Indoors and out, we are surrounded with
Electromagnetic Fields (EMFs).
Some are natural, but many are not, and in one way or another . . .
they will interact with any entity that is electrically based.
Humans fall within that category - EMFs are us.
Some of the primary concerns revolving around EMFs presented to this author are "How many milliGauss (mG) are bad?", or "I read 0 mG on my meter, yet I still react, to something . . .". However, Magnetic Field strength (mG) is only one component of Electromagnetic Fields (EMFs). For those that want the full picture, EMF implies that something Electric and something Magnetic are involved (the physics law of Induction states that "an Alternating Electric Field will produce an Alternating Magnetic Field, and vice versa").
EMFs by definition then include
1) Electric Fields,
2) Magnetic Fields,
3) Wideband Emissions (many frequencies simultaneously,
sometimes associated with transient phenomena such as lightning), and
4) Radio Frequency (RF).
While the non-changing Electric and Magnetic fields associated with our planet are necessary for good health, all of the bad contributors are Alternating in quality. That is, they continuously change in size and orientation with time.
Ideally, a Healthy habitat should be free of all Alternating fields. However, reality is far from this ideal.
By necessity this document can only touch on the highlights of the most prevalent field types, but to produce a framework where everyone has a similar knowledge level, a beginning from basics is paramount.
Electromagnetic fields are by definition created by motion of elemental charges (electrons (e-)), either in free space, or constrained within a wire. When that motion or flow is relatively constant, we define it as Direct Current (DC). When it is changing with time, we define it as Alternating Current (AC).
The motion of these elemental charges is created by a difference of charge distribution wanting to come to equilibrium relative to each other, akin to two containers of water with different levels in them, connected by a tube at the bottom. If the charge distributions are prevented from equalizing by any form of Electrical Resistance, then the difference is measurable as a potential difference, or Voltage. Any Voltage source will produce an Electric field in free space. Allowing a limited amount of current flow will allow the Voltage to remain fairly constant, and yet provide useful output, or work. If the Voltage is relatively constant, we define it as DC Voltage. If the Voltage is changing with time, we define it as AC Voltage.
In DC, a current is produced when a resistance is placed across a source as follows:
When the switch is closed current will flow, and since the electrical resistance of the wire within the bulb is much higher than that in the wire, the entire battery voltage is impressed across the bulb. Since it is much thinner than the wire outside the bulb, it glows red hot.
The chemical reaction drives a passage of Electrons (Current) through the connections until the chemistry has exhausted its driving mechanism (Voltage). [9, 10] The proper convention is that current exits the source from the Negative terminal and returns to the Positive terminal.
Both fields will have directional properties that depend on the direction of current flow. [8, 10] While it may be comforting to think that these fields remain constrained within the insulation surrounding the wire, unfortunately they do not. That is the reason why these fields impact biological systems, and the pressing question becomes not "IF", but "how much" and "for how long". Below is a sketch of the fields as seen from the end of the wire.
The above are exemplified in the majority of electrical wiring schemes in an automobile, except for the Ignition wiring. Because there is no connection between the automobile's electrical system and the Earth, we describe the wiring system as "Floating". That is, touching any "ONE" connection in the 12 Volt system, there is no chance of shock. Similarly, trying to measure the voltage of any one point in this system, relative to "Earth ground", will render an unstable and unpredictable value.
When DC was employed for public and long distance domestic usage, it became a dismal failure, because of Wire Resistance. While most wire is made of Copper and Aluminum, and its resistance is quite low, over a considerable distance of several or many miles, the resistance becomes a limiting factor. In a DC scheme, the generating station would have to feed the customers directly at the required voltages. So if a customer next to the station needed 120 volts, the station would produce 120 volts. If another customer several miles away needed 120 volts the station would produce 120 volts, plus the voltage required to overcome the wires' resistance. This is where standard formulas begin to fit in, as the current needed (I) times the wire resistance (R) will produce a Voltage Drop (E), (E=I x R), over the length of the wire (being subtracted from that produced). This situation spelled the end of the DC distribution system. In an automobile this length/wire-resistance issue does not exist, so it can function quite well.
A normal electromagnetic system exists within and around our planet that is necessary for our survival. It produces DC voltage and current. These steady-state Magnetic and Electric fields have been our normal everyday setting, from before recorded history until the late 1800s. [1, 6] The planetary Magnetic field, and the gently changing Electric field have connected us to the Earth's periodic rhythms.  However, this was soon to change.
In the mid 1800s, experimenters noticed that when a current was pulsed through a wire coil (the Primary), it would produce a similar pulse of current through a nearby coil of wire (the Secondary), where changing the numbers of turns on one side or the other allowed them to increase or decrease the voltage on the Secondary coil. This is the foundation of the modern Transformer.(This process is now known as Induction. It can create currents and voltages within any electrically conductive system (biological or inanimate) in reach of its fields. These time-varying fields are of biological interest because they have been shown to produce an increase in various forms of illness.)
The Electric Fields of interest are those that are Alternating, or changing
with time. They can be produced from Power Distribution wiring, Structural
Cavity wiring, or Appliance Cordage.
Most residential structures are transparent to electric fields. The emissions from a Power line nearby are usually dwarfed by those from structural cavity wiring, while those from a fixture nearby one reading a book dwarfs those from structural cavity wiring. Shown to the right is a cycle of Alternating Voltage, with a depiction of molecular alignment changing with each portion of each cycle, and in the extreme shown on the horizontal axis, even atomic orbits become distorted. When biological structures are exposed to such fields, every molecule will consistently try to align with each field variation. The same happens within a microwave oven, to such an extent that molecular friction is produced that manifests itself as heat. At power line frequency (60 or 50 cycles/second) molecular friction is quite reduced, although interference with chemical synthesis persists, because random alignment is continuously interfered with, possibly preventing certain reactions. While true scientists and junk scientists (those paid by vested interests) duke it out as to what exactly is happening, exposure continues possibly promoting a variety of diseases that cannot be associated with any other factor(s), such as Chronic Fatigue, Fibromyalgia, general irritability, etc. Regardless of the uncertainties, those with environmental hypersensitivity can feel immediate relief when the source of power is turned off, eliminating the electric field presence.
The Magnetic Fields of interest are those that are Alternating. They can be
produced from Power Distribution wiring, Grounding Interconnections to mask a
fire hazard, wiring errors, and locally from appliances. While those from
appliances are point sources, whose level of emission drops off dramatically
with increasing distance from the source, they are nonetheless important if
exposure is lengthy (as from a stove-top exhaust fan).
The fire hazard occurs because grounding connections fail, causing unstable voltages (170 in the sketch above).
Multiple connections between multiple systems causes Stray Current flow everywhere, as below.
Fields from wiring errors are more insidious because they only occur when the mis-wired circuit(s) is(are) in use. What happens is that the current going from the breaker panel to the using device sees multiple paths to return through. In doing so the current splits, reducing cancellation effects from nearby opposing currents, and generating fields that may engulf the structure.
Most residential structures are transparent to Magnetic Fields. The interaction, however, is more complex than from Electric fields, causing strange "windowing" effects. That is, effects that manifest most easily at certain intensities or frequencies, although even for the single-frequency exposure to power line frequencies (60 or 50 cycles/second) one of the marked effects of extended exposure to more than a few milliGauss is an increase in the occurrence of Leukemia.
Wideband Emissions, typically triggered by high voltage devices, equipment close to end of life displaying failure symptoms, rapid current turn-off (or turn-on as in dimmers), or Digital electronics, have several peculiar characteristics:
1) each burst will produce a ringing of the EMF spectrum (trigger many frequencies simultaneously ("wideband emissions")), whose Frequency extent will vary with the energy content of the burst,This latter feature is employed in Transcutaneous Electrical Nerve Stimulators (TENS) that are used to alleviate pain. This is an example of a controlled and beneficial biological electrical application. Similar rapid transitions are employed in TASER guns, used by law enforcement to inflict pain. Many Transient Phenomena produced by common residential electrical devices ride on the 60 Hz Voltage  and can likewise penetrate the skin and interfere with the Central Nervous System (CNS). The CNS performs Muscle control by electrical pulses (Action Potential) that are characteristic to the electrochemical messages constantly occurring within the body.  When an electrical pulse (or pulses) of similar waveform is (are) able to enter the highly conductive structure below the skin, interference in the form of irritation, pain, or outright failure to control physical activity may occur. Other pulses wholly within the brain can similarly be interfered with. When these wideband emissions have a convenient carrier, such as a whole-house Alternating Electric or Magnetic Field, then these emissions become immediate and whole-body exposure concerns (a former client wished to use a digital widescreen television, but due to the power supplies' rapid transitions, and the home's Electric fields from structural cavity wiring acting as carriers, she could not tolerate it (it was almost as if the emissions were occurring within her anywhere inside the home)). These are examples of uncontrolled and detrimental biological electrical applications.
2) although caused by individual transients, the emission bursts may appear as a continuous stream, when detected by simple devices such as an AM radio, and
3) they are able to penetrate insulating barriers more easily.
These Wideband Emissions can usually be detected with an AM radio. Events as simple as operating a light switch will produce transients that can be easily detected anywhere in the AM spectrum. That is because any step-change in current flow will excite the EMF spectrum like a spark discharge. A dimmer in use will produce this type of electrical emission continuously, throughout the AM spectrum, blanketing all frequencies in an otherwise quiet background.
While Wideband emissions are easily controllable at the source, or by appropriate filtering, some unscrupulous marketers are selling "filters" of various sizes with the claim to "clean" "dirty" electricity. While "clean" electricity is continuously varying with time, and in and of itself is an irritant,Wideband riding on the AC can be especially irritating. However, indiscriminately installing filters without investigating the residence's electrical system, and verifying there are no wiring errors, will cause more harm than good. Read more at Capacitive Filter recommendations.
Irritating Wideband or Transient Phenomena can manifest themselves through the Auditory, Visual, Tactile senses, or directly by EMF interaction with the CNS.
The study associated with this close-up of a portion of the frequency spectrum, involved Photosensitive stimulation of epileptic and/or convulsive behavior. Although the study noted involved only a small group of primarily young individuals, Environmentally Sensitive individuals may suffer sensitivity and irritability when exposed to these frequencies at any age, be they produced visually, or otherwise, in any form.
There are certain low frequencies that occur naturally, such as Lightning-induced Atmospheric Schumann Resonance, and Lunar and Solar cycles that are very low in frequency. These various frequencies are needed by humans, animals, and plants to synchronize with normal and periodic cycles characteristic of growth and good health.  The encroachment of this frequency region by artificial means is especially troubling, as hinted at by the above study.
When one considers the benefit of shielding from artificial sources, one needs to consider the detriment of also shielding from the Natural Electrical Background.
The 120-Volt power distribution system within a home needs to be considered as a "permanently energized grid" of wires, because even though there are many loads connected to it, it is still and always essentially at 120 Volts (within the limits of its engineered design).
This "permanently energized grid" will absorb and echo impinging Radio Frequencies (RF). RF has properties that behave differently with biological systems primarily due to the frequencies involved, and the energy or information associated with that frequency (another example of a windowing property). As the frequency involved becomes progressively faster the energy becomes more directional to the point where, like light energy, it can be "beamed".
The EMF Spectrum (of which RF is only a small part) is a continuous grouping of frequencies. This continuum encompasses frequencies from 0 (DC) to infinite variations/second. Within this realm are energies that Conduct through a physical medium (wire), and energies that Radiate through space. The transition area between Radiation and Conduction occurs at about 30 MHz (Megahertz (MHz), or millions of cycles/second). 
Below 30 MHz, Voltage and Magnetic components (which Radiate into the space surrounding the conductor at the speed of light) need to be considered and treated as separate entities. The predominant entity can be either Electric or Magnetic.
Above this frequency the two components are so intertwined as to be inseparable, and require a different treatment. The predominant entity is Electric.
The general consideration is that energies slower than Visible Light do not have enough energy to produce physical changes in matter such as Ionization. Ionization, however, can easily be produced when even a minuscule amount of electrical current is involved.
The primary interaction with matter from RF, as with all Electric fields, is a polar molecular alignment that is forced to change with each cycle.
As the electric field becomes more intense, even atomic orbits become distorted. At certain frequencies this manifests itself as a molecular friction that is known as heat (a classic example occurs within a microwave oven). Although this is the basis for Thermal Biological effects (and exposure recommendations), there are other effects that are more subtle that interfere with normal body chemistry. At faster frequencies chemical changes can be brought about directly, forming such compounds as cataracts. 
An additional consideration with RF impinging on a biological system is that the latter is not Linear. That is, biological systems have certain behavioral characteristics that resemble semiconductors , allowing for Heterodyning, where the impinging energies are combined to form sum and difference frequencies.  These can provide for avenues of interaction not considered when only the original frequencies are considered. This mixing and combining can produce synergies that are beyond the scope of this paper, as well as beyond the scope of most studies to date.
To answer the first question of how many milliGauss is bad, when one takes into perspective that we exist in a sea of non-alternating Planetary Magnetism whose value ranges around 500 mG in most places on this planet, and that many studies have already shown an association with various illnesses with a background of as little as one or two (1 - 2) mG of alternating field, it should seem obvious that any Presence should be cause for concern. That is, any presence that is a wide-area field that you cannot walk away from, to an area of much lower intensity, or a field whose duration spans a substantial part of your day.
For the other aspects of EMF components, being Voltage, Wideband, and RF, the answer is more difficult, if indeed an answer can be given. When one considers that every day new applications are found for wireless or other electrical devices, it is obvious that the Wideband and RF background is on a rapid increase. Voltage, on the other hand, is the more insidious of irritants, as it is a given that if a voltage environment is not additionally created from wires within the walls/floors/ceilings, it will Always be created by appliance cordage within the living space. When one considers that the frailest humans are infants, the elderly, and the injured, it is just a matter of time before one falls into one of those categories and obvious consequences follow.
For infants especially, the reality of the connection can be dramatic. This author is familiar with a child that moved into a fairly new home and within a few days developed a sleep dysfunction that lasted for the entire time of exposure (eight months). When the author learned of it, and convinced the parents to relocate the crib away from energized power cords, the child's sleep pattern reverted to an expected full night's sleep within a few days.  Had the conditions not been changed, the child could have possibly suffered life-long repercussions
"Since the early 1980s about 100 occupational and 40 residential epidemiological studies have been published (NIEHS - Health effects from exposure to power line electric and magnetic fields. Research Triangle Park. US GPO Publ. No. 99-4493). Interestingly, of the approximately 500 separate risk ratios published in these studies, six are elevated for every one that is reduced." 
While the major emphasis in most of the published studies has been on Magnetic fields exclusively, the confounding factor of not including Electric fields, and not including the interaction with the Earth's background Magnetic field, which in most cases dwarfs the Alternating contribution required to produce statistically significant incidence of diseases (500 mG vs 2mG), has rendered most of the associations weak.
The author of the present document contends that Electric fields are the more ominous factor to consider. Electric fields are present in a living environment 100% of the time, at 100% intensity. Additionally, ALL appliance and light fixture cordage, grounded or not, is manufactured unshielded and becomes a prolific emitter of Electric fields. Magnetic fields, on the other hand, are caused by wiring errors, multi-grounding arrangements (to "protect" an innocent and ignorant public), and wiring separation in High Voltage Power Distribution wiring. These may almost be considered minor, compared to the prevalence of Electric fields in the living environment. Magnetic fields, are most difficult to shield from, and field reduction is a source-reduction engineering task. Electric fields, however, are present in ALL residences, and are easiest to shield from.
The advent of Transcutaneous Electrical Nerve Stimulation (TENS) devices clearly depicts that very sharp and small voltage waveforms can easily penetrate the skin barrier and interact directly with the Central Nervous System (CNS). There is an uncanny similarity between these waveforms and electrical "noise" produced by intermittent contacts, which is broadcast between consumers without reduction due to the common ties to supply transformers. This electrical "noise" may be small in value, but when it is brought directly to the skin surface of every occupant due to the ambient Electric fields it rides on, the potential for harm can be (and has been) woefully underestimated. Environmentally hypersensitive individuals who may have progressed to Electrical Sensitivity are especially at risk.
Every individual is electrically sensitive to some degree. The awareness of
this sensitivity is not always obvious, but objectivity about various forms of
irritation can make for a quick association. When one's immune system has been
damaged or compromised from injury, the sensitivity becomes enhanced, and the
irritation can become extreme. It is at this point that the association becomes
too obvious, and it is at this point that drastic field reduction measures
achieve only partial relief. The individual is then left to regress to a
non-electric living environment. A radical departure from the electrical
"conveniences" one has become accustomed to.
A glimpse into effects from Radio Frequencies
Why are recommended exposure
Common formulas applicable to single phase and DC
** © BASIC ELECTRICITY 
P = Power in Watts I = Current in Amps
E = Voltage in Volts R =
Resistance in Ohms
Alternation - Cyclic change between arbitrary reference points.
Conductivity - Electrical characteristic that allows easy passage of charged particles on its surface or within its structure. A human's skin is primarily a non-conductor, unless wet or moist, whereas the interior organs are generally conductors.
Electric Field - Volumetric (3-D) property brought about by a difference of charged particle distribution (Potential Difference, or Voltage).
EMF - Classically defined as an ElectroMagnetic Field, a volumetric property brought about by a combination of inseparable Magnetic and Electric fields. At lower frequencies the two fields need to be treated separately.
Faraday Cage - Metal-clad enclosure for Electric isolation (some non-metallic, but electrically conductive, materials may also be used).
Gauss - CGS (English) measure of Magnetic field density.
Gaussmeter - Generally an instrument used to detect Alternating Magnetism.
Hertz - Measure depicting Cycles/second.
Ion - Atom that is electrically charged due to imbalance between its + (Protons) and - (Electron) charge distribution. The imbalance may occur as an unequal sharing between the atom and the molecule (or another atom) it is attached to. This generally leads to a Polarized Molecule as described below.
INT - Induction Neutralizing Transformer, device used to remove unwanted alternating electric components from specific wiring, such as Telephone.
Magnetic Field - Volumetric property brought about by a flow of charged particles (Electrons), or Atomic Alignment.
MC / Metal Clad, wire type that uses a metallic armor as part of its protective cover. BX is a common trade name for this type of wire.
Net Current - Difference between the current supplied and the current returned in any particular circuit.
NM / Non Metal-clad wire type that uses a soft PVC jacket for insulation. Romex is a common trade name for this type of wire.
Polarized - Uneven charge distribution about a molecule that allows it to interact with any environmental Electric (Voltage) field. Humans are about 75% water, a polarized molecule.
RF / Radio Frequency, generally alternating fields faster than about 30 MHz.
Tesla - MKS (Metric) measure of Magnetic field density.
1 Gauss = 0.0001 Tesla
10,000 Gauss = 1 Tesla
1 milliGauss (mG) = 0.1 microTesla (uT)
10 mg = 1 uT
1) ENERGY MEDICINE: The Scientific Basis - James L. Oschman, Candace Pert - Publisher: Churchill Livingstone, Inc., - 2000, ISBN: 0-443-06261-7.
The above highlights newer material that has become obvious by recent biophysical research.
2) CROSS CURRENTS, The Perils of Electropollution, The Promise of Electromedicine - Robert O. Becker M.D., - Publisher: James P. Tarcher Inc. 1990, ISBN 0-87477-609-0.
The above is a foundational book that elaborates on the electrical aspects of anatomy and physiology.
3) Historical Evidence that residential electrification caused the emergence of the childhood Leukemia Peak S. Milham, E. M. Ossiander - 2001
Available on the Internet as a PDF file.
While the authors for the above, make a subtle inference to Magnetic fields as the causative agent, the author of this paper contends that the occurrence of the Leukemia Peak was primarily due to exposure to Voltage, not Magnetism. Early electrification did not immediately drive everyone to the electrical appliance store (as most of today's appliances did not then exist), which would have resulted in the Magnetism they claim. However, immediately upon electrification, there was an ambient voltage that was present at 100% strength, 100% of the time.
4) PHOTOSENSITIVE EPILEPSY - Graham F.A. Harding, Peter M. Jeavons - Publisher: Cambridge University Press 1994 - ISBN 0 898683 02 6.
5) AC POWER HANDBOOK, Problems and Solutions - Authors and Publishers: RTE Deltec Corp. San Diego CA - 1984.
6) RADIO-FREQUENCY AND ELF ELECTROMAGNETIC ENERGIES, A Handbook For Health Professionals - R. Timothy Hitchcock, Robert M. Patterson - Publisher: Van Nostrand Reinhold - 1995, ISBN 0-442-00945-3.
The above follows the "accepted" standards and guidelines.
7) Questions and Answers about EMF, Electric and Magnetic Fields Associated with the Use of Electric Power - 1995 - National Institute of Environmental Health Services and U.S. Department of Energy - -DOE/EE-0040- - USGPO.
8) FUNDAMENTALS OF PHYSICS - David Halliday, Robert Resnick - Publisher: John Wiley and Sons Inc. - 1970 - SBN 471 34430 3.
9) CHEMISTRY, A Conceptual Approach - Charles E. Mortimer - Publisher: Van Nostrand Reinhold Company - 1971 - Library of Congress Catalog Card No.78-133428.
10) BASIC ELECTRICITY - Bureau of Naval Personnel, Rate Training Manual - Navpers 10086-B - 1969 - Stock No. 0500-030-0010.
11) BASIC ELECTRONICS, Vol. 1 - Bureau of Naval Personnel, Rate Training Manual - Navpers 10087-C - Stock No. 0500-031-0110.
12) ELECTRICAL SENSITIVITY NEWS, Vol. 5, No. 3, May-June 2000, A Wordless Electrical Sensitivity Case, Sal La Duca.
13) Evidence that Electromagnetic Radiation Is Genotoxic: The Implications For the Epidemiology of Cancer and Cardiac, Neurological and Reproductive Effects Dr. Neil Cherry June 2000, available for purchase as a PDF file at http://www.neilcherry.com/, or free as an HTM file (with a few typos) on the Internet.
The above is an excellent paper and is recommended for nursing, doctoral, or other health-related professionals, as well as those individuals with the patience to peruse detailed technical matter. Read about damage at the cellular and molecular level with detailed drawings. Also read how RF is simply a faster application of the same concepts discussed above.
Full text and graphics © 2009
Environmental Assay Inc. / Sal La Duca ,
Except as otherwise noted.
Sal La Duca
Indoor Environmental Specialist
BS, BBEC/BBEI, CIEC
792 Green St.
Phillipsburg NJ 08865 USA
Voltage from Stray Currents
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