United States
Environmental Protection
Agency
Office Of Radiation
And Indoor Air
(6603J)
402-R-92-008
December 1992
EMF In Your Environment
Magnetic Field Measurements
Of Everyday Electrical Devices
-------
Mention of trade names, products, or services
does not convey, and should not be interpreted as
conveying, official EPA approval, endorsement,
or recommendation.
Recyctod/R8cydabk>
Printed on paper that contains
at toast 50% recycled fflxir
For sale by the U.S. Government Printing Office
Superintendent of Documents, Mail Stop: SSOP, Washington, DC 20402-9328
ISBN 0-16-036282-2
r
ISBN 0-16-036282-2
90000
J
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CONTENTS
EMF In Your Environment
What Are Electric and
Magnetic Fields? 3
The Electromagnetic
Spectrum 5
60 Hertz Electric and
Magnetic Fields 6
Other Electromagnetic Frequencies 7
Potential Health Concerns
Associated With
Electric and Magnetic Fields 7
Magnetic Field Measurements of
Everyday Electrical Devices 9
Appliances and Magnetic
Field Strength
How Magnetic Field
Measurements Were Taken 10
Tables ; 13.25
How Can I Use This Information _______ 26
Appendix A !
Technical Notes 28
Data Sources 31
Appendix B
Additional Reading and
Information Sources 33
-------
-------
EMF IN YOUR ENVIRONMENT
What are electric and magnetic fields
(EMFs)? What common EMF sources do we
encounter during a typical day? This publication
compares the strength of 60 hertz magnetic fields
produced by common electrical items and shows
you how their strength diminishes as you move
farther away from them.
We still have a great deal to learn about
electric and magnetic fields (EMFs). We really
don't know if typical, everyday exposures to EMFs
affect human health. Some studies indicate that
they might - others suggest otherwise. Most of
the recent research on possible biological effects of
60 hertz EMFs suggests that the magnetic, rather
than the electric, fields are more likely to produce
significant effects. Therefore, this publication
focuses on them. The information presented here
has to do with the strength of the magnetic field;
however, we aren't certain that the strength of the
field is the only important consideration. It may
turn out that other factors are also important,
such as how long the exposure lasts or whether
particular characteristics of the field change
rapidly. Future research is likely to reveal that
the information given in this publication is only
part of the story - that is the chance we take in
providing a public information document this early
in the study of a complex environ-
mental health issue.
What Are Electric
and Magnetic Fields ?
Electric charges create
electric fields. Electric charges
which move (i.e., electric current)
create magnetic fields. An appli-
ance that is plugged in, and
therefore connected to a source of
electricity, has an electric field
-------
Electromagnetic Spectrum
Gamma
rays
X-rays
4-
t
Ultraviolet
radiation
Visible light
I
Infrared
radiation
Microwaves
UHF
VHF
Short
wave
Radio Medium
waves wave
Long
wave
t
Extremely low
frequency (ELF)
1
Frequency
(in hertz)
10
102
101
102L-
10
105
10
10
10
m
I U
10'
10
10
10
-10
-60 hertz -
10
Wavelength
(in meters)
10
10
10
,-11
10'
10
10
10
10
1fV6
i u
10
10
10'3
1 Q-2 _
10
1
10
10
10
104
105
10
10
This illustrates
the point that
the higher the
frequency, the
shorter the
wavelength. The
wavelengths are
infinitely long at
the bottom and
infinitessimally
short at the top
of the spectrum
so, obviously, the
drawing cannot
be done to scale.
-------
even when the appliance is turned off. To produce
a magnetic field, however, the appliance must be
not only plugged in, but also operating, so that the
current is flowing.
The electric current we use in our everyday
life produces certain kinds of electric and magnetic
fields. There are many other kinds of electric and
magnetic fields as well, found throughout nature.
The term "electromagnetic" field implies that the
electric and magnetic fields are interrelated.
These fields can be characterized by either
their wavelength or their frequency, which are
related. The amount of energy an electric or
magnetic field can carry depends on the frequency
and wavelength of the field. The wavelength
describes how far it is between one peak on the
wave and the next peak. The frequency, measured
in hertz, describes how many wave peaks pass by
in one second of time.
The Electromagnetic Spectrum
If you take all the different kinds of electro-
magnetic fields we know about and place them on
a chart, from the lowest frequency (i.e., lowest
energy) to the highest, you have a chart of the
electromagnetic spectrum. (See chart on the
previous page.) The low end of the spectrum
includes electric and magnetic fields produced by
everyday electrical appliances. At the top of the
spectrum are X-rays and gamma rays.
When you hear about "EMFs" in the news
media, the term usually refers to electric and
magnetic fields at the extremely low frequency (or
ELF) end of the spectrum, such as those associ-
ated with our use of electric power. The term
"EMF" can be used in a much broader sense as
well, encompassing electromagnetic fields across
the spectrum. When we use "EMF" in this bro-
chure we mean extremely low frequency (ELF)
electric and magnetic fields. We should note that
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 actually
more accurate to refer to them as "electric and
magnetic fields" rather than as "electromagnetic
fields." In the popular press, however, you will see
both terms used, abbreviated as "EMF."
Electric fields from most appliances primarily create charges or
current on or near the surface of the body and not in the internal
organs. Magnetic fields, however, pass through the body and
actually induce electric currents within the body. We don't know
exactly what effect, if any, this has on the different internal organs,
but many studies are now underway to try to find out.
60 Hertz Electric And Magnetic Fields
It is relatively easy to shield people from
exposure to electric fields using commonly avail-
able materials. Magnetic fields, however, can pass
through anything. Even though both are present
around appliances and power lines, more recent
interest and research have focused on potential
health and biological effects of magnetic fields of
various strengths.
This publication presents information re-
garding magnetic fields associated with 60 hertz
alternating current (AC) electric power - that is,
the kind of electric power we use in North America
which flows back and forth or alternates at a rate
of 60 times per second (60 hertz). We will not
focus here on equipment that is powered by "direct
current" (DC) such as battery-operated appli-
ances. The magnetic fields created by
direct current are primarily static;
that is, they do not vary with time
as do AC fields. Direct current
(DC) magnetic fields have not
raised as many questions
about potential health
-------
concerns as have the time-varying fields created
by alternating ffurrent (AG). We should point out,
however, that some DC-powered equipment can
produce alternating magnetic fields, but these are
usually not 60 hertz fields.
Other Electromagnetic Frequencies
Although the information presented here has
to do with the low frequency magnetic fields
associated with 60 hertz electrical current, we
should note that some appliances, such as micro-
wave ovens, baby monitors, and video display
terminals, use 60 hertz electrical energy to create
other electromagnetic frequencies.
The measurements we give for microwave
ovens, for example, describe the magnetic field
that results from the 60 hertz electrical current
used to operate the oven. We are not describing
the magnetic field associated with the approxi-
mately three billion hertz microwaves inside the
oven which heat the food and from which people
are protected when the door is secured properly.
Oddly enough, we can be easily shielded from
the higher frequency microwaves' magnetic fields,
but not from the 60 hertz magnetic fields. This is
because even though the microwave's frequency
is higher, its length is much, much shorter (about
1 cm) than the wavelength of a, 60 hertz field
(about 5000 kilometers). The shorter wave can be
blocked by materials such as thin metal sheets,
whereas the much longer wave cannot.
Potential Health Concerns Associated
With Electric and Magnetic Fields
Electric and magnetic fields from 60 hertz
electric power (as well as microwaves and radio
waves) are sometimes called non-ionizing radia-
tion. The term "radiation" simply means energy
7
-------
transmitted by waves. "Ionizing" radiation has
enough energy to strip electrons from atoms. (X-
rays are a form of ionizing radiation.) Extremely
low frequency EMF cannot do this. Higher
frequency non-ionizing radiation, such as micro-
waves, can heat up biological tissue by vibrating
molecules. The lower frequency 60 hertz EMFs
cannot. Because of their relatively lower energy,
60 hertz EMFs were not, until recently, thought to
be connected with any potential health problems.
There are no national standards in the United States for exposure to
60 hertz electromagnetic fields. Several states have formally adopted
standards to limit the permissible magnetic field strength along rights
of way of electric transmission lines. Federal legislation has been
enacted to establish and support national EMF research and public
information programs, but no exposure standards have been pro-
posed.
Some recent scientific studies have suggested
a link a statistical association between expo-
sure to 60 hertz EMFs and specific types of cancer,
primarily leukemia and brain cancer. Other
studies have found no such association (see Appen-
dix B). In a sense, this can be compared to circum-
stantial evidence in a court of law. Laboratory
studies have shown electromagnetic fields to affect
cells in various ways, but whether these effects are
important in terms of human health is still not
clear. Almost everyone involved in EMF research
agrees that much more needs to be learned before
conclusions can be reached about the relative
safety or harm of 60 hertz EMF exposure.
Some people doubt that the EMFs generated
by 60 hertz electrical appliances and internal
household wiring have any significant effect on
human health, because they know that the earth's
magnetic field, to which we are all constantly
exposed, is stronger (sometimes over 100 times
stronger) than the magnetic fields produced by
8
-------
many of the appliances listed in this publication.
However, the earth's magnetic field is primarily a
DC field rather than a time-varying field. Our
bodies seem to react differently to these
different types of fields so comparing
them can be misleading.
At this point, we are not at all
sure that exposure to EMFs such as
we find in our everyday environment
has an adverse effect on our health.
However, we cannot say with certainty
that such exposure is safe for us, either.
More research is needed and is underway.
Meanwhile, many people have expressed an
interest in having information about everyday
sources of EMF exposure. This booklet is in
response to that interest.
©
MAGNETIC FIELD MEASUREMENTS
OF EVERYDAY ELECTRICAL DEVICES
This publication gives information about the
strength of the magnetic fields generated by
everyday 60 hertz electrically powered equipment.
It shows how the magnetic field strength dimin-
ishes with increased distance from the object.
Appliances and
Magnetic Field Strengths
Magnetic fields from individual appliances
can vary considerably, depending on the way they
were designed and manufactured. One brand of
toaster, for example, may generate a much stron-
ger magnetic field than another. The strength of
the magnetic field is measured in units of gauss
(G) or milligauss (mG). A milligauss is l/1000th
of a gauss. (The international standard unit is
microtesla which is the same as 10 milligauss.)
It is important to keep in mind that a typical
-------
American home has a background magnetic field
level (away from any appliances) ranging from 0.5
mG to 4 mG. The actual strength of the field at a
given place in a room depends upon the number
and kinds of sources, how far away they are, and
how many are operating at one time. Walls
generally do not block magnetic fields. An electri-
cal appliance located near a wall extends its
magnetic field into the room on the other side of
the wall as well.
How Magnetic Field
Measurements Were Taken
The data in the tables (beginning on page 13)
came from three different organizations: the
Electric Power Research Institute (EPRI), the
Illinois Institute of Technology Research Institute
(IITRI), and the U.S. Environmental Protection
Agency (EPA). What we present here will give you
an idea of the relative strength of magnetic fields
produced by electrical items you are likely to use
in your home or at work.
The strength of the magnetic fields has been
measured at 6 inches from the item, and then at
distances of 1, 2, and 4 feet. These distances do
10
-------
not, in every case, correspond to the distance you
would typically be from the appliance when you
use it, but we kept the measurements consistent
so that the magnetic field strength could be com-
pared from appliance to appliance. It should also
be mentioned that different body parts will be
exposed to different magnetic field levels from the
same appliance, depending on how far that part of
the body is from the appliance when it is in use.
An electric shaver when used, for example, may be
three inches from the brain and two feet from the
liver. Notice in the chart below how the strength
of the magnetic field diminishes dramatically just
a foot or two away from the appliance.
o
LJJ
O
2
UJ
o
UJ
cc
200
E 160
120-
0.00
0.50
1.00
1.50
2.00
DISTANCE FROM APPLIANCE (fe'et)
11
-------
-------
TABLES
In the following tables, you will see three numbers listed for each
appliance at each distance. First is the lowest measurement we have,
followed by the median, and then the highest measurement taken. For
some appliance categories, hundreds of individual items were measured.
In other cases, the data gathering was less extensive. The median
measurement is simply the middle number in a series of measurements.
The appliances are organized according to where you might en-
counter them during the day (in the kitchen, the office, the bedroom,
etc). The magnetic field strength is measured in milligauss (mG).
For a detailed description of the methodology used by each of the
three groups that conducted these measurements, please refer to Ap-
pendix A. Also in Appendix A .is a reference chart showing the source of
the data.
^ *« "--*»- ;
*» ^^IsEiMJiljSSlWjJUHCillU^Gft^fe
P^SPftwll^MHm!BaiJl .''±f f '
Distance from Source
6"
1'
2'
4'
HAIR DRYERS
Lowest
Median
Highest
1
300
700
_
1
70
_
-
10
.
_
1
ELECTRIC SHAVERS
Lowest ;
Median
Highest
4
100
600
_
20
100
_
_
10
_
_
1
Magnetic field measurements in units of milligauss (mG)
The dash (-) in the above table means that the magnetic field measurement at this
distance from the operating appliance could not be distinguished from background
measurements taken before the appliance had been turned on.
13
-------
Distance from Source
6"
1'
2'
4'
BLENDERS
Lowest
Median
Highest
30
70
100
5
10
20
_
2
3
_
.
-
CAN OPENERS
Lowest
Median
Highest
500
600
1500
40
150
300
3
20
30
..
2
4
COFFEE MAKERS
Lowest
Median
Highest
4
7
10
..
-
1
_
.
-
_
_
-
CROCK POTS
Lowest
Median
Highest
3
6
9
_
1
1
_
-
-
_
-
-
DISHWASHERS
Lowest
Median
Highest
10
20
100
6
10
30
2
4
7
_
-
1
FOOD PROCESSORS
Lowest
Median
Highest
20
30
130
5
6
20
.
2
3
_
.
-
Magnetic field measurements in units of milligauss (mG)
The dash (-) in the above table means that the magnetic field measurement at this
distance from the operating appliance could not be distinguished from background
measurements taken before the appliance had been turned on.
14
-------
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Distance from Source
6"
1'
2'
4'
GARBAGE DISPOSALS
Lowest
Median
Highest
60
80
100
8
10
20
1
2
3
_
.
MICROWAVE OVENS
Lowest
Median
Highest
100
200
300
1
40
200
1
10
30
.
2
20
MIXERS
Lowest
Median
Highest
30
100
600
5
10
100
1
10
.
-
ELECTRIC OVENS
Lowest
Median
Highest
4
9
20 .
1
4
5
_
.
1
_
.
-
ELECTRIC RANGES
Lowest
Median
Highest
20
30
200
_
8
30
_
2
9
_
_
6
REFRIGERATORS
Lowest
Median
Highest
_
2
40
.
2
20
_
1
10
_
_
10
TOASTERS
Lowest
Median
Highest :
5
10
20
_
3
7
_
_
-
_
.
-
Magnetic field measurements in units of milligauss (mG)
15
-------
"- " - " ^'WW^AM^^
Distance from Source
6"
1'
2'
4'
CEILING FANS
Lowest
Median
Highest
3
50
6
1
WINDOW AIR CONDITIONERS
Lowest
Median
Highest
3
20
1
6
4
TUNERS/TAPE PLAYERS
Lowest
Median
Highest
1
3
1
-
-
COLOR TVs
Lowest
Median
Highest
7
20
2
8
4
BLACK AND WHITE TVs
Lowest
Median
Highest
1
3
10
2
1
Magnetic field measurements in units of milligauss (mG)
The dash (-) in the above table means that the magnetic field measurement at this distance
from the operating appliance could not be distinguished from background measurements
taken before the appliance had been turned on.
16
-------
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^BfflHHfflHHIBBHK^^^fej'i? "~,.~-~ ~-=~,,: ._;. ",:.:.' ;=., ----- .^~-:~~
Distance from Source
6"
1 J a jj ^ jjfcSj^^^^i^^^^^^jfe^^^^
r
2'
4'
ELECTRIC CLOTHES DRYERS
Lowest
Median
Highest
2
3
10
_
2
3
_
-
-
_
-
-
WASHING MACHINES
Lowest
Median
Highest
4
20
100
1
7
30
.
1
6
- _
.
-
IRONS
Lowest
Median
Highest
6
8
20
1
1
3
_
-
.
.
.
-
PORTABLE HEATERS
Lowest
Median
Highest
5
100
150
1
20
40
_
4
8
_
_
1
VACUUM CLEANERS
Lowest
Median
Highest
100
300
700
20
60
200
4
10
50
_
1
10
Magnetic field measurements in units of milligauss (mG)
-------
Distance from Source
6"
1'
2'
4'
DIGITAL CLOCKS
Lowest
Median
Highest
_
1
.8
w
-
2
_
-
1
ANALOG (CONVENTIONAL CLOCK-FACE) CLOCKS
Lowest
Median
Highest
1
15
30
_
2
5
_
_
3
BABY MONITORS
Lowest
Median
Highest
4
6
15
.
1
2
_
-
_ >
_
-
Magnetic field measurements in units of milligauss (mG)
The clocks described in the above table are electrically powered
using alternating current (AC), as are all the appliances described in
these tables. The measurements for baby monitors were taken for the
unit nearest the child.
The dash (-) in the above table means that the magnetic field measurement at this distance
from the operating appliance could not be distinguished from background measurements
taken before the appliance had been turned on.
18
-------
o
£
45
40
35
30
25
20
15
10
5
0
Measurements taken 5 cm. from the blanket surface
39.4
* ' 5 cm peak
Y//A 5 cm average
21.8
Conventional
PTC
Low-Magnetic-
Field
Information courtesy of the Center for Devices and Radiological Health, U.S. Food
and Drug Administration
The above graph presents information regarding magnetic fields
produced by electric blankets, including conventional 110 volt electric
blankets as well as the newer model PTC (Positive Temperature
Coefficient) Low Magnetic Field blankets. The fields were measured
at a distance of five centimeters (a little less than 2 inches) from the
surface of the blanket, roughly approximating the distance from the
blanket to the users' internal organs. Because of the way blankets
are wired, magnetic field strengths vary from point to point on the
blanket. The graph reflects this and gives you both the peak as well
as the average measurement.
-------
Distance from Source
6"
1'
2'
4'
AIR CLEANERS
Lowest
Median
Highest
110
180
250
20
35
50
3
5
8
1
2
COPY MACHINES
Lowest
Median
Highest
4
90
200
2
20
40
1
7
13
_
1
4
FAX MACHINES
Lowest
Median
Highest
4
6
9
«.
-
2
_
.
-
.
_
-
FLUORESCENT LIGHTS
Lowest
Median
Highest
20
40
100
_
6
30
_
2
8
_
_
4
ELECTRIC PENCIL SHARPENERS
Lowest
Median
Highest
20
200
300
8
70
90
5
20
30
_
2
30
VIDEO DISPLAY TERMINALS
(PCs WITH COLOR MONITORS) (See note on following page)
Lowest
Median
Highest
7
14
20
2
5
6
1
2
3
_
_
-
Magnetic field measurements in units of milligauss (mG)
The dash (-) in the above table means that the magnetic field measurement at this distance
from the operating appliance could not be distinguished from background measurements
taken before the appliance had been turned on.
20
-------
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! iS«Ssssi;f|tv3ffll;SKC^S;i^Sy/yQ RKS H O P\SO U R G KS'is^smSSttSSSaSiisSSK
MMBHMM«KSi^^^;^^--"^ -.--- -- :v^~ -:« c^s^-ii
Distance from Source
6"
1'
2'
4'
BATTERY CHARGERS
Lowest
Median
Highest
3
30
50
2
3
4
-
-
DRILLS
Lowest :
Median
Highest
100
150
200
20
30
40
3
4
6
-
POWER SAWS
Lowest
Median
Highest
50
200
1000
9
40
300
1
5
40
4
ELECTRIC SCREWDRIVERS (while charging)
Lowest
Median ;
Highest
-
-
-
Magnetic field measurements in units of milligauss (mG)
Although the U.S. has set no standards for magnetic fields from video
display terminals (VDTs), the Swedish government has. Its standard
. of 2.5 milligauss (mG) at a distance of 50 centimeters (about 1 '8") from
the VDT has become a de facto standard in the VDT industry
worldwide.
-------
ELfeCt RIC POWER WES
Another obvious source of everyday exposure to 60 hertz EMFs is
from electric power lines.
Transmission
69 kV to 765 kV
Substation
step-down
transformer
Generation
20 kV
Step-up
transformer
Distribution
primaries
5-35 kV
Distribution
step-down
transformer
Circuit o
breakers
End User
115 230 Volts
Distribution
secondaries
115/230 Volts
From Carnegie Mellon brochure: Electric and Magnetic Fields from 60 Hertz Electric
Power, 1989.
Substations: Some people are particularly concerned about the
magnetic fields generated by electric substations. In fact, as with
appliances, the fields produced by substation equipment quickly
diminish in strength a short distance away and do not extend beyond
the substation boundaries. However, magnetic fields near substations
can be stronger than those in other parts of the neighborhood because
the power lines drop down closer to the ground as they go in and out
of the substation, bringing their accompanying magnetic fields closer
to people on the ground.
22
-------
The next table (see page 24) gives typical magnetic field measure-
ments for several types of single circuit electric power lines at varying
distances from the lines, both at times of average electricity usage and
at peak usage times. A single circuit power line is actually a set of three
lines. If you see more than three lines, it means that more than one
circuit runs along the same right-of-way (ROW), in which case higher
fields are possible. The first measurement on the table gives the maxi-
mum magnetic field strength measured within the power line ROW.
The next four measurements are at distances of 50', 100', 200', and 300'.
Power line ROW widths vary among utilities. All measurements were
taken at a height of one meter above the ground.
The measurements shown here are from electric "transmission"
lines, which use very high voltages and go long distances. The electrical
lines you see in typical neighborhoods are "distribution" lines, which
usually carry less voltage than transmission lines. Voltage is not,
however, the critical issue with regard to magnetic field strength.
Rather, magnetic field strength is directly proportional to current, which
can be high in distribution lines as well as in transmission lines. Resi-
dential exposures to distribution lines are usually under 5 mG, but have
been reported to be as high as 50 mG where the lines pass within a few
feet of living space in densely populated areas.
It is interesting to note that the highest magnetic field strength
measurement we have directly on the right of way of 500 kV transmis-
sion lines during peak usage is lower than the median measurement we
have for magnetic field strength within 6 inches of many household
appliances, such as hair dryers and vacuum cleaners. However, the
duration of exposure to EMFs from power lines near a home is typically
much longer than the duration of exposure to EMFs from most appli-
ances. Is this an important distinction? We just don't know yet.
23
-------
Types of
Transmission
Lines
Maximum
on Right-
of-Way
Dis
50'
stance
100'
from li
200'
nes
300'
115 Kilovolts (kV)
Average usage
Peak usage
30
63
7
14
2
4
0.4
0.9
0.2
0.4
230 Kilovolts (kV)
Average usage
Peak usage
58
118
20
40
7
15
1.8
3.6
0.8
1.6
500 Kilovolts (kV)
Average usage
Peak usage
87
183
29
62
13
27
3.2
6.7
1.4
3.0
Magnetic field measurements in units of milligauss (mG)
Information courtesy of Bonneville Power Administration.
Burying power lines underground often does reduce their magnetic
fields. This is not because they are underground, however, since dirt
does not act as a shield. Instead, the lower magnetic field is due to the
way lines are arranged and encased when they are buried, which can
have the effect of cancelling part of the field. Underground power lines,
are still capable of exposing you to magnetic fields if you are very close
to them.
24
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Inside a car, the dominant sources of 60 hertz 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). Car phones are also battery-powered and are therefore not
sources of 60 hertz magnetic fields, although they do transmit and
receive fields in the radio frequency range. Some car components, such
as alternators, can create alternating fields, but not necessarily in the
60 hertz frequency.
Trains present a more complicated picture. Some electrically
powered trains operate on alternating current, such as the New York
City subway and the Baltimore/Washington commuter train. Measure-
ments taken on the Baltimore/Washington train in 1991* showed 25
hertz magnetic field strengths as high as 500 mG in the passenger
areas at seat height. Other trains, such as the Washington D.C. Metro
and the San Francisco Bay Area Rapid Transit (BART), run on direct
current, but even these trains are not free of AC fields. Areas of strong
AC magnetic fields have been measured on the Washington D.C. Metro,
close to the floor, presumably near equipment located underneath some
train cars. Train motors and other equipment create some very intense
alternating fields at higher than 60 hertz frequencies. In addition to
sources of magnetic field exposure from the train itself, train passengers
are exposed to magnetic fields from sources the train passes on its
route.
* 24-Hour Exposure Measurements to 60 Hertz Magnetic Fields: A Pilot Project,
presented by Lynne Gillette, U.S. EPA, at the Air and Waste Management Association
Annual Meeting, June 1992.
25
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HOW CAN I USE THIS
INFORMATION?
Many people are surprised when they com-
pare magnetic field measurement data from
appliance to appliance and see that magnetic field
strength does not depend on how large, complex,
powerful or noisy the appliance is. In fact, the
magnetic fields near large appliances are often
weaker than those near smaller devices. There
are many reasons why this can happen, all of them
related to product design. The stronger
MAGNETIC HELD CHARACTERISTICS
STRE.N6TH
DURATIOM
CHANGES
DISTANCES
magnetic fields from smaller appliances tend to
diminish in strength more quickly as distance
increases than do the fields from larger appli-
ances, however.
If you are trying to determine your potential
exposure to a magnetic field from a particular
appliance, it is important that you consider
how close you are to the appliance and how long
you use it. The electric alarm clock at the head of
your bed may expose you to a magnetic field of 15
mG for 7 or 8 hours each night. The electric can
opener in the kitchen is also capable of producing
a magnetic field of 15-20 mG at a distance of one
26
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foot away, but your potential ^exposure to that field
is for a much shorter duration.
Does it matter how long we are exposed to a
magnetic field? We don't know. Magnetic fields
that are cycled on and off repeatedly, such as those
from photocopiers, may have a different kind of
effect on us than those from appliances that run
constantly, such as alarm clocks.
Obviously, many remaining questions about
EMF need to be answered before we can say what
is safe or unsafe. The government and the private
sector are currently working together to sponsor
research that attempts to answer some of these
questions.
This publication presents what we hope are
some helpful pieces of the EMF puzzle - informa-
tion about how magnetic field strengths of various
everyday appliances compare with each other and
how their strength diminishes the farther away
you are from the appliances. In many instances,
you can substantially reduce your exposure to
magnetic fields by simply putting more distance
between yourself and EMF sources.
27
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APPENDIX A
Technical Notes
The data in the tables came from three
different organizations: the Electric Power Re-
search Institute (EPRI), J.R. Gauger of the Illinois
Institute of Technology Research Institute (IITRI),
and the U.S. Environmental Protection Agency
(EPA). Each set of data was collected in a differ-
ent manner.
EPRI DATA
The EPRI data comes from the September
1992 Interim Report of EPRI's nationwide Survey
of Residential Magnetic Field Sources. (EPRI TR-
100194, Project 2942-06.) The survey involved 707
homes. Data was collected with Star magnetic
field instruments at different distances from the
appliances' front surfaces, at a height of 3 feet
from the ground. The Star magnetic field meter
measures only 60 hertz magnetic fields. EPRI did
not measure magnetic field strengths at a distance
of 6 inches from the appliance, as did IITRI and
EPA. Therefore, the missing 6 inch measurements
for appliances covered in the EPRI survey was
provided either by ITTRI or by the EPA. It is
important to note that although the tables in this
publication give measurements at distances of 6
inches, 1 foot, 2 feet, and 4 feet from the source,
the EPRI measurements were actually made at
slightly closer distances from the appliances:
approximately 10.5", 22.3", and 46". The number
of appliances of each type measured by EPRI
ranged from 60 to 400. EPRI researchers collected
information on manufacturer and model of the
appliances they measured, but they did not report
that information.
28
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HTRIDATA
The IITRI data set is from a 1984 report by
J.R. Gauger of IITRI, prepared for the U.S. Naval
Electronic Systems Command, entitled "House-
hold Appliance Magnetic Field Survey" Technical
Report E06549-3, Contract No. N00039-84-C-0070.
IITRI used measurement equipment of their own
design. They measured the maximum 60 hertz
magnetic field for appliances in the location in
which they were normally used, and turned off or
otherwise minimized all other EMF sources in the
vicinity of the appliance being measured. The
IITRI data set is based on a smaller sample of
appliances than EPRI used. About five appli-
ances of each type were measured.
EPA DATA
EPA staff conducted measurements of
commonly used electrical appliances for which
data had not already been collected. At least five
different types of a given appliance were mea-
sured. The measurement protocol used by the
EPA in its data collection was the following:
1) Equipment consisted of a measuring tape
and an Emdex II magnetic field meter measuring
in the broadband magnetic field resultant mode
every 1.5 seconds.
2) Sources being measured were left in their
original positions in the environment. Other
operating sources within 3 feet of the object source
were turned off when the measurements were
taken.
3) Measurement sites were at given dis-
tances from the center of the source surface closest
to the most likely source user position. The
measurement sites were on a line from the center
of this surface, in the direction of the user position
and parallel to the floor.
29
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4) For each of the measurement sites, before
turning on the source to be measured, an initial
measurement of the background EMF was taken.
This measurement was based on the average of
ten consecutive Emdex II readings, rounded to the
nearest tenth of a milligauss. With the source
operating at its maximum output, the measure-
ments were taken with the same averaging tech-
nique. Background measurements were taken
again after the source was turned off.
5) In cases where the source field changed
periodically (such as with some copy machines) the
measurements were taken during the period of
.operation when the field was strongest.
30
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The following chart shows, for each appliance listed in the publica-
tion, which organization provided the data.
j^^^^^^^^^^^^^^ijKifc^^SBjjitiN^^^i^ * -
V K- _ .
__
EPRI
IITRI
-a ^ ^ -i »
-------
1 .' " V'"M/^
EPRI
IITRI
MM.
EPA
WORKSHOP
Battery Chargers
Drills
Power Saws
Screw Drivers
LIVING/FAMILY ROOM
Ceiling Fans
Window Air Conditioners
Stereo Tuners
Color Televisions
Black & White Televisions
OFFICE SOURCES
Air Cleaners
Copy Machines
Fax Machines
Fluorescent Lights
Electric Pencil Sharpeners
Video Display Terminals
*
BEDROOM
Digital Clocks
Analog Clocks
Baby Monitors
* Indicates Source of 6" Measurements
32
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APPENDIX B
Additional Reading and Information Sources
Public Information Brochures
Electric and Magnetic Fields from 60 Hertz Electric Power: What do
we know about possible health risks?, Department of Engineering and
Public Policy, Carnegie Mellon University, Pittsburgh, PA 15213,
1989. Available from Carnegie Mellon: (412)268-2670. ($3.00)
Electric Magnetic Fields Brochures Series, Edison Electric Institute
(EEI). A series of brochures targeted for various audiences (consum-
ers, employees, realtors, teachers, physicians, etc.). Available from
EEI: (202)508-5424. ($1.25+)
Research Reviews
Biological Effects of Power Frequency Electric and Magnetic Fields-
Background Paper, Office of Technology Assessment, May 1989.
OTA-BP-E-53. Available from the U.S. Government Printing Office:
(202) 783-3238. GPO# 052-003-01152-2. ($4.70+)
Electric and Biological Effects of Transmission Lines: A Review,
Bonneville Power Administration, 1989. Available from BP: 1-800-
622-4520. Publication number: DOE/BP-945. Free. 107 pages.
Basic Science
Electric and Magnetic Field Fundamentals: An EMF Health Effects
Research Paper, Electric Power Research Institute (EPRI), January
1991. Available from EPRI: (510)934-4212. Publication number:
EN-7066. ($5.00)
Basic Electromagnetic Theory, by Demetrius T. Paris and F. Kenneth
Kurd, McGraw Hill, 1969. Available in public libraries and book-
stores.
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For more information contact:
Office of Radiation and Indoor Air
Radiation Studies Division
U.S. Environmental Protection Agency
(6603J)
Washington, D.C. 20460
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