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EMF's
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Energy
What are electromagnetic fields?
Electric fields are
created by differences in voltage: the
higher the voltage, the stronger will be the
resultant field. Magnetic fields are created
when electric current flows: the greater the
current, the stronger the magnetic field. An
electric field will exist even when there is
no current flowing. If current does flow,
the strength of the magnetic field will vary
with power consumption but the electric
field strength will be constant.
Natural sources of
electromagnetic fields
Electromagnetic fields
are present everywhere in our environment
but are invisible to the human eye. Electric
fields are produced by the local build-up of
electric charges in the atmosphere
associated with thunderstorms. The earth's
magnetic field causes a compass needle to
orient in a North-South direction and is
used by birds and fish for navigation.
Human-made sources
of electromagnetic fields
Besides natural
sources the electromagnetic spectrum also
includes fields generated by human-made
sources: X-rays are employed to diagnose a
broken limb after a sport accident. The
electricity that comes out of every power
socket has associated low frequency
electromagnetic fields. And various kinds of
higher frequency radiowaves are used to
transmit information – whether via TV
antennas, radio stations or mobile phone
base stations.
The basics of
wavelength and frequency
What makes the
various forms of electromagnetic fields so
different? One of the main
characteristics which defines an
electromagnetic field (EMF) is its frequency
or its corresponding wavelength. Fields of
different frequencies interact with the body
in different ways. One can imagine
electromagnetic waves as series of very
regular waves that travel at an enormous
speed, the speed of light. The frequency
simply describes the number of oscillations
or cycles per second, while the term
wavelength describes the distance between
one wave and the next. Hence wavelength and
frequency are inseparably intertwined: the
higher the frequency the shorter the
wavelength.
A simple analogy
should help to illustrate the concept: Tie a
long rope to a door handle and keep hold of
the free end. Moving it up and then down
slowly will generate a single big wave; more
rapid motion will generate a whole series of
small waves. The length of the rope remains
constant, therefore, the more waves you
generate (higher frequency) the smaller will
be the distance between them (shorter
wavelength).
What is the
difference between non-ionizing
electromagnetic fields and ionising
radiation?
Wavelength and frequency determine another
important characteristic of electromagnetic
fields: Electromagnetic waves are carried by
particles called quanta. Quanta of higher
frequency (shorter wavelength) waves carry
more energy than lower frequency (longer
wavelength) fields. Some electromagnetic
waves carry so much energy per quantum that
they have the ability to break bonds between
molecules. In the electromagnetic spectrum,
gamma rays given off by radioactive
materials, cosmic rays and X-rays carry this
property and are called 'ionizing
radiation'. Fields whose quanta are
insufficient to break molecular bonds are
called 'non-ionizing radiation'. Man-made
sources of electromagnetic fields that form
a major part of industrialized life -
electricity, microwaves and radiofrequency
fields – are found at the relatively long
wavelength and low frequency end of the
electromagnetic spectrum and their quanta
are unable to break chemical bonds.
Electric fields
1.
Electric fields arise
from voltage.
2.
Their strength is measured in Volts per
metre (V/m)
3.
An electric field can be present even when a
device is switched off.
4.
Field strength decreases with distance from
the source.
5.
Most building materials shield electric
fields to some extent.
Magnetic fields
1.
Magnetic fields arise from current flows.
2.
Their strength is measured in amperes per
meter (A/m). Commonly, EMF investigators use
a related measure, flux density (in
microtesla (µT) or millitesla (mT) instead.
3.
Magnetic fields exist as soon as a device is
switched on and current flows.
4.
Field strength decreases with distance from
the source.
5.
Magnetic fields are
not attenuated by most materials.
Electric fields
Plugging a wire into an outlet creates
electric fields in the air surrounding the
appliance. The higher the voltage the
stronger the field produced. Since the
voltage can exist even when no current is
flowing, the appliance does not have to be
turned on for an electric field to exist in
the room surrounding it.
Magnetic fields
Magnetic
fields are created only when the electric
current flows. Magnetic fields and electric
fields then exist together in the room
environment. The greater the current the
stronger the magnetic field. High voltages
are used for the transmission and
distribution of electricity whereas
relatively low voltages are used in the
home. The voltages used by power
transmission equipment vary little from day
to day, currents through a transmission line
vary with power consumption. Electric fields
around the wire to an appliance only cease
to exist when the appliance is unplugged or
switched off at the wall. They will still
exist around the cable behind the wall.
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How do static fields
differ from time-varying fields?
A static field does not vary over time. A
direct current (DC) is an electric current
flowing in one direction only. In any
battery-powered appliance the current flows
from the battery to the appliance and then
back to the battery. It will create a static
magnetic field. The earth's magnetic field
is also a static field. So is the magnetic
field around a bar magnet which can be
visualized by observing the pattern that is
formed when iron filings are sprinkled
around it. In contrast, time-varying
electromagnetic fields are produced by
alternating currents (AC). Alternating
currents reverse their direction at regular
intervals. In most European countries
electricity changes direction with a
frequency of 50 cycles per second or 50
Hertz. Equally, the associated
electromagnetic field changes its
orientation 50 times every second. North
American electricity has a frequency of 60
Hertz.
What are the main sources of low,
intermediate and high frequency fields?
The time-varying electromagnetic fields
produced by electrical appliances are an
example of extremely low frequency (ELF)
fields. ELF fields generally have
frequencies up to 300 Hz. Other technologies
produce intermediate frequency (IF) fields
with frequencies from 300 Hz to 10 MHz and
radiofrequency (RF) fields with frequencies
of 10 MHz to 300 GHz. The effects of
electromagnetic fields on the human body
depend not only on their field level but on
their frequency and energy. Our electricity
power supply and all appliances using
electricity are the main sources of ELF
fields; computer screens, anti-theft devices
and security systems are the main sources of
IF fields; and radio, television, radar and
cellular telephone antennas, and microwave
ovens are the main sources of RF fields.
These fields induce currents within the
human body, which if sufficient can produce
a range of effects such as heating and
electrical shock, depending on their
amplitude and frequency range. (However, to
produce such effects, the fields outside the
body would have to be very strong, far
stronger than present in normal
environments.)
Electromagnetic
fields at high frequencies
Mobile
telephones, television and radio
transmitters and radar produce RF fields.
These fields are used to transmit
information over long distances and form the
basis of telecommunications as well as radio
and television broadcasting all over the
world. Microwaves are RF fields at high
frequencies in the GHz range. In microwaves
ovens, we use them to quickly heat food.
At radio frequencies, electric and magnetic
fields are closely interrelated and we
typically measure their levels as power
densities in watts per square metre (W/m2).
Are EMFs
Hazardous to Our Health?
Can
electromagnetic fields (EMF) from power
lines, home wiring, airport and military
radar, substations, transformers, computers
and appliances cause brain tumors, leukemia,
birth defects, miscarriages, chronic
fatigue, headaches, cataracts, heart
problems, stress. nausea, chest pain,
forgetfulness, cancer and other health
problems?
Numerous studies have
produced contradictory results, yet some
experts are convinced that the threat is
real.
Dr. David Carpenter, Dean at the School of
Public Health, State University of New York
believes it is likely that up to 30% of all
childhood cancers come from exposure to EMFs.
The Environmental Protection Agency (EPA)
warns "There is reason for concern" and
advises prudent avoidance".
Martin Halper, the EPA's Director of
Analysis and Support says "I have never seen
a set of epidemiological studies that
remotely approached the weight of evidence
that we're seeing with EMFs. Clearly there
is something here."
Concern over EMFs
exploded after Paul Brodeur wrote a series
of articles in the New Yorker Magazine in
June 1989. Because of Paul Brodeur's
reputation. his articles had a catalytic
effect on scientists, reporters and
concerned people throughout the world.
In November 1989, the
Department of Energy reported that "It has
now become generally accepted that there
are, indeed, biological effects due to field
exposure."
The EMF issue gained
more publicity in 1990 when alarming reports
appeared in Time, the Wall Street Journal,
Business Week and popular computer
publications. ABC's Ted Koppel and CBS's Dan
Rather both aired special segments on EMFs.
In addition to the
long-term health concerns, buying a house
with high fields will be an economic
disaster. In a few years, when power line
radiation is as well known as asbestos and
radon, a house with high fields will be
practically impossible to sell. Already
there are hundreds of lawsuits regarding
EMFs and property devaluation.
EPA Says the Threat
Is Real
By 1990,
over one hundred studies had been conducted
worldwide. Of these, at least two dozen
epidemiological studies on humans indicated
a link between EMFs and serious health
problems. In response to public pressure,
the Environmental Protection Agency IEPA)
began reviewing and evaluating the available
literature.
In a draft report
issued in March 1990, the EPA recommended
that EMFs be classified as a Class B
carcinogen -- -a "probable human carcinogen
and joined the ranks of formaldehyde, DDT,
dioxins and PCBs.
After the EPA draft report was released,
utility, military and computer lobbyists
came down hard on the EPA. The EPA's final
revision did NOT classify EMFs as a Class B
carcinogen Rather, the following explanation
was added:"
At this time such a
characterization regarding the link between
cancer and exposure to EMFs is not
appropriate because the basic nature of the
interaction between EMFs and biological
processes leading to cancer is not
understood."
Curiously, this rather
unusual logic appears on the same page as
the following: "In conclusion, several
studies showing leukemia, Iymphoma and
cancer of the nervous system in children
exposed to supported by similar findings in
adults in several/ occupational studies also
involving electrical power frequency
exposures, show a consistent pattern of
response that suggest a causal link. "
When questioned about
the contradictory nature of these
statements, the EPA responded that it was
"not appropriate" to use the probable
carcinogen label until it could demonstrate
how EMFs caused cancer and exactly how much
EMF is harmful.
This explanation does
not satisfy many critics who claim that the
EPAs upper management was influenced by
political and economic considerations
exerted by utility, computer and military
lobbyists.
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How Do I Measure
EMFs?
A Gauss is a common
unit of measurement of magnetic field
strength. A Gauss meter is an instrument
which measures the strength of magnetic
fields. Inside a Gauss meter there is a coil
of thin wire, typically with hundreds of
turns. As a magnetic field radiates through
the coil, it induces a current, which is
amplified by the circuitry inside the Gauss
meter.
Gauss meters may vary
in the strength of the magnetic field they
are capable of measuring. A meter used for
measuring EMFs from power lines,
transformers, substations and appliances
around the home, for example, should be able
to measure as low as .1 mg.
Gauss meters vary
widely in price and accuracy. Meters have
either a single axis coil or a triple axis
coil. Single axis meters are much simpler
than triple axis meters to manufacture and
thus, are less expensive.
To use a single axis meter you must point
the meter's one sensor in three directions
-- -the x, y and z axis. Then, you combine
the three readings in a mathematical
equation to calculate the combined field
strength. Obviously, its far easier and more
accurate to use a 3-axis meter. Triple axis
Gauss meters are quite accurate, but they
are also more expensive.
Another thing to watch
out for when purchasing or renting a Gauss
meter is whether or not it is frequency
weighted. Most meters will read the same EMF
strength no mater what the frequency.
As the human body appears to be sensitive to
both the field strength AND the frequency,
Gauss meters used for biological purposes
should be "frequency weighted".
This means that if the
field is different than 60 Hz the meter will
consider the frequency and use it in
calculating and displaying the EMF's
strength. This feature is why frequency
weighted meters will show a higher EMF
reading than those meters typically used by
electricians and engineers.
Power Lines
An enormous amount of
electricity is created at power generating
stations and sent across the country through
wires that carry high voltages. All power
lines radiate electromagnetic fields. The
question is: how much are the
power lines near YOUR home radiating? The
amount of EMFs coming from a power line
depends on its particular configuration.
Power companies know which power line
configurations are best for reducing EMFs
but most don't feel the evidence supports
costly changes in the way they deliver
electricity.
Substations
A substation is an
assemblage of circuit breakers,
disconnecting switches and transformers
designed to substations have been blamed for
causing cancer clusters among nearby
residents. Paul Brodeur wrote about several
such cancer clusters in the July 9, 1990
issue of the New Yorker Magazine.
Transformers
A key component of a
utility's electrical distribution network
depends upon numerous, small transformers
mounted on power poles. A transformer looks
like a small metal trash can, usually
cylindrical.
Even when the electrical service is
underground, you will often see a metal box
(usually square} located on the ground near
the street. Many people don't realize that
when they see a transformer, the power line
feeding the transformer is 4000 to 13,800
volts.
The transformer then
reduces the voltage to the 120/240 volts
needed by nearby homes. Since these
transformers can be seen in almost every
neighborhood, they are a source of concern.
EMFs near a transformer can be quite high,
but due to its small structure, the field
strength diminishes rapidly with distance,
as it does from any point source. For this
reason, having a transformer located near
your home is usually not a major source of
concern, although just to make sure,
everyone should measure the field strength
around it.
Home Wiring
If your home has high
EMF readings, it is important to determine
the sources of the EMF so that remedial
action can be taken, if possible. Many times
a particular room will have a higher EMF
reading. Check to see if the electricity is
coming into the house on the wall outside
that room. When this is the case, it is
usually a good idea to block off that room
and only use it for storage purposes.
Sometimes, the source of a high magnetic
field is incorrect wiring. If you suspect
that your home is wired improperly, obtain
the services of a licensed electrician.
Warning: Do not touch electric wires, even
if you think the current is turned off. If
you need to disconnect electrical circuits
to determine the source of magnetic fields,
you should call a licensed electrician.
Computers
Computers are a
complicated subject. Know this: EMFs radiate
from all sides of the computer. Thus, you
must not only be concerned with sitting in
front of the monitor but also if you are
sitting near a computer or if a computer is
operating in a nearby room.
The Swedish safety
standard, effective 711/90, specifies a
maximum of 0.25 mG at 50 cm from the
display. Many US manufactured computers have
EMFs of 5 - 100 mG at this distance. And
know this too: the screens placed over
monitors do NOT block EMFs. Not even a lead
screen will block ELF and VLF magnetic
fields.
Space does not permit a more thorough
discussion of computers. If you use a
computer, it is important that you
measure your EMF exposure with a Gauss meter
and review the literature concerning the
health impacts of computer use.
Electric
Blankets and Waterbeds
Electric blankets
create a magnetic field that penetrates
about 6-7 inches into the body. Thus it is
not surprising that an epidemiological study
has linked electric blankets with
miscarriages and childhood leukemia.
This pioneering work was performed by Dr.
Nancy Wertheimer and Ed Leeper, who
originally discovered that magnetic fields
were linked to childhood leukemia. Similar
health effects have been noted with users of
many electric blankets and waterbed heaters
will emit EMFs even when turned off.
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The devices must be
unplugged to delete the EMF exposure
Additionally, there is the issue regarding
the vibrations that are generated by
sleeping on standing water. There is less
hard data in this area but some experts are
concerned about the consequences.
Electric Clocks
Electric clocks have a
very high magnetic field, as much as 5 to 10
mG up to three feet away. If you are using a
bedside clock, you are probably sleeping in
an EMF equivalent to that of a powerline
Studies have linked high rates of brain
tumors with chronic exposure to magnetic
fields, so it is wise to place all clocks
and other electrical devices (such as
telephones and answering devices) at least 6
feet from your bed.
Fluorescent
Lights
Fluorescent lights
produce much more EMFs than incandescent
bulbs. A typical fluorescent lamp of a
office
ceiling have readings of 160 to 200 mg 1
inch away.
Microwave
Ovens and Radar
Microwave ovens and
radar from military installations and
airports emit two types of radiation --
microwave and ELF. Microwaves are measured
in milliwatt per centimeter squared (mW/cm2)
As of 1/1/93, the U.S. safety limit for
microwave exposure is 1 mW/cm2, down from a
previous 10 mW/cm2. The Russian safety limit
is .01 mW/cm2. All microwave ovens leak and
exceed the Russian safety limit. In
addition, recent Russian studies have shown
that normal microwave cooking coverts food
protein molecules into carcinogenic
substances.
When measuring microwaves from military and
airport radar sources, 100% accurate
readings can only be found with extremely
expensive digital peak-hold meters. Why?
Because analog devices begin to drop their
reading immediately after the radar sweep
passes. Thus, while an analog meter can show
whether or not you are being exposed to
radar EMFs, analog meters can't show your
true exposure. Although thousands of dollars
to purchase, digital-hold meters capable of
accurately detecting radar EMFs can be
rented for several hundred to over a
thousand dollars per month.
Telephones
and Answering Machines
Telephones can emit
surprisingly strong EMFs, especially from
the handset. This is a problem because we
hold the telephone so close to our head.
Place the Gauss meter right against the ear
piece and the mouth piece before buying a
phone.
Some brands emit no measurable fields and
others emit strong fields that travel
several inches....right into your brain.
Answering machines, particular those with
adapter plugs (mini-transformers), give off
high levels of EMFs.
Electric Razors and
Hair Dryers
Electric razors and
hair dryers emit EMFs as high as 200 to 400
mG. This seems alarming, but we don't know
if this is worse (or better) than a chronic
exposure to a 2-3 mG field. Some EMF
consultants recommend that hair dryers not
be used on children as the high fields are
held close to their rapidly developing brain
and nervous system.
Prudent
Avoidance
Electricity is an
inseparable part of our modern day society.
This means that EMFs will continue to be all
around us. But as Discover Magazine
postulated, aside from making our life
easier, is electricity also making our lives
shorter?
Most experts agree that limited, non-chronic
exposure to EMFs is not a threat. For
example, it is probably acceptable for a
person to be near a toaster in the morning.
BUT, it is not
advisable for a person to sleep under an
electric blanket, up close, live near a
powerline/substation, and sleep in a room
where the power enters the home. This person
is under an extreme case of chronic
exposure. This condition, unfortunately,
applies to millions of Americans.
If you wish to follows the EPA's advice and
practice "prudent avoidance" then the
following advice is offered:
Measure your home, work and school
environments with a Gauss meter Measure EMFs
both inside and outside your home. Don't let
your children play near power lines,
transformers, radar domes and microwave
towers.
Avoid areas where the
field is above 1 mG. Measure the EMFs from
appliances both when they are operating and
when they are turned off. Some appliances
(like TVs) are still drawing current even
when they are off.
Don't sleep under an electric blanket or on
a waterbed. If you insist on using these,
unplug them before going to bed (don't just
turn it off). Even though there is no
magnetic field when they are turned off,
there may still be a high electric field.
Don't sit too close to
your TV set. Distance yourself at least 6
feet away. Use a Gauss meter to help you
decide where it is safe to sit.
Rearrange your office
and home area so that you are not exposed to
EMFs from the sides/backs of electric
appliances and computers. In the home, it is
best that all major electrical appliances,
such as computers, TVs, refrigerators etc,
be placed up against outside walls. That way
you are not creating an EMF field in the
adjoining room.
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Don't sit too close to
your computer. Computer monitors vary
greatly in the strength of their EMFs, so
you should check yours with a meter. Don't
stand close to your microwave oven. Move all
electrical appliances at least 6 feet from
your bed. Eliminate wires running under your
bed. Eliminate dimmers and 3-way switches.
Be wary of cordless appliances such as
electric toothbrushes and razors. You may
choose not to wear a quartz-analog watch
because it radiates pulsating EMFs along
your acupuncture meridians.
An older mechanical
windup watch would be an acceptable
alternative. It is also recommended to wear
as little jewelry as possible and to take it
off at night. Many people have metal
sensitivity which can be aggravated by
placing it right on the skin. Measure with a
gauss meter to be sure.
And last, but not least, always always
always remember that EMFs pass right through
walls. The EMF you are reading on your Gauss
meter could be radiating from the next
room...or from outside your home.
Additional Radiation Info:
Eyeglass frames should
ideally be made from plastic with no wires
in them, otherwise they can serve as an
antenna to focus the radio and cellular
phone waves directly into your brain.
What EMF
Level Is Safe?
There's a heated
debate as to what electromagnetic field (EMF)
level is considered safe. Since the experts
have not come to an consensus, you'll have
to decide for yourself... Many government
and utility documents report the usual
ambient level of 60-Hz magnetic field to be
0.5 mG.
Thus, any reading higher than 0.5 mG is
above the "usual" ambient exposure. Many
experts and public officials, as well as the
few governments that have made an effort to
offer public protection, have adopted the 3
mG cutoff point. The EPA has proposed a
safety standard of 1 mG. Sweden has set a
maximum safety limit of 1 mG.
Health and safety
The potential health
effects of the very low frequency EMFs
surrounding power lines and electrical
devices are the subject of on-going research
and a significant amount of public debate.
In workplace environments, where EMF
exposures can be up to 10,000 times greater
than the average, the US National Institute
for Occupational Safety and Health (NIOSH)
has issued some cautionary advisories but
stresses that the data is currently too
limited to draw good conclusions.
The potential effects
of electromagnetic fields on human health
vary widely depending on the frequency and
intensity of the fields. For more
information on the health effects due to
specific parts of the electromagnetic
spectrum, see the following articles with
details of possible dangers (MRI) and some
currently unfounded fears (mobile phones):
Static electric
fields: see Electric shock
Static magnetic fields: see MRI/Safety for
one of the few applications in which
magnetic fields are strong enough to have
safety implications
Extremely low frequency (ELF): see Power
lines/health concerns
Radio frequency (RF): see Electromagnetic
radiation and health
Light: see Laser safety
Ultraviolet (UV): see Sunburn
Gamma rays: see Gamma ray
Mobile telephony: see Mobile phone radiation
and health
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