vvEPA
United States
Environmental Protection
Agency
Air And Radiation
(ANR-459)
21A-4001
February 1991
Electric And Magnetic
Fields From 60 Hertz
Electric Power
What Do We Know
About Possible
Health Risks?
Printed on Recycled Paper
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Table of Contents
What are 60 hertz electric and magnetic 1-10
fields?
Do 60 hertz fields pose significant 10-21
health risks?
Are weaker fields safer than stronger 21-23
fields?
With all the uncertainty, what can 24-31
we do?
Do 60 hertz fields from power lines 34-36
pose significant risks to farm crops
and animals?
Who wrote this brochure? 37-38
Summary ot this brochure 39
Glossary 40
Appendix: How to learn more 43
This brochure was written by Prof. M. Granger Morgan who is Head of the Department of Engineering and
Public Policy and a Professor of Electrical and Computer Engineering at Carnegie Mellon University. He was
assisted in the preparation of the brochure by Ms. Connie Cortes. Ms. Wendy Davis. Prof. Baruch Fischhoff. Dr.
Keith Florig. Mr. Gordon Hester. Prof. Jim Hoburg. Prof. Lester Lave. Dr. Indira Nair and Dr. Emilie Roth, all of
Carnegie Mellon University, and by Dr. Paul Slovic and Dr. Don MacGregor of Decision Research (Eugene.
Oregon). While the author and his associates are solely responsible for the contents of this brochure, thanks
are due to the following for assistance with reviews: Dr. Anita Curran, Mr. Jack Lee, Prof. Kai Lee, Mr. Hamilton .
Oven, Prof. Gilbert Omenn. Mr. Jack Sahl, Prof. David Savitz. Dr. Asher Sheppard, Dr. Maria A. Stuchly. Prof.
Ola Svenson. Mr. Richard Tell, Ms. Susan White, Ms. Susan Wiltshire, Dr. Nancy Wertheimer. and several
dozen non-expert concerned citizens. The drawings in the brochure were done by Frederick H. Carlson.
Research on possible risks from exposure to 60 Hz electric and magnetic fields and the problems of com-
municating about these risks has been supported at Carnegie Mellon University by the United States Depart-
ment of Energy, the Electric Power Research Institute (EPRI) and the National Science Foundation (NSF).
Preparation of this brochure was supported by grant SES-8715564 from the National Science Foundation. Pro-
duction costs were supported by EPRI contract number RP 2955-3. Neither NSF nor EPRI reviewed, approved.
or has any responsibility for the contents of this brochure.
Copyright 1989 (Sixth Printing)
isupynynt isos (Oi*ui rummy;
This material may be reproduced for free distribution. It may not
be reproduced for sale in any form without the written permission
f\t thtA aiilhxtr
Of the author.
Department of Engineering and Public Policy
Carnegie Mellon University
Pittsburgh. PA 15213
What is the point of this brochure?
There are electric and magnetic fields wherever there is electric power. This means there
are fields associated with big and small power lines, wiring in homes and places of work,
and all electrical appliances. Increasingly scientists, regulators and lay people are asking
whether human exposure to these fields involves risks to health or the environment. A lot
of good scientific research has now been done. However, because the biological effects
of fields are complicated and still not fully understood, answers to simple questions
about whether there are risks are not straightforward. This brochure discusses in non-
technical language what is known, what is still not known, and things that might be done
about this potential risk. We have tried very hard to be balanced in our treatment, but we
have not avoided expressing judgments or opinions when we think that is necessary.
The brochure is long, and sometimes a little complicated, because the subject is
complicated.
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Why is it called 60 hertz electric power?
The electric power that we use in our homes, offices and
factories uses AC, or alternating current. This is in con-
trast to the DC, or direct current, that is produced by bat-
teries. An alternating current does not flow steadily in
one direction. It alternates back and forth. The power we
use in North America alternates back and forth 60 times
each second. Scientists call this 60 hertz (Hz) power. In
Europe and some other parts of the world the frequency
of electric power is 50 Hz rather than 60 Hz.
What are 60 Hz electric and magnetic
fields?
They are fields associated with 60 Hz power. These
fields are created by electric charges. Charges produce
two kinds of fields; electric fields which result just from
the strength of the charge and magnetic fields which
result from the motion of the charge. Taken together
these are often referred to as electromagnetic fields.
Electric fields represent the forces that electric charges
exert on other charges at a distance because they are
charged. You may recall from school that charges with
which makes a compass needle point north, is made by
flowing charges, or currents, in the earth's molten
interior. The molecules in our bodies and in all other liv-
ing and non-living things are held together by fields. The
messages that flow in our nervous systems involve
fields. When you get a shock from static electricity by
touching someone on a rug on a dry winter day, the
spark is caused by strong electric fields from the many
charges you have picked up from the rug (in more
humid weather these charges from the rug leak off. so
they don't build up as much).
-Fields may be steady (DC) or they may change their
strength and direction regularly in time (AC). Sixty Hz
electric power involves charges which move in currents
that have a frequency of 60 Hz. Thus, all 60 Hz power
produces electric and magnetic fields that change their
strength and direction with a frequency of 60 Hz. For
example, wiring and appliances in the home and office
produce such fields. Because 60 Hz power is so widely
used in our modern society, there are 60 Hz electric and
magnetic fields almost everywhere we go.
f
the same sign (two positive charges for example) repel
each other. Dissimilar charges (a positive and a negative
charge) attract each other. These forces of attraction or
repulsion are carried from charge to charge through
space by the electric field.
When charges move they create additional forces on
each other. These additional forces are carried through
space by magnetic fields. A magnetic field represents
the forces that a moving charge exerts on other moving
charges because they are moving. A group of charges
all moving in roughly the same direction is called an
electric current. All currents produce magnetic fields.
Electric fields begin on positive charges and end on
negative charges. Magnetic fields form closed con-
tinuous loops around currents. Everything that has an
electric charge has fields associated with it. Hence,
electric and magnetic fields are found throughout nature
and in all living things. The magnetic field of the earth,
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Do fields get weaker as you move away from
electrical objects?
Yes, the strengths of electric and magnetic fields
diminish as you move away from electrical objects just
as the light from a candle grows dimmer as you move
away from it or the heat from a campfire falls off with
greater distance. The drawing to the left shows roughly
how the strengths of fields decrease with distance from
transmission lines, distribution lines, and household
appliances. The different patterns result from the dif-
ferent electrical properties of the objects.
What else affects the strength of a field?
The strength of an electric field depends on the voltage
of the object creating it. For example, a high voltage
power line usually produces stronger electric fields than
a low voltage power line. Current does not have to be
flowing in the object for an electric field to exist. Thus, a
toaster or an electric blanket that is plugged in, but not
operating, may still produce an electric field.
Currents produce magnetic fields. Stronger currents
produce stronger fields. For example, the magnetic field
generated by a hair dryer will be higher when the dryer
is operated on its "high heat" setting (when it draws lots
of current) than when it is operated on its "low heat" set-
ting (when it draws much less current). However the
electric field from the dryer will be about the same in
both cases since the electric field comes from the
amount of charge (voltage), not from the movement of
charge (current). Since magnetic fields are created only
when current is flowing, appliances which are plugged
in but turned off do not produce magnetic fields.
Fields and currents that occur at the same place can
interact to add or subtract. Thus the strength of the elec-
tric'and magnetic fields associated with objects like
power lines, wiring, and appliances depends upon
things such as the location of the object, the location of
other near-by objects, and the electrical conditions of
use. Some details are provided in the box on the next
page.
Magnetic fields pass through most common objects
without being significantly affected. Electric fields
are affected by objects, especially objects that can
conduct electricity. Some of the field lines can end
on charges in the object. For example, things like
trees or a garden gazebo can partially block or
shield out electric fields from a power line. Normal
houses can also partially shield electric fields. The
amount of shielding varies somewhat with construc-
tion material. A typical house shields about 90% of
the electric field from outside. If such a house is
next to a power line that makes an electric field of
1 kV/m1 just outside the house, the electric field inside
the house will be only about 10% as large or about
100 V/m. The fraction of the electric field that a
house blocks can be increased with the proper use
of shielding materials such as grounded aluminum
roofing and siding.
1 kV/m =1000 volts/meter. (See the question "How are fields
measured?" in the box on page 6 for a discussion of the units in which
electric and magnetic fields are measured.)
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More Defa/7s About 60 Hertz (Hz) Electric And Magnetic Fields.
How are fields measured?
The strength of 60 Hz electric and magnetic fields can be measured with special instru-
ments. The words used in describing measurements of field strength sound technical,
but the basic ideas are no more complicated than measuring weight in pounds or
distance in miles. The strength of an electric field is measured in units of volts per meter,
abbreviated V/m. When the field is strong, larger units of a thousand volts per meter or
"kilo" volts per meter are used. This is abbreviated as kV/m. Several different units are
commonly used to report the strength of magnetic fields. The two most common units
are the gauss and the tesla. Like gallons and ounces or miles and feet, gauss and tesla
are just different units for measuring the same thing. The gauss is a fairly large unit so
magnetic field strength is often reported in thousandths of a gauss or "milli" gauss
(abbreviated mG). There are 10,000 gauss in one tesla. In this brochure we will use
gauss.
A number of electric utility companies now own field measuring instruments and are will-
ing to send trained technicians to make measurements in homes or other locations for
concerned customers. There are also a number of engineering consulting firms that
make measurements as a commercial service. Your local utility should be able to identify
the ones nearest to you. Before you go to any significant effort to get measurements
made, ask yourself what you will do with the information once you have gotten it.
Can the strength of fields be calculated or does it have to be
measured?
In simple situations, like a transmission line crossing an open field, field strengths can
be calculated very accurately using formulas from physics and electrical engineering.
Such calculations are often done in designing or approving transmission lines. In more
complex settings it may be harder to compute the fields because of the complex shapes
of some of the objects involved, or because the patterns of currents and voltages are
complex. In these cases, it may be easier just to measure the field rather than to try to
calculate it.
Can fields add together or cancel each other out?
Yes. Fields can add to and subtract from each other. Suppose we have set up two
separate 60 Hz electric fields at the same place in space. Each has a strength of 4 V/m
(volts per meter) and they are exactly in phase, that is, they are alternating in strength
and direction together at 60 Hz. If we measure the field we will measure 8 V/m. The two
4 V/m electric fields have added. On the other hand, if the two fields are exactly out of
phase, that is if one reaches its greatest strength in one direction exactly when the other
reaches its greatest strength in the reverse direction, we will measure a field of 0 V/m,
because the two fields will cancel. This same kind of adding and subtracting also works
for magnetic fields.
Can 60 Hz fields make currents flow in objects or change their
voltage?
Yes. Sixty Hz electric and magnetic fields move charges in conducting objects (including
our bodies). This makes currents flow. Such redistribution of.charges can also change
the voltage of an object. Strong fields "induce" stronger changes than weak fields.
If you touch a conducting object that carries an induced voltage, a "contact current" will
flow. If it is large enough you will get a shock. Contact currents from most electrical
devices, such as refrigerators or other appliances, are usually too small to feel. Occa-
sionally, they are large enough to be noticeable. For example, a high enough voltage
might be induced on a long ungrounded fence wire that runs parallel to a high voltage
transmission line to give someone an electrical shock. Similarly, a large rubber-tired farm
vehicle parked under a transmission line might give an operator a shock when he first
touches it. There are safety regulations which control the field strengths of transmission
lines to limit such "induction effects" in order to guard against injury or accidents.
Responsible utilities also take steps to correct unsafe situations along their high voltage
transmission lines and to inform people who work and live along such lines about safe
practices.
Our bodies are conducting. Hence, whenever we are in a 60 Hz field, currents will flow In
our bodies because of induction. The patterns of current flow induced by electric and ._
magnetic fields are different. In the case of electric fields, the size of the current also ,
depends on whether and how the body is grounded. Except when we are in very strong
fields, the currents that are directly induced are typically small when compared with the
contact currents we get when we touch large appliances such as a refrigerator.
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-------
Are 60 Hz fields like X-rays or microwaves?
Not really, although they are all forms of electromagnetic
energy. X-rays (and other forms of "ionizing radiation"
such as gamma rays) produce effects in living systems
because the energy carried by the X-rays is so large that
it can break molecular bonds. It can actually break apart
DMA, the molecules that make the genes. This is the
way X-ray exposure can lead to cancer. However, the
energy carried in 60 Hz fields is much too small to break
molecular or chemical bonds.
Microwaves do not carry enough energy to break
chemical or molecular bonds but they are absorbed by
the water in tissue where they can also set up strong
currents. This causes heating. This heat is what makes
a microwave oven work.2 If a person like a maintenance
worker gets right in front of a very powerful microwave
antenna, such as some of those used for radar or com-
munication, significant health damage can result from
heating body tissue. There are safety standards design-
ed to protect people from such exposure.
While 60 Hz fields can also set up currents in tissue,
these currents are much weaker. The amount of heat
they generate is trivial compared to the natural heat that
comes from the cells of the body. There is no reason to
believe that health effects can be caused by such
minuscule amounts of heat.
For many years some scientists and engineers argued
that because 60 Hz fields cannot break molecular or
chemical bonds and cannot produce significant heat in
the body they could not possibly produce significant
biological changes or effects. As we explain below, this
argument has turned out to be incorrect because there
are other ways in which fields can interact with individual
cells to produce biological changes. Whether these
changes can lead to health risks remains unclear.
Do 60 Hz fields pose health risks?
The honest answer is that nobody knows for sure. Scien-
tists have found that fields can produce a variety of
biological effects, like changes in the levels of specific
chemicals the body makes and changes in the function-
ing of individual nerve cells and the nervous system.
Whether any of these changes can lead to health risks is
less clear. We discuss many of the specifics in the sec-
tions that follow.
Scientists have also studied the statistics on death and
disease for people who are exposed to fields in their
normal course of living and work. Such studies are
termed "epidemiological studies." Some of them suggest
that there may be an association3 between field exposure
and certain forms of cancer. Other similar studies show
no such association. The evidence is not conclusive.
2Modern microwave ovens are designed to keep all the microwaves
inside. As soon as the oven turns off. the currents in the food stop. So,
once the food is taken out of the oven it is just like any other cooked
food. It has not "picked up" any radiation.
3ln epidemiology the word "association" is not a synonym for "causes"
or for "contributes to." It means that statistically the things occur
together but not necessarily that one causes the other. A more com-
plete discussion of this point occurs on page. 17.
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Some careful responsible scientists examine all the
scientific evidence and remain unconvinced that there
are any significant health risks from 60 Hz fields. Others,
equally careful and responsible, look at the same
evidence and conclude that there may be risks.
The disagreements result because the available scien-
tific evidence is complex. Current knowledge is
fragmentary and insufficient to explain everything that is
observed. Responsible scientists can have legitimate
disagreements about how the available evidence should
be interpreted. Until more scientific studies are done,
these disagreements will remain and simple yes or no
answers to questions about possible health risks will not
be possible.
As with many controversial technical problems, there are
a handful of "experts" who are less careful and responsi-
ble than they should be. They are the source of the con-
fident but contradictory statements you may have heard
which make it sound like the experts are completely con-
fused. These people complicate life because in addition
to having to come to grips with a very complicated sub-
ject, lay people and public officials have to identify and
sort out these biased experts from the majority who are
careful and responsible.
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The electric power system.
Electric power is produced by large generating plants and then transferred to homes,
businesses, and factories by a transmission and distribution system. Transmission lines
use very high voltages and go long distances. Distribution lines consist of primaries
which operate at intermediate voltages and serve a region and secondaries which bring
power to individual homes. Transmission lines, and many distribution lines, use three
"hot" wires. While the voltages on all three wires oscillate at 60 Hz, the oscillations are
not "in phase" with one another. As the voltage on one wire is peaking, the voltage on
one of the others is one-third of a cycle ahead and the voltage on the remaining wire is
one-third of a cycle behind.
For this reason, the three wires are referred to as the three phases of a power network.
Although commercial and industrial facilities use three-phase power to run large motors
and other heavy loads, the 115V power in homes is generally supplied by just a single
phase. Utility companies try to connect equal numbers of houses to each phase of a
residential distribution network in order to balance the load across the phases.
Throughout the system there are circuit breakers (not shown in the drawings) which will
automatically disconnect if a short circuit or other safety problem occurs.
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What kinds of studies of possible biological
effects from 60 Hz fields have been done?
Basically three kinds of studies have been done: 1)
laboratory studies that expose single cells, groups of
cells, or organs to fields under a variety of conditions
and look for effects; 2) laboratory studies that expose
animals or humans to fields and look for effects in body
function, chemistry, disease, or behavior; and 3) epi-
demiological studies of various human populations which
look for an association between exposure to 60 Hz fields
and various diseases.
You said that 60 Hz fields can have some
biological effects. Just what do you mean
by that?
There are two basic kinds of effects that have been
observed. Strong electric fields can stimulate the skin of
animals, by vibrating hairs or by triggering various sen-
sors in the skin. If a person stands in an electric field of
more than about 20 kV/m he or she is likely to feel a
slight tingling sensation. There have been a variety of
studies which indicate that animals can also feel strong
electric fields. People cannot sense the presence of
magnetic fields.4 While these "perception" effects are
interesting, and have received quite a lot of research
attention, few people ever spend time in fields that are
strong enough to be felt.
Potentially more important results come from experi-
ments which show that under certain circumstances
fields can interact with the surfaces of cells and trigger
changes inside these cells. Modern biology tells us that
the surface of the cell is made up of a double layer of
"phospholipid" molecules, similar to a double-layered
soap bubble. In this "bi-layer" float various large complex
molecules which act as receptors to communicate
4There are exceptions. People can sometimes sense the presence of
extraordinarily strong magnetic fields because these fields cause
flashes of light in the eye. However, fields this strong are found only in
laboratories and other special situations. Some animals have
developed special exquisitely sensitive sense organs that can sense
the presence of very weak electric or magnetic fields. These organs
are used in navigation and in looking for prey. While they are very
special, the existence of these organs makes it clear that at least
some biological systems can be affected by very weak fields.
between the cell and its surroundings and to serve as
channels that can move selected material into and out of
the cell.
While the details remain unclear, a variety of experiments
have shown that fields, even fairly weak fields, can inter-
act with the cell surface, or with some of the receptor
molecules in that surface, and produce changes in how
the cell operates. The fields contain very little energy. In
some way the cell surface or its receptors act as an
amplifier to send a signal into the cell that can change
things like the rate at which the cell makes hormones,
enzymes and other proteins. These chemicals play roles
in the operation of the cell and in signaling to other cells
and tissues.
What kinds of specific findings have been
reported from the laboratory studies?
While a number of biological effects have now been
observed, they haven't been easy to find. Early studies
of fields exposed large numbers of rats, mice and other
animals, as well as various individual cells to see if
anything happened. Most of these "screening studies"
didn't find any differences between animals or tissues
exposed to fields and those not exposed to fields. The
few studies that did find interesting changes have been
followed up with more detailed experiments. Effects that
have been reported include: changes in the production
of various chemical messengers, including chemicals
like melatonin that are important in daily biological
cycles called circadian rhythms, and chemicals called
neurotransmitters which send signals between nerves;
changes in the rate at which the genetic material DNA is
made and in the rate of errors when RNA is copied from
it; changes in the amount of calcium found inside or on
the surface of cells; and changes in the rate of growth
and cell division of some cells. While all of these effects
may prove significant for our eventual understanding of
how fields affect cells, it is important to understand that
some of the experiments involve conditions that are very
different from those that occur when people are exposed
to fields.
Most studies have used individual cells or animals, but
there have also been a few which have used people.
Studies of people exposed to fairly strong fields in
special exposure rooms have reported effects on heart
rate and on reaction time. There is some indication that
some people respond more than others. Some of the
effects appear to be more pronounced when the fields
are turned on and off repeatedly rather than left on con-
tinuously. Studies which have sent weak currents
through volunteers with electrodes attached to their skin
report no observed effects after exposures of several
hours. Studies of people sleeping with electric blankets
report changes in the level of the hormone melatonin.
All these different effects or biological changes are inter-
esting. However, it is not clear if they have significant
implications for people's health.
If you would like to look at some detailed reviews of the
health effects literature you can find an introductory
guide to reviews of that literature in the Appendix at the
end of this brochure.
-------
What about the studies of cancer?
There have been two kinds of "epidemiological" studies
which have looked for an association between exposure
to 60 Hz fields and cancer. The first set of studies has
looked at the death rates from different diseases for peo-
ple who are employed in "electrically related" occupa-
tions and compared them with the death rates from the
same diseases for all other people. The second has
compared the magnetic field exposures received by
people with specific cancers, especially leukemia, with
the exposures received by other similar people who did
not have cancer. Most of these latter studies have
involved exposure at home from power distribution lines
(lines on the big poles in the street). The cancer that has
been studied the most is childhood leukemia.
Some of these studies of both kinds have found a statis-
tical association between increases in field exposure
and increased cancer rates. As we discuss on the next
page in an example involving roosters and sunrise, the
phrase "statistical association" is not a synonym for
"causes" or for "contributes to." Depending on the study
and the type of cancer, the incidence of cancer in
exposed populations may be up'to two to three times
higher than that experienced by unexposed or less
exposed populations.5 Most of these cancers are fairly
rare, for example childhood leukemia affects about one
in every 14,000 children per year or about 1 in 1,100 per
lifetime. A two-fold increase would raise the incidence to
one in 7,000 per year or 1 in 550 per lifetime.
Many investigators believe that if they play some role,
fields alone will not turn out to cause cancer (i.e. fields
will not be an "initiator"). Rather they are more likely to
work together with one or more other environmental fac-
tors (i.e., fields will be a "promoter")-
All of the epidemiological studies involve some level of
statistical uncertainty. The results are summarized in the
figure on the next page with bars that show "confidence
intervals." Studies in which the confidence interval
includes the result "no change in the rate of cancer
incidence" are generally referred to as negative studies.
The others are generally referred to as positive studies.
The two most widely discussed positive studies involve
childhood leukemia. Both were conducted in the Denver,
Colorado, area, the first by Nancy Wertheimer and Ed
Leeper, the second by David Savitz and several col-
leagues. Both these two studies, which involve different
groups of children, report an increase in the incidence
of childhood leukemia in homes close to heavy duty
distribution linesthe big wires found on the tops of
many large poles in the street. Other studies demonstrate
that these lines typically produce strong magnetic fields.
It is important to remember that the positive epidemio-
logical studies show a statistical association. They can-
not prove that fields are involved in causing cancer. For
an illustration of a statistical association that does not
show causation, consider the fact that roosters crow
every morning and on most mornings a little while after
the rooster crows the temperature rises. A statistical
study would show a correlation between roosters crow-
ing and rising temperatures. In this case we know that
the sunrise causes both of these phenomena. Despite
the statistical association, the crowing rooster is not
causing the temperature to rise!
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There is great controversy about whether the various
epidemiological studies show any true relation between
field exposure and cancer. Some careful responsible
scientists argue that they do. Other responsible scien-
tists point to a variety of very real problems in the design
and interpretation of these studies. They argue that the
reported findings may be the result of statistical prob-
lems or that the cancers may come from various other
causes. For example, most of the occupational studies
have not "controlled" for other important known car-
cinogens such as smoking and chemicals in the work
place. The number of people exposed to the strongest
fields in the Denver studies is small. This increases the
chance that the results are due to coincidence rather
than to a real association between field exposure and
cancer. Such uncertainty, and the resulting debate about
the meaning of data, are fairly common occurrences in
epidemiological studies. Resolution of these issues will
require more and better data. Additional epidemiological
studies are now in progress. However, in the past when
epidemiological studies have succeeded in clearly iden-
tifying a hazard (e.g., cigarettes or asbestos) the risks
have involved increases of more than tenfold. If fields
present a risk of cancer, but the increase in risk is some-
thing like two or three, epidemiology may never be able
to resolve the uncertainty. For this, large expensive
animal studies may be necessary.
You can find references to more detailed introductions to
some of the epidemiological literature in the Appendix at
the back of this brochure.
5ln contrast, cigarette smoking increases the risk of lung cancer by 20
to 60 times.
8
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Suppose 60 Hz field exposure does promote
cancer. How serious could the problem be?
There are just under half a million deaths each year
from cancers of all kinds in the United States. Cancers
account for roughly a quarter of all deaths. Cancer
deaths occurred in significant numbers well before 60
Hz fields became a common feature of everyday life.
Their number has not shown any dramatic increase as
the country has electrified. Hence, it seems unlikely that
fields could be a major contributor to cancer today. How-
ever, with the evidence now available we cannot rule out
the possibility that 60 Hz fields are a significant factor in
cancer risks. Frustrating as the uncertainty may be, we
also cannot rule out the possibility that fields have
nothing to do with cancer.
Besides cancer, are there other health
effects of possible concern?
Research on cancer has received most of the attention.
However, work has also been done to explore the
possibility of birth defects using mice, rats and small
pigs. The mouse and rat studies showed no convincing
evidence of birth defects from exposure to fields.
Results in the pig study are more ambiguous and are
complicated by several problems in the way the experi-
ment was designed and conducted.
A large study, recently completed in several laboratories,
exposed chicken eggs to short pulses of magnetic fields
that repeated at 100 times per second (100 Hz). The
pulses used turned on rapidly. This study observed a
larger fraction of defects in exposed eggs than in eggs
that were not exposed to fields. Because the fields were
very different from 60 Hz fields and the defects were not
found in all the laboratories, the implications of these
results for 60 Hz field exposure are not clear. There are
many electronic products'like video displays, TVs, speed
controllers and dimmer switches which produce low fre-
quency pulsed fields which turn on rapidly, so these
results cannot be ignored.
Scientists are now conducting a large study of the pos-
sible effects of electric blankets on human pregnancies.
Earlier studies of this issue have been suggestive but
have involved too few women to allow reliable
conclusions.
Some animal studies suggest 60 Hz fields may interact
with the system that runs the body's biological clock (cir-
cadian rhythm) or with the nervous system. There is
some reason to think that field exposure might be
involved in chronic depression or other systemic
neurological disorders. However, there is so little
evidence about these effects that, at this point, such
arguments are really just speculation.
If there is a risk, are weaker fields safer than
stronger fields?
Experience with hazards like air and water pollution lead
most people to answer yes. But we must be careful. If
we are talking about very weak versus very strong fields
the answer probably is yes. But suppose we are talking
about smaller differences. For example, if fields pose
any risk, is an electric field of 50 V/m safer than a field of
200 V/m? Is a magnetic field of 3 milli-Gauss safer than
a magnetic field of 10 milli-Gauss? We do not know.
Some people use the epidemiological evidence to argue
yes. But there are also reasons to believe the answer
could be no. If fields do pose a risk, at these levels of
exposure, weaker fields may not be safer than stronger
fields. In short: more may not be worse. This is a hard
point to understand because more is worse for most
pollutants. More is worse for chemicals in drinking water,
or for air pollution. How could this simple rule not hold
for 60 Hz electric and magnetic fields?
The reasons for doubt come mainly from the laboratory
experimental studies. Some of these studies show very
complex relations between exposure patterns and ef-
fects. For example there are experiments that show
"resonant" processes. That is, effects appear for fields
with some frequencies and field strengths (amplitudes)
and not others. A simple way to understand this is to
think of a yo-yo. A yo-yo is a "resonant system." To make
it go you must move your hand up and down at the right
times (that is at the right frequency) with just the right
amount of distance (the right amplitude). If you do use
the right frequency and amplitude, the yo-yo works. If
you don't, the yo-yo doesn't work. Some of the processes
by which fields interact with the surfaces of cells appear
to have these same "resonant" characteristics. Thus, for
example there are experiments that show no effect with
a strong field but, when the field strength is reduced a
little bit the effect appears. In at least some of these
experiments it appears that the frequencies and ampli-
tudes at which the resonant responses occur depend
upon the strength of the DC (i.e. steady) magnetic field
that is present.
There are other experiments in which biological effects
are seen only after being in the field for a very long time.
In other cases, effects appear above a certain field
strength but then show no additional changes as field
strength increases further. Some effects appear only for
the first few moments in the field. Others are seen only
with pulsed fields that have special pulse shapes. It will
be some time before scientists can sort out all this com-
plicated evidence and explain it. In the meantime, it
seems wise not to assume that weaker fields are neces-
sarily safer than stronger fields, at least across the
range of commonly experienced fields.
10
-------
What is dose?
We do not know what aspect of fields (if any) is important in determining human risks
from exposure to 60 Hz fields. It could be the average peak field strength; it could be the
peak field strength; it could be the average or the peak current which the fields set up in
the body; it could be a variety of other things like time spent in the field, or number of
times you pass into or out of the field. The problem is that since we do not know which is
the right measure we have difficulty saying which source of exposure gives people the
greatest "dose." The word "dose" means exposure that produces effects. As the figure
below shows, you get different answers to the question "which source of fields produces
the biggest exposure" depending on what measurement you look at.
1
" *OLui «*'«"
, 1
1
1
.,
I-6") .-,
(Miwtff ftr "*[
*y,l4{o "\
«/«ty,
may. )
frvaseei
\
\
1 i
9 i
B i i
' ' 1
1 1 I g
s ' ' ' s
1 , t - s
111
I "
11
-------
What can be done? What should be done?
First, continue and expand the research, focusing
especially on issues of human health, so that we can
have some clear answers. Almost everyone who has
thought carefully about the issues of 60 Hz fields agrees
that this is needed. Unfortunately, many of the busy
decision makers who control the resources that are
needed for this support have not thought as much about
this issue as they need to. They need to be better
informed.
Second...well, here things get difficult. It would be nice if
we could spell out a few clear conclusions about
actions. We can't. The reason is that the science is not
complete enough today to support such conclusions.
Anything more we say will go beyond science and
involve judgments and values. Basically there are three
approaches available:
1. Conclude that there is not yet enough evidence to
warrant any action. Don't make any changes in the
way we do things until new research tells us clearly
whether there is a risk and, if so, how big it is.
2. Conclude that there is some-basis for concern. Adopt
a position of "prudent avoidance," which means
limiting exposures which can be avoided with small
investments of money and effort. Don't do anything
drastic or expensive until research provides a clearer
picture of whether there is any risk and, if there is,
how big it is.
3. Conclude we have a real problem and spend some
serious time and money on an aggressive program of
limiting field exposures now, while recognizing that
we may eventually learn that some or all of this effort
and money has been wasted, either bepause it wasn't
needed or we spent it the wrong way because we
didn't understand the science well enough to spend it
effectively.
In the three questions that follow we discuss the pros
and cons of each of these, possible conclusions.
Can we justify doing nothing?
Some people answer yes. They argue that doing nothing
is the right response given the scientific ambiguity that
exists today.
Whether we should do nothing, exercise "prudent
avoidance," or take more dramatic action is not a scien-
tific question. It is a matter of making a value judgment.
Individuals and state regulators have to look at the
available evidence. They must also consider the attitude
they want to take toward risk. Then they must make a
judgment about whether they find the evidence suffic-
iently troubling to warrant taking action and spending
resources that might be spent on other things. Different
attitudes toward risk can lead to different actions even
among people who agree about the evidence. Some
people have concluded that the current scientific
ambiguities about possible health effects from fields are
so large that no action is justified at this stage. They
argue that we should limit our safety efforts and expen-
ditures to demonstrated hazards where we can really be
sure we are getting some benefits for our efforts.
What are the arguments for "prudent
avoidance"? Why do you use the word
prudent?
If exposure to fields involves risks, we'd like to be able to
set some safety standards. We'd like to be able to say
which field conditions are safe and which are not and
should be avoided. If you have read the earlier discus-
sion you've learned that the available scientific knowl-
edge won't allow us to do this.
But suppose an individual or a regulator is concerned,
thinks the evidence points toward the possibility of some
risk, and feels that something should be done. In this
case, they can try to exercise some prudence by keep-
ing people out of fields when this can be done with
modest amounts of money and trouble. However, in cir-
cumstances where the cost and problems associated
with doing anything would be large, these people would
argue that the prudent thing to do is wait until better
information is available.
In our private lives we exercise prudence all the time
when we face an uncertain risk. In public decision mak-
ing we have more trouble being "prudent" about uncer-
tainty. Public risk management activities tend to treat
things as either dangerous or safe, with no middle
ground. It may take some guts for a regulator to adopt a
"prudent avoidance" strategy.
Prudence means "exercising sound judgment in prac-
tical matters." It means being "cautious, sensible, not
rash in conduct." How, for example, are people prudent
about cancer in their private lives? They don't smoke.
They eat diets with little charbroiled food and lots of
fiber. Bur prudent people do not: refuse to go to an
important business meeting because one of the par-
ticipants occasionally smokes; go without breakfast
when all that is available on the menu is regular cereal
rather than their usual high fiber cereal; or, order lobster
for their children because it is the only food on the menu
that isn't charbroiled. Prudence means you take steps to
control risks but at a modest cost. You keep some sense
of proportion and you don't go overboard.
How could prudent people manage their risks from 60
Hz electric and magnetic fields if they wanted to? Not by
tearing all the wiring out of their house. That would be
extreme. But, they could put away their electric blanket
(or electrically heated water bed) and go back to using
12
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regular blankets.6 Or, they could use the electric blanket
to pre-heat the bed, and then unplug it before going to
bed (the magnetic field disappears when the blanket is
switched off, the electric field may remain as long as the
blanket is plugged in). Small electric motors produce
strong magnetic fields. If you want to reduce your field
exposure you might look around for small electric
motors that you are often close to. For example, a motor
driven electric clock on your bedside table may produce
a fairly strong magnetic field by your head. If you want to
practice prudent avoidance you could move it to a
dresser across the room or replace it with one of the
newer digital clocks or with a travel clock or wind-up
clock.
If you are buying a new home it might be prudent to con-
sider the location of distribution and transmission lines
as one of many things you consider. However, remember
that even if fields are ultimately demonstrated to pose a
health risk, things like traffic patterns in the streets and
radon levels in the house are likely to be more important
for your own or your children's overall safety than
anything related to fields. If you are already in a home,
moving in order to get away from existing lines goes
beyond what we would consider prudent.
State regulators who wish to exercise prudence about
the exposures that people receive from power lines
should, until more is known, limit their concern to new
facilities. This is because even under the most
pessimistic assumptions it is hard to justify the costs of
modifying old facilities. Regulators who want to exercise
prudence should site new facilities so as to keep people
or
out of fields, but only up to some practical limit. Spen-
ding amounts as high as a few thousand dollars to avoid
exposing someone might be justified.7 Much larger
expenditures can almost certainly not be justified. There
are various ways to implement prudent avoidance.6 Set-
ting a field strength limit for the edge of the right of way
may not be the best strategy. However, if this approach
is chosen, regulators should make it clear that they are
motivated by a desire to achieve "prudent avoidance"
and that the levels chosen do not constitute "safe field
levels." We just don't know how to choose such levels to-
day.
Can an aggressive program of regulation
and control be justified?
Taking more drastic action than that indicated by "pru-
dent avoidance" will cost a lot of money and create a fair
amount of disruption. Few people would object if they
were confident that 60 Hz fields pose a serious health
risk. But, because our understanding of the science of
this problem is still very incomplete, there is a real
chance that some or all of the expense and associated
trouble that would result from "aggressive action" taken
now, would ultimately turn put to have been ineffective.
There are two ways this could happen. First, it could
turn out that there are no health risks from fields or that
there are risks but they are very small. Second, it could
turn out that while there are risks, we've done the wrong
things to control them and gotten little or no improve-
ment for our money because of our incomplete under-
standing of dose (see the discussion on "more may not
be worse" on page 11).
In our discussion of the strategy of "prudent avoidance"
we argued that today it is hard to justify spending more
than a few thousand dollars per person exposed in order
to reduce exposures. We said this because we believe
that if fields pose health risks, only a very small fraction
of all the people exposed can be expected to develop
adverse health consequences (probably no more than
one in many thousands). That means that spending a
few thousand dollars per exposure avoided amounts to
spending millions of dollars or more per possible health
effect avoided.9
"There may be a few people, such as those who have circulatory prob-
lems, for whom an electric blanket is very important. For these people
the cost of going without an electric blanket may be too high to make
this a prudent step.
7If exposure to fields does involve health risks, only a small fraction of
those exposed are likely to have their health affected. Hence, an
investment of $1000 per exposure avoided could amount to an invest-
ment of millions of dollars or more per health effect avoided.
"Readers interested in more detailed discussions of this issue and the
judgments involved can find them in two articles by Granger Morgan,
Keith Florig, Indira Nair and Gordon Hester: "Controlling Exposure to
Transmission Line Electromagnetic Fields: A regulatory approach that
is compatible with the available science," which appeared in Public
Utilities Fortnightly, March 17.1988, pages 49-58 and "Power Frequen-
cy Fields: the regulatory dilemma," which appeared in Issues in
Science and Technology, Summer 1987, pages 81-91.
*The U.S. spends up to a few million dollars per death avoided in job
safety programs. However, it only spends a few hundred thousand
dollars per death avoided on more common risks like preventing motor
vehicle accidents. The amount most people want to spend to avoid
risks depends on other things besides the odds of death. Considera-
tions such as equity, controllability and the extent to which exposure is
voluntary are all important. Thus, the arguments that follow are
approximate.
13
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If someone concludes that drastic action on fields is
appropriate today, and does not wish to make safety
expenditures for fields which are dramatically larger
than the expenditures we make to guard against other
risks in our society, they must have concluded that the
health risks from fields are significantly more common
than one in several thousand people exposed.10
In order to understand what this means, consider the
table on the next page which lists the approximate
number of deaths that occur each year in the United
States from a variety of causes. For example, auto
accidents kill about 50,000 of the roughly 2,100,000
Americans who die each year. This means that when the
average American dies, the chances are about 1 in 40
that his or her death will result from an auto accident.
10
Remember that there have not been dramatic increases in the
numbers of deaths or illnesses as electrification has occurred. Of
course, on the other hand, some might argue that the improvements in
life expectancy that have occurred over the past half century might
have been even greater without field exposure.
We argued above that someone could justify "aggressive
action" today only if they believe that the lifetime risk
faced by people exposed to fields is well above one in
several thousand. Electrocution has an average lifetime
mortality risk of about 1 in 2500. Appendicitis has an
average lifetime mortality risk of about 1 in 4000. That
means that someone would have to believe that the risk
of death in populations exposed to fields is as large as
those risks faced by the general population that lie well
above the shaded band in the table before they would
be justified in calling for "aggressive action" today. If you
think the risk, if any, for exposed people probably does
not lie well above this shaded band, you should seriously
consider selecting either the strategy of "prudent
avoidance" or "no action," at least until the situation is
better understood. Otherwise you will end up calling for
society to spend far more to protect its members against
possible deaths from this uncertain risk than it does to
protect its members against deaths from other known
risks.
.Data on Deaths in the United States.
Cause of
death.
Approximate number of
Americans who die each
year from this cause.
Approximate odds that
when the average American
dies it will be from this cause.
Disease (all kinds)
Heart disease
Cancer (all kinds)
Accidents (all kinds)
Auto accidents
Diabetes
Suicide
Homicide
Drowning
Fire
Asthma
Swarm accidents
Viral hepatitis
Electrocution
Car-train accidents
Appendicitis
Pregnancy and related
Lightning
Floods
Tornado
Fireworks
Botulism
2,000,000
770,000
480,000
95,000
48,000
37,000
31,000
21,000
5,900
4,800
4,000
1,500
1,000
850
570
510
470
78
58
58
8
2
1 in 1.1
1 in 2.7
1 in 4.4
1 in 22
1 in 44
1 in 57
1 in 68
1 in 100
1 in 360
1 in 440
1 in 530
1 in 1400
1 in 2100
1 in 2500
1 in 3700
1 in 4100
1 in 2200
1 in 27,000
1 in 36,000
1 in 36,000
1 in 260,000
1 in 1,100,000
Notes: The total population of the United States is about 242,000,000. About 2,100,000
Americans die from all causes each year. The table reports data for some of these
causes. The numbers in this table have been rounded to two figures (for example, 67.742
is reported as 68). The odds reported in the right-hand column are for the average
American. Note the odds reported for pregnancy and related causes are only for women.
Since people have different backgrounds and behaviors the individual risks they face will
generally be somewhat different than these numbers. For example, someone who never
smokes will probably have a smaller risk of dying from cancer than the 1 in 5 odds
reported here. Someone who scuba dives frequently probably stands a higher chance of
drowning than the average American. Numbers based on Vital Statistics for the United
States, 1986, U.S. Dept. of Health and Human Services publication PHS88r1122,
Washington, DC, 1988.
14
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Haven't some states passed standards for
fields from transmission lines?
Yes, several states have established standards for the
strength of electric fields from high voltage transmission
lines and Florida has also established magnetic field
standards. While some of these have been set as "safe
field" standards, some states, especially Florida, have
understood that with the incomplete science now
available only "prudent exposure avoidance" can be
used as a justification for establishing a standard. Cur-
rent state standards are summarized in the table on the
top of the next page. No states have set standards for
distribution lines.
State regulations that limit field strengths
on transmission line rights of way
State
' Field Limit
Montana 1 kV/m at edge of RoW in residential areas
Minnesota 8 kV/m maximum in RoW
New Jersey 3 kV/m at edge of RoW
New York 1 £ kV/m at edge of RoW
North Dakota 9 kV/m maximum in RoW
Oregon 9 kV/m maximum in RoW
Florida 10 kV/m (for 500 kV), 8 kV/m (for 230 kV)
maximum in RoW
2 kV/m at edge of RoW all new lines,
200 mG (for 500 kV single circuit), 250 mG (for
500 kV double circuit) and 150 mG (tor 230 kV)
maximum at edge of RoW
Other Things People Sometimes Ask About.
How about cardiac pacemakers? Can strong fields affect them?
Most modern cardiac pacemakers are unaffected by even the fairly strong fields produced
by high voltage transmission lines. The operation of a few models, including a number
manufactured by Cordis, reportedly have been affected by strong 60 Hz fields. If you use
a cardiac pacemaker, it is best to consult with your physician before going into strong
fields.
What about being close to water? Would that figure In any health risk
from 60 Hz fields?
No. There Is an electrical hazard associated with being dose to water: a greater chance
of shock and electrocution. If you are in water you are usually well grounded. If. while
you are well grounded, you touch something like a defective electric appliance you could
get a much more severe shock than you would get if you touched it when you were not
weU grounded. This is one reason why you should never use appliances in the bath
(another is the electrocution risk if the appliance is dropped in the bath water, which
would have the effect of connecting you to the electric line).
But, none of this has anything to do with possible health risks from 60 Hz fields. If there
are such risks, there is no reason to think that being close to water, such as lakes or
rivers, would have significant consequences.
Is there some link between fields and ozone?
None that is of any environmental importance.
If an electric field is strong enough it can break down or 'ionize" molecules in the air and
cause sparks or torona" This can generate small amounts of ozone. K also makes the
crackling noise you may have heard around some high voltage lines, ft takes energy to
make corona. Since energy costs money, electric companies try to design high voltage
power lines so as to minimize corona. The conditions under which air will break down
depend a bit on weather. Sometimes, especially in foggy or humid weather, very high
voltage lines will produce corona. When this happens small amounts of ozone are
generated.
The amount of ozone generated by a power line is much less than the amount generated
by other sources such as factory emissions and motorvehicle exhaust. Ozone produced
by power lines is not a significant contributor to local or regional air pollution problems
and poses no significant risk to people or the environment.
While some places have an air pollution problem resulting from too much ozone in the
low atmosphere (the troposphere), you may also have heard that there is not enough
ozone in the high atmosphere (the stratosphere). Ozone in the stratosphere is important
because it blocks out ultraviolet light from the sun. Air in the troposphere does not usually
mix with air in the stratosphere. Power lines and 60 Hz fields have nothing to do with the
issue of stratospheric ozone.
Material oeTongs to:
Office of Toxic Substances Library "~
U.S. E.V.-;.-.;,---,. ,, ^-.election Agency
401 M ': -.;. TJ-793
W;ishi::^::,b.C. 20460
(202) 382-3944
15
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Are there standards for field exposure
outside the U.S.?
Standards or guidelines for exposures to power-
frequency electric fields exist in Britain, Japan, Poland,
and the Soviet Union. These foreign standards are not
significantly different than state standards in the U.S. For
example, guidelines in the Soviet Union recommend that
fields in publicly-accessible areas be no greater than 10
kV/m and that fields in permanently occupied areas be
no greater than 2 kV/m. There are presently no national
regulations in any country limiting exposures to power-
frequency magnetic fields from power lines or
appliances.
The International Radiation Protection Association,
whose mission is to review scientific evidence and pro-
pose safety standards, has issued draft exposure guide-
lines for power-frequency electric and magnetic fields.
They call for a limit of 5 kV/m for continuous exposures
to electric fields and 2 Gauss (2000 mG) for magnetic
fields.
Do 60 Hz fields from power lines pose
significant risks to farm crops and animals?
The answer is a simple no. There have been quite a
number of studies of field crops grown in strong fields.
There have also been quite a number of studies of
things like meat and milk production. All of these studies
show no significant effects.
If it turns out that fields do pose health risks to people,
similar effects may of course be seen in farm animals.
But even under the worst assumptions, these effects
would be pretty rare. They might be common enough for
us to worry about them as a health risk in people, but
they will be rare enough that they will have no significant
economic implications for farmers. For example, skin
cancer from sunlight is something we as people worry
about. But farmers don't worry about their pigs getting
skin cancer. It's just too rare to matter. That is why we
say the answer to this question is a simple no.
There is one aspect of electric power that can have very
real implications for dairy farmers. This is the so-called
stray voltage problem. When metal feeders, water
troughs, or milking machines are inadequately grounded,
cows can be subjected to small but perceptible electrical
shocks. This can lead to changes in animal behavior
(reluctance to enter a milking stall for instance) and
reductions in milk production. The problem can usually
be fixed with proper grounding or other technical pro-
cedures. The problem does not come from the direct
effect of exposing the cows'to fields.
The only other situation that has been identified in
which power lines can be important in agriculture is
when bee hives are installed directly underneath very
high voltage power lines. Again the problem is not from
exposing the bees to the field. Rather it comes from
voltages that are induced in the hive. Effectively, the
bees get shocks as they walk around and, not surpris-
ingly, .honey production can drop substantially. If a
shield, such as a piece of grounded chicken wire, is
installed over the hive, then the problem is eliminated
and honey production returns to normal. Still, it is best
not to locate bee hives under transmission lines.
Do 60 Hz fields pose significant risks to the
environment?
As with agriculture, the answer is again a simple no.
Studies of trees and ecosystems have shown no signifi-
cant effects from 60 Hz or other low frequency electric
and magnetic fields. As with agriculture, if there do turn
out to be health risks for people we might expect to see
occasional effects in other living things as well. But even
under the worst conditions these effects will be so rare
that they will only involve individual plants and animals
and will not affect the operation of the overall
ecosystem.
Some migratory animals like birds and fish appear to
use naturally occurring fields as one of their cues in
navigation. However there is no evidence of manmade
fields from power lines, radio antennas or other field
creating objects causing serious disruptions.
There are experimental studies in which coniferous
trees (pines, spruce, firs, etc.) grown right next to very
high voltage power lines have experienced needle
damage. This is because the fields at the tips of the
needles on these trees were so high that they caused
the air to break down electrically (like the blue flashes
you may see when you stroke a cat in the dark on a dry
winter night). Normally trees are trimmed far enough
back from transmission lines to preclude this effect.
16
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Who is supporting research on possible
health risks from 60 Hz electric and
magnetic fields?
In the United States major support for research on
possible health risks from low frequency electric and
magnetic fields comes primarily from the Electric Power
Research Institute (EPRI), the U.S. Department of Energy
and the U.S. Navy. In the past there was substantial sup-
port from the State of New York but most of this has now
ended. In the past there was also modest support from
the Environmental Protection Agency but that has
stopped. Several individual utilities, including Bonneville
Power Administration and Southern California Edison,
support research.
After a number of years of growing support, the past few
years have witnessed a marked decline in the level of
federal support. Department of Energy expenditures fell
from a high of just under $5 million in 1985 to about $2
million in 1988 but have apparently now begun to recover.
The drop in funding was not because the problem had
been solved. Quite the contrary. The funding drop simply
resulted from general federal budget cutting. If the 60
Hz fields problem is ever going to be properly under-
stood, a strong and stable program of federal research
support will be necessary.
Outside of the United States there are significant
research programs underway in a number of other coun-
tries including (in approximate descending order of
funding levels) Sweden, the United Kingdom, West
Germany, Canada, Japan, Italy, France, Finland, and
Norway. Some research is also being done in the Soviet
Union, Eastern Europe and China.
Most research has focused on possible health effects.
Recently EPRI has begun research on how fields asso-
ciated with electrical systems might be reduced. More
work on this issue is needed, especially for distribution
lines, house wiring, and appliances.
Who wrote this brochure?
As we explained on the inside of the front cover, the
primary author for this brochure was Dr. Granger
Morgan of Carnegie Mellon University. He had help from
a number of colleagues. Before the brochure was pub-
lished it was reviewed by a large number of experts and
lay people who offered extensive advice on how the
brochure could be improved. While we followed much of
this advice, the final product is Dr. Morgan's responsibil-
ity. The judgments expressed in the brochure are his.
Granger Morgan is Head of the Department of Engineer-
ing and Public Policy at Carnegie Mellon University
where he is also a professor in the Department of Elec-
trical and Computer Engineering. He was trained in
science and engineering at Harvard, Cornell and the
University of California. He has worked for many years
on environmental problems and in risk analysis. Most of
his work on these topics has been funded by the U.S.
National Science Foundation. He has served as a
member of a number of scientific advisory panels for the
U.S. Environmental Protection Agency. He is currently a
consulting member of the EPA's Clean Air Science
Advisory Committee. He is a Fellow of the Institute of
Electrical and Electronics Engineers.
In 1982 Dr. Morgan was asked by the U.S. Department of
Energy to put a group together at Carnegie Mellon to do
risk analysis on the issue of possible risks of 60 Hz
fields. The group studied the problem intensively for
three years, carefully reviewing the scientific literature,
visiting many of the key investigators in their laboratories,
and participating in many national research conferences.
The Carnegie Mellon group has published a number of
research papers on the risk and public policy aspects of
this subject. However, because of the many scientific
ambiguities in the field, the group concluded that it
would not be possible to perform a meaningful risk
assessment on 60 Hz fields until more complete scien-
tific understanding was available. Rather than continue
to use up scarce DoE research money they informed
DoE of their conclusion and the work ended.
More recently, both the Department of Environmental
Resources of the State of Florida and the Office of
Technology Assessment of the United States Congress
have contracted with Dr. Morgan and his associates for
help in dealing with assessment and regulatory prob-
lems related to 60 Hz fields.
Dr. Morgan has worked hard to remain impartial on this
very controversial topic. He has never testified on behalf
of any electric utility company. He has never been a par-
ticipant in any power line siting controversy. The bulk of
his research support has been, and remains, in areas
outside of the topic of 60 Hz fields.
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Summary of This Brochure
Here's a brief summary of the key points in this brochure.
Electric and magnetic fields are found throughout nature and in all living things. They
hold matter together. They are necessary for the operation of the nervous system.
60 Hz (60 cycles per second) electric and magnetic fields come from electric power.
They are found around all electrical appliances, house wiring, power lines in the
street, and high voltage transmission lines.
There is clear evidence that 60 Hz fields can produce various hormonal and other
changes in living things. It is not yet clear if these changes can result in risks to public
health.
Possible risks of concern include the promotion of cancer (i.e. helping the growth of
existing cancer); developmental abnormalities (i.e. birth defects); and various
neurological effects such as chronic depression.
There have been many very good scientific studies of the possible health risks of
fields. Taken together, the results are very complicated. Careful and responsible scien-
tists do not yet agree on whether 60 Hz fields pose a risk to public health and, if they
do, how serious that risk might be.
It is not clear what aspect of 60 Hz fields (if any) poses a risk. There is evidence that
suggests that across the range of field strengths commonly encountered by people,
stronger fields may not pose greater risks than weaker fields. This means that the
usual assumption that "more is worse" may not be correct for the case of 60 Hz fields
With the scientific evidence that is now available, it is not possible to establish a "safe
field" standard.
If individuals and society are concerned about the possible risks from fields they can
take prudent steps to avoid exposure to fields, while avoiding large unjustified expen-
ditures. For example, individuals can stop using electric blankets, and society can try
to avoid building new lines very close to people.
60 Hz fields do not pose a significant risk to agriculture or to ecosystems.
There is a great deal of research going on to learn more about the possible health
risks of 60 Hz fields. New evidence from this research should help to reduce some of
the current uncertainty.
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Glossary
AC: The abbreviation for alternating current. An AC current, or an AC field, changes
strength and direction in a rhythmically repeating cycle.
amp: The units used to measure current. Abbreviated A.
charge: The electrical property of matter which is responsible for creating electric fields.
There are two kinds of charge labeled positive and negative. Electric fields begin on
positive charges and end on negative charges. Like charges repel each other. Unlike
charges attract each other.
circadian rhythm: The rhythmic biological cycle (of things like hormone concentrations
in the body) that usually recurs at approximately 24 hour intervals.
contact current: The current that flows in the body when a person touches a conducting
object (e.g., a metal refrigerator) that has a voltage induced on it because it is in an AC
field.
current: An organized flow of electric charge. Current in a power line is analogous to the
rate of fluid flow in a pipeline. All currents produce magnetic fields. Current is measured
in amps.
DC: The abbreviation for direct current. A DC current, or a DC field, is steady and does
not change strength or direction over time.
distribution line: A power line used to distribute power in a local region. Distribution
lines typically operate at voltages of between 5 and 35 kV, much lower than the voltages
of transmission lines. However, the currents on some distribution lines can be com-
parable to transmission line currents.
DMA: Deoxyribonucleic acid, the complex, usually helically shaped chemical com-
pounds from which the genetic material of genes and chromosomes is made.
dose: The amount of exposure of a kind that produces effects. In the case of chemical
pollutants, dose is usually the amount of chemical that gets into the body. In the case of
fields, it is often unclear what aspect of the field, if any, is involved in producing effects.
Hence, it is not clear how to measure dose from electromagnetic fields.
electric field: A representation of the forces that fixed electric charges exert on other
charges at a distance. The electric field has a strength and direction at all points in space
which is often represented diagrammatically by field lines. Electric field lines begin on
positive charges and end on negative charges.
electromagnetic field: A field made up of a combination of electric and magnetic fields.
epidemiology: The study of the distribution and factors that cause health related condi-
tions and events in groups of people, often making use of statistical data on the incidence
of disease or death.
gauss: A common unit of measure for magnetic fields. Abbreviated G. There are 10,000
gauss in one tesla.
hertz: A cycle per second. A unit used to measure frequency. In America, AC power has
a frequency of 60 Hz. In most of Europe, AC power has a frequency of 50 Hz. Radio
waves have frequencies of many thousands or millions of hertz. Abbreviated Hz.
Hz: The abbreviation for hertz. A cycle per second.
hormone: A chemical substance produced by a part of the body and used to send infor-
mation to some other part of the body. Many people associate the word hormone with
sex hormones, substances produced by the sex glands. There are many other kinds of
hormones such as insulin which helps the body use sugar, and cortisol which helps to
control inflammation.
impedance: The electrical property of a conductor or circuit which resists the flow of an
electric current. Impedance is similar to resistance (see below) but may involve a change
in the current's phase.
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initiator: Any agent, such as ionizing radiation and some chemicals, which can start the
process of turning normal cells into cancer cells.
kV: The abbreviation for kilovolt. A thousand volts.
kV/m: The abbreviation for kilovolt per meter. A thousand volts per meter. The strength of
an electric field is measured in volts per meter.
leukemia: A general word used to refer to a number of different types of cancers of the
blood forming tissues.
magnetic field: A representation of the forces that a moving charge exerts on other mov-
ing charges because they are moving. The magnetic field has a strength and direction at
all points in space which is often represented diagrammatically by field lines. Magnetic
field lines form closed continuous loops around currents. All currents produce magnetic
fields.
microwaves: Electromagnetic waves which have a frequency of between roughly 1
billion and 300 billion Hz (a wave length of between roughly 30 centimeters and 1
millimeter). Microwaves have a frequency higher than normal radio waves but lower than
heat (infrared) and light. In contrast to x-rays, microwaves are a form of non-ionizing
radiation (see x-rays below). Strong microwaves can produce biological damage by
heating tissue. Sixty Hz fields cannot do this.
phase: The timing with which an alternating current, voltage or field is changing strength
and direction. See "three phase power" below.
pineal melatonin: The endocrine hormone melatonin that is produced by the pineal
gland in the brain. Melatonin is involved in the control of circadian rhythm in at least
some animals.
promoter: any agent, such as some chemicals, which can aid or accelerate the growth
of cancer.
radiation: Any of a variety of forms of energy propagated through space. Radiation may
involve either particles (for example alpha-rays or beta-rays) or waves (for example,
x-rays, light, microwaves or radio waves). Ionizing radiation such as x-rays carries
enough energy to break chemical and electrical bonds. Non-ionizing radiation like
microwaves does not. Most of the energy in the 60 Hz fields associated with power lines,
wiring and appliances does not propagate away from them through space. Hence, it is
best not to refer to these fields as radiation.
resistance: The electrical property of a conductor that resists the flow of an electric cur-
rent without changing its phase.
RNA: Ribonucleic acid. Complex chemical compounds in cells that are copied from
DNA. RNA carries information and material that cells use to make proteins.
stray voltage: A condition occurring on dairy farms in which cows are subjected to small
but perceptible electrical shocks which can lead to changes in animal behavior and
reductions in milk production. The problem can usually be fixed with proper grounding of
equipment. The problem is not a direct effect of exposing the cows to fields and can
occur without large power lines being involved.
three phase power: Ordinary 60 Hz current involves only one "hot" wire or phase. Most
high voltage transmission lines involve three "hot" wires or phases. The voltage and cur-
rent in these three wires do not all reach their peak values at the same time. First one,
then the next, then the third, reaches maximum, 1/180th of a second apart. The three
work together as one line for transmitting electric energy. Three phase power is used
because it is a more efficient way to transmit electric power than single phase power.
tesla: A unit of measure for magnetic fields. Abbreviated T. There are 10,000 gauss in
one tesla. A microtesla (/iT) is one millionth of a tesla or .01 gauss.
transmission line: A power line used to carry large quantities of electric power at high
voltage, usually over long distances. Transmission lines typically operate at voltages of
between 69 and 765 kV. They are usually built on steel towers or very large wooden
poles.
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voltage: A measure of electric potential, the amount of work that must be done to move
a charge from ground to a location in space such as a power line conductor. Voltage in a
power line is analogous to pressure in a pipeline. Voltage is measured in volts.
Abbreviated V.
V/m: Abbreviation for a volt per meter. The strength of an electric field is measured in
volts per meter, or sometimes in thousands of volts per meter (kV/m).
X-rays: A form of electromagnetic waves similar to light but with a shorter wavelength
(higher frequency). X-rays are a form of ionizing radiation. They can damage biological
systems by breaking chemical or molecular bonds. Sixty Hz fields cannot do this.
Appendix: How to learn more.
The scientific literature on 60 Hz fields is large and is growing rapidly. Published every
three months by the Bioelectromagnetics Society, Bioelectromagnetics is the single most
important scientific journal in this field. Many of the most important results are published
here. There are two commercial newsletters (both fairly expensive but both well done)
Transmission and Distribution Report (720 Washington Avenue, Southeast, Suite 201,
Minneapolis, Minnesota 55414-2917) and Microwave News (P.O. Box 1799, Grand Central
Station, New York, NY 10163) which carry non-technical reports on the latest scientific,
regulatory and other developments in this field. There are two large scientific meetings
each year at which many of the scientific investigators present their latest research find-
ings: the annual meeting of the Bioelectromagnetics Society (usually in June) and the
annual DoE/EPRI Research Contractors Meeting (usually in November). Both are open
to the public.
There are a number of published reviews of the scientific literature. They vary con-
siderably in coverage and level of technical detail. Unfortunately the best reviews are in
the form of reports, not books. It may take a bit of effort to track down copies of some of
them.
At the request of the Office of Technology Assessment of the United States Congress we
have recently completed:
U.S. Congress, Office of Technology Assessment, Biological Effects of Power Fre-
quency Electric and Magnetic Fields Background Paper, prepared by I. Nair, M.G.
Morgan, H.K. Florig, of the Department of Engineering and Public Policy, Carnegie
Mellon University, OTA-BP-E-53 (Washington, DC: U.S. Government Printing Office,
May 1989).
This report, written for a Congressional audience, explains what 60 Hz fields are,
discusses human exposure to fields, summarizes many of the biological effects, dis-
cusses the epidemiological evidence and discusses alternative policies that might be
adopted.
Another recent review intended for a general audience is:
Electrical and Biological Effects of Transmission Lines: A Review, Technical Report
prepared by J. Lee, J.H. Brunke, G.E. Lee, G.L. Reiner and F.L. Shon of the Bon-
neville Power Administration of the U.S. Department of Energy (Portland, Oregon
97208), 1989.
The Bonneville Power Administration (BPA) is the big federal power system in the Pacific
Northwest. This report reviews 60 Hz biological effects as part of the BPA documentation
required by the National Environmental Policy Act dealing with environmental impacts of
electrical transmission facilities. The report focuses heavily on high voltage transmission
lines and their associated fields.
While they are getting a bit old, two special reports prepared for the states of Florida and
Montana contain fairly comprehensive semi-technical reviews. They are:
Biological Effects of High Voltage AC transmission lines with reference to the Co/strip
Project Garrison-Spokane HVTL, Technical Report prepared by Dr. Asher Sheppard
for the Montana Department of Natural Resources and Conservation, Helena, Mon-
tana, 1983. Available from the National Technical Information Services (5285 Port
Royal Road, Springfield, Virginia 22161) as Report No. PB83 207241.
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Biological Effects of 60 Hz Power Transmission Lines, Technical Report prepared by
Florida Electric and Magnetic Fields Science Advisory Commission for the Florida
Electric Power Coordinating Group, Inc. (Tampa, Florida 33609), March, 1985.
Dr. Sheppard is a scientist in the research group at Loma Linda Veteran's Hospital work-
ing on the biological effects of fields. His report provides a critical review of experimental
results up to 1982 from the perspective of determining their implications for human
health. The review includes a fairly extended discussion of results obtained from experi-
ments on cells. The Florida report was prepared by a six-member committee appointed
by the Department of Environmental Regulation of the State of Florida. It contains a fairly
complete review of the literature up to 1985. It places somewhat less emphasis on
cellular level results than the Sheppard review.
One other general review is:
Biological and Human Health Effects of Extremely Low Frequency Electromagnetic
Fields, Technical Report prepared by the Committee on Biological and Human
Health Effects of Extremely Low Frequency Electromagnetic Fields, American
Institute of Biological Sciences, Arlington, Virginia, March 1985. Available from:
National Technical Information Service, U.S. Department of Commerce (Springfield,
Virginia 22161) as Report No. AD/A152 731.
This report was prepared by a committee of twelve scientists, organized by the American
Institute of Biological Sciences in response to a request from the Naval Electronics
Systems Command. The Navy has an interest because powerful low frequency radio
transmitters are used to communicate to submarines at sea. Thirty-one scientists, with
very different experience'and opinions about the potential biological effects of low fre-
quency fields, acted as consultants to the Committee. The report summarizes research
done between 1977 and 1985 in all aspects of the biological effects of electromagnetic
fields in the frequency range from 1 to 300 Hz.
The details of interactions between fields and biological systems at the level of individual
cells has emerged as an especially important portion of the literature on low frequency
fields. While most of the reviews of this topic are quite technical, the Veteran's Adminis-
tration has produced a 15-minute video tape (made at the Walt Disney studios with illus-
trations by Frank Armitage who did The Fantastic Voyage"). The video tape is intended
for semi-technical and non-technical audiences. It is:
"Cell Membranes and Intercellular Communications," U. S. Veterans Administration,
distributed by National Audio Visual Center (8700 Edgeworth Drive, Capital Heights,
MD 20743-3701, tel: 301-763-1896).
Some of the ideas presented in this movie are still quite controversial within the research
community.
Dr. Ross Adey, who heads the Research Service at Jerry Pettis Memorial Veteran's
Hospital in Loma Linda, California, has produced two detailed technical reviews of this
topic. They are:
Tissue Interactions with Nonionizing Electromagnetic Fields by W. Ross Adey in the
scientific journal, Physiological Reviews, Volume 61, Number 2, April 1981, pp.
435-514.
"Electromagnetic Fields: Cell membrane amplification and cancer promotion," W.
Ross Adey, Review paper presented at the National Council on Radiation Protec-
tion and Measurements Annual Meeting, National Academy of Sciences
(Washington, D.C. 20418), 1986.
Dr. Jerome Beers, a radiologist of the Boston University Medical Center, has prepared an
extensive review of the biological effects of magnetic fields. It is:
Biological Effects of Weak Electromagnetic Fields from OHzto 200 MHz: A survey of
the literature with special emphasis on possible magnetic resonance effects by G.
Jerome Beers in the scientific journal Magnetic Resonance Imaging, Volume 7,
1989, pp. 309-331.
Readers without significant biological and other technical training will find these reviews
very hard going.
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