X-rays, about 1 billion billion Hz, 1 co
can penetrate the body and X-rays C
damage internal organs and4, t
tissues by damaging important N 1018-
molecules such as DNA. This c
process Is called "ionization." a
Ultraviolet —
` radiation 1016—
,..___ 0 _
Visible
� N.
light 1014—
Infrared 1012_
radiation
Microwaves, several billion Hz, 1`
• can have "thermal" or heating
effects on body tissues. t 1010
Cell phone sT. Microwaves
800-900 MHz 4
1800-1900 MHz 108—t o
Radiowaves
D Computer if 106
I 15-30 kHz
& Very low
50-90 Hz frequency (VLF) 104—
3000-30,000 Hz
Power-frequency EMF, 50 or 60 Hz,
carries very little energy, has no
ionizing effects and usually Extremely low 102—
no thermal effects. It frequency (ELF)
can, however, cause 3-3000 Hz 60 Hz
very weak electric
currents to flow Direct current
in the body.
The wavy line at the right illustrates the concept that the higher the frequency, the more
rapidly the field varies. The fields do not vary at 0 Hz (direct current) and vary trillions of
times per second near the top of the spectrum. Note that 104 means 10 x 10 x 10 x 10 or
10,000 Hz. 1 kilohertz (kHz) = 1 ,000 Hz. 1 megahertz (MHz) = 1 ,000,000 Hz.
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EMF Basics
produces a "static" or stationary magnetic field, also called a direct current field.
Some battery-operated equipment can produce time-varying magnetic fields as
part of its normal operation.
Q What happens when I am exposed to EMF?
AIn most practical situations, DC electric power does not induce electric currents in
humans. Strong DC magnetic fields are present in some industrial environments,
can induce significant currents when a person moves, and may be of concern for
other reasons, such as potential effects on implanted medical devices (see page 47
for more information on pacemakers and other medical devices) .
AC electric power produces electric and magnetic fields that create weak electric
currents in humans. These are called "induced currents." Much of the research on
how EMF may affect human health has focused on AC-induced currents.
Electric fields
A person standing directly under a high-voltage transmission line may feel a mild
shock when touching something that conducts electricity. These sensations are
caused by the strong electric fields from the high-voltage electricity in the lines.
They occur only at close range because the electric fields rapidly become weaker as
the distance from the line increases. Electric fields may be shielded and further
• weakened by buildings, trees, and other objects that conduct electricity.
Magnetic fields
Alternating magnetic fields produced by AC electricity can induce the flow of weak
electric currents in the body. However, such currents are estimated to be smaller
than the measured electric currents produced naturally by the brain, nerves, and
heart.
Q Doesn't the earth produce EMF?
AYes, The earth produces EMF, mainly in the form of static fields, similar to the
fields generated by DC electricity. Electric fields are produced by air turbulence and
other atmospheric activity. The earth's magnetic field of about 500 mG is thought
to be produced by electric currents flowing deep within the earth's core. Because
these fields are static rather than alternating, they do not induce currents in
stationary objects as do fields associated with alternating current. Such static fields
can induce currents in moving and rotating objects.
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Evaluating Effects
s6 Evaluating Potential Health Effects
This chapter explains how scientific studies are conducted and evaluated
to assess potential health effects.
Q How do we evaluate whether EMF exposures cause
health effects?
ft Animal experiments, laboratory studies of cells, clinical studies, computer simulations,
and human population (epidemiological) studies all provide valuable information.
When evaluating evidence that certain exposures cause disease, scientists consider
results from studies in various disciplines. No single study or type of study is definitive.
all Does ENV Exposure Couse di e. se ? Laboratory studies
: . Laboratory studies with cells and
4,y°fit � animals can provide evidence to
�i = help determine if an agent such as
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EMF causes disease. Cellular
studies can increase our
s.x �t °° ` understanding of the biological
animal
mechanisms by which disease
studies occurs. Experiments with animals
provide a means to observe effects
r of specific agents under carefully
controlled conditions. Neither
cellular nor animal studies,
however, can recreate the complex
nature of the whole human
organism and its environment.
Therefore, we must use caution in
applying the results of cellular or
animal studies directly to humans
or concluding that a lack of an
effect in laboratory studies proves
that an agent is safe. Even with
Laboratory studies and human studies provide pieces of the puzzle, but no single these limitations, cellular and
study can give us the whole picture. animal studies have proven very
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useful over the years for identifying and understanding the toxicity of numerous
chemicals and physical agents.
Very specific laboratory conditions are needed for researchers to be able to detect
EMF effects, and experimental exposures are not easily comparable to human
exposures. In most cases, it is not clear how EMF actually produces the effects
observed in some experiments. Without understanding how the effects occur, it is
difficult to evaluate how laboratory results relate to human health effects.
Some laboratory studies have reported that EMF exposure can produce biological
effects, including changes in functions of cells and tissues and subtle changes in
hormone levels in animals. It is important to distinguish between a biological effect
and a health effect. Many biological effects are within the normal range of variation
and are not necessarily harmful. For example, bright light has a biological effect on
our eyes, causing the pupils to constrict, which is a normal response.
Clinical studies
In clinical studies, researchers use sensitive instruments to monitor human physiology
during controlled exposure to environmental agents. In EMF studies, volunteers are
exposed to electric or magnetic fields at higher levels than those commonly
• encountered in everyday life. Researchers measure heart rate, brain activity, hormonal
levels, and other factors in exposed and unexposed groups to look for differences
resulting from EMF exposure.
Epidemiology j O`4a . ,
A valuable tool to identify
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human health risks is to study ' li
a human population that has ' t ,' ) If f . 1
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experienced the exposure. : i
This type of research is called 1 i R
epidemiology.
The epidemiologist observes M .. - .
and compares groups of .
people who have had or have '"
f
not had certain diseases and •
exposures to see if the risk of op t "t "; 1 ,
disease is different between 1 - i
the exposed and unexposed l
groups. The epidemiologist
. . .
does not control the exposure I
and cannot experimentally
control all the factors that
might affect the risk of Most researchers agree that epidemiology—the study of patterns and possible causes
disease. of diseases—is one of the most valuable tools to identify human health risks.
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Q How do we evaluate the results of epidemiological
studies of EMF?
Many factors need to be considered when determining whether an agent
causes disease. An exposure that an epidemiological study associates with
increased risk of a certain disease is not always the actual cause of the disease.
To judge whether an agent actually causes a health effect, several issues are
considered.
Strength of association
The stronger the association between an exposure and disease, the more confident
we can be that the disease is due to the exposure being studied. With cigarette
smoking and lung cancer, the association is very strong-20 times the normal risk.
In the studies that suggest a relationship between EMF and certain rare cancers,
the association is much weaker (see page 19).
Dose-response
Epidemiological data are more convincing if disease rates increase as exposure
levels increase. Such dose-response relationships have appeared in only a few
EMF studies.
• Consistency
Consistency requires that an association found in one study appears in other
studies involving different study populations and methods. Associations found
consistently are more likely to be causal. With regard to EMF, results from different
studies sometimes disagree in important ways, such as what type of cancer is
associated with EMF exposure. Because of this inconsistency, scientists cannot be
sure whether the increased risks are due to EMF or other factors.
Biological plausibility
When associations are weak in an epidemiological study, results of laboratory
studies are even more important to support the association. Many scientists remain
skeptical about an association between EMF exposure and cancer because laboratory
studies thus far have not shown any consistent evidence of adverse health effects,
nor have results of experimental studies revealed a plausible biological explanation
for such an association.
Reliability of exposure information
Another important consideration with EMF epidemiological studies is how the
exposure information was obtained. Did the researchers simply estimate people's
EMF exposures based on their job titles or how their houses were wired, or did
they actually conduct EMF measurements? What did they measure (electric fields,
magnetic fields, or both)? How often were the EMF measurements made and at
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Evaluatin Effects
what time? In how many different places were the fields measured? More recent
studies have included measurements of magnetic field exposure. Magnetic fields
measured at the time a study is conducted can only estimate exposures that
occurred in previous years (at the time a disease process may have begun). Lack of
comprehensive exposure information makes it more difficult to interpret the results
of a study, particularly considering that everyone in the industrialized world has
been exposed to EMF.
Confounding
Epidemiological studies show relationships or correlations between disease and
other factors such as diet, environmental conditions, and heredity. When a disease
is correlated with some factor, it does not necessarily mean that the correlated
factor causes the disease. It could mean that the factor occurs together with some
other factor, not measured in the study, that actually causes the disease. This is
called confounding.
For example, a study might show that alcohol consumption is correlated with
lung cancer. This could occur if the study group consists of people who drink and
also smoke tobacco, as often happens. In this example, alcohol use is correlated
with lung cancer, but cigarette smoking is a confounding factor and the true cause
of the disease.
Statistical significance
Researchers use statistical methods to determine the likelihood that the association
between exposure and disease is due simply to chance. For a result to be
considered "statistically significant," the association must be stronger than would be
expected to occur by chance alone.
Meta-analysis
One way researchers try to get more information from epidemiological studies is
to conduct a meta-analysis. A meta-analysis combines the summary statistics of
many studies to explore their differences and, if appropriate, calculates an overall
summary risk estimate. The main challenge faced by researchers performing
meta-analyses is that populations, measurements, evaluation techniques,
participation rates, and potential confounding factors vary in the original studies.
These differences in the studies make it difficult to combine the results in a
meaningful way.
Pooled analysis
Pooled analysis combines the original data from several studies and conducts a new
analysis on the primary data. It requires access to the original data from individual
studies and can only include diseases or factors included in all the studies, but it
has the advantage that the same parameters can be applied to all studies. As with
meta-analysis, pooled analysis is still subject to the limitations of the experimental
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Evaluating Effects
design of the original studies (for example, evaluation techniques, participation
rates, etc.) . Pooled analysis differs from meta-analysis, which combines the
summary statistics from different studies, not their original data.
Q How do we characterize EMF exposure?
A No one knows which aspect of EMF exposure, if any, affects human health. Because
a e of this uncertainty, in addition to the field strength, we must ask how long an
exposure lasts, how it varies, and at what time of day or night it occurs. House
wiring, for example, is often a significant source of EMF exposure for an individual,
but the magnetic fields produced by the wiring depend on the amount of current
flowing. As heating, lighting, and appliance use varies during the day, magnetic field
exposure will also vary.
For many studies, researchers describe EMF exposures by estimating the average
field strength. Some scientists believe that average exposure may not be the best
measurement of EMF exposure and that other parameters, such as peak exposure
or time of exposure, may be important.
Q What is the average field strength?
•
A In EMF studies, the information reported most often has been a person's EMF
exposure averaged over time (average field strength). With cancer-causing
chemicals, a person's average exposure over many years can be a good way to
predict his or her chances of getting the disease.
There are different ways to calculate average magnetic field exposures. One method
involves having a person wear a small monitor that takes many measurements over
a work shift, a day, or longer. Then the average of those measurements is calculated.
Another method involves placing a monitor that takes many measurements in a
residence over a 24-hour or 48-hour period. Sometimes averages are calculated for
people with the same occupation, people working in similar environments, or
people using several brands of the same type or similar types of equipment.
Q How is EMF exposure measured in epidemiological
studies?
Epidemiologists study patterns and possible causes of diseases in human
populations. These studies are usually observational rather than experimental.
This means that the researcher observes
Association and compares groups of people who have
In epidemiology, a positive association between an exposure (such as had certain diseases and exposures and
EMF)and a disease is not necessarily proof that the exposure caused looks for possible "associations." The
the disease. However, the more often the exposure and disease epidemiologist must find a way to
occur together, the stronger the association, and the stronger is the estimate the exposure that people had at
possibility that the exposure may increase the risk of the disease. an earlier time.
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Some exposure estimates for residential studies have been based on designation of
households in terms of "wire codes." In other studies, measurements have been
made in homes, assuming that EMF levels at the time of the measurement are
similar to levels at some time in the past. Some studies involved "spot
measurements." Exposure levels change as a person moves around in his or her
environment, so spot measurements taken at specific locations only approximate
the complex variations in exposure a person experiences. Other studies measured
magnetic fields over a 24-hour or 48-hour period. Exposure levels for some
occupational studies are measured by having certain employees wear personal
monitors. The data taken from these monitors are sometimes used to estimate
typical exposure levels for employees with certain job titles. Researchers can then
estimate exposures using only an employee's job title and avoid measuring
exposures of all employees.
Methods to Estimate EMF Exposure
Wire Codes
A classification of homes based on characteristics of power lines outside the home (thickness of the wires,
wire configuration, etc.) and their distance from the home. This information is used to code the homes
into groups with higher and lower predicted magnetic field levels.
• Spot Measurement
An instantaneous or very short-term (e.g., 30-second) measurement taken at a designated location.
Time-Weighted Average
A weighted average of exposure measurements taken over a period of time that takes into account the
time interval between measurements. When the measurements are taken with a monitor at a fixed
sampling rate, the time-weighted average equals the arithmetic mean of the measurements.
Personal Monitor
An instrument that can be worn on the body for measuring exposure over time.
Calculated Historical Fields
An estimate based on a theoretical calculation of the magnetic field emitted by power lines using historical
electrical loads on those lines.
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200) Results of EMF Research
This chapter summarizes the results of EMF research worldwide, including
epidemiological studies of children and adults, clinical studies of how
humans react to typical EMF exposures, and laboratory research with
animals and cells.
Q Is there a link between EMF exposure and childhood
leukemia?
A Despite more than two decades of research to determine whether elevated EMF
. exposure, principally to magnetic fields, is related to an increased risk of childhood
leukemia, there is still no definitive answer. Much progress has been made,
however, with some lines of research leading to reasonably clear answers and
others remaining unresolved. The best available evidence at this time leads to the
following answers to specific questions about the link between EMF exposure and
childhood leukemia:
Is there an association between power line configurations (wire codes) and
childhood leukemia? No.
Is there an association between measured fields and childhood leukemia? Yes, but
the association is weak, and it is not clear whether it represents a cause-
and-effect relationship.
Q What is the epidemiological evidence for evaluating a
link between EMF exposure and childhood leukemia?
A. The initial studies, starting with the pioneering research of Dr. Nancy Wertheimer
and Ed Leeper in 1979 in Denver, Colorado, focused on power line configurations
near homes. Power lines were systematically evaluated and coded for their
presumed ability to produce elevated magnetic fields in homes and classified into
groups with higher and lower predicted magnetic field levels (see discussion of wire
codes on page 15) . Although the first study and two that followed in Denver and
Los Angeles showed an association between wire codes indicative of elevated
magnetic fields and childhood leukemia, larger, more recent studies in the central
part of the United States and in several provinces of Canada did not find such an
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association. In fact, combining the National Cancer Institute Study
evidence from all the studies, we can In 1997, after eight years of work, Dr. Martha lanes and colleagues at the
conclude with some confidence that National Cancer Institute (NCI) reported the results of their study of
wire codes are not associated with a childhood acute tymphoblastic leukemia (ALL). The case-control study
measurable increase in the risk of involved more than 1,000 children living in 9 eastern and midwestern
childhood leukemia. U.S. states and is the largest epidemiological study of childhood
The other approach to assessing EMF leukemia to date in the United States. To help resolve the question of
exposure in homes focused on the wire versus measured magnetic fields, the NCI researchers carried
out both types of exposure assessment. Overall, Linet reported little
measurements of magnetic fields. evidence that living in homes with higher measured magnetic-field levels
Unlike wire codes, which are only was a disease risk and found no evidence that living in a home with a
applicable in North America due to the high wire code configuration increased the risk of ALL in children.
nature of the electric power distribution
system, measured fields have been
studied in relation to childhood United Kingdom Childhood Cancer Study
leukemia in research conducted around
the world, including Sweden, England, In December 1999, Sir Richard Doll and colleagues in the United
Germany, New Zealand, and Taiwan. Kingdom announced that the largest study of childhood cancer ever
Large, detailed studies have recently undertaken involving nearly 4,000 children with cancer in England,
been completed in the United States, Wales, and Scotland—found no evidence of excess risk of childhood
Canada, and the United Kingdom that leukemia or other cancers from exposure to power-frequency magnetic
• fields. It should be noted, however, that because most power lines in
provide the most evidence for making the United Kingdom are underground, the EMF exposures of these
an evaluation. These studies have children were mostly lower than 0.2 microtesla or 2 milligauss.
produced variable findings, some
reporting small associations, others
finding no associations.
After reviewing all the data, the U.S. National Institute of Environmental Health
Sciences (NIEHS) concluded in 1999 that the evidence was weak, but that it was
still sufficient to warrant limited concern. The NIEHS rationale was that no
individual epidemiological study provided convincing evidence linking magnetic
field exposure with childhood leukemia, but the overall pattern of results for some
methods of measuring exposure suggested a weak association between increasing
exposure to EMF and increasing risk of childhood leukemia. The small number of
cases in these studies made it impossible to firmly demonstrate this association.
However, the fact that similar results had been observed in studies of different
populations using a variety of study designs supported this observation.
A major challenge has been to determine whether the most highly elevated, but
rarely encountered, levels of magnetic fields are associated with an increased risk of
leukemia. Early reports focused on the risk associated with exposures above 2 or 3
milligauss, but the more recent studies have been large enough to also provide
some information on levels above 3 or 4 milligauss. It is estimated that 4.5% of
homes in the United States have magnetic fields above 3 milligauss, and 2.5% of
homes have levels above 4 milligauss.
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What is Cancer?
Cancer
"Cancer" is a term used to describe at least 200 different diseases, all involving uncontrolled cell growth.
The frequency of cancer is measured by the incidence—the number of new cases diagnosed each year.
Incidence is usually described as the number of new cases diagnosed per 100,000 people per year.
The incidence of cancer in adults in the United States is 382 per 100,000 per year, and childhood cancers
account for about 1 % of all cancers. The factors that influence risk differ among the forms of cancer.
Known risk factors such as smoking, diet, and alcohol contribute to specific types of cancer. (For example,
smoking is a known risk factor for lung cancer, bladder cancer, and oral cancer.) For many other cancers,
the causes are unknown.
Leukemia
Leukemia describes a variety of cancers that arise in the bone marrow where blood cells are formed. The
leukemias represent less than 4% of all cancer cases in adults but are the most common form of cancer
in children. For children age 4 and under, the incidence of childhood leukemia is approximately 6 per
100,000 per year, and it decreases with age to about 2 per 100,000 per year for children 10 and older. In
the United States, the incidence of adult leukemia is about 1O cases per 100,000 people per year. Little is
known about what causes leukemia, although genetic factors play a role. The only known causes are
ionizing radiation, benzene, and other chemicals and drugs that suppress bone marrow function, and a
human T-cell leukemia virus.
Brain Cancer
• Cancer of the central nervous system (the brain and spinal cord) is uncommon, with incidence in the
United States now at about 6 cases in 100,000 people per year. The causes of the disease are largely
unknown, although a number of studies have reported an association with certain occupational chemical
exposures. Ionizing radiation to the scalp is a known risk factor for brain cancer. Factors associated with
an increased risk for other types of cancer—such as smoking, diet, and excessive alcohol use have not
been found to be associated with brain cancer.
To determine what the integrated information from all the studies says about
magnetic fields and childhood leukemia, two groups have conducted pooled
analyses in which the original data from relevant studies were integrated and
analyzed. One report (Greenland et al., 2000) combined 12 relevant studies with
magnetic field measurements, and the other considered 9 such studies (Ahlbom et
al., 2000) . The details of the two pooled analyses are different, but their findings
are similar. There is weak evidence for an association (relative risk of
approximately 2) at exposures above 3 mG. However, few individuals had high
exposures in these studies; therefore, even combining all studies, there is
uncertainty about the strength of the association.
The following table summarizes the results for the epidemiological studies of EMF
exposure and childhood leukemia analyzed in the pooled analysis by Greenland et
al. (2000) . The focus of the summary review was the magnetic fields that occurred
three months prior to diagnosis. The results were derived from either calculated
historical fields or multiple measurements of magnetic fields. The North American
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Residential Exposure to Magnetic Fields and Childhood Leukemia
Magnetic field category (rG)
>1 -- s2mG >2 - s3mG >3mG
First author Estimate 95% CL Estimate 95% CL Estimate 95% CL
Coghill 0.54 0.17, 1 .74 No controls No controls
Dockerty 0.65 0.26, 1 .63 2.83 0.29, 27.9 No controls
Feychting 0.63 0.08, 4.77 0.90 0.12, 7.00 4.44 1 .67, 11 .7
Linet 1 .07 0.82, 1 .39 1 .01 0.64, 1 .59 1 .51 0.92, 2.49
London 0.96 0.54, 1 .73 0.75 0.22, 2.53 1 .53 0.67, 3.50
McBride 0.89 0.62, 1 .29 1 .27 0.74, 2.20 1 .42 0.63, 3.21
Michaelis 1 .45 0.78, 2.72 1 .06 0.27, 4.16 2.48 0.79, 7.81
Olsen 0.67 0.07, 6.42 No cases 2.00 0.40, 9.93
Savitz 1 .61 0.64, 4.11 1 .29 0.27, 6.26 3.87 0.87, 17.3
Tornenius 0.57 0.33, 0.99 0.88 0.33, 2.36 1 .41 0.38, 5.29
Tynes 1 .06 0.25, 4.53 No cases No cases
Verkasalo 1 .11 0.14, 9.07 No cases 2.00 0.23, 17.7
Study summary 0.95 0.80, 1 .12 1 .06 0.79, 1 .42 1 .69* 1 .25, 2.29
1 - c2 mG 2 -- <4 mG a4 mG
**United Kingdom 0.84 0.57, 1 .24 0.98 0.50, 1 .93 1 .00 0.30, 3.37
95% a 95% confidence limits.
• Source: Greenland et al., 2000.
* Mantel-#4aenszel analysis (p = 0.01). Maximum-likelihood summaries differed by less than 1% from these
summaries; based on 2,656 cases and 7,084 controls. Adjusting for age, sex, and other variables had little effect on
summary results.
**These data are from a recent United Kingdom study not included in the Greenland analysis but included in another
pooled analysis (Ahlbom et at. 2000). The United Kingdom study induded 1,073 cases and 2,224 controls.
For this table, the column headed "estimate" describes the relative risk. Relative risk is the ratio of the risk of childhood
leukemia for those in a magnetic field exposure group compared to persons with exposure levels of 1 .0 mG or less. For
example, Coghill estimated that children with exposures between 1 and 2 mG have 0.54 times the risk of children whose
exposures were less than 1 mG. London's study estimates that children whose exposures were greater than 3 mG have
1.53 times the risk of children whose exposures were less than 1 mG. The column headed "95% CL" (confidence limits)
describes how much random variation is in the estimate of relative risk. The estimate may be off by some amount due to
random variation, and the width of the confidence limits gives some notion of that variation. For example, in Coghill's
estimate of 0.54 for the relative risk, values as low as 0.17 or as high as 1 .74 would not be statistically significantly
different from the value of 0.54. Note there is a wide range of estimates of relative risk across the studies and wide
confidence limits for many studies. In light of these findings, the pooling of results can be extremely helpful to calculate
an overall estimate, much better than can be obtained from any study taken alone.
studies (Linet, London, McBride, Savitz) were 60 Hz; all other studies were 50 Hz.
Results from the recent study from the United Kingdom (see page 17) are also
included in the table. This study was included in the analysis by Ahlbom et al.
(2000) . The relative risk estimates from the individual studies show little or no
association of magnetic fields with childhood leukemia. The study summary for the
pooled analysis by Greenland et al. (2000) shows a weak association between
childhood leukemia and magnetic field exposures greater 3 mG.
June 2002 http:f/www.niehs.nih.gov/ernfrapid ;. 19
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•
Q Is there a link between EMF exposure and childhood
brain cancer or other forms of cancer in children?
A Although the earliest studies suggested an association between EMF exposure and all
forms of childhood cancer, those initial findings have not been confirmed by other
studies. At present, the available series of studies indicates no association between
EMF exposure and childhood cancers other than leukemia. Far fewer of these studies
have been conducted than studies of childhood leukemia.
Q Is there a link between residential EMF exposure and
cancer in adults?
_ The few studies that have been conducted to address EMF and adult cancer do not
k provide strong evidence for an association. Thus, a link has not been established
between residential EMF exposure and adult cancers, including leukemia, brain
cancer, and breast cancer (see table below) .
Residential Exposure to Magnetic Fields and Adult Cancer
Results (odds ratios)
• First author Location Type of exposure data Leukemia CNS tumors All cancers
Coleman United Kingdom Calculated historical fields 0.92 NA NA
Feychting and Ahlbom Sweden Calculated & spot measurements 1 .5* 0.7 NA
Li Taiwan Calculated historical fields 1 .4* 1 .1 NA
Li Taiwan Calculated historical fields 1 . 1 (breast cancer)
McDowall United Kingdom Calculated historical fields 1 .43 NA 1 .03
Severson Seattle Wire codes & spot measurements 0.75 NA NA
Wrensch San Francisco Wire codes & spot measurements NA 0.9 NA
Youngson United Kingdom Calculated historical fields 1 .88 NA NA
CNS = central nervous system.
*The number is statistically significant (greater than expected by chance).
Study results are listed as "odds ratios" (OR), An odds ratio of 1 .00 means there was no increase or decrease in risk. In other words, the odds
that the people in the study who had the disease (in this case, cancer) and were exposed to a particular agent (in this case, EMF) are the
same as for the people in the study who did not have the disease. An odds ratio greater than 1 may occur simply by chance, unless it is
statistically significant.
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Q Have clusters of cancer or other adverse health effects
been linked to EMF exposure?
An unusually large number of cancers, miscarriages, or other adverse health effects
that occur in one area or over one period of time is called a "cluster." Sometimes
clusters provide an early warning of a health hazard. But most of the time the
reason for the cluster is not known. There have been no proven instances of cancer
clusters linked with EMF exposure.
The definition of a "cluster" depends on
X X how large an area is included. Cancer cases
(x's in illustration) in a city, neighborhood,• `? or workplace may occur in ways that
suggest a cluster due to a common
X 9 X X environmental cause. Often these patterns
• turn out to be due to chance. Delineation
- - `7i X of a cluster is subjective where do you
draw the circles?
K
• If EMF does cause or promote cancer, shouldn't cancer
Q
rates have increased along with the increased use of
electricity?
Not necessarily. Although the <'-,Y....
fr : use of electricity has increased ` ''
�' a, :;a. -
greatly over the years, EMF i I: .
exposures may not have '3t ' "
increased. Changes in building • -".,: .
wiring codes and in the design :,� :Ft.:.•_
of electrical appliances have in ,a
some cases resulted in lower �, elf .
magnetic field levels. Rates for �', '
various types of cancer have i •
~�~
shown both increases and .t
decreases through the years, duel
irl t,
in part to improved prevention, i 1 ,, 1.1
diagnosis, reporting, and
treatment. '
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Q is there a link between EMF exposure in electrical
occupations and cancer?
For almost as long as we have been concerned with residential exposure to EMF and
childhood cancers, researchers have been studying workplace exposure to EMF and adult
cancers, focusing on leukemia and brain cancer. This research began with surveys of job
titles and cancer risks, but has progressed to include very large, detailed studies of the
health of workers, especially electric utility workers, in the United States, Canada, France,
England, and several Northern European countries. Some studies have found evidence
that suggests a link between EMF exposure and both leukemia and brain cancer, whereas
other studies of similar size and quality have not found such associations.
California
A 1993 study of 36,000 California electric utility workers reported no
strong, consistent evidence of an association between magnetic fields and
any type of cancer.
Canada/France
A 1994 study of more than 200,000 utility workers in 3 utility companies
in Canada and France reported no significant association between all
leukemias combined and cumulative exposure to magnetic fields. There
• was a slight, but not statistically significant, increase in brain cancer. The
researchers concluded that the study did not provide clear-cut evidence
that magnetic field exposures caused leukemia or brain cancer.
North Carolina
Results of a 1995 study involving more than 138,000 utility workers at
5 electric utilities in the United States did not support an association
between occupational magnetic field exposure and leukemia, but
suggested a link to brain cancer.
Denmark
In 1997 a study of workers employed in all Danish utility companies
reported a small, but statistically significant, excess risk for all cancers
combined and for lung cancer. No excess risk was observed for leukemia,
brain cancers, or breast cancer.
United Kingdom
A 1997 study among electrical workers in the United Kingdom did not find
an excess risk for brain cancer. An extension of this work reported in 2001
also found no increased risk for brain cancer.
Efforts have also been made to pool the findings across several of the above studies
to produce more accurate estimates of the association between EMF and cancer
(Kheifets et al., 1999). The combined summary statistics across studies provide
insufficient evidence for an association between EMF exposure in the workplace
and either leukemia or brain cancer.
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Q Have studies of workers in other industries suggested
a link between EMF exposure and cancer?
AOne of the largest studies to report an association between cancer
and magnetic field exposure in a broad range of industries was
conducted in Sweden (1993). The study included an assessment
of EMF exposure in 1 ,015 different workplaces and involved
more than 1 ,600 people in 169 different occupations. An
association was reported between estimated EMF exposure and
increased risk for chronic lymphocytic leukemia. An association
was also reported between exposure to magnetic fields and brain
cancer, but there was no dose-response relationship.
Another Swedish study (1994) found an excess risk of lymphocytic
leukemia among railway engine drivers and conductors. However,
the total cancer incidence (all tumors included) for this group of :,.
workers was lower than in the general Swedish population. A * -: ,a��e. :,.,'. -\.
study of Norwegian railway workers found no evidence for an • • 3= `
association between EMF exposure and leukemia or brain cancer. ' "
•
Although both positive and negative effects of EMF exposure have
been reported, the majority of studies show no effects.
• Q Is there a link between EMF exposure and breast
cancer?
Researchers have been interested in the possibility that EMF exposure might cause
l a breast cancer, in part because breast cancer is such a common disease in adult women.
Early studies identified a few electrical workers with male breast cancer, a very rare
disease. A link between EMF exposure and alterations in the hormone melatonin was
considered a possible hypothesis (see page 24) . This idea provided motivation to
conduct research addressing a possible link between EMF exposure and breast cancer.
Overall, the published epidemiological studies have not shown such an association.
Q What have we learned from clinical studies?
![ Laboratory studies with human volunteers have attempted to answer questions
y:
such as,
Does EMF exposure alter normal brain and heart function?
Does EMF exposure at night affect sleep patterns?
Does EMF exposure affect the immune system?
Does EMF exposure affect hormones?
The following kinds of biological effects have been reported. Keep in mind that a
biological effect is simply a measurable change in some biological response. It may
or may not have any bearing on health.
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Heart rate
An inconsistent effect on heart rate by EMF exposure has been reported. When
observed, the biological response is small (on average, a slowing of about three to
five beats per minute) , and the response does not persist once exposure has ended.
Two laboratories, one in the United States and one in Australia, have reported effects
of EMF on heart rate variability. Exposures used in these experiments were relatively
high (about 300 mG) , and lower exposures failed to produce the effect. Effects have
not been observed consistently in repeated experiments.
Sleep electrophysiology
A laboratory report suggested that overnight exposure to 60-Hz magnetic fields may
disrupt brain electrical activity (EEG) during night sleep. In this study subjects were
exposed to either continuous or intermittent magnetic fields of 283 mG. Individuals
exposed to the intermittent magnetic fields showed alterations in traditional EEG
sleep parameters indicative of a pattern of poor and disrupted sleep. Several studies
have reported no effect with continuous exposure.
Hormones, immune system, and blood chemistry
Several clinical studies with human volunteers have evaluated the effects of power-
• frequency EMF exposure on hormones, the immune system, and blood chemistry.
These studies provide little evidence for any consistent effect.
Melatonin
The hormone melatonin is secreted mainly at night and primarily by the pineal
gland, a small gland attached to the brain. Some laboratory experiments with
cells and animals have shown that melatonin can slow the growth of cancer cells,
including breast cancer cells. Suppressed nocturnal melatonin levels have been
observed in some studies of laboratory animals exposed to both electric and
magnetic fields. These observations led to the hypothesis that EMF exposure might
reduce melatonin and thereby weaken one of the body's defenses against cancer.
Many clinical studies with human volunteers have now examined whether
various levels and types of magnetic field exposure affect blood levels of
melatonin. Exposure of human volunteers at night to power-frequency EMF
under controlled laboratory conditions has no apparent effect on melatonin. Some
studies of people exposed to EMF at work or at home do report evidence for a
small suppression of melatonin. It is not clear whether the decreases in melatonin
reported under environmental conditions are related to the presence of EMF
exposure or to other factors.
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Q What effects of EMF have been reported in laboratory
studies of cells?
,� Over the years, scientists have conducted more than 1 ,000 laboratory studies to
investigate potential biological effects of EMF exposure. Most have been in vitro
studies; that is, studies carried out on cells isolated from animals and plants, or on
cell components such as cell membranes. Other studies involved animals, mainly
rats and mice. In general, these studies do not demonstrate a consistent effect of
EMF exposure.
Most in vitro studies have used magnetic fields of 1,000 mG (100 iT) or higher,
exposures that far exceed daily human exposures. In most incidences, when one
laboratory has reported effects of EMF exposure on cells, other laboratories have not
been able to reproduce the findings. For such research results to be widely accepted
by scientists as valid, they must be replicated—that is, scientists in other laboratories
should be able to repeat the experiment and get similar results. Cellular studies have
investigated potential EMF effects on cell proliferation and differentiation, gene
expression, enzyme activity, melatonin, and DNA. Scientists reviewing the EMF
research literature find overall that the cellular studies provide little convincing
evidence of EMF effects at environmental levels.
Q Have effects of EMF been reported in laboratory
studies in animals?
Researchers have published more than 30 detailed reports on both long-term and
short-term studies of EMF exposures in laboratory animals (bioassays). Long-term
animal bioassays constitute an important group of studies in EMF research. Such
studies have a proven record for predicting the carcinogenicity of chemicals, physical
agents, and other suspected cancer-causing agents. In the EMF studies, large groups
of mice or rats were continuously exposed to EMF for two years or longer and were
then evaluated for cancer. The U.S. National Toxicology Program (http://ntp-
server.niehs.nih.govl) has an extensive historical database for hundreds of different
chemical and physical agents evaluated using this model. EMF long-term bioassays
examined leukemia, brain cancer, and breast cancer—the diseases some
epidemiological studies have associated with EMF exposure (see pages 16-23) .
Several different approaches have been used to evaluate effects of EMF exposure in
animal bioassays. To investigate whether EMF could promote cancer after genetic
damage had occurred, some long-term studies used cancer initiators such as
ultraviolet light, radiation, or certain chemicals that are known to cause genetic
damage. Researchers compared groups of animals treated with cancer initiators to
groups treated with cancer initiators and then exposed to EMF, to see if EMF
exposure promoted the cancer growth (initiation-promotion model). Other studies
tested the cancer promotion potential of EMF using mice that were predisposed to
cancer because they had defects in the genes that control cancer.
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Animal Leukemia Studies: Long-Term, Continuous Exposure Studies, 'Wm or More Years in Length
First author Sex/species Exposure/animal numbers Results
Babbitt (U.S.) Female mice 14,000 mG, 190 or 380 mice per group. No effect
Some groups treated with ionizing radiation.
Boorman (U.S.) Mate and female rats 20 to 10,000 mG, 100 per group No effect
McCormick (U.S.) Male and female mice 20 to 10,000 mG, 100 per group No effect
Mandeville (Canada) Female rats 20 to 20,000 mG, 50 per group No effect
In utero exposure
Yasui (Japan) Male and female rats 5,000 to 50,000 mG, 50 per group No effect
10 milligauss (mG) = 1 microtesla (µi) = 0.001 millitesla (MT)
Leukemia
Fifteen animal leukemia studies have been completed and reported. Most tested for
effects of exposure to power-frequency (60-Hz) magnetic fields using rodents.
Results of these studies were largely negative. The Babbitt study evaluated the
subtypes of leukemia. The data provide no support for the reported epidemiology
findings of leukemia from EMF exposure. Many scientists feel that the lack of
effects seen in these laboratory leukemia studies significantly weakens the case for
EMF as a cause of leukemia.
Breast cancer
Researchers in the Ukraine, Germany, Sweden, and the United States have used
initiation-promotion models to investigate whether EMF exposure promotes breast
cancer in rats.
The results of these studies are mixed; while the German studies showed some
effects, the Swedish and U.S. studies showed none. Studies in Germany reported
effects on the numbers of tumors and tumor volume. A National Toxicology
Program long-term bioassay performed without the use of other cancer-initiating
substances showed no effects of EMF exposure on the development of mammary
tumors in rats and mice.
The explanation for the observed difference among these studies is not readily
apparent. Within the limits of the experimental rodent model of mammary
carcinogenesis, no conclusions are possible regarding a promoting effect of EMF on
chemically induced mammary cancer.
Other cancers
Tests of EMF effects on skin cancer, liver cancer, and brain cancer have been
conducted using both initiation-promotion models and non-initiated long-term
bioassays. All are negative.
Three positive studies were reported for a co-promotion model of skin cancer in
mice. The mice were exposed to EMF plus cancer-causing chemicals after cancers
26 ; http:i/www.niehs.nih.gov/emfrapid June 2002
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EMF Research
had already been initiated. The same research team as well as an independent
laboratory were unable to reproduce these results in subsequent experiments.
Non-cancer effects
Many animal studies have investigated whether EMF can cause health problems
other than cancer. Researchers have examined many endpoints, including birth
defects, immune system function, reproduction, behavior, and learning. Overall,
animal studies do not support EMF effects on non-cancer endpoints.
Q Can EMF exposure damage DNA?
Studies have attempted to determine whether EMF has genotoxic potential; that is,
whether EMF exposure can alter the genetic material of living organisms. This
question is important because genotoxic agents often also cause cancer or birth
defects. Studies of genotoxicity have included tests on bacteria, fruit flies, and some
tests on rats and mice. Nearly 100 studies on EMF genotoxicity have been reported.
Most evidence suggests that EMF exposure is not genotoxic. Based on experiments
with cells, some researchers have suggested that EMF exposure may inhibit the cell's
ability to repair normal DNA damage, but this idea remains speculative because of
the lack of genotoxicity observed in EMF animal studies.
•
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your EMF Environment .......� ...T..��y. �._�, _� _
Your EMF Environment
This chapter discusses typical magnetic field exposures in home and work
environments and identifies common EMF sources and field intensities
associated with these sources.
Q How do we define EMF exposure?
A Scientists are still uncertain about the best way to define "exposure" because
experiments have yet to show which aspect of the field, if any, may be relevant to
reported biological effects. Important aspects of exposure could be the highest
intensity, the average intensity, or the amount of time spent above a certain
baseline level. The most widely used measure of EMF exposure has been the time-
• weighted average magnetic field level (see discussion on page 15).
Q How is EMF exposure measured?
Several kinds of personal exposure meters are now available. These automatically
record the magnetic field as it varies over time. To determine a person's EMF
exposure, the personal exposure meter is usually worn at the waist or is placed as
close as possible to the person during the course of a work shift or day.
EMF can also be measured using survey meters, sometimes called "gaussmeters."
These measure the EMF levels in a given location at a given time. Such
measurements do not necessarily reflect personal EMF exposure because they are
not always taken at the distance from the EMF source that the person would
typically be from the source. Measurements are not always made in a location for
the same amount of time that a person spends there. Such "spot measurements"
also fail to capture variations of the field over time, which can be significant.
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Your E M F Environment
Q What are some typical EMF exposures?
The figure below is an example of data collected with a personal exposure meter.
Personal Magnetic Field Exposure
20
16 - Mean magnetic field
exposure during
w this 24-hour period
was 0.5 mG.
'O 12
he
La Latiuswariji'
4
• 6 pm Midnight 6 am Noon 6 pm
Around Sleeping (no Going Work Lunch Work Going
house electric blanket)to work out home
In the above example, the magnetic field was measured every 1 .5 seconds over a
period of 24 hours. For this person, exposure at home was very low. The occasional
spikes (short exposure to high fields) occurred when the person drove or walked
under power lines or over underground power lines or was close to appliances in
the home or office.
Several studies have used personal exposure meters to measure field exposure in
different environments. These studies tend to show that appliances and building
wiring contribute to the magnetic field exposure that most people receive while at
home. People living close to high voltage power lines that carry a lot of current tend
to have higher overall field exposures. As shown on page 32, there is considerable
variation among houses.
Q What are typical EMF exposures for people living in
the United States?
A Most people in the United States are exposed to magnetic fields that average less
than 2 milligauss (mG) , although individual exposures vary,
The following table shows the estimated average magnetic field exposure of the
U.S. population, according to a study commissioned by the U.S. government as part
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Your EMF Environment
of the EMF Research and Public Information Dissemination (EMF RAPID) Program
(see page 50) . This study measured magnetic field exposure of about 1 ,000 people
of all ages randomly selected among the U.S. population. Participants wore or
carried with them a small personal exposure meter and kept a diary of their
activities both at home and away from home. Magnetic field values were
automatically recorded twice a second for 24 hours. The study reported that
exposure to magnetic fields is similar in different regions of the country and similar
for both men and women.
Estimated Average Magnetic Field Exposure of the U.S. Population
Average 24-hour Population 95% confidence People exposed*
field (mG) exposed (%) interval (°6) (millions)
> 0.5 76.3 73.8-78.9 197-211
> 1 43.6 40.9-46.5 109-124
> 2 14.3 11 .8-17.3 31 .5-46.2
> 3 63 4.7-8.5 12.5-22.7
> 4 3.6 2.5-5.2 6.7-13.9
> 5 2.42 1 .65-3.55 4.4-9.5
> 7.5 0.58 0.29-1 .16 0.77-3. 1
> 10 0.46 0.20-1 .05 0.53-2.8
> 15 0.17 0.035- 0.83 0.09-2.2
• *Based on a population of 267 million. This table summarizes some of the results of a study that sampled about 1,000 people
in the United States. In the first row, for example, we find that 76.3% of the sample population had a 24-hour average
exposure of greater than 0.5 mG. Assuming that the sample was random, we can use statistics to say that we are 95%
confident that the percentage of the overall U.S. population exposed to greater than 0.5 mG is between 73,8% and 78,9%.
Source: Zaffanella, 1993.
The following table shows average magnetic fields experienced during different
types of activities. In general, magnetic fields are greater at work than at home.
Estimated Average Magnetic Field Exposure of the U.S. Population
for Various Activities
Average Population exposed (%)
field (mG) Home Bed Work School BYavel
> 0.5 69 48 81 63 87
> 1 38 30 49 25 48
> 2 14 14 20 3.5 13
> 3 7.8 7.2 13 1 .6 4.1
> 4 4.7 4.7 8.0 < 1 1.5
> 5 3.5 3.7 4.6 1 .0
> 7.5 1 .2 1 .6 2.5 0.5
> 10 0.9 0.8 13 < 0.2
> 15 0.1 0.1 0.9
Source: Zaffanella, 1993.
30 http:llwww.niehs.nih.govlemfrapid June 2002
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Your EMF Environment
Q What levels of EMF are found in common environments?
AMagnetic field exposures can vary greatly from site to site for any type of
environment. The data shown in the following table are median measurements
taken at four different sites for each environment category.
EMF Exposures in Common Environments
Magnetic fields measured in milligauss (mG)
Median* Top 5th Median* Top 5th
Environment exposure percentile Environment exposure percentile
OFFICE BUILDING MACHINE SHOP
Support staff 0.6 3.7 Machinist 0.4 6.0
Professional 0.5 2.6 Welder 1 .1 24.6
Maintenance 0.6 3.8 Engineer 1 .0 5.1
Visitor 0.6 2.1 Assembler 0.5 6.4
SCHOOL Office staff 0.7 4.7
Teacher 0.6 3.3 GROCERY STORE
Student 0.5 2.9 Cashier 2.7 11 .9
Custodian 1 .0 4.9 Butcher 2.4 12.8
Administrative staff 1 .3 6.9 Office staff 2.1 7.1
HOSPITAL Customer 1 .1 7.7
IP Patient 0.6 3.6 *The median of four measurements, For this table, the
Medical staff 0.8 5.6 median is the average of the two middle measurements.
Visitor 0.6 2.4 Source: National Institute for Occupational Safety and
Maintenance 0.6 5.9 Health.
Q What EMF field levels are encountered in the home?
A Electric fields
Electric fields in the home, on average, range from 0 to 10 volts per meter. They can
be hundreds, thousands, or even millions of times weaker than those encountered
outdoors near power lines. Electric fields directly beneath power lines may vary from
a few volts per meter for some overhead distribution lines to several thousands of
volts per meter for extra high voltage power lines. Electric fields from power lines
rapidly become weaker with distance and can be greatly reduced by walls and roofs
of buildings.
Magnetic fields
Magnetic fields are not blocked by most materials. Magnetic fields encountered in
homes vary greatly. Magnetic fields rapidly become weaker with distance from
the source.
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_.... ._.._. _. -. ._. � ._. . ......�. _.....__ r. .. . . .,-,-..-.... w:........a ..a.�..� ....._._
The chart on the left summarizes data from a study
Magnetic Field Measured in 992 Homes by the Electric Power Research Institute (EPRI) in
which spot measurements of magnetic fields were
A o.m Mats ` % of kakis that exceeded made in the center of rooms in 992 homes
Makent101011. tragic flab *new loft . throughout the United States. Half of the houses
25% 50% studied had magnetic field measurements of 0.6
__ mG or less, when the average of measurements
from all the rooms in the house was calculated
0'5 "'G 50%
�° (the all-room mean magnetic field) . The all-room
i mG mean magnetic field for all houses studied was 0.9
1. mG. The measurements were made away from
2.1 mG 15. • electrical appliances and reflect primarily the
fields from household wiring and outside
2.9 mG 5% power lines.
If you are comparing the information in this chart
ia.s mG % with measurements in your own home, keep in
mind that this chart shows averages of
• Source:Zaffanella, 1993 measurements taken throughout the homes, not
the single highest measurement found in the home.
• Q What are EMF levels close to electrical appliances?
A Magnetic fields close to electrical appliances are often much stronger than those
- ` from other sources, including magnetic fields directly under power lines. Appliance
fields decrease in strength with distance more quickly than do power line fields.
The following table, based on data gathered in 1992, lists the EMF levels generated
by common electrical appliances. Magnetic field strength (magnitude) does not
depend on how large, complex, powerful, or noisy the appliance is. Magnetic fields
near large appliances are often weaker than those near small devices. Appliances in
your home may have been redesigned since the data in the table were collected,
and the EMF they produce may differ considerably from the levels shown here.
Electric Blankets
Measurements taken 5 cm from the blanket surface. The graph shows magnetic fields produced by electric
G. a5 39.4 blankets, including conventional 110-V electric
tail 5{m peak I blankets as well as the PTC (positive temperature
E 35 5{m average p
30 coefficient) low-magnetic-field blankets. The fields
25 21.8 were measured at a distance of about 2 inches from
,la 15 the blanket's surface, roughly the distance from the
2-4 t5E 2.7
blanket to the user's internal organs. Because of the
0.9 wiring, magnetic field strengths vary from point to
,
0 Conventional arc point on the blanket. The graph reflects this and gives
Low-Magnetic Field both the peak and the average measurement.
Source:Center for Devices and Radiological Health,
US Food and Drug Administration.
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Your EMF Environment
Sources of Magnetic Fields (mG)*
Distance from source Distance from source
6" 1 ' 2' 4' 6" 1 ' 2' 4'
Office Sources Workshop Sources
AIR CLEANERS BATTERY CHARGERS
Lowest 110 20 3 - Lowest 3 2 - --
Median 180 35 5 1 Median 30 3 - -
Highest 250 50 8 2 Highest 50 4 - -
COPY MACHINES DRILLS
Lowest 4 2 1 - Lowest 100 20 3 -
Median 90 20 7 1 Median 150 30 4 -
Highest 200 40 13 4 Highest 200 40 6 -
FAX MACHINES POWER SAWS
Lowest 4 - - - Lowest 50 9 1 -
Median 6 - --- - Median 200 40 5 -
Highest 9 2 -- - Highest 1000 300 40 4
FLUORESCENT LIGHTS ELECTRIC SCREWDRIVERS (while charging)
Lowest 20 - - - Lowest - - - -
Median 40 6 2 - Median - - - -
Highest 100 30 8 4 Highest - -- - --
0 ELECTRIC PENCIL SHARPENERS Lowest 20 8 5 -
Distance from source
Median 200 70 20 2 1 ' 2' 4'
Highest 300 90 30 30 Living/Family Room Sources
VIDEO DISPLAY TERMINALS (see page 48) CEILING FANS
(PC with color monitors)** Lowest - - -
Lowest 7 2 1 - Median 3 - -
Median 14 5 2 - Highest 50 6 1
Highest 20 6 3 WINDOW AIR CONDITIONERS
Lowe
Bathroom Sources
Median t
3 1
HAIR DRYERS Highest 20 6 4
Lowest 1 -- W - COLOR TELEVISIONS**
Median 300 1
Highest 700 70 10 1 Lowest - - -
Median 7 2 -
ELECTRIC SHAVERS Highest 20 8 4
Lowest 4 - - -
Median 100 20 -- -
Highest 600 100 10 1
Continued
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Your EME Environment _. ___
Sources of Magnetic Fields (mG)*
Distance from source Distance from source
6" 1 ' 2' 4' 6" 1 ' 2' 4'
Kitchen Sources Kitchen Sources
BLENDERS ELECTRIC OVENS
Lowest 30 5 - - Lowest 4 1 - -
Median 70 10 2 — Median 9 4 — —
Highest 100 20 3 -- Highest 20 5 1 —
CAN OPENERS ELECTRIC RANGES
Lowest 500 40 3 - Lowest 20 - - -
Median 600 150 20 2 Median 30 8 2 —
Highest 1500 300 30 4 Highest 200 30 9 6
COFFEE MAKERS REFRIGERATORS
Lowest 4 - - - Lowest - -- - -
Median 7 - - - Median 2 2 1 -
Highest 10 1 — — Highest 40 20 10 10
DISHWASHERS TOASTERS
Lowest 10 6 2 - Lowest 5 - - -
Median 20 10 4 — Median 10 3 — —
Highest 100 30 7 1 Highest 20 7 - -
0 FOOD PROCESSORS Lowest 20 5 - -
Bedroom Sources
Median 30 6 2 - DIGITAL CLOCK****
Highest 130 20 3 -
GARBAGE DISPOSALS
Median 1 - -
Lowest - - -
Lowest 60 8 1 —
Median 80 10 2 — High 8 2 1
Highest 100 20 3 -- ANALOG CLOCKS
MICROWAVE OVENS*** (conventional clockface)****
Lowest 100 1 1 - Lowest 1 - -
Median 200 4 10 2 Median 15 2 —
Highest 300 200 30 20 Highest 30 5 3
MIXERS BABY MONITOR (unit nearest child)
Lowest 30 5 - - Lowest 4 - - -
Median 100 10 1 - Median 6 1 - -
Highest 600 100 10 - Highest 15 2 - -
Continued
34 http:llwww.niehs.nih.gov/emfrapid June 2002
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Your EMF Environment.
Sources of Magnetic Fields (mG)*
Distance from source Distance from source
6" 1 ' 2' 4' 6" 1 ' 2' 4'
Laundry/Utility Sources Laundry/Utility Sources
ELECTRIC CLOTHES DRYERS PORTABLE HEATERS
Lowest 2 - - - Lowest 5 1 - -
Median 3 2 - - Median 100 20 4 -
Highest 10 3 - - Highest 150 40 8 1
WASHING MACHINES VACUUM CLEANERS
Lowest 4 1 - - Lowest 100 20 4 -
Median 20 7 1 - Median 300 60 10 1
Highest 100 30 6 -- Highest 700 200 50 10
IRONS SEWING MACHINES
Lowest 6 1 - - Home sewing machines can produce magnetic fields
Median 8 1 - - of 12 mG at chest level and 5 mG at head level.
Highest 20 3 - - Magnetic fields as high as 35 mG at chest level and
215 mG at knee level have been measured from
industrial sewing machine models (Sobel, 1994).
Source: EMF in Your Environment, U.S. Environmental Protection Agency, 1992.
• * Dash (—) means that the magnetic field at this distance from the operating appliance could not be distinguished
from background measurements taken before the appliance had been turned on.
** Some appliances produce both 60-Hz and higher frequency fields. For example, televisions and computer screens
produce fields at 10,000-30,000 Hz (10-30 kHz) as well as 60-Hz fields.
*** Microwave ovens produce 60-Hz fields of several hundred milligauss, but they also create microwave energy
inside the appliance that is at a much higher frequency(about 2.45 billion hertz). We are shielded from the higher
frequency fields but not from the 60-Hz fields.
**** Most digital clocks have low magnetic fields. In some analog clocks, however, higher magnetic fields are produced
by the motor that drives the hands. In the above table, the clocks are electrically powered using alternating current,
as are all the appliances described in these tables.
Q What EMF levels are found near power lines?
APower transmission lines bring power from a generating station to an electrical
` substation. Power distribution lines bring power from the substation to your home.
Transmission and distribution lines can be either overhead or underground. Overhead
lines produce both electric fields and magnetic fields. Underground lines do not
produce electric fields above ground but may produce magnetic fields above ground.
Power transmission lines
Typical EMF levels for transmission lines are shown in the chart on page 37. At a
distance of 300 feet and at times of average electricity demand, the magnetic fields
from many lines can be similar to typical background levels found in most homes.
The distance at which the magnetic field from the line becomes indistinguishable
from typical background levels differs for different types of lines.
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Your EMF Environment
Power distribution lines
Typical voltage for power distribution lines in North America ranges from 4 to 24
kilovolts (kV) . Electric field levels directly beneath overhead distribution lines may
vary from a few volts per meter to 100 or 200 volts per meter. Magnetic fields
directly beneath overhead distribution lines typically range from 10 to 20 mG for
main feeders and less than 10 mG for laterals. Such levels are also typical directly
above underground lines. Peak EMF levels, however, can vary considerably
depending on the amount of current carried by the line. Peak magnetic field levels as
high as 70 mG have been measured directly below overhead distribution lines and as
high as 40 mG above underground lines.
Q How strong is the EMF from electric power substations?
In general, the strongest EMF around the outside of a substation comes from the
power lines entering and leaving the substation. The strength of the EMF from
equipment within the substations, such as transformers, reactors, and capacitor
banks, decreases rapidly with increasing distance. Beyond the substation fence or
wall, the EMF produced by the substation equipment is typically indistinguishable
from background levels.
• Q Do electrical workers have higher EMF exposure than
other workers?
` Most of the information we have about occupational EMF exposure comes from
�.. studies of electric utility workers. It is therefore difficult to compare electrical
workers' EMF exposures with those of other workers because there is less
information about EMF exposures in work environments other than electric utilities.
Early studies did not include actual measurements of EMF exposure on the job but
used job titles as an estimate of EMF exposure among electrical workers. Recent
studies, however, have included extensive EMF exposure assessments.
A report published in 1994 provides some information about estimated EMF
exposures of workers in Los Angeles in a number of electrical jobs in electric
utilities and other industries. Electrical workers had higher average EMF exposures
(9.6 mG) than did workers in other jobs (1 .7 mG). For this study, the category
"electrical workers" included electrical engineering technicians, electrical engineers,
electricians, power line workers, power station operators, telephone line workers,
TV repairers, and welders.
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36 http:llwww.niehs.nih.govlemfrapid June 2002
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�..._.__. �_.__..._.�._.. �_ ._. __..�.___ _w____ _ Your EMF Environment
Typical EMF Levels for Power Transmission Lines *
115kV ir ,i:ght-of%of .
15m 30m 61m 91m
(50 ft) (100 ft) (200 ft) (300 ft)
f l I I 1
Electric Field (kV/m) 1.0 0.5 0.07 0.01 0.003
Mean Magnetic Field(mG) 29.7 6.5 1.7 0.4 0.2
230 kV 'Y' op itht-o y
"' 15m 30m 61 m 91 m
(50 ft) (100 ft) (200 ft) (300 ft)
l I t - 1
Electric Field (kV/m) 2.0 1.5 0.3 0.05 0.01
Mean Magnetic Field(mG) 57.5 19.5 7.1 1.8 0.8
500 kV ge .
y arc
20m 30m _ 61m 91m
'; (65ft) (100 ft) (200 ft) (300 ft)
I I 1 I f
Electric Field (kV/m) 7.0 3.0 1.0 0.3 0.1
Mean Magnetic Field(m6) 86.7 29.4 12.6 3.2 1.4
• Matt irtetic Field from a 500 kV Tiransmission
1 ne al:old ro on tho RtphtfiWay Electric fields from power lines are relatively
Every 5 Minutes for 1 Week stable because line voltage doesn't change
70
very much. Magnetic fields on most lines
60 fluctuate greatly as current changes in
S 5° A \ response to changing loads. Magnetic fields
must be described statistically in terms of
3 averages, maximums, etc. The magnetic fields
above are means calculated for 321 power
i 30141\1O1\pkiiii\l1f; lines for 1990 annual mean loads. During peak
loads (about 1 % of the time), magnetic fields
20 --- Far This t•Wnk Periodic are about twice as strong as the mean levels
Mean field a 38.6 mG
Minim mfield a 22.4 mG above. The graph on the left is an example of
10 Maximum field = 62.7 mG how the magnetic field varied during one week
0 1 1 3 I 1 1 i for one 500-kV transmission line.
Thurs Fri Sat Sun Mon The Wed Thur
*These are typical EMFs at 1 m (3.3 ft) above ground for various distances from power lines in the Pacific
Northwest. They are for general information. For information about a specific line, contact the utility that
operates the line.
Source: Bonneville Power Administration, 1994.
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Q What are possible EMF exposures in the workplace?
The figures below are examples of magnetic field exposures determined with
in exposure meters worn by four workers in different occupations. These
measurements demonstrate how EMF exposures vary among individual workers.
They do not necessarily represent typical EMF exposures for workers in these
occupations.
Magnetic Field Exposures of Workers (rnG)
Sewing machine operator in garment factory Maintenance mechank
50
ihri i Jilt i
40 Mead 32.0 • 40 Mean: 1.0
Geanetrk Geometric
30
mean: 24.0* 30 mean: 0.7*
E r . t
20 1 ,l 20
• 10 ililikiirI I
' U, 10 Ji
ii
o
7:00 am 9:00 am 11:00 am 1:00 pm 3:00 pm 830 am 9:00 am 9:30 am 10:00 am 10:30 am 11:00 am 11:30 am 12:12 pm
The sewing machine operator worked all day took a 1-hour lunch The mechanic repaired a compressor at 9:45 am and 11:10 am.
break at 11:15 am, and took 10-minute breaks at 8:55 am and
Electrician Government office worker
50 50 roil_ _
40 Mean: 0.9 40 i I Mean: 9.1
Geometric Geometric
30 mean: 0.7* 30 mean: 7.0*
t7 ci
E E
20 20
E
, i , fkaansam; I
10 10
_ A
i_
0 0 - L -
7:00 am 8:00 am 9:00 am 1at00 am 11:00 am 12:00 am 1:00 pm 7:00 am 9:00 am 11:00 am 1:00 pm 3:00 pm 5:00 pm
The electrician repaired a large air-conditioning motor at 9:10 am The government worker was at the copy machine at 8.:00 am, at the
and at 11:45 am. computer from 11:00 am to 1:00 pm and also from 2:30 pm to 4:30 pm.
'The geometric mean is calculated by squaring the values, adding the squares, and then taking the square root of the sum.
Source: National Institute for Occupational Safety and Health and U.S. Department of Energy
_ .... _.
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Your EMF Environment
The tables below and on page 41 can give you a general idea about magnetic field
levels for different jobs and around various kinds of electrical equipment. It is
important to remember that EMF levels depend on the actual equipment used in
EMF Measurements During a Workday
ELF magnetic fields
measured in niQ
Median for Range for 90%
Industry and occupation occupation* of workers**
ELECTRICAL WORKERS IN VARIOUS INDUSTRIES
Electrical engineers 1 .7 0.5-12.0
Construction electricians 3.1 1 :6--12.1
TV repairers 4.3 0.6-,8.6
Welders 9.5 1 .4-66.1
ELECTRIC UTILITIES
Clerical workers without computers 0.5 0.2-2.0
Clerical workers with computers 1 .2 0.5-4.5
Line workers 2.5 0.5-34.8
Electricians 5.4 0.8-34.0
Distribution substation operators 7.2 1 .1-36.2
Workers off the job (home, travel, etc.) 0.9 0.3-3.7
TELECOMMUNICATIONS
• Install, maintenance, & repair technicians 1 .5 0.7-3.2
Central office technicians 2.1 0.5-8.2
Cable splicers 3.2 0.7-15.0
AUTO TRANSMISSION MANUFACTURE
Assemblers 0.7 0.2-4.9
Machinists 1 .9 0.6-27.6
HOSPITALS
Nurses 1 .1 05-2.1
X-ray technicians 1 .5 1 .0-2.2
SELECTED OCCUPATIONS FROM ALL ECONOMIC SECTORS
Construction machine operators 0.5 0.1-1 .2
Motor vehicle drivers 1 .1 0.4-2.7
School teachers 1 .3 0.6-3.2
Auto mechanics 2.3 0.6-8.7
Retail sales 2.3 1 .0-5.5
Sheet metal workers 3.9 0.3-48.4
Sewing machine operators 6.8 0.9-32.0
Forestry and logging jobs 7.6 0.6-95.5***
Source: National Institute for Occupational Safety and Health.
ELF (extremely low frequency)—frequencies 3-3,000 Hz.
* The median is the middle measurement in a sample arranged by size. These personal exposure
measurements reflect the median magnitude of the magnetic field produced by the various EMF
sources and the amount of time the worker spent in the fields.
** This range is between the 5th and 95th percentiles of the workday averages for an occupation.
*** Chain saw engines produce strong magnetic fields that are not pure 60-Hz fields.
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the workplace. Different brands or models of the same type of equipment can have
different magnetic field strengths. It is also important to keep in mind that the
strength of a magnetic field decreases quickly with distance.
If you have questions or want more information about your EMF exposure at
work, your plant safety officer, industrial hygienist, or other local safety official can
be a good source of information. The National Institute for Occupational Safety and
Health (NIOSH) is asked occasionally to conduct health hazard evaluations in
workplaces where EMF is a suspected cause for concern. For further technical
assistance contact NIOSH at 800-356-4674.
Q What are some typical sources of EMF in the workplace?
4 Exposure assessment studies so far have shown that most people's EMF exposure
k at work comes from electrical appliances and tools and from the building's power
supply. People who work near
transformers, electrical closets,
circuit boxes, or other high-
current electrical equipment may
, have 60-Hz magnetic field
exposures of hundreds of
• milligauss or more. In offices,
► ` . magnetic field levels are often
similar to those found at home,
typically 0.5 to 4.0 mG. However,
" - ..07 •'� � these levels can increase
•1914 r .s dramatically near certain types of
equipment.
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EMF Spot Measurements
ELF magnetic fields
Industry and sources (MG) Other frequencies Comments
ELECTRICAL EQUIPMENT USED IN MACHINE MANUFACTURING
Electric resistance heater 6,000-14,000 VLF
Induction heater. 10-460 High VLF
Hand-held grinder 3,000 — Tool exposures measured at operator's chest.
Grinder 110 — Tool exposures measured at operator's chest.
Lathe, drill press, etc. 1-4 — Tool exposures measured at operator's chest.
ALUMINUM REFINING
Aluminum pot rooms 3.4-30 Very high static field Highly-rectified DC current (with an ELF ripple)
refines aluminum.
Rectification room 300-3,300 High static field
STEEL FOUNDRY
Ladle refinery
Furnace active 170-1,300 High ULF from the ladle's big Highest ELF field was at the chair of control room operator.
magnetic stirrer
Furnace inactive 0.6-3.7 High ULF from the ladle's big Highest ELF field was at the chair of control room operator.
magnetic stirrer
Electrogalvanizing unit 2-1,100 High VLF
TELEVISION BROADCASTING
Video cameras 7.2-24.0 VLF
(studio and minicams)
• Video tape degaussers 160-3,300 - Measured 1 ft away.
Light control centers 10-300 - Walk-through survey.
Studio and newsrooms 2-5 Walk-through survey.
HOSPITALS
Intensive care unit 0.1-220 VLF Measured at nurse's chest.
Post-anesthesia care unit 0.1-24 VLF
Magnetic resonance imaging (MRI) 0.5-280 Very high static field, VLF and RF Measured at technician's work locations.
TRANSPORTATION
Cars, minivans, and trucks 0.1-125 Most frequencies less than 60 Hz Steel-belted tires are the principal ELF source for
gas/diesel vehicles.
Bus (diesel powered) 0.5--146 Most frequencies less than 60 Hz
Electric cars 0.1-81 Some elevated static fields
Chargers for electric cars 4-63 - Measured 2 ft from charger.
Electric buses 0.1-88 - Measured at waist. Fields at ankles 2-5 times higher.
Electric train passenger cars 0.1-330 25 & 60 Hz power on U.S. trains Measured at waist. Fields at ankles 2-5 times higher.
Airliner 0.8x24.2 400 Hz power on airliners Measured at waist.
GOVERNMENT OFFICES
Desk work locations 0.1-7 — Peaks due to laser printers.
Desks near power center 18-50
Power cables in floor 15-170 —
Building power supplies 25-1,800 —
Can opener 3,000 — Appliance fields measured 6 in. away.
Desktop cooling fan 1,000 — Appliance fields measured 6 in. away.
Other office appliances 10-200 —
Source: National Institute for Occupational Safety and Health, 2001 .
ULF (ultra low frequency)--frequencies above 0, below 3 Hz.
ELF (extremely low frequency)—frequencies 3-3,000 Hz.
VLF (very low frequency)—frequencies 3,000-30,000 Hz (3-30 kilohertz).
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Q What EMF exposure occurs during travel?
Inside a car or bus, the main sources of magnetic field exposure are those you pass
by (or under) as you drive, such as power lines. Car batteries involve direct
current (DC) rather than alternating current (AC). Alternators can create EMF,
but at frequencies other than 60 Hz. The rotation of steel-belted tires is also a
source of EMF.
Most trains in the United States are diesel powered. Some electrically powered
trains operate on AC, such as the passenger trains between Washington, D.C. and
New Haven, Connecticut. Measurements taken on these trains using personal
exposure monitors have suggested that average 60-Hz magnetic field exposures for
passengers and conductors may exceed 50 mG. A U.S. government-sponsored
exposure assessment study of electric rail systems found average 60-Hz magnetic
field levels in train operator compartments that ranged from 0.4 mG (Boston high
speed trolley) to 31 . 1 mG (North Jersey transit). The graph on the next page shows
average and maximum magnetic field measurements in operator compartments of
several electric rail systems. It illustrates that 60 Hz is one of several
electromagnetic frequencies to which train operators are exposed.
Workers who maintain the tracks on electric rail lines, primarily in the
northeastern United States, also have elevated magnetic field exposures at both
25 Hz and 60 Hz. Measurements taken by the National Institute for Occupational
Safety and Health show that typical average daily exposures range from 3 to
18 mG, depending on how often trains pass the work site.
Rapid transit and light rail systems in the United States, such as the Washington
D.C. Metro and the San Francisco Bay Area Rapid Transit, run on DC electricity.
These DC-powered trains contain equipment that produces AC fields. For example,
areas of strong AC magnetic fields have been measured on the Washington Metro
close to the floor, during braking and acceleration, presumably near equipment
located underneath the subway cars.
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Magnetic Field Measurements in Train Operators` Compartments
Magnetic field measured in i»i$gauss(MG}.
'
mG mG
300 � b0
200 �° _ 5W2560 Hz 40°4 1
ao� Aga. � j r� � ' .406--
5-d5 Hz
5-2560 Hz 20 /: �
100 5-45 Hz 10 r e 5 60 Hx
50-b0 H:
0 1 a ear 65--300 Hz
0 • 65-300 Hz A 304-2560 Hz
A 305-2560 Hz
Boston Trolley Bus
t. Amtrak Northeast Corridor
NorwietMal Rail Boston High Speed Trolley
North Jersey Transit Long Branch Washington D.C. Mstrarall (all cars)
Amtrak Northeast Corridor(60 Hz) — Boston Subway
..� Amtrak Northeast Corridor(25 Hz)
Source: U.S. Department of Transportation, 1993
These graphs illustrate that 60 Hz is one of several electromagnetic frequencies to which train operators are exposed.
The maximum exposure is the top of the blue (upper) portion of the bar; the average exposure is the top of the red
(lower) portion.
Q How can I find out how strong the EMF is where I live
and work?
rk The tables throughout this chapter can give you a general idea about magnetic field
levels at home, for different jobs, and around various kinds of electrical equipment.
For specific information about EMF from a particular power line, contact the utility
that operates the line. Some will perform home EMF measurements.
You can take your own EMF measurements with a magnetic field meter. For a spot
measurement to provide a useful estimate of your EMF exposure, it should be
taken at a time of day and location when and where you are typically near the
equipment. Keep in mind that the strength of a magnetic field drops off quickly
with distance.
Independent technicians will conduct EMF measurements for a fee. Search the
Internet under "EMF meters" or "EMF measurement." You should investigate the
experience and qualifications of commercial firms, since governments do not
standardize EMF measurements or certify measurement contractors.
June 2002 • http:llwww.niehs.nrh.govlemfraprd
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At work, your plant safety officer, industrial hygienist, or other local safety official
can be a good source of information. The National Institute for Occupational Safety
and Health (NIOSH) sometimes conducts health hazard evaluations in workplaces
where EMF is a suspected cause for concern. For further technical assistance,
contact NIOSH at 800-356-4674.
Q How much do computers contribute to my EMF
exposure?
Personal computers themselves produce very little EMF. However, the video
display terminal (VDT) or monitor provides some magnetic field exposure unless it
is of the new flat-panel design.
Conventional VDTs containing
.0 y w; cathode ray tubes use magnetic
fields to produce the image on the
teas screen, and some emission of those
magnetic fields is unavoidable.
..,.< J4^ate/. .� ..: i.
• ' 1 5M' " ' ' "'' �.; Unlike most other appliances which
pPE.+..;.�;.k>: ..1:. ..,1.
n\,., (;.x L`', ; : produce predominantly 60-Hz
magnetic fields, VDTs emit magnetic
•
fields in both the extremely low
' frequency (ELF) and very low
frequency (VLF) frequency ranges
(see page 8) . Many newer VDTs
have been designed to minimize
magnetic field emissions, and those
identified as "TCO'99 compliant"
-.ft;
i meet a standard for low emissions
')I.•=.,. J.( ' (.
: may:: "'�•�✓..tl
(see page 48).
Q What can be done to limit EMF exposure?
Personal exposure to EMF depends on three things: the strength of the magnetic
field sources in your environment, your distance from those sources, and the time
you spend in the field.
If you are concerned about EMF exposure, your first step should be to find out
where the major EMF sources are and move away from them or limit the time you
spend near them. Magnetic fields from appliances decrease dramatically about an
arm's length away from the source. In many cases, rearranging a bed, a chair, or a
work area to increase your distance from an electrical panel or some other EMF
source can reduce your EMF exposure.
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Your EMF Environment.
Another way to reduce EMF exposure is to use equipment designed to have
relatively low EMF emissions. Sometimes electrical wiring in a house or a building
can be the source of strong magnetic field exposure. Incorrect wiring is a common
source of higher-than-usual magnetic fields. Wiring problems are also worth
correcting for safety reasons.
In its 1999 report to Congress, the National Institute of Environmental Health
Sciences suggested that the power industry continue its current practice of siting
power lines to reduce EMF exposures.
There are more costly actions, such as burying power lines, moving out of a home,
or restricting the use of office space that may reduce exposures. Because scientists
are still debating whether EMF is a hazard to health, it is not clear that the costs of
such measures are warranted. Some EMF reduction measures may create other
problems. For instance, compacting power lines reduces EMF but increases the
danger of accidental electrocution for line workers.
We are not sure which aspects of the magnetic field exposure, if any, to reduce.
Future research may reveal that EMF reduction measures based on today's limited
understanding are inadequate or irrelevant. No action should be taken to reduce
EMF exposure if it increases the risk of a known safety hazard.
•
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Exposure Standards • q' i••W'Ri.:•v'ra wVwxwu''w.rr�w�.✓.w�Y.W ..�'V."we':am_____ rri:
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EMF Exposure Standards
This chapter describes standards and guidelines established by state, national,
and international safely organizations for some EMF sources and exposures.
Q Are there exposure standards for 60-Hz EMF?
In the United States, there are no federal standards limiting occupational or
t . residential exposure to 60-Hz EMF.
At least six states have set standards for transmission line electric fields; two of
these also have standards for magnetic fields (see table below) . In most cases, the
maximum fields permitted by each state are the maximum fields that existing lines
produce at maximum load-carrying conditions. Some states further limit electric
field strength at road crossings to ensure that electric current induced into large
metal objects such as trucks and buses does not represent an electric shock hazard.
State 1lransmission Line Standards and Guidelines
Electric Field Magnetic Field
State On R.O.W.* Edge R.O.W. On R.O.W. Edge R.O.W.
Florida 8 kV/ma 2 kV/m — 150 mGa (max, load)
10 kV/mb 200 mGb (max. load)
250 mG< (max. load)
Minnesota 8 kV/m — — --
Montana 7 kV/md 1 kV/me
New Jersey — 3 kV/rn
New York 11 .8 kV/rn 1 .6 kV/m -- 200 mG (max. load)
11 .0 kV/mf
7.0 kV/rnd
Oregon 9 kV/m — --- —
*R.O.W. = right-of-way (or in the Florida standard, certain additional areas adjoining the right-of-way). kV/m = kilovolt
per meter. One kilovolt = 1,000 volts. aFor lines of 69-230 kV. t)For 500 kV lines. cFor 500 kV lines on certain existing
R.O.W. dMaximum for highway crossings. °May be waived by the landowner. (Maximum for private road crossings.
Two organizations have developed voluntary occupational exposure guidelines for
EMF exposure. These guidelines are intended to prevent effects, such as induced
currents in cells or nerve stimulation, which are known to occur at high magnitudes,
much higher (more than 1 ,000 times higher) than EMF levels found typically in
46 http:I/www,niehs.nih,gov/emfrapid June 2002
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occupational and residential environments. These guidelines are summarized in the
tables on the right.
The International Commission ICNIRP Guidelines for EMF Exposure
on Non-Ionizing Radiation Exposure (60 Hz) Electric field Magnetic field
Protection (ICNIRP) Occupational 8.3 kV/m 4.2 G (4,200 mG)
concluded that available data General Public 4.2 kV/m 0.833 G (833 mG)
regarding potential long-term International Commission on Non-Ionizing Radiation Protection (ICNIRP) is an organization of
effects, such as increased risk 15,000 scientists from 40 nations who specialize in radiation protection.
of cancer, are insufficient to Source: ICNIRP, 1998.
provide a basis for setting
exposure restrictions.
The American Conference ACGIH Occupational Threshold Limit Values for 60-Hz EMF
of Governmental Industrial Electric field Magnetic field
Hygienists (ACGIH) Occupational exposure should not exceed 25 kV/m 10 G (10,000 mG)
publishes "Threshold Limit Prudence dictates the use of protective 15 kV/m
Values" (TLVs) for various clothing above
physical agents. The TLVs Exposure of workers with cardiac 1 kV/m 1 G (1 ,000 mG)
for 60-Hz EMF shown in pacemakers should not exceed
the table are identified as
American Conference of Governmental Industrial Hygienists (ACGIH) is a professional
guides to control exposure; organization that facilitates the exchange of technical information about worker health
they are not intended to protection. it is not a government regulatory agency.
demarcate safe and Source: ACGIH, 2001.
dangerous levels.
Q Does EMF affect people with pacemakers or other
medical devices?
AAccording to the U.S. Food and Drug Administration (FDA) , interference from
EMF can affect various medical devices including cardiac pacemakers and
implantable defibrillators. Most current research in this area focuses on higher
frequency sources such as cellular phones, citizens band radios, wireless computer
links, microwave signals, radio and television transmitters, and paging transmitters.
Sources such as welding equipment, power lines at electric generating plants, and
rail transportation equipment can produce lower frequency EMF strong enough to
interfere with some models of pacemakers and defibrillators. The occupational
exposure guidelines developed by ACGIH state that workers with cardiac
pacemakers should not be exposed to a 60-Hz magnetic field greater than 1 gauss
(1 ,000 mG) or a 60-Hz electric field greater than 1 kilovolt per meter (1 ,000 V/m)
(see ACGIH guidelines above) . Workers who are concerned about EMF exposure
effects on pacemakers, irnplantable defibrillators, or other implanted electronic
medical devices should consult their doctors or industrial hygienists.
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Exposure Standards
Nonelectronic metallic medical implants (such as artificial joints, pins, nails, screws,
and plates) can be affected by high magnetic fields such as those from magnetic
resonance imaging (MRI) devices and aluminum refining equipment, but are
generally unaffected by the lower fields from most other sources.
The FDA MedWatch program is collecting information about medical device
problems thought to be associated with exposure to or interference from EMF.
Anyone experiencing a problem that might be due to such interference is
encouraged to call and report it (800-332- 1088).
Q What about products advertised as producing low or
reduced magnetic fields?
Virtually all electrical appliances and devices emit electric and magnetic fields. The
in strengths of the fields vary appreciably both between types of devices and among
manufacturers and models of the same type of device. Some appliance manufacturers
are designing new models that, in general, have lower EMF than older models. As a
result, the words "low field" or "reduced field" may be relative to older models and
not necessarily relative to other manufacturers or devices. At this time, there are no
domestic or international standards or guidelines limiting the EMF emissions of
appliances.
• The U.S. government has set no standards for magnetic fields from computer
monitors or video display terminals (VDTs). The Swedish Confederation of
Professional Employees (TCO) established in 1992 a standard recommending strict
limits on the EMF emissions of computer monitors. The VDTs should produce
magnetic fields of no more than 2 mG at a distance of 30 cm (about 1 ft) from the
front surface of the monitor and 50 cm (about 1 ft 8 in) from the sides and back of
the monitor. The TCO'92 standard has become a de facto standard in the VDT industry
worldwide. A 1999 standard, promulgated by the Swedish TCO (known as the
TCO'99 standard), provides for international and environmental labeling of personal
computers. Many computer monitors marketed in the U.S. are certified as compliant
with TCO'99 and are thereby assured to produce low magnetic fields.
Beware of advertisements claiming that the federal government has certified that the
advertised equipment produces little or no EMF. The federal government has no such
general certification program for the emissions of low-frequency EMF. The U.S. Food
and Drug Administration's Center for Devices and Radiological Health (CDRH) does
certify medical equipment and equipment producing high levels of ionizing radiation
or microwave radiation. Information about certain devices as well as general
information about EMF is available from the CDRH at 888-463-6332.
.�..........?....._.s _.,.._ .a..a.w.. y-...A,...a.__W ..��
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Q Are cellular telephones and towers sources of EMF
exposure?
ACellular telephones and towers involve radio-frequency and microwave-frequency
electromagnetic fields (see page 8) . These are in a much higher frequency range
than are the power-frequency electric and magnetic fields associated with the
transmission and use of electricity.
The U.S. Federal Communications Commission (FCC) licenses communications
systems that use radio-frequency and microwave electromagnetic fields and
ensures that licensed facilities comply with exposure standards. Public information
on this topic is published on two FCC Internet sites: http://www.fcc.gov/oet/info/
documents/bulletins/#5S and http://www.fcc.gov/oet/rfsafety/
The U.S. Food and Drug Administration also provides information about cellular
telephones on its web site (http://www.fda.gov/cdrh/ocd/mobilphone.html).
•
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June 2002 http:Ilwww.niehs.nih.govlemfrapid . 49
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re
3 National and International EMF Reviews
This chapter presents the findings and recommendations of major
EMF research reviews, including the U. S. government's EMF RAPID
Program.
Q What have national and international agencies
concluded about the impact of EMF exposure on
human health?
ft Since 1995, two major U.S. reports have concluded that limited evidence exists for
an association between EMF exposure and increased leukemia risk, but that when
all the scientific evidence is considered, the link between EMF exposure and cancer
III is weak. The World Health Organization in 1997 reached a similar conclusion.
The two reports were the U.S. National Academy of Sciences report in 1996 and, in
P P
1999, the National Institute of Environmental Health Sciences report to the U.S.
Congress at the end of the U.S. EMF Research and Public Information
Dissemination (RAPID) Program.
The U.S. EMF RAPID Program
Initiated by the U.S. Congress and established by law in 1992, the
ENIFIINTO U.S. EMF Research and Public Information Dissemination (EMF
RAPID) Program set out to study whether exposure to electric and
Cara codmog4setisits PastachrOtteciticrfoorD sett hgar magnetic fields produced by the generation, transmission, or use of
electric power posed a risk to human health. For more information
about the EMF RAPID Program, visit the web site (http://www.niehs.nih.gov/
emfrapid).
The U.S. Department of Energy (DOE) administered the overall EMF RAPID
Program, but health effects research and risk assessment were supervised by the
National Institute of Environmental Health Sciences (NIEHS) , a branch of the U.S.
National Institutes of Health (NIH) . Together, DOE and NIEHS oversaw more than
100 cellular and animal studies, as well as engineering and exposure assessment
studies. Although the EMF RAPID Program did not fund any additional
epidemiological studies, an analysis of the many studies already conducted was an
important part of its final report.
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EMF Reviews
The electric power industry contributed about half, or $22.5 million, of the $45
million eventually spent on EMF research over the course of the EMF RAPID
Program. The NIEHS received $30. 1 million from this program for research, public
outreach, administration, and the health assessment evaluation of extremely low
frequency (ELF) EMF. The DOE received approximately $ 15 million from this
program for engineering and EMF mitigation research. The NIEHS contributed an
additional $ 14.5 million for support of extramural and intramural research
including long-term toxicity and
EMF RAPID Program carcinogenicity studies conducted by
Interagency Committee the National Toxicology Program.
• National Institute of Environmental Health Sciences An interagency committee was
• Department of Energy established by the President of the
• Department of Defense United States to provide oversight
• Department of Transportation
• Environmental Protection Agency and program management support
• Federal Energy Regulatory Commission for the EMF RAPID Program. The
• National Institute of Standards and Technology interagency committee included
• Occupational Safety and Health Administration representatives from NIEHS, DOE,
• Rural Electrification Administration and seven other federal agencies with
EMF-related responsibilities.
The EMF RAPID Program also received advice from a National EMF Advisory
Committee (NEMFAC), which included representatives from citizen groups, labor,
utilities, the National Academy of Sciences, and other groups. They met regularly with
DOE and NIEHS staff to express their views. NEMFAC meetings were open to the
public. The EMF RAPID Program sponsored citizen participation in some scientific
meetings as well. A broad group of citizens reviewed all major public
information materials produced for the program.
NIEHS Working Group Report 1998
t�tii•„rtit r,t
In preparation for the EMF RAPID Program's goal of reporting to the Ir' 'Iwidtth I tte4 1s
Irmo I siirmur4' to
U.S. Congress on possible health effects from exposure to EMF from I >utic I me I re-rierrrrr
I tee rru find Magill hi I It teh
power lines, the NIEHS convened an expert working group in June
1998. Over 9 days, about 30 scientists conducted a complete review of
EMF studies, including those sponsored by the EMF RAPID Program
and others. Their conclusions offered guidance to the NIEHS as it
prepared its report to Congress.
Using criteria developed by the International Agency for Research on
Cancer, a majority of the members of the working group concluded that
exposure to power-frequency EMF is a possible human carcinogen.
The majority called their opinion "a conservative public health decision based on
limited evidence for an increased occurrence of childhood leukemias and an increased
occurrence of chronic lymphocytic leukemia (CLL) in occupational settings." For these
June 2002 http:llwww.nfehs.nih.govlemfraprd
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EMF Revievtrs.
diseases, the working group reported that animal and cellular studies neither confirm
nor deny the epidemiological studies' suggestion of a disease risk. This report is
available on the NIEHS EMF RAPID web site (http://www.niehs.nih.gov/emfrapid) .
NIEHS Report to Congress at Conclusion of EMF RAPID Program
In June 1999, the NIEHS reported to the U.S. Congress that scientific
evidence for an EMF-cancer link is weak.
Ar The following are excerpts from the 1999 NIEHS report:
The NIEHS believes that the probability that ELF-EMF exposure is truly a
health hazard is currently small. The weak epidemiological associations and
niORion lack of any laboratory support for these associations provide only marginal,
R alth laroctz fromhews, to
scientific support that exposure to this agent is causing any degree of harm.
Monk Fads
M a se IP92 Ent, � The scientific evidence suggesting that extremely low frequency EMF
QOM exposures pose any health risk is weak. The strongest evidence for health
effects comes from associations observed in human populations with two
-••-q forms of cancer: childhood leukemia and chronic lymphocytic leukemia in
pirsipm
occupationally exposed adults. While the support from individual studies
is weak, the epidemiological studies demonstrate, for some methods of
measuring exposure, a fairly consistent pattern of a small, increased risk
with increasing exposure that is somewhat weaker for chronic
• lymphocytic leukemia than for childhood leukemia. In contrast, the
mechanistic studies and the animal toxicology literature fail to demonstrate any
consistent pattern across studies, although sporadic findings of biological effects
(including increased cancers in animals) have been reported. No indication of
increased leukemias in experimental animals has been observed.
The full report is available on the NIEHS EMF RAPID web site
(http://www.niehs.nih.gov/emfrapid) .
No regulatory action was recommended or taken based on the NIEHS report. The NIEHS
director, Dr. Kenneth Olden, told the Congress that, in his opinion, the conclusion of the
NIEHS report was not sufficient to warrant aggressive regulatory action.
The NIEHS did not recommend adopting EMF standards for electric appliances or
burying electric power lines. Instead, it recommended providing public information
about practical ways to reduce EMF exposure. The NIEHS also suggested that
power companies and utilities "continue siting power lines to reduce exposures
and . . . explore ways to reduce the creation of magnetic fields around transmission
and distribution lines without creating new hazards." The NIEHS encouraged
manufacturers to reduce magnetic fields at a minimal cost, but noted that the risks
do not warrant expensive redesign of electrical appliances.
The NIEHS also encouraged individuals who are concerned about EMF in their homes
to check to see if their homes are properly wired and grounded, since incorrect wiring
or other code violations are a common source of higher-than-usual magnetic fields.
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National Academy of Sciences Report
In October 1996, a National Research Council committee of the National Academy
of Sciences (NAS) released its evaluation of research on potential associations
between EMF exposure and cancer, reproduction, development, learning, and
behavior. The report concluded:
Based on a comprehensive evaluation of published studies relating to the effects of
power-frequency electric and magnetic fields on cells, tissues, and organisms
(including humans), the conclusion of the committee is that the current body of
evidence does not show that exposure to these fields presents a human-health
hazard. Specifically, no conclusive and consistent evidence shows that exposures to
residential electric and magnetic fields produce cancer, adverse neurobehavioral
effects, or reproductive and developmental effects.
The NAS report focused primarily on the association of childhood leukemia with
the proximity of the child's home to power lines. The NAS panel found that
although a link between EMF exposure and increased risk for childhood leukemia
was observed in studies that had estimated EMF exposure using the wire code
method (distance of home from power line) , such a link was not found in studies
that had included actual measurements of magnetic fields at the time of the study.
The panel called for more research to pinpoint the unexplained factors causing
• small increases in childhood leukemia in houses close to power lines.
World Health Organization International EMF Project
The World Health Organization (WHO) International EMF Project, with
headquarters in Geneva, Switzerland, was launched at a 1996 meeting with
representatives of 23 countries attending. It was intended to respond to growing
concerns in many member states over possible EMF health effects and to address the
conflict between such concerns and technological and economic progress. In its
advisory role, the WHO International EMF Project is now reviewing laboratory and
epidemiological evidence, identifying gaps in scientific knowledge, developing an
agenda for future research, and
developing risk communication booklets ;w
and other public information. The WHO ~ '
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As part of this project, in 1997 a working
group of 45 scientists from around the
world surveyed the evidence for adverse
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EMF health effects. They reported that, "taken together, the findings of all
published studies are suggestive of an association between childhood leukemia and
estimates of ELF (extremely low frequency or power-frequency) magnetic fields."
Much like the 1996 U.S. NAS report, the WHO report noted that living in homes near
power lines was associated with an approximate 1.5-fold excess risk of childhood
leukemia. But unlike the NAS panel, WHO scientists had seen the results of the 1997 U.S.
National Cancer Institute study of EMF and childhood leukemia (see page 17). This work
showed even more strongly the inconsistency between results of studies that used a wire
code to estimate EMF exposure and studies that actually measured magnetic fields.
Regarding health effects other than cancer, the WHO scientists reported that the
epidemiological studies "do not provide sufficient evidence to support an
association between extremely-low-frequency magnetic-field exposure and adult
cancers, pregnancy outcome, or neurobehavioural disorders."
World Health Organization International Agency for Research on Cancer
The WHO International Agency for Research on Cancer (IARC) produces a
monograph series that reviews the scientific evidence regarding potential
carcinogenicity associated with exposure to environmental agents. An international
scientific panel of 21 experts from 10 countries met in June 2001 to review the
• scientific evidence regarding the potential carcinogenicity of static and ELF
(extremely low frequency or power-frequency) EMF. The panel categorized its
conclusions for carcinogenicity based on the IARC classification system—a system
that evaluates the strength of evidence from epidemiological, laboratory (human
and cellular), and mechanistic studies. The panel classified power-frequency EMF
as "possibly carcinogenic to humans" based on a fairly consistent statistical
association between a doubling of risk of childhood leukemia and magnetic field
exposure above 0.4 microtesla (0.4 pT, 4 milligauss or 4 mG).
In contrast, they found no consistent evidence that childhood EMF exposures are
associated with other types of cancer or that adult EMF exposures are associated with
increased risk for any kind of cancer. The IARC panel reported that no consistent
carcinogenic effects of EMF exposure have been observed in experimental animals and
that there is currently no scientific explanation for the observed association between
childhood leukemia and EMF exposure. Further information can be obtained at the
IARC web sites (http://www.iarc.fr and http://monographs.iarc.fr) .
International Commission on Non-Ionizing Radiation Protection
The International Commission on Non-Ionizing Radiation Protection (ICNIRP) issued
exposure guidelines to guard against known adverse effects such as stimulation of
nerves and muscles at very high EMF levels, as well as shocks and burns caused by
touching objects that conduct electricity (see page 47) . In April 1998, ICNIRP revised
its exposure guidelines and characterized as "unconvincing" the evidence for an
association between everyday power-frequency EMF and cancer.
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European Union
In 1996, a European Union (EU) advisory panel provided an overview of the state
of science and standards among EU countries. With respect to power-frequency
EMF, the panel members said that there is no clear evidence that exposure to EMF
results in an increased risk of cancer.
Australia—Radiation Advisory Committee Report to Parliament
In 1997, Australia's Radiation Advisory Committee briefly reviewed the EMF
scientific literature and advised the Australian Parliament that, overall, there is
insufficient evidence to come to a firm conclusion regarding possible health effects
from exposure to power-frequency magnetic fields.
The committee also reported that "the weight of opinion as expressed in the U.S.
National Academy of Sciences report, and the negative results from the National
Cancer Institute study (Linet et al., 1997) would seem to shift the balance of probability
more towards there being no identifiable health effects" (see pages 17 and 53).
Canada—Health Canada Report
In December 1998, a working group of public health officers at Health Canada, the
federal agency that manages Canada's health care system, issued a review of the
• scientific literature regarding power-frequency EMF health effects. They found the
evidence to be insufficient to conclude that EMF causes a risk of cancer.
The report concluded that while EMF effects may be observed in biological systems
in a laboratory, no adverse health effects have been demonstrated at the levels to
which humans and animals arc typically exposed.
As for epidemiology, 25 years of study results are inconsistent and inconclusive, the
panel said, and a plausible EMF-cancer mechanism is missing. Health Canada
pledged to continue monitoring EMF research and to reassess this position as new
information becomes available.
Germany—Ordinance 26
On January 1 , 1997, Germany became the first nation to adopt a national rule
on EMF exposure for the general public. Ordinance 26 applies only to facilities
such as overhead and underground transmission and distribution lines,
transformers, switchgear and overhead lines for electric-powered trains. Both
electric (5 kV/m) and magnetic field exposure limits (1 Gauss) are high enough
that they are unlikely to be encountered in ordinary daily life. The ordinance
also requires that precautionary measures be taken on a case-by-case basis
when electric facilities are sited or upgraded near homes, hospital, schools.
day care centers, and playgrounds.
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Great Britain—National Radiological Protection Board Report
The National Radiological Protection Board (NRPB) in Great Britain advises the
government of the United Kingdom regarding standards of protection for exposure
to non-ionizing radiation. The NRPB's advisory group on non-ionizing radiation
periodically reviews new developments in EMF research and reports its findings.
Results of the advisory group's latest review were published in 2001 . The report
reviewed residential and occupational epidemiological studies, as well as cellular,
animal, and human volunteer studies that had been published.
The advisory group noted that there is "some epidemiological evidence that
prolonged exposure to higher levels of power frequency magnetic fields is associated
with a small risk of leukaemia in children." Specifically, the NRPB advisory group's
analysis suggests "that relatively heavy average exposures of 0.4 µT [4 mG] or more
are associated with a doubling of the risk of leukaemia in children under 15 years of
age." The group pointed out, however, that laboratory experiments have provided
"no good evidence that extremely low frequency electromagnetic fields are capable
of producing cancer."
Scandinavia—EMF Developments
In October 1995, a group of Swedish researchers and government officials published
a report about EMF exposure in the workplace. This "Criteria Group" reviewed EMF
• scientific literature and, using the IARC classification system, ranked occupational
EMF exposure as "possibly carcinogenic to humans." They also endorsed the
Swedish government's 1994 policy statement that public exposure limits to EMFs
were not needed, but that people might simply want to use caution with EMFs.
In 1996, five Swedish government agencies further explained their precautionary
advice about EMF. EMF exposure should be reduced, they said, but only when
practical, without great inconvenience or cost.
Health experts in Norway, Denmark, and Finland generally agreed in reviews
published in the 1990s that if an EMF health risk exists, it is small. They
acknowledged that a link between residential magnetic fields and childhood
leukemia cannot be confirmed or denied. In 1994, several Norwegian government
ministries also recommended increasing the distance between residences and
electrical facilities, if it could be done at low cost and with little inconvenience.
Q What other U.S. organizations have reported on EMF?
A American Medical Association
In 1995, the American Medical Association advised physicians that no scientifically
documented health risk had been associated with "usually occurring" EMF, based on
a review of EMF epidemiological, laboratory studies, and major literature reviews.
American Cancer Society
In 1996, the American Cancer Society released a review of 20 years of EMF
epidemiological research including occupational studies and residential studies of
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adult and childhood cancer. The society noted that some data support a possible
relationship of magnetic field exposure with leukemia and brain cancer, but further
research may not be justified if studies continue to find uncertain results. Of
particular interest is the summary of results from eight studies of risk from use of
household appliances with relatively high magnetic fields, such as electric blankets
and electric razors. The summary suggested that there is no persuasive evidence for
increased risk with more frequent or longer use of these appliances.
American Physical Society
The American Physical Society (APS) represents thousands of U.S. physicists.
Responding to the NIEHS Working Group's conclusion that EMF is a possible
human carcinogen, the APS executive board voted in 1998 to reaffirm its 1995
opinion that there is "no consistent, significant link between cancer and power
line fields."
California's Department of Health Services
In 1996, California's Department of Health Services (DHS) began an ambitious five-
year effort to assess possible EMF public health risk and offer guidance to school
administrators and other decision-makers. The California Electric and Magnetic Fields
(EMF) Program is a research, education, and technical assistance program concerned
with the possible health effects of EMF from power lines, appliances, and other uses of
• electricity. The program's goal is to find a rational and fair approach to dealing with
the potential risks, if any, of exposure to EMF. This is done through research, policy
analysis, and education. The web site has educational materials on EMF and related
health issues for individuals, schools, government agencies, and professional
organizations (http://wvvw.dhs.ca.gov/ps/deodc/ehibiemf).
Q What can we conclude about EMF at this time?
AElectricity is a beneficial part of our daily lives, but whenever electricity is
generated, transmitted, or used, electric and magnetic fields are created. Over the
past 25 years, research has addressed the question of whether exposure to power-
frequency EMF might adversely affect human health. For most health outcomes,
there is no evidence that EMF exposures have adverse effects. There is some
evidence from epidemiology studies that exposure to power-frequency EMF is
associated with an increased risk for childhood leukemia. This association is
difficult to interpret in the absence of reproducible laboratory evidence or a
scientific explanation that links magnetic fields with childhood leukemia.
EMF exposures are complex and come from multiple sources in the home and
workplace in addition to power lines. Although scientists are still debating whether
EMF is a hazard to health, the NIEHS recommends continued education on ways of
reducing exposures. This booklet has identified some EMF sources and some simple
steps you can take to limit your exposure. For your own safety, it is important that
any steps you take to reduce your exposures do not increase other obvious hazards
such as those from electrocution or fire. At the current time in the United States,
there are no federal standards for occupational or residential exposure to 60-Hz EMF.
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References
Selected references on EMF topics.
Basic Science
Kovetz A. Electromagnetic Theory. New York: Oxford University Press (2000).
Vanderlinde J. Classical Electromagnetic Theory. New York: Wiley (1993).
EMF Levels and Exposures
Dietrich FM & Jacobs WI. Survey and Assessment of Electric and Magnetic (EMF)
Public Exposure in the Transportation Environment. Report of the U. S. Department of
Transportation. NTIS Document PB99-130908. Arlington, VA: National Technical
Information Service (1999).
Kaune WT. Assessing human exposure to power-frequency electric and magnetic fields.
Environmental Health Perspectives 101 : 121 -133 (1993).
Kaune WT & Zaffanella L. Assessing historical exposure of children to power frequency
magnetic fields. Journal of Exposure Analysis Environmental Epidemiology 4: 149-170
(1994).
Tarone RE, Kaune WT, Linet MS, Hatch EE, Kleinerman RA, Robison LL, Boice JD & Wacholder
S. Residential wire codes: Reproducibility and relation with measured magnetic fields.
Occupational and Environmental Medicine 55:333-339 (1998).
U.S. Environmental Protection Agency. EMF in your environment: magnetic field
measurements of everyday electrical devices. Washington, DC: Office of Radiation and
Indoor Air, Radiation Studies Division, U.S. Environmental Protection Agency, Report No.
402-R-92-008 (1992).
Zaffanella L. Survey of residential magnetic field sources. Volume 1 : Goals, Results and
Conclusions. EPRI Report No. TR-102759. Palo Alto, CA:Electric Power Research Institute
(EPRI), 1993;1 -224.
EMF Standards and Regulations
Documentation of the Threshold Limit Values and Biological Exposure Indices, 7th Ed.
Publication No. 0100. Cincinnati, OH: American Conference of Governmental Industrial
Hygienists (2001 ).
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ICNIRP International Commission on Non-Ionizing Radiation Protection. Guidelines for Limiting
Exposure to Time-Varying Electric, Magnetic, and Electromagnetic Fields (up to 300 GHz).
Health Physics 74:494-522 (1998).
Swedish National Board of Occupational Safety and Health. Low-Frequency Electrical and
Magnetic Fields (SNBOSH): The Precautionary Principle for National Authorities. Guidance
for Decision-Makers. Solna (1996).
U.S. Department of Transportation, F.R.A. Safety of High Speed Guided Ground Transportation
Systems, Magnetic and Electric Field Testing of the Amtrak Northeast Corridor and New
Jersey Coast Line Rail Systems, Volume I: Analysis. Washington, DC: Office of Research
and Development (1993).
• Residential Childhood Cancer Studies
Ahlbom A, Day N, Feychting M, Roman E, Skinner J, Dockerty J, Linet M, McBride M, Michaelis
J, Olsen JH, Tynes T & Verkasalo PK. A pooled analysis of magnetic fields and childhood
leukemia. British Journal of Cancer 83:692-698 (2000).
Coghill RW, Steward J & Philips A. Extra low frequency electric and magnetic fields in the
bedplace of children diagnosed with leukemia: A case-control study. European Journal of
Cancer Prevention 5: 153-158 (1996).
Dockerty JD, Elwood JM, Skegg DC, & Herbison GP. Electromagnetic field exposures and
childhood cancers in New Zealand. Cancer Causes and Control 9:299-309 (1998).
Feychting M & Ahlbom A. Magnetic fields and cancer in children residing near Swedish high-
voltage power lines. American Journal of Epidemiology 138:467-481 (1993).
Greenland 5, Sheppard AR, Kaune WT, Poole C & Kelsh MA. A pooled analysis of magnetic
fields, wire codes and childhood leukemia. EMF Study Group. Epidemiology 11 :624-634
(2000).
Linet MS, Hatch EE, Kleinerman RA, Robison LL, Kaune WT, Friedman DR, Severson RK, Haines
CM, Hartsock CT, Niwa 5, Wacholder S & Tarone RE. Residential exposure to magnetic
fields and acute lymphoblastic leukemia in children. New England Journal of Medicine
337: 1 -7 (1997)4
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London SJ, Thomas DC, Bowman JD, Sobel E, Cheng TC & Peters JM. Exposure to residential
electric and magnetic fields and risk of childhood leukemia. American Journal of
Epidemiology 134:923-937 (1991).
McBride ML, Gallagher RR, Theriault G, Armstrong BG, Tamaro S, Spinelli JJ, Deadman JE,
Fincham B, Robson D & Choi W. Power-frequency electric and magnetic fields and risk of
childhood leukemia in Canada. American Journal of Epidemiology 149:831 -842 (1999).
Michaelis J, Schuz J, Meinert R, Zemann E, Grigat JP, Kaatsch P, Kaletsch U, Miesner A,
Brinkmann K, Kalkner W, & Karner H. Combined risk estimates for two German
population-based case-control studies on residential magnetic fields and childhood
leukemia. Epidemiology 9:92-94 (1998).
Olsen JH, Nielsen A & Schulgen G. Residence near high voltage facilities and risk of cancer in
children. British Medical Journal 307:891 -895 (1993).
Savitz DA, Wachtel H, Barnes FA, John EM & Tvrdik JG. Case-control study of childhood cancer
and exposure to 60-Hz magnetic fields. American Journal of Epidemiology 128:21 -38
(1988).
Tomenius L. 50-Hz electromagnetic environment and the incidence of childhood tumors in
Stockholm county. Bioelectromagnetics 7: 191 -207 (1986).
Tynes T & Haldorsen T. Electromagnetic fields and cancer in children residing near Norwegian
high-voltage power lines. American Journal of Epidemiology 145:219-226 (1997).
• UK Childhood Cancer Study Investigators. Exposure to power frequency magnetic fields and
the risk of childhood cancer: a case/control study. Lancet 354:1925-1931 (1999).
Verkasalo PK, Pukkala E, Hongisto MY, Valjus JE, Jarvinen Pi, Heikkila KV & Koskenvuo M. Risk
of cancer in Finnish children living close to power lines. British Medical Journal 307:895-
899 (1993).
Residential Adult Cancer Studies
Coleman MP, Bell CM, Taylor HL & Primie-Zakelj M. Leukemia and residence near electricity
transmission equipment: a case-control study. British Journal of Cancer 60:793-798
(1989).
Feychting M & Ahlbom A. Magnetic fields, leukemia, and central nervous system tumors in
Swedish adults residing near high-voltage power lines. Epidemiology 5:501 -509 (1994).
Li CY, Theriault G & Lin RS. Residential exposure to 60-hertz magnetic fields and adult cancers
in Taiwan. Epidemiology 8:25-30 (1997).
McDowall ME. Mortality of persons resident in the vicinity of electricity transmission facilities.
British Journal of Cancer 53:271 -279 (1986).
Severson RK, Stevens RG, Kaune WT, Thomas DB, Heuser L, Davis S & Sever LE. Acute
nonlymphocytic leukemia and residential exposure to power frequency magnetic fields.
American Journal of Epidemiology 128: 10-20 (1988).
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Wrensch M, Yost M, Miike R, Lee G & Touchstone J. Adult glioma in relation to residential
power-frequency electromagnetic field exposures in the San Francisco Bay area.
Epidemiology 10:523-527 (1999).
Youngson JH, Clayden AD, Myers A & Cartwright RA. A case/control study of adult
haematological malignancies in relation to overhead powerlines. British Journal of Cancer
63:977-985 (1991 ).
Occupational EMF Cancer Studies
Coogan PF, Clapp RW, Newcomb PA, Wenzl T8, Bogdan G, Mittendorf R, Baron JA &
Longnecker MP. Occupational exposure to 60-Hertz magnetic fields and risk of breast
cancer in women. Epidemiology 7:459-464 (1996).
Floderus B, Persson T, Stenlund C, Wennberg A, Ost A, & Knave B. Occupational exposure to
electromagnetic fields in relation to leukemia and brain tumors: a case-control study in
Sweden. Cancer Causes Control 4:465-476 (1993).
Floderus B, Tornqvist S, & Stenlund C. Incidence of selected cancers in Swedish railway
workers, 1961 -79. Cancer Causes Control 5: 189-194 (1994).
Sorahan T, Nichols L, van Tongeren M, & Harrington 1M. Occupational exposure to magnetic
fields relative to mortality from brain tumours: updated and revised findings from a study
of United Kingdom electricity generation and transmission workers, 1973-97.
• Occupational and Environmental Medicine 58(10):626-630 (2001 ).
Johansen C, & Olsen JH Risk of cancer among Danish utility workers - A nationwide cohort
study. American Journal of Epidemiology, 147:548-555 (1998).
Kheifets LI, Gilbert ES, Sussman SS, Guenel P, Sahl JO, Savitz DA, & Theriault G. Comparative
analyses of the studies of magnetic fields and cancer in electric utility workers: studies
from France, Canada, and the United States. Occupational and Environmental Medicine
56(8):567-574 (1999).
London SJ, Bowman JD, Sobel E, Thomas DC, Garabrant DH, Pearce N, Bernstein L & Peters
JM . Exposure to magnetic fields among electrical workers in relation to leukemia risk in
Los Angeles County. American Journal of Industrial Medicine 26:47-60 (1994).
Matanoski GM, Breysse PN & Elliott EA. Electromagnetic field exposure and male breast cancer.
Lancet 337:737 (1991 ).
Sahl JO, Kelsh MA, & Greenland S. Cohort and nested case-control studies of hematopoietic
cancers and brain cancer among utility worker. Epidemiology 4:21 -32 (1994).
Savitz DA & Loomis DR Magnetic field exposure in relation to leukemia and brain cancer
mortality among electric utility workers. American Journal of Epidemiology 141 : 123-134
(1995).
Sorahan T, Nichols L, van Tongeren M, & Harrington JM. Occupational exposure to magnetic
fields relative to mortality from brain tumours: updated and revised findings from a study
of United Kingdom electricity generation and transmission workers, 1973-97.
Occupational and Environmental Medicine 58:626-630 (2001).
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>�y Y.;' r'M'.. •E:y: �g�Ci '%:i(:.L y,co _!y:Ss,., . ,i 2
Theriault G, Goldberg M, Miller AB, Armstrong B, Guenel P, Deadman J, lmbernon E, To T,
Chevalier A, Cyr D, & Wall C. Cancer risks associated with occupational exposure to
magnetic fields among electric utility workers in Ontario and Quebec, Canada and France:
1970-1989. American Journal of Epidemiology 139:550-572 (1994).
Tynes T, Jynge H, & Vistnes Al. Leukemia and brain tumors in Norwegian railway workers, a
nested case-control study. American Journal of Epidemiology 139:645-653 (1994).
Laboratory Animal EMF Studies
Anderson LE, Boorman GA, Morris JE, Sasser LB, Mann PC, Grumbein SL, Hailey JR, McNally
A, Sills RC & Haseman JK. Effect of 13-week magnetic field exposures on DMBA-initiated
mammary gland carcinomas in female Sprague-Dawley rats. Carcinogenesis
20:1615-1620 (1999).
Baum A, Mevissen M, Kamino K, Mohr U & LOscher W. A histopathological study on
alterations in DMBA-induced mammary carcinogenesis in rats with 50 Hz, 100 mT
magnetic field exposure. Carcinogenesis 16: 119-125 (1995).
Babbitt JT, Kharazi Al, Taylor JMG, Rafferty CN, Kovatch R, Bonds CB, Mirell SG, Frumkin E,
Dietrich F, Zhuang D & Hahn TJM. Leukemia/lymphoma in mice exposed to 60-Hz
magnetic fields: Results of the chronic exposure study TR-110338. Los Angeles: Electric
Power Research Institute (EPRI) (1998).
• Babbitt 1T, Kharazi Al, Taylor JMG, Rafferty CN, Kovatch R, Bonds CB, Mirell SG, Frumkin E,
Dietrich F, Zhuang D & Hahn TJM. Leukemia/lymphoma in mice exposed to 60-Hz
magnetic fields: Results of the chronic exposure study, Second Edition. Electric Power
Research Institute (EPRI) and B. C. Hydro, Palo Alto, California and Burnaby, British
Columbia, Canada (1999).
Boorman GA, Anderson LE, Morris JE, Sasser LB, Mann PC, Grumbein SL, Hailey JR, McNally
A, Sills RC & Haseman JK. Effect of 26-week magnetic field exposures in a DMBA
initiation-promotion mammary gland model in Sprague-Dawley rats. Carcinogenesis
20:899-904 (1999).
Boorman GA, McCormick DL, Findlay JC, Hailey JR, Gauger JR, Johnson TR, Kovatch RM, Sills
RC & Haseman JK. Chronic toxicity/oncogenicity of 60 Hz (power frequency) magnetic
fields in F344/N rats. Toxicological Pathology 27:267-278 (1999).
Boorman GA, McCormick DL, Ward JM, Haseman JK & Sills RC. Magnetic fields and mammary
cancer in rodents: A critical review and evaluation of published literature. Radiation
Research 153:617-626 (2000).
Boorman GA, Rafferty CN, Ward JM & Sills RC. Leukemia and lymphoma incidence in rodents
exposed to low-frequency magnetic fields. Radiation Research 153:627-636 (2000).
Ekstrom T, Mild KH & Holmberg B. Mammary tumours in Sprague-Dawley rats after initiation
with DMBA followed by exposure to 50 Hz electromagnetic fields in a promotional
scheme. Cancer Letters 123: 107-111 (1998).
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Mandeville R, Franco E, Sidrac-Ghali S, Paris-Nadon L, Rocheleau N, Mercier G, Desy M &
Gaboury L. Evaluation of the potential carcinogenicity of 60 Hz linear sinusoidal
continuous-wave magnetic fields in Fisher F344 rats. Federation of the American Society
of Experimental Biology Journal 11 : 1127-1136 (1997).
McCormick DL, Boorman GA, Findlay JC, Hailey JR, Johnson TR, Gauger JR, Pletcher JM, Sills
RC & Haseman JK. Chronic toxicity/oncogenicity of 60 Hz (power frequency) magnetic
fields in B6C3F1 mice. Toxicological Pathology 27:279-285 (1999).
Mevissen M, Lerch' A, Szamel M & Loscher W. Exposure of DMBA-treated female rats in a 50-
Hz, 50 microTesla magnetic field: Effects on mammary tumor growth, melatonin levels
and 1-lymphocyte activation. Carcinogenesis 17:903-910 (1996).
Yasui M, Kikuchi T, Ogawa M, Otaka Y, Tsuchitani M & lwata H. Carcinogenicity test of 50 Hz
sinusoidal magnetic fields in rats. Bioelectromagnetics 18:531 -540 (1997).
Laboratory Cellular EMF Studies
Balcer-Kubiczek EK, Harrison GH, Zhang XF, Shi ZM, Abraham JM, McCready WA, Ampey LL,
III, Meltzer SJ, Jacobs MC, & Davis CC. Rodent cell transformation and immediate early
gene expression following 60-Hz magnetic field exposure. Environmental Health
Perspectives 104: 1188-1198 (1996).
Boorman GA, Owen RD, Lotz WG & Galvin MJ, Jr. Evaluation of in vitro effects of 50 and 60
• Hz magnetic fields in regional EMF exposure facilities. Radiation Research 153:648-657
(2000).
Lacy-Hulbert A, Metcalfe JC, & Hesketh R. Biological responses to electromagnetic fields.
Federation of the American Society of Experimental Biology (FASEB) Journal 12:395-420
(1998).
Morehouse CA & Owen RD. Exposure of Daudi cells to low-frequency magnetic fields does not
elevate MYC steady-state mRNA levels. Radiation Research 153:663-669 (2000).
Snawder JE, Edwards RM, Conover DL & Lotz WG. Effect of magnetic field exposure on
anchorage-independent growth of a promoter-sensitive mouse epidermal cell line (JB6).
Environmental Health Perspectives 107: 195-198 (1999).
Wey HE, Conover DL, Mathias P, Toraason MA & Lotz WG. 50-Hz magnetic field and calcium
transients in Jurkat cells: Results of a research and public information dissemination
(RAPID) program study. Environmental Health Perspectives 108:135-140 (2000).
National Reviews of EMF Research
American Medical Association. Council on Scientific Affairs. Effects of Electric and Magnetic
Fields. Chicago: American Medical Association (December 1994).
National Institute for Occupational Safety and Health, National Institute of Environmental
Health Sciences, U.S. Department of Energy. Questions and Answers: EMF in the
Workplace. Electric and Magnetic Fields Associated with the Use of Electric Power. Report
No. DOE/GO-10095-218 (September 1996).
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National Radiological Protection Board. ELF Electromagnetic Fields and the Risk of Cancer. Volume 12: 1 ,
Chilton, Didcot, Oxon, UK OX11 ORQ (2001).
National Research Council, Committee on the Possible Effects of Electromagnetic Fields on Biologic
Systems. Possible Health Effects of Exposure to Residential Electric and Magnetic Fields.
Washington: National Academy Press (1997).
National Institute of Environmental Health Sciences Report on Health Effects from Exposure to Power-
Line Frequency Electric and Magnetic Fields. NIH Publication No. 99-4493. Research Triangle Park,
National Institute of Environmental Health Sciences (1999).
Portier CJ & Wolfe MS, Eds. Assessment of Health Effects from Exposure to Power-Line Frequency
Electric and Magnetic Fields—NIEHS Working Group Report NIH Publication No. 98-3981 .
Research Triangle Park, National Institute of Environmental Health Sciences (1998).
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